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Merge branches 'bugzilla-14668' and 'misc-2.6.35' into release

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2
Documentation/00-INDEX
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@ -250,6 +250,8 @@ numastat.txt
- info on how to read Numa policy hit/miss statistics in sysfs.
oops-tracing.txt
- how to decode those nasty internal kernel error dump messages.
padata.txt
- An introduction to the "padata" parallel execution API
parisc/
- directory with info on using Linux on PA-RISC architecture.
parport.txt

31
Documentation/ABI/obsolete/sysfs-bus-usb Normal file
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@ -0,0 +1,31 @@
What: /sys/bus/usb/devices/.../power/level
Date: March 2007
KernelVersion: 2.6.21
Contact: Alan Stern <stern@rowland.harvard.edu>
Description:
Each USB device directory will contain a file named
power/level. This file holds a power-level setting for
the device, either "on" or "auto".
"on" means that the device is not allowed to autosuspend,
although normal suspends for system sleep will still
be honored. "auto" means the device will autosuspend
and autoresume in the usual manner, according to the
capabilities of its driver.
During normal use, devices should be left in the "auto"
level. The "on" level is meant for administrative uses.
If you want to suspend a device immediately but leave it
free to wake up in response to I/O requests, you should
write "0" to power/autosuspend.
Device not capable of proper suspend and resume should be
left in the "on" level. Although the USB spec requires
devices to support suspend/resume, many of them do not.
In fact so many don't that by default, the USB core
initializes all non-hub devices in the "on" level. Some
drivers may change this setting when they are bound.
This file is deprecated and will be removed after 2010.
Use the power/control file instead; it does exactly the
same thing.

29
Documentation/ABI/obsolete/sysfs-class-rfkill Normal file
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@ -0,0 +1,29 @@
rfkill - radio frequency (RF) connector kill switch support
For details to this subsystem look at Documentation/rfkill.txt.
What: /sys/class/rfkill/rfkill[0-9]+/state
Date: 09-Jul-2007
KernelVersion v2.6.22
Contact: linux-wireless@vger.kernel.org
Description: Current state of the transmitter.
This file is deprecated and sheduled to be removed in 2014,
because its not possible to express the 'soft and hard block'
state of the rfkill driver.
Values: A numeric value.
0: RFKILL_STATE_SOFT_BLOCKED
transmitter is turned off by software
1: RFKILL_STATE_UNBLOCKED
transmitter is (potentially) active
2: RFKILL_STATE_HARD_BLOCKED
transmitter is forced off by something outside of
the driver's control.
What: /sys/class/rfkill/rfkill[0-9]+/claim
Date: 09-Jul-2007
KernelVersion v2.6.22
Contact: linux-wireless@vger.kernel.org
Description: This file is deprecated because there no longer is a way to
claim just control over a single rfkill instance.
This file is scheduled to be removed in 2012.
Values: 0: Kernel handles events

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@ -0,0 +1,67 @@
rfkill - radio frequency (RF) connector kill switch support
For details to this subsystem look at Documentation/rfkill.txt.
For the deprecated /sys/class/rfkill/*/state and
/sys/class/rfkill/*/claim knobs of this interface look in
Documentation/ABI/obsolete/sysfs-class-rfkill.
What: /sys/class/rfkill
Date: 09-Jul-2007
KernelVersion: v2.6.22
Contact: linux-wireless@vger.kernel.org,
Description: The rfkill class subsystem folder.
Each registered rfkill driver is represented by an rfkillX
subfolder (X being an integer > 0).
What: /sys/class/rfkill/rfkill[0-9]+/name
Date: 09-Jul-2007
KernelVersion v2.6.22
Contact: linux-wireless@vger.kernel.org
Description: Name assigned by driver to this key (interface or driver name).
Values: arbitrary string.
What: /sys/class/rfkill/rfkill[0-9]+/type
Date: 09-Jul-2007
KernelVersion v2.6.22
Contact: linux-wireless@vger.kernel.org
Description: Driver type string ("wlan", "bluetooth", etc).
Values: See include/linux/rfkill.h.
What: /sys/class/rfkill/rfkill[0-9]+/persistent
Date: 09-Jul-2007
KernelVersion v2.6.22
Contact: linux-wireless@vger.kernel.org
Description: Whether the soft blocked state is initialised from non-volatile
storage at startup.
Values: A numeric value.
0: false
1: true
What: /sys/class/rfkill/rfkill[0-9]+/hard
Date: 12-March-2010
KernelVersion v2.6.34
Contact: linux-wireless@vger.kernel.org
Description: Current hardblock state. This file is read only.
Values: A numeric value.
0: inactive
The transmitter is (potentially) active.
1: active
The transmitter is forced off by something outside of
the driver's control.
What: /sys/class/rfkill/rfkill[0-9]+/soft
Date: 12-March-2010
KernelVersion v2.6.34
Contact: linux-wireless@vger.kernel.org
Description: Current softblock state. This file is read and write.
Values: A numeric value.
0: inactive
The transmitter is (potentially) active.
1: active
The transmitter is turned off by software.

40
Documentation/ABI/testing/sysfs-bus-pci
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@ -133,6 +133,46 @@ Description:
The symbolic link points to the PCI device sysfs entry of the
Physical Function this device associates with.
What: /sys/bus/pci/slots/...
Date: April 2005 (possibly older)
KernelVersion: 2.6.12 (possibly older)
Contact: linux-pci@vger.kernel.org
Description:
When the appropriate driver is loaded, it will create a
directory per claimed physical PCI slot in
/sys/bus/pci/slots/. The names of these directories are
specific to the driver, which in turn, are specific to the
platform, but in general, should match the label on the
machine's physical chassis.
The drivers that can create slot directories include the
PCI hotplug drivers, and as of 2.6.27, the pci_slot driver.
The slot directories contain, at a minimum, a file named
'address' which contains the PCI bus:device:function tuple.
Other files may appear as well, but are specific to the
driver.
What: /sys/bus/pci/slots/.../function[0-7]
Date: March 2010
KernelVersion: 2.6.35
Contact: linux-pci@vger.kernel.org
Description:
If PCI slot directories (as described above) are created,
and the physical slot is actually populated with a device,
symbolic links in the slot directory pointing to the
device's PCI functions are created as well.
What: /sys/bus/pci/devices/.../slot
Date: March 2010
KernelVersion: 2.6.35
Contact: linux-pci@vger.kernel.org
Description:
If PCI slot directories (as described above) are created,
a symbolic link pointing to the slot directory will be
created as well.
What: /sys/bus/pci/slots/.../module
Date: June 2009
Contact: linux-pci@vger.kernel.org

28
Documentation/ABI/testing/sysfs-bus-usb
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@ -14,34 +14,6 @@ Description:
The autosuspend delay for newly-created devices is set to
the value of the usbcore.autosuspend module parameter.
What: /sys/bus/usb/devices/.../power/level
Date: March 2007
KernelVersion: 2.6.21
Contact: Alan Stern <stern@rowland.harvard.edu>
Description:
Each USB device directory will contain a file named
power/level. This file holds a power-level setting for
the device, either "on" or "auto".
"on" means that the device is not allowed to autosuspend,
although normal suspends for system sleep will still
be honored. "auto" means the device will autosuspend
and autoresume in the usual manner, according to the
capabilities of its driver.
During normal use, devices should be left in the "auto"
level. The "on" level is meant for administrative uses.
If you want to suspend a device immediately but leave it
free to wake up in response to I/O requests, you should
write "0" to power/autosuspend.
Device not capable of proper suspend and resume should be
left in the "on" level. Although the USB spec requires
devices to support suspend/resume, many of them do not.
In fact so many don't that by default, the USB core
initializes all non-hub devices in the "on" level. Some
drivers may change this setting when they are bound.
What: /sys/bus/usb/devices/.../power/persist
Date: May 2007
KernelVersion: 2.6.23

20
Documentation/ABI/testing/sysfs-class-power Normal file
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@ -0,0 +1,20 @@
What: /sys/class/power/ds2760-battery.*/charge_now
Date: May 2010
KernelVersion: 2.6.35
Contact: Daniel Mack <daniel@caiaq.de>
Description:
This file is writeable and can be used to set the current
coloumb counter value inside the battery monitor chip. This
is needed for unavoidable corrections of aging batteries.
A userspace daemon can monitor the battery charging logic
and once the counter drops out of considerable bounds, take
appropriate action.
What: /sys/class/power/ds2760-battery.*/charge_full
Date: May 2010
KernelVersion: 2.6.35
Contact: Daniel Mack <daniel@caiaq.de>
Description:
This file is writeable and can be used to set the assumed
battery 'full level'. As batteries age, this value has to be
amended over time.

2
Documentation/ABI/testing/sysfs-devices-memory
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@ -43,7 +43,7 @@ Date: September 2008
Contact: Badari Pulavarty <pbadari@us.ibm.com>
Description:
The file /sys/devices/system/memory/memoryX/state
is read-write. When read, it's contents show the
is read-write. When read, its contents show the
online/offline state of the memory section. When written,
root can toggle the the online/offline state of a removable
memory section (see removable file description above)

7
Documentation/ABI/testing/sysfs-devices-node Normal file
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@ -0,0 +1,7 @@
What: /sys/devices/system/node/nodeX/compact
Date: February 2010
Contact: Mel Gorman <mel@csn.ul.ie>
Description:
When this file is written to, all memory within that node
will be compacted. When it completes, memory will be freed
into blocks which have as many contiguous pages as possible

9
Documentation/ABI/testing/sysfs-devices-platform-_UDC_-gadget Normal file
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@ -0,0 +1,9 @@
What: /sys/devices/platform/_UDC_/gadget/suspended
Date: April 2010
Contact: Fabien Chouteau <fabien.chouteau@barco.com>
Description:
Show the suspend state of an USB composite gadget.
1 -> suspended
0 -> resumed
(_UDC_ is the name of the USB Device Controller driver)

43
Documentation/ABI/testing/sysfs-driver-hid-picolcd Normal file
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@ -0,0 +1,43 @@
What: /sys/bus/usb/devices/<busnum>-<devnum>:<config num>.<interface num>/<hid-bus>:<vendor-id>:<product-id>.<num>/operation_mode
Date: March 2010
Contact: Bruno Prémont <bonbons@linux-vserver.org>
Description: Make it possible to switch the PicoLCD device between LCD
(firmware) and bootloader (flasher) operation modes.
Reading: returns list of available modes, the active mode being
enclosed in brackets ('[' and ']')
Writing: causes operation mode switch. Permitted values are
the non-active mode names listed when read.
Note: when switching mode the current PicoLCD HID device gets
disconnected and reconnects after above delay (see attribute
operation_mode_delay for its value).
What: /sys/bus/usb/devices/<busnum>-<devnum>:<config num>.<interface num>/<hid-bus>:<vendor-id>:<product-id>.<num>/operation_mode_delay
Date: April 2010
Contact: Bruno Prémont <bonbons@linux-vserver.org>
Description: Delay PicoLCD waits before restarting in new mode when
operation_mode has changed.
Reading/Writing: It is expressed in ms and permitted range is
0..30000ms.
What: /sys/bus/usb/devices/<busnum>-<devnum>:<config num>.<interface num>/<hid-bus>:<vendor-id>:<product-id>.<num>/fb_update_rate
Date: March 2010
Contact: Bruno Prémont <bonbons@linux-vserver.org>
Description: Make it possible to adjust defio refresh rate.
Reading: returns list of available refresh rates (expressed in Hz),
the active refresh rate being enclosed in brackets ('[' and ']')
Writing: accepts new refresh rate expressed in integer Hz
within permitted rates.
Note: As device can barely do 2 complete refreshes a second
it only makes sense to adjust this value if only one or two
tiles get changed and it's not appropriate to expect the application
to flush it's tiny changes explicitely at higher than default rate.

29
Documentation/ABI/testing/sysfs-driver-hid-prodikeys Normal file
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@ -0,0 +1,29 @@
What: /sys/bus/hid/drivers/prodikeys/.../channel
Date: April 2010
KernelVersion: 2.6.34
Contact: Don Prince <dhprince.devel@yahoo.co.uk>
Description:
Allows control (via software) the midi channel to which
that the pc-midi keyboard will output.midi data.
Range: 0..15
Type: Read/write
What: /sys/bus/hid/drivers/prodikeys/.../sustain
Date: April 2010
KernelVersion: 2.6.34
Contact: Don Prince <dhprince.devel@yahoo.co.uk>
Description:
Allows control (via software) the sustain duration of a
note held by the pc-midi driver.
0 means sustain mode is disabled.
Range: 0..5000 (milliseconds)
Type: Read/write
What: /sys/bus/hid/drivers/prodikeys/.../octave
Date: April 2010
KernelVersion: 2.6.34
Contact: Don Prince <dhprince.devel@yahoo.co.uk>
Description:
Controls the octave shift modifier in the pc-midi driver.
The octave can be shifted via software up/down 2 octaves.
0 means the no ocatve shift.
Range: -2..2 (minus 2 to plus 2)
Type: Read/Write

111
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@ -0,0 +1,111 @@
What: /sys/bus/usb/devices/<busnum>-<devnum>:<config num>.<interface num>/actual_dpi
Date: March 2010
Contact: Stefan Achatz <erazor_de@users.sourceforge.net>
Description: It is possible to switch the dpi setting of the mouse with the
press of a button.
When read, this file returns the raw number of the actual dpi
setting reported by the mouse. This number has to be further
processed to receive the real dpi value.
VALUE DPI
1 800
2 1200
3 1600
4 2000
5 2400
6 3200
This file is readonly.
What: /sys/bus/usb/devices/<busnum>-<devnum>:<config num>.<interface num>/actual_profile
Date: March 2010
Contact: Stefan Achatz <erazor_de@users.sourceforge.net>
Description: When read, this file returns the number of the actual profile.
This file is readonly.
What: /sys/bus/usb/devices/<busnum>-<devnum>:<config num>.<interface num>/firmware_version
Date: March 2010
Contact: Stefan Achatz <erazor_de@users.sourceforge.net>
Description: When read, this file returns the raw integer version number of the
firmware reported by the mouse. Using the integer value eases
further usage in other programs. To receive the real version
number the decimal point has to be shifted 2 positions to the
left. E.g. a returned value of 138 means 1.38
This file is readonly.
What: /sys/bus/usb/devices/<busnum>-<devnum>:<config num>.<interface num>/kone_driver_version
Date: March 2010
Contact: Stefan Achatz <erazor_de@users.sourceforge.net>
Description: When read, this file returns the driver version.
The format of the string is "v<major>.<minor>.<patchlevel>".
This attribute is used by the userland tools to find the sysfs-
paths of installed kone-mice and determine the capabilites of
the driver. Versions of this driver for old kernels replace
usbhid instead of generic-usb. The way to scan for this file
has been chosen to provide a consistent way for all supported
kernel versions.
This file is readonly.
What: /sys/bus/usb/devices/<busnum>-<devnum>:<config num>.<interface num>/profile[1-5]
Date: March 2010
Contact: Stefan Achatz <erazor_de@users.sourceforge.net>
Description: The mouse can store 5 profiles which can be switched by the
press of a button. A profile holds informations like button
mappings, sensitivity, the colors of the 5 leds and light
effects.
When read, these files return the respective profile. The
returned data is 975 bytes in size.
When written, this file lets one write the respective profile
data back to the mouse. The data has to be 975 bytes long.
The mouse will reject invalid data, whereas the profile number
stored in the profile doesn't need to fit the number of the
store.
What: /sys/bus/usb/devices/<busnum>-<devnum>:<config num>.<interface num>/settings
Date: March 2010
Contact: Stefan Achatz <erazor_de@users.sourceforge.net>
Description: When read, this file returns the settings stored in the mouse.
The size of the data is 36 bytes and holds information like the
startup_profile, tcu state and calibration_data.
When written, this file lets write settings back to the mouse.
The data has to be 36 bytes long. The mouse will reject invalid
data.
What: /sys/bus/usb/devices/<busnum>-<devnum>:<config num>.<interface num>/startup_profile
Date: March 2010
Contact: Stefan Achatz <erazor_de@users.sourceforge.net>
Description: The integer value of this attribute ranges from 1 to 5.
When read, this attribute returns the number of the profile
that's active when the mouse is powered on.
When written, this file sets the number of the startup profile
and the mouse activates this profile immediately.
What: /sys/bus/usb/devices/<busnum>-<devnum>:<config num>.<interface num>/tcu
Date: March 2010
Contact: Stefan Achatz <erazor_de@users.sourceforge.net>
Description: The mouse has a "Tracking Control Unit" which lets the user
calibrate the laser power to fit the mousepad surface.
When read, this file returns the current state of the TCU,
where 0 means off and 1 means on.
Writing 0 in this file will switch the TCU off.
Writing 1 in this file will start the calibration which takes
around 6 seconds to complete and activates the TCU.
What: /sys/bus/usb/devices/<busnum>-<devnum>:<config num>.<interface num>/weight
Date: March 2010
Contact: Stefan Achatz <erazor_de@users.sourceforge.net>
Description: The mouse can be equipped with one of four supplied weights
ranging from 5 to 20 grams which are recognized by the mouse
and its value can be read out. When read, this file returns the
raw value returned by the mouse which eases further processing
in other software.
The values map to the weights as follows:
VALUE WEIGHT
0 none
1 5g
2 10g
3 15g
4 20g
This file is readonly.

15
Documentation/ABI/testing/sysfs-firmware-sfi Normal file
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@ -0,0 +1,15 @@
What: /sys/firmware/sfi/tables/
Date: May 2010
Contact: Len Brown <lenb@kernel.org>
Description:
SFI defines a number of small static memory tables
so the kernel can get platform information from firmware.
The tables are defined in the latest SFI specification:
http://simplefirmware.org/documentation
While the tables are used by the kernel, user-space
can observe them this way:
# cd /sys/firmware/sfi/tables
# cat $TABLENAME > $TABLENAME.bin

10
Documentation/ABI/testing/sysfs-wacom Normal file
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@ -0,0 +1,10 @@
What: /sys/class/hidraw/hidraw*/device/speed
Date: April 2010
Kernel Version: 2.6.35
Contact: linux-bluetooth@vger.kernel.org
Description:
The /sys/class/hidraw/hidraw*/device/speed file controls
reporting speed of wacom bluetooth tablet. Reading from
this file returns 1 if tablet reports in high speed mode
or 0 otherwise. Writing to this file one of these values
switches reporting speed.

2
Documentation/Changes
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@ -49,7 +49,7 @@ o oprofile 0.9 # oprofiled --version
o udev 081 # udevinfo -V
o grub 0.93 # grub --version
o mcelog 0.6
o iptables 1.4.1 # iptables -V
o iptables 1.4.2 # iptables -V
Kernel compilation

81
Documentation/DMA-API-HOWTO.txt
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@ -639,6 +639,36 @@ is planned to completely remove virt_to_bus() and bus_to_virt() as
they are entirely deprecated. Some ports already do not provide these
as it is impossible to correctly support them.
Handling Errors
DMA address space is limited on some architectures and an allocation
failure can be determined by:
- checking if dma_alloc_coherent returns NULL or dma_map_sg returns 0
- checking the returned dma_addr_t of dma_map_single and dma_map_page
by using dma_mapping_error():
dma_addr_t dma_handle;
dma_handle = dma_map_single(dev, addr, size, direction);
if (dma_mapping_error(dev, dma_handle)) {
/*
* reduce current DMA mapping usage,
* delay and try again later or
* reset driver.
*/
}
Networking drivers must call dev_kfree_skb to free the socket buffer
and return NETDEV_TX_OK if the DMA mapping fails on the transmit hook
(ndo_start_xmit). This means that the socket buffer is just dropped in
the failure case.
SCSI drivers must return SCSI_MLQUEUE_HOST_BUSY if the DMA mapping
fails in the queuecommand hook. This means that the SCSI subsystem
passes the command to the driver again later.
Optimizing Unmap State Space Consumption
On many platforms, dma_unmap_{single,page}() is simply a nop.
@ -703,46 +733,29 @@ to "Closing".
1) Struct scatterlist requirements.
Struct scatterlist must contain, at a minimum, the following
members:
Don't invent the architecture specific struct scatterlist; just use
<asm-generic/scatterlist.h>. You need to enable
CONFIG_NEED_SG_DMA_LENGTH if the architecture supports IOMMUs
(including software IOMMU).
struct page *page;
unsigned int offset;
unsigned int length;
2) ARCH_KMALLOC_MINALIGN
The base address is specified by a "page+offset" pair.
Architectures must ensure that kmalloc'ed buffer is
DMA-safe. Drivers and subsystems depend on it. If an architecture
isn't fully DMA-coherent (i.e. hardware doesn't ensure that data in
the CPU cache is identical to data in main memory),
ARCH_KMALLOC_MINALIGN must be set so that the memory allocator
makes sure that kmalloc'ed buffer doesn't share a cache line with
the others. See arch/arm/include/asm/cache.h as an example.
Previous versions of struct scatterlist contained a "void *address"
field that was sometimes used instead of page+offset. As of Linux
2.5., page+offset is always used, and the "address" field has been
deleted.
2) More to come...
Handling Errors
DMA address space is limited on some architectures and an allocation
failure can be determined by:
- checking if dma_alloc_coherent returns NULL or dma_map_sg returns 0
- checking the returned dma_addr_t of dma_map_single and dma_map_page
by using dma_mapping_error():
dma_addr_t dma_handle;
dma_handle = dma_map_single(dev, addr, size, direction);
if (dma_mapping_error(dev, dma_handle)) {
/*
* reduce current DMA mapping usage,
* delay and try again later or
* reset driver.
*/
}
Note that ARCH_KMALLOC_MINALIGN is about DMA memory alignment
constraints. You don't need to worry about the architecture data
alignment constraints (e.g. the alignment constraints about 64-bit
objects).
Closing
This document, and the API itself, would not be in it's current
This document, and the API itself, would not be in its current
form without the feedback and suggestions from numerous individuals.
We would like to specifically mention, in no particular order, the
following people:

2
Documentation/DocBook/Makefile
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@ -14,7 +14,7 @@ DOCBOOKS := z8530book.xml mcabook.xml device-drivers.xml \
genericirq.xml s390-drivers.xml uio-howto.xml scsi.xml \
mac80211.xml debugobjects.xml sh.xml regulator.xml \
alsa-driver-api.xml writing-an-alsa-driver.xml \
tracepoint.xml media.xml
tracepoint.xml media.xml drm.xml
###
# The build process is as follows (targets):

839
Documentation/DocBook/drm.tmpl Normal file
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@ -0,0 +1,839 @@
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
"http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
<book id="drmDevelopersGuide">
<bookinfo>
<title>Linux DRM Developer's Guide</title>
<copyright>
<year>2008-2009</year>
<holder>
Intel Corporation (Jesse Barnes &lt;jesse.barnes@intel.com&gt;)
</holder>
</copyright>
<legalnotice>
<para>
The contents of this file may be used under the terms of the GNU
General Public License version 2 (the "GPL") as distributed in
the kernel source COPYING file.
</para>
</legalnotice>
</bookinfo>
<toc></toc>
<!-- Introduction -->
<chapter id="drmIntroduction">
<title>Introduction</title>
<para>
The Linux DRM layer contains code intended to support the needs
of complex graphics devices, usually containing programmable
pipelines well suited to 3D graphics acceleration. Graphics
drivers in the kernel can make use of DRM functions to make
tasks like memory management, interrupt handling and DMA easier,
and provide a uniform interface to applications.
</para>
<para>
A note on versions: this guide covers features found in the DRM
tree, including the TTM memory manager, output configuration and
mode setting, and the new vblank internals, in addition to all
the regular features found in current kernels.
</para>
<para>
[Insert diagram of typical DRM stack here]
</para>
</chapter>
<!-- Internals -->
<chapter id="drmInternals">
<title>DRM Internals</title>
<para>
This chapter documents DRM internals relevant to driver authors
and developers working to add support for the latest features to
existing drivers.
</para>
<para>
First, we'll go over some typical driver initialization
requirements, like setting up command buffers, creating an
initial output configuration, and initializing core services.
Subsequent sections will cover core internals in more detail,
providing implementation notes and examples.
</para>
<para>
The DRM layer provides several services to graphics drivers,
many of them driven by the application interfaces it provides
through libdrm, the library that wraps most of the DRM ioctls.
These include vblank event handling, memory
management, output management, framebuffer management, command
submission &amp; fencing, suspend/resume support, and DMA
services.
</para>
<para>
The core of every DRM driver is struct drm_device. Drivers
will typically statically initialize a drm_device structure,
then pass it to drm_init() at load time.
</para>
<!-- Internals: driver init -->
<sect1>
<title>Driver initialization</title>
<para>
Before calling the DRM initialization routines, the driver must
first create and fill out a struct drm_device structure.
</para>
<programlisting>
static struct drm_driver driver = {
/* don't use mtrr's here, the Xserver or user space app should
* deal with them for intel hardware.
*/
.driver_features =
DRIVER_USE_AGP | DRIVER_REQUIRE_AGP |
DRIVER_HAVE_IRQ | DRIVER_IRQ_SHARED | DRIVER_MODESET,
.load = i915_driver_load,
.unload = i915_driver_unload,
.firstopen = i915_driver_firstopen,
.lastclose = i915_driver_lastclose,
.preclose = i915_driver_preclose,
.save = i915_save,
.restore = i915_restore,
.device_is_agp = i915_driver_device_is_agp,
.get_vblank_counter = i915_get_vblank_counter,
.enable_vblank = i915_enable_vblank,
.disable_vblank = i915_disable_vblank,
.irq_preinstall = i915_driver_irq_preinstall,
.irq_postinstall = i915_driver_irq_postinstall,
.irq_uninstall = i915_driver_irq_uninstall,
.irq_handler = i915_driver_irq_handler,
.reclaim_buffers = drm_core_reclaim_buffers,
.get_map_ofs = drm_core_get_map_ofs,
.get_reg_ofs = drm_core_get_reg_ofs,
.fb_probe = intelfb_probe,
.fb_remove = intelfb_remove,
.fb_resize = intelfb_resize,
.master_create = i915_master_create,
.master_destroy = i915_master_destroy,
#if defined(CONFIG_DEBUG_FS)
.debugfs_init = i915_debugfs_init,
.debugfs_cleanup = i915_debugfs_cleanup,
#endif
.gem_init_object = i915_gem_init_object,
.gem_free_object = i915_gem_free_object,
.gem_vm_ops = &amp;i915_gem_vm_ops,
.ioctls = i915_ioctls,
.fops = {
.owner = THIS_MODULE,
.open = drm_open,
.release = drm_release,
.ioctl = drm_ioctl,
.mmap = drm_mmap,
.poll = drm_poll,
.fasync = drm_fasync,
#ifdef CONFIG_COMPAT
.compat_ioctl = i915_compat_ioctl,
#endif
},
.pci_driver = {
.name = DRIVER_NAME,
.id_table = pciidlist,
.probe = probe,
.remove = __devexit_p(drm_cleanup_pci),
},
.name = DRIVER_NAME,
.desc = DRIVER_DESC,
.date = DRIVER_DATE,
.major = DRIVER_MAJOR,
.minor = DRIVER_MINOR,
.patchlevel = DRIVER_PATCHLEVEL,
};
</programlisting>
<para>
In the example above, taken from the i915 DRM driver, the driver
sets several flags indicating what core features it supports.
We'll go over the individual callbacks in later sections. Since
flags indicate which features your driver supports to the DRM
core, you need to set most of them prior to calling drm_init(). Some,
like DRIVER_MODESET can be set later based on user supplied parameters,
but that's the exception rather than the rule.
</para>
<variablelist>
<title>Driver flags</title>
<varlistentry>
<term>DRIVER_USE_AGP</term>
<listitem><para>
Driver uses AGP interface
</para></listitem>
</varlistentry>
<varlistentry>
<term>DRIVER_REQUIRE_AGP</term>
<listitem><para>
Driver needs AGP interface to function.
</para></listitem>
</varlistentry>
<varlistentry>
<term>DRIVER_USE_MTRR</term>
<listitem>
<para>
Driver uses MTRR interface for mapping memory. Deprecated.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>DRIVER_PCI_DMA</term>
<listitem><para>
Driver is capable of PCI DMA. Deprecated.
</para></listitem>
</varlistentry>
<varlistentry>
<term>DRIVER_SG</term>
<listitem><para>
Driver can perform scatter/gather DMA. Deprecated.
</para></listitem>
</varlistentry>
<varlistentry>
<term>DRIVER_HAVE_DMA</term>
<listitem><para>Driver supports DMA. Deprecated.</para></listitem>
</varlistentry>
<varlistentry>
<term>DRIVER_HAVE_IRQ</term><term>DRIVER_IRQ_SHARED</term>
<listitem>
<para>
DRIVER_HAVE_IRQ indicates whether the driver has a IRQ
handler, DRIVER_IRQ_SHARED indicates whether the device &amp;
handler support shared IRQs (note that this is required of
PCI drivers).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>DRIVER_DMA_QUEUE</term>
<listitem>
<para>
If the driver queues DMA requests and completes them
asynchronously, this flag should be set. Deprecated.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>DRIVER_FB_DMA</term>
<listitem>
<para>
Driver supports DMA to/from the framebuffer. Deprecated.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>DRIVER_MODESET</term>
<listitem>
<para>
Driver supports mode setting interfaces.
</para>
</listitem>
</varlistentry>
</variablelist>
<para>
In this specific case, the driver requires AGP and supports
IRQs. DMA, as we'll see, is handled by device specific ioctls
in this case. It also supports the kernel mode setting APIs, though
unlike in the actual i915 driver source, this example unconditionally
exports KMS capability.
</para>
</sect1>
<!-- Internals: driver load -->
<sect1>
<title>Driver load</title>
<para>
In the previous section, we saw what a typical drm_driver
structure might look like. One of the more important fields in
the structure is the hook for the load function.
</para>
<programlisting>
static struct drm_driver driver = {
...
.load = i915_driver_load,
...
};
</programlisting>
<para>
The load function has many responsibilities: allocating a driver
private structure, specifying supported performance counters,
configuring the device (e.g. mapping registers &amp; command
buffers), initializing the memory manager, and setting up the
initial output configuration.
</para>
<para>
Note that the tasks performed at driver load time must not
conflict with DRM client requirements. For instance, if user
level mode setting drivers are in use, it would be problematic
to perform output discovery &amp; configuration at load time.
Likewise, if pre-memory management aware user level drivers are
in use, memory management and command buffer setup may need to
be omitted. These requirements are driver specific, and care
needs to be taken to keep both old and new applications and
libraries working. The i915 driver supports the "modeset"
module parameter to control whether advanced features are
enabled at load time or in legacy fashion. If compatibility is
a concern (e.g. with drivers converted over to the new interfaces
from the old ones), care must be taken to prevent incompatible
device initialization and control with the currently active
userspace drivers.
</para>
<sect2>
<title>Driver private &amp; performance counters</title>
<para>
The driver private hangs off the main drm_device structure and
can be used for tracking various device specific bits of
information, like register offsets, command buffer status,
register state for suspend/resume, etc. At load time, a
driver can simply allocate one and set drm_device.dev_priv
appropriately; at unload the driver can free it and set
drm_device.dev_priv to NULL.
</para>
<para>
The DRM supports several counters which can be used for rough
performance characterization. Note that the DRM stat counter
system is not often used by applications, and supporting
additional counters is completely optional.
</para>
<para>
These interfaces are deprecated and should not be used. If performance
monitoring is desired, the developer should investigate and
potentially enhance the kernel perf and tracing infrastructure to export
GPU related performance information to performance monitoring
tools and applications.
</para>
</sect2>
<sect2>
<title>Configuring the device</title>
<para>
Obviously, device configuration will be device specific.
However, there are several common operations: finding a
device's PCI resources, mapping them, and potentially setting
up an IRQ handler.
</para>
<para>
Finding &amp; mapping resources is fairly straightforward. The
DRM wrapper functions, drm_get_resource_start() and
drm_get_resource_len() can be used to find BARs on the given
drm_device struct. Once those values have been retrieved, the
driver load function can call drm_addmap() to create a new
mapping for the BAR in question. Note you'll probably want a
drm_local_map_t in your driver private structure to track any
mappings you create.
<!-- !Fdrivers/gpu/drm/drm_bufs.c drm_get_resource_* -->
<!-- !Finclude/drm/drmP.h drm_local_map_t -->
</para>
<para>
if compatibility with other operating systems isn't a concern
(DRM drivers can run under various BSD variants and OpenSolaris),
native Linux calls can be used for the above, e.g. pci_resource_*
and iomap*/iounmap. See the Linux device driver book for more
info.
</para>
<para>
Once you have a register map, you can use the DRM_READn() and
DRM_WRITEn() macros to access the registers on your device, or
use driver specific versions to offset into your MMIO space
relative to a driver specific base pointer (see I915_READ for
example).
</para>
<para>
If your device supports interrupt generation, you may want to
setup an interrupt handler at driver load time as well. This
is done using the drm_irq_install() function. If your device
supports vertical blank interrupts, it should call
drm_vblank_init() to initialize the core vblank handling code before
enabling interrupts on your device. This ensures the vblank related
structures are allocated and allows the core to handle vblank events.
</para>
<!--!Fdrivers/char/drm/drm_irq.c drm_irq_install-->
<para>
Once your interrupt handler is registered (it'll use your
drm_driver.irq_handler as the actual interrupt handling
function), you can safely enable interrupts on your device,
assuming any other state your interrupt handler uses is also
initialized.
</para>
<para>
Another task that may be necessary during configuration is
mapping the video BIOS. On many devices, the VBIOS describes
device configuration, LCD panel timings (if any), and contains
flags indicating device state. Mapping the BIOS can be done
using the pci_map_rom() call, a convenience function that
takes care of mapping the actual ROM, whether it has been
shadowed into memory (typically at address 0xc0000) or exists
on the PCI device in the ROM BAR. Note that once you've
mapped the ROM and extracted any necessary information, be
sure to unmap it; on many devices the ROM address decoder is
shared with other BARs, so leaving it mapped can cause
undesired behavior like hangs or memory corruption.
<!--!Fdrivers/pci/rom.c pci_map_rom-->
</para>
</sect2>
<sect2>
<title>Memory manager initialization</title>
<para>
In order to allocate command buffers, cursor memory, scanout
buffers, etc., as well as support the latest features provided
by packages like Mesa and the X.Org X server, your driver
should support a memory manager.
</para>
<para>
If your driver supports memory management (it should!), you'll
need to set that up at load time as well. How you intialize
it depends on which memory manager you're using, TTM or GEM.
</para>
<sect3>
<title>TTM initialization</title>
<para>
TTM (for Translation Table Manager) manages video memory and
aperture space for graphics devices. TTM supports both UMA devices
and devices with dedicated video RAM (VRAM), i.e. most discrete
graphics devices. If your device has dedicated RAM, supporting
TTM is desireable. TTM also integrates tightly with your
driver specific buffer execution function. See the radeon
driver for examples.
</para>
<para>
The core TTM structure is the ttm_bo_driver struct. It contains
several fields with function pointers for initializing the TTM,
allocating and freeing memory, waiting for command completion
and fence synchronization, and memory migration. See the
radeon_ttm.c file for an example of usage.
</para>
<para>
The ttm_global_reference structure is made up of several fields:
</para>
<programlisting>
struct ttm_global_reference {
enum ttm_global_types global_type;
size_t size;
void *object;
int (*init) (struct ttm_global_reference *);
void (*release) (struct ttm_global_reference *);
};
</programlisting>
<para>
There should be one global reference structure for your memory
manager as a whole, and there will be others for each object
created by the memory manager at runtime. Your global TTM should
have a type of TTM_GLOBAL_TTM_MEM. The size field for the global
object should be sizeof(struct ttm_mem_global), and the init and
release hooks should point at your driver specific init and
release routines, which will probably eventually call
ttm_mem_global_init and ttm_mem_global_release respectively.
</para>
<para>
Once your global TTM accounting structure is set up and initialized
(done by calling ttm_global_item_ref on the global object you
just created), you'll need to create a buffer object TTM to
provide a pool for buffer object allocation by clients and the
kernel itself. The type of this object should be TTM_GLOBAL_TTM_BO,
and its size should be sizeof(struct ttm_bo_global). Again,
driver specific init and release functions can be provided,
likely eventually calling ttm_bo_global_init and
ttm_bo_global_release, respectively. Also like the previous
object, ttm_global_item_ref is used to create an initial reference
count for the TTM, which will call your initalization function.
</para>
</sect3>
<sect3>
<title>GEM initialization</title>
<para>
GEM is an alternative to TTM, designed specifically for UMA
devices. It has simpler initialization and execution requirements
than TTM, but has no VRAM management capability. Core GEM
initialization is comprised of a basic drm_mm_init call to create
a GTT DRM MM object, which provides an address space pool for
object allocation. In a KMS configuration, the driver will
need to allocate and initialize a command ring buffer following
basic GEM initialization. Most UMA devices have a so-called
"stolen" memory region, which provides space for the initial
framebuffer and large, contiguous memory regions required by the
device. This space is not typically managed by GEM, and must
be initialized separately into its own DRM MM object.
</para>
<para>
Initialization will be driver specific, and will depend on
the architecture of the device. In the case of Intel
integrated graphics chips like 965GM, GEM initialization can
be done by calling the internal GEM init function,
i915_gem_do_init(). Since the 965GM is a UMA device
(i.e. it doesn't have dedicated VRAM), GEM will manage
making regular RAM available for GPU operations. Memory set
aside by the BIOS (called "stolen" memory by the i915
driver) will be managed by the DRM memrange allocator; the
rest of the aperture will be managed by GEM.
<programlisting>
/* Basic memrange allocator for stolen space (aka vram) */
drm_memrange_init(&amp;dev_priv->vram, 0, prealloc_size);
/* Let GEM Manage from end of prealloc space to end of aperture */
i915_gem_do_init(dev, prealloc_size, agp_size);
</programlisting>
<!--!Edrivers/char/drm/drm_memrange.c-->
</para>
<para>
Once the memory manager has been set up, we can allocate the
command buffer. In the i915 case, this is also done with a
GEM function, i915_gem_init_ringbuffer().
</para>
</sect3>
</sect2>
<sect2>
<title>Output configuration</title>
<para>
The final initialization task is output configuration. This involves
finding and initializing the CRTCs, encoders and connectors
for your device, creating an initial configuration and
registering a framebuffer console driver.
</para>
<sect3>
<title>Output discovery and initialization</title>
<para>
Several core functions exist to create CRTCs, encoders and
connectors, namely drm_crtc_init(), drm_connector_init() and
drm_encoder_init(), along with several "helper" functions to
perform common tasks.
</para>
<para>
Connectors should be registered with sysfs once they've been
detected and initialized, using the
drm_sysfs_connector_add() function. Likewise, when they're
removed from the system, they should be destroyed with
drm_sysfs_connector_remove().
</para>
<programlisting>
<![CDATA[
void intel_crt_init(struct drm_device *dev)
{
struct drm_connector *connector;
struct intel_output *intel_output;
intel_output = kzalloc(sizeof(struct intel_output), GFP_KERNEL);
if (!intel_output)
return;
connector = &intel_output->base;
drm_connector_init(dev, &intel_output->base,
&intel_crt_connector_funcs, DRM_MODE_CONNECTOR_VGA);
drm_encoder_init(dev, &intel_output->enc, &intel_crt_enc_funcs,
DRM_MODE_ENCODER_DAC);
drm_mode_connector_attach_encoder(&intel_output->base,
&intel_output->enc);
/* Set up the DDC bus. */
intel_output->ddc_bus = intel_i2c_create(dev, GPIOA, "CRTDDC_A");
if (!intel_output->ddc_bus) {
dev_printk(KERN_ERR, &dev->pdev->dev, "DDC bus registration "
"failed.\n");
return;
}
intel_output->type = INTEL_OUTPUT_ANALOG;
connector->interlace_allowed = 0;
connector->doublescan_allowed = 0;
drm_encoder_helper_add(&intel_output->enc, &intel_crt_helper_funcs);
drm_connector_helper_add(connector, &intel_crt_connector_helper_funcs);
drm_sysfs_connector_add(connector);
}
]]>
</programlisting>
<para>
In the example above (again, taken from the i915 driver), a
CRT connector and encoder combination is created. A device
specific i2c bus is also created, for fetching EDID data and
performing monitor detection. Once the process is complete,
the new connector is regsitered with sysfs, to make its
properties available to applications.
</para>
<sect4>
<title>Helper functions and core functions</title>
<para>
Since many PC-class graphics devices have similar display output
designs, the DRM provides a set of helper functions to make
output management easier. The core helper routines handle
encoder re-routing and disabling of unused functions following
mode set. Using the helpers is optional, but recommended for
devices with PC-style architectures (i.e. a set of display planes
for feeding pixels to encoders which are in turn routed to
connectors). Devices with more complex requirements needing
finer grained management can opt to use the core callbacks
directly.
</para>
<para>
[Insert typical diagram here.] [Insert OMAP style config here.]
</para>
</sect4>
<para>
For each encoder, CRTC and connector, several functions must
be provided, depending on the object type. Encoder objects
need should provide a DPMS (basically on/off) function, mode fixup
(for converting requested modes into native hardware timings),
and prepare, set and commit functions for use by the core DRM
helper functions. Connector helpers need to provide mode fetch and
validity functions as well as an encoder matching function for
returing an ideal encoder for a given connector. The core
connector functions include a DPMS callback, (deprecated)
save/restore routines, detection, mode probing, property handling,
and cleanup functions.
</para>
<!--!Edrivers/char/drm/drm_crtc.h-->
<!--!Edrivers/char/drm/drm_crtc.c-->
<!--!Edrivers/char/drm/drm_crtc_helper.c-->
</sect3>
</sect2>
</sect1>
<!-- Internals: vblank handling -->
<sect1>
<title>VBlank event handling</title>
<para>
The DRM core exposes two vertical blank related ioctls:
DRM_IOCTL_WAIT_VBLANK and DRM_IOCTL_MODESET_CTL.
<!--!Edrivers/char/drm/drm_irq.c-->
</para>
<para>
DRM_IOCTL_WAIT_VBLANK takes a struct drm_wait_vblank structure
as its argument, and is used to block or request a signal when a
specified vblank event occurs.
</para>
<para>
DRM_IOCTL_MODESET_CTL should be called by application level
drivers before and after mode setting, since on many devices the
vertical blank counter will be reset at that time. Internally,
the DRM snapshots the last vblank count when the ioctl is called
with the _DRM_PRE_MODESET command so that the counter won't go
backwards (which is dealt with when _DRM_POST_MODESET is used).
</para>
<para>
To support the functions above, the DRM core provides several
helper functions for tracking vertical blank counters, and
requires drivers to provide several callbacks:
get_vblank_counter(), enable_vblank() and disable_vblank(). The
core uses get_vblank_counter() to keep the counter accurate
across interrupt disable periods. It should return the current
vertical blank event count, which is often tracked in a device
register. The enable and disable vblank callbacks should enable
and disable vertical blank interrupts, respectively. In the
absence of DRM clients waiting on vblank events, the core DRM
code will use the disable_vblank() function to disable
interrupts, which saves power. They'll be re-enabled again when
a client calls the vblank wait ioctl above.
</para>
<para>
Devices that don't provide a count register can simply use an
internal atomic counter incremented on every vertical blank
interrupt, and can make their enable and disable vblank
functions into no-ops.
</para>
</sect1>
<sect1>
<title>Memory management</title>
<para>
The memory manager lies at the heart of many DRM operations, and
is also required to support advanced client features like OpenGL
pbuffers. The DRM currently contains two memory managers, TTM
and GEM.
</para>
<sect2>
<title>The Translation Table Manager (TTM)</title>
<para>
TTM was developed by Tungsten Graphics, primarily by Thomas
Hellström, and is intended to be a flexible, high performance
graphics memory manager.
</para>
<para>
Drivers wishing to support TTM must fill out a drm_bo_driver
structure.
</para>
<para>
TTM design background and information belongs here.
</para>
</sect2>
<sect2>
<title>The Graphics Execution Manager (GEM)</title>
<para>
GEM is an Intel project, authored by Eric Anholt and Keith
Packard. It provides simpler interfaces than TTM, and is well
suited for UMA devices.
</para>
<para>
GEM-enabled drivers must provide gem_init_object() and
gem_free_object() callbacks to support the core memory
allocation routines. They should also provide several driver
specific ioctls to support command execution, pinning, buffer
read &amp; write, mapping, and domain ownership transfers.
</para>
<para>
On a fundamental level, GEM involves several operations: memory
allocation and freeing, command execution, and aperture management
at command execution time. Buffer object allocation is relatively
straightforward and largely provided by Linux's shmem layer, which
provides memory to back each object. When mapped into the GTT
or used in a command buffer, the backing pages for an object are
flushed to memory and marked write combined so as to be coherent
with the GPU. Likewise, when the GPU finishes rendering to an object,
if the CPU accesses it, it must be made coherent with the CPU's view
of memory, usually involving GPU cache flushing of various kinds.
This core CPU&lt;-&gt;GPU coherency management is provided by the GEM
set domain function, which evaluates an object's current domain and
performs any necessary flushing or synchronization to put the object
into the desired coherency domain (note that the object may be busy,
i.e. an active render target; in that case the set domain function
will block the client and wait for rendering to complete before
performing any necessary flushing operations).
</para>
<para>
Perhaps the most important GEM function is providing a command
execution interface to clients. Client programs construct command
buffers containing references to previously allocated memory objects
and submit them to GEM. At that point, GEM will take care to bind
all the objects into the GTT, execute the buffer, and provide
necessary synchronization between clients accessing the same buffers.
This often involves evicting some objects from the GTT and re-binding
others (a fairly expensive operation), and providing relocation
support which hides fixed GTT offsets from clients. Clients must
take care not to submit command buffers that reference more objects
than can fit in the GTT or GEM will reject them and no rendering
will occur. Similarly, if several objects in the buffer require
fence registers to be allocated for correct rendering (e.g. 2D blits
on pre-965 chips), care must be taken not to require more fence
registers than are available to the client. Such resource management
should be abstracted from the client in libdrm.
</para>
</sect2>
</sect1>
<!-- Output management -->
<sect1>
<title>Output management</title>
<para>
At the core of the DRM output management code is a set of
structures representing CRTCs, encoders and connectors.
</para>
<para>
A CRTC is an abstraction representing a part of the chip that
contains a pointer to a scanout buffer. Therefore, the number
of CRTCs available determines how many independent scanout
buffers can be active at any given time. The CRTC structure
contains several fields to support this: a pointer to some video
memory, a display mode, and an (x, y) offset into the video
memory to support panning or configurations where one piece of
video memory spans multiple CRTCs.
</para>
<para>
An encoder takes pixel data from a CRTC and converts it to a
format suitable for any attached connectors. On some devices,
it may be possible to have a CRTC send data to more than one
encoder. In that case, both encoders would receive data from
the same scanout buffer, resulting in a "cloned" display
configuration across the connectors attached to each encoder.
</para>
<para>
A connector is the final destination for pixel data on a device,
and usually connects directly to an external display device like
a monitor or laptop panel. A connector can only be attached to
one encoder at a time. The connector is also the structure
where information about the attached display is kept, so it
contains fields for display data, EDID data, DPMS &amp;
connection status, and information about modes supported on the
attached displays.
</para>
<!--!Edrivers/char/drm/drm_crtc.c-->
</sect1>
<sect1>
<title>Framebuffer management</title>
<para>
In order to set a mode on a given CRTC, encoder and connector
configuration, clients need to provide a framebuffer object which
will provide a source of pixels for the CRTC to deliver to the encoder(s)
and ultimately the connector(s) in the configuration. A framebuffer
is fundamentally a driver specific memory object, made into an opaque
handle by the DRM addfb function. Once an fb has been created this
way it can be passed to the KMS mode setting routines for use in
a configuration.
</para>
</sect1>
<sect1>
<title>Command submission &amp; fencing</title>
<para>
This should cover a few device specific command submission
implementations.
</para>
</sect1>
<sect1>
<title>Suspend/resume</title>
<para>
The DRM core provides some suspend/resume code, but drivers
wanting full suspend/resume support should provide save() and
restore() functions. These will be called at suspend,
hibernate, or resume time, and should perform any state save or
restore required by your device across suspend or hibernate
states.
</para>
</sect1>
<sect1>
<title>DMA services</title>
<para>
This should cover how DMA mapping etc. is supported by the core.
These functions are deprecated and should not be used.
</para>
</sect1>
</chapter>
<!-- External interfaces -->
<chapter id="drmExternals">
<title>Userland interfaces</title>
<para>
The DRM core exports several interfaces to applications,
generally intended to be used through corresponding libdrm
wrapper functions. In addition, drivers export device specific
interfaces for use by userspace drivers &amp; device aware
applications through ioctls and sysfs files.
</para>
<para>
External interfaces include: memory mapping, context management,
DMA operations, AGP management, vblank control, fence
management, memory management, and output management.
</para>
<para>
Cover generic ioctls and sysfs layout here. Only need high
level info, since man pages will cover the rest.
</para>
</chapter>
<!-- API reference -->
<appendix id="drmDriverApi">
<title>DRM Driver API</title>
<para>
Include auto-generated API reference here (need to reference it
from paragraphs above too).
</para>
</appendix>
</book>

712
Documentation/DocBook/kgdb.tmpl
View File

@ -4,7 +4,7 @@
<book id="kgdbOnLinux">
<bookinfo>
<title>Using kgdb and the kgdb Internals</title>
<title>Using kgdb, kdb and the kernel debugger internals</title>
<authorgroup>
<author>
@ -17,33 +17,8 @@
</affiliation>
</author>
</authorgroup>
<authorgroup>
<author>
<firstname>Tom</firstname>
<surname>Rini</surname>
<affiliation>
<address>
<email>trini@kernel.crashing.org</email>
</address>
</affiliation>
</author>
</authorgroup>
<authorgroup>
<author>
<firstname>Amit S.</firstname>
<surname>Kale</surname>
<affiliation>
<address>
<email>amitkale@linsyssoft.com</email>
</address>
</affiliation>
</author>
</authorgroup>
<copyright>
<year>2008</year>
<year>2008,2010</year>
<holder>Wind River Systems, Inc.</holder>
</copyright>
<copyright>
@ -69,41 +44,76 @@
<chapter id="Introduction">
<title>Introduction</title>
<para>
kgdb is a source level debugger for linux kernel. It is used along
with gdb to debug a linux kernel. The expectation is that gdb can
be used to "break in" to the kernel to inspect memory, variables
and look through call stack information similar to what an
application developer would use gdb for. It is possible to place
breakpoints in kernel code and perform some limited execution
stepping.
The kernel has two different debugger front ends (kdb and kgdb)
which interface to the debug core. It is possible to use either
of the debugger front ends and dynamically transition between them
if you configure the kernel properly at compile and runtime.
</para>
<para>
Two machines are required for using kgdb. One of these machines is a
development machine and the other is a test machine. The kernel
to be debugged runs on the test machine. The development machine
runs an instance of gdb against the vmlinux file which contains
the symbols (not boot image such as bzImage, zImage, uImage...).
In gdb the developer specifies the connection parameters and
connects to kgdb. The type of connection a developer makes with
gdb depends on the availability of kgdb I/O modules compiled as
builtin's or kernel modules in the test machine's kernel.
Kdb is simplistic shell-style interface which you can use on a
system console with a keyboard or serial console. You can use it
to inspect memory, registers, process lists, dmesg, and even set
breakpoints to stop in a certain location. Kdb is not a source
level debugger, although you can set breakpoints and execute some
basic kernel run control. Kdb is mainly aimed at doing some
analysis to aid in development or diagnosing kernel problems. You
can access some symbols by name in kernel built-ins or in kernel
modules if the code was built
with <symbol>CONFIG_KALLSYMS</symbol>.
</para>
<para>
Kgdb is intended to be used as a source level debugger for the
Linux kernel. It is used along with gdb to debug a Linux kernel.
The expectation is that gdb can be used to "break in" to the
kernel to inspect memory, variables and look through call stack
information similar to the way an application developer would use
gdb to debug an application. It is possible to place breakpoints
in kernel code and perform some limited execution stepping.
</para>
<para>
Two machines are required for using kgdb. One of these machines is
a development machine and the other is the target machine. The
kernel to be debugged runs on the target machine. The development
machine runs an instance of gdb against the vmlinux file which
contains the symbols (not boot image such as bzImage, zImage,
uImage...). In gdb the developer specifies the connection
parameters and connects to kgdb. The type of connection a
developer makes with gdb depends on the availability of kgdb I/O
modules compiled as built-ins or loadable kernel modules in the test
machine's kernel.
</para>
</chapter>
<chapter id="CompilingAKernel">
<title>Compiling a kernel</title>
<title>Compiling a kernel</title>
<para>
<itemizedlist>
<listitem><para>In order to enable compilation of kdb, you must first enable kgdb.</para></listitem>
<listitem><para>The kgdb test compile options are described in the kgdb test suite chapter.</para></listitem>
</itemizedlist>
</para>
<sect1 id="CompileKGDB">
<title>Kernel config options for kgdb</title>
<para>
To enable <symbol>CONFIG_KGDB</symbol> you should first turn on
"Prompt for development and/or incomplete code/drivers"
(CONFIG_EXPERIMENTAL) in "General setup", then under the
"Kernel debugging" select "KGDB: kernel debugging with remote gdb".
"Kernel debugging" select "KGDB: kernel debugger".
</para>
<para>
While it is not a hard requirement that you have symbols in your
vmlinux file, gdb tends not to be very useful without the symbolic
data, so you will want to turn
on <symbol>CONFIG_DEBUG_INFO</symbol> which is called "Compile the
kernel with debug info" in the config menu.
</para>
<para>
It is advised, but not required that you turn on the
CONFIG_FRAME_POINTER kernel option. This option inserts code to
into the compiled executable which saves the frame information in
registers or on the stack at different points which will allow a
debugger such as gdb to more accurately construct stack back traces
while debugging the kernel.
<symbol>CONFIG_FRAME_POINTER</symbol> kernel option which is called "Compile the
kernel with frame pointers" in the config menu. This option
inserts code to into the compiled executable which saves the frame
information in registers or on the stack at different points which
allows a debugger such as gdb to more accurately construct
stack back traces while debugging the kernel.
</para>
<para>
If the architecture that you are using supports the kernel option
@ -116,38 +126,160 @@
this option.
</para>
<para>
Next you should choose one of more I/O drivers to interconnect debugging
host and debugged target. Early boot debugging requires a KGDB
I/O driver that supports early debugging and the driver must be
built into the kernel directly. Kgdb I/O driver configuration
takes place via kernel or module parameters, see following
chapter.
Next you should choose one of more I/O drivers to interconnect
debugging host and debugged target. Early boot debugging requires
a KGDB I/O driver that supports early debugging and the driver
must be built into the kernel directly. Kgdb I/O driver
configuration takes place via kernel or module parameters which
you can learn more about in the in the section that describes the
parameter "kgdboc".
</para>
<para>
The kgdb test compile options are described in the kgdb test suite chapter.
<para>Here is an example set of .config symbols to enable or
disable for kgdb:
<itemizedlist>
<listitem><para># CONFIG_DEBUG_RODATA is not set</para></listitem>
<listitem><para>CONFIG_FRAME_POINTER=y</para></listitem>
<listitem><para>CONFIG_KGDB=y</para></listitem>
<listitem><para>CONFIG_KGDB_SERIAL_CONSOLE=y</para></listitem>
</itemizedlist>
</para>
</sect1>
<sect1 id="CompileKDB">
<title>Kernel config options for kdb</title>
<para>Kdb is quite a bit more complex than the simple gdbstub
sitting on top of the kernel's debug core. Kdb must implement a
shell, and also adds some helper functions in other parts of the
kernel, responsible for printing out interesting data such as what
you would see if you ran "lsmod", or "ps". In order to build kdb
into the kernel you follow the same steps as you would for kgdb.
</para>
<para>The main config option for kdb
is <symbol>CONFIG_KGDB_KDB</symbol> which is called "KGDB_KDB:
include kdb frontend for kgdb" in the config menu. In theory you
would have already also selected an I/O driver such as the
CONFIG_KGDB_SERIAL_CONSOLE interface if you plan on using kdb on a
serial port, when you were configuring kgdb.
</para>
<para>If you want to use a PS/2-style keyboard with kdb, you would
select CONFIG_KDB_KEYBOARD which is called "KGDB_KDB: keyboard as
input device" in the config menu. The CONFIG_KDB_KEYBOARD option
is not used for anything in the gdb interface to kgdb. The
CONFIG_KDB_KEYBOARD option only works with kdb.
</para>
<para>Here is an example set of .config symbols to enable/disable kdb:
<itemizedlist>
<listitem><para># CONFIG_DEBUG_RODATA is not set</para></listitem>
<listitem><para>CONFIG_FRAME_POINTER=y</para></listitem>
<listitem><para>CONFIG_KGDB=y</para></listitem>
<listitem><para>CONFIG_KGDB_SERIAL_CONSOLE=y</para></listitem>
<listitem><para>CONFIG_KGDB_KDB=y</para></listitem>
<listitem><para>CONFIG_KDB_KEYBOARD=y</para></listitem>
</itemizedlist>
</para>
</sect1>
</chapter>
<chapter id="EnableKGDB">
<title>Enable kgdb for debugging</title>
<para>
In order to use kgdb you must activate it by passing configuration
information to one of the kgdb I/O drivers. If you do not pass any
configuration information kgdb will not do anything at all. Kgdb
will only actively hook up to the kernel trap hooks if a kgdb I/O
driver is loaded and configured. If you unconfigure a kgdb I/O
driver, kgdb will unregister all the kernel hook points.
<chapter id="kgdbKernelArgs">
<title>Kernel Debugger Boot Arguments</title>
<para>This section describes the various runtime kernel
parameters that affect the configuration of the kernel debugger.
The following chapter covers using kdb and kgdb as well as
provides some examples of the configuration parameters.</para>
<sect1 id="kgdboc">
<title>Kernel parameter: kgdboc</title>
<para>The kgdboc driver was originally an abbreviation meant to
stand for "kgdb over console". Today it is the primary mechanism
to configure how to communicate from gdb to kgdb as well as the
devices you want to use to interact with the kdb shell.
</para>
<para>
All drivers can be reconfigured at run time, if
<symbol>CONFIG_SYSFS</symbol> and <symbol>CONFIG_MODULES</symbol>
are enabled, by echo'ing a new config string to
<constant>/sys/module/&lt;driver&gt;/parameter/&lt;option&gt;</constant>.
The driver can be unconfigured by passing an empty string. You cannot
change the configuration while the debugger is attached. Make sure
to detach the debugger with the <constant>detach</constant> command
prior to trying unconfigure a kgdb I/O driver.
<para>For kgdb/gdb, kgdboc is designed to work with a single serial
port. It is intended to cover the circumstance where you want to
use a serial console as your primary console as well as using it to
perform kernel debugging. It is also possible to use kgdb on a
serial port which is not designated as a system console. Kgdboc
may be configured as a kernel built-in or a kernel loadable module.
You can only make use of <constant>kgdbwait</constant> and early
debugging if you build kgdboc into the kernel as a built-in.
</para>
<sect2 id="kgdbocArgs">
<title>kgdboc arguments</title>
<para>Usage: <constant>kgdboc=[kbd][[,]serial_device][,baud]</constant></para>
<sect3 id="kgdbocArgs1">
<title>Using loadable module or built-in</title>
<para>
<orderedlist>
<listitem><para>As a kernel built-in:</para>
<para>Use the kernel boot argument: <constant>kgdboc=&lt;tty-device&gt;,[baud]</constant></para></listitem>
<listitem>
<para>As a kernel loadable module:</para>
<para>Use the command: <constant>modprobe kgdboc kgdboc=&lt;tty-device&gt;,[baud]</constant></para>
<para>Here are two examples of how you might formate the kgdboc
string. The first is for an x86 target using the first serial port.
The second example is for the ARM Versatile AB using the second
serial port.
<orderedlist>
<listitem><para><constant>kgdboc=ttyS0,115200</constant></para></listitem>
<listitem><para><constant>kgdboc=ttyAMA1,115200</constant></para></listitem>
</orderedlist>
</para>
</listitem>
</orderedlist></para>
</sect3>
<sect3 id="kgdbocArgs2">
<title>Configure kgdboc at runtime with sysfs</title>
<para>At run time you can enable or disable kgdboc by echoing a
parameters into the sysfs. Here are two examples:</para>
<orderedlist>
<listitem><para>Enable kgdboc on ttyS0</para>
<para><constant>echo ttyS0 &gt; /sys/module/kgdboc/parameters/kgdboc</constant></para></listitem>
<listitem><para>Disable kgdboc</para>
<para><constant>echo "" &gt; /sys/module/kgdboc/parameters/kgdboc</constant></para></listitem>
</orderedlist>
<para>NOTE: You do not need to specify the baud if you are
configuring the console on tty which is already configured or
open.</para>
</sect3>
<sect3 id="kgdbocArgs3">
<title>More examples</title>
<para>You can configure kgdboc to use the keyboard, and or a serial device
depending on if you are using kdb and or kgdb, in one of the
following scenarios.
<orderedlist>
<listitem><para>kdb and kgdb over only a serial port</para>
<para><constant>kgdboc=&lt;serial_device&gt;[,baud]</constant></para>
<para>Example: <constant>kgdboc=ttyS0,115200</constant></para>
</listitem>
<listitem><para>kdb and kgdb with keyboard and a serial port</para>
<para><constant>kgdboc=kbd,&lt;serial_device&gt;[,baud]</constant></para>
<para>Example: <constant>kgdboc=kbd,ttyS0,115200</constant></para>
</listitem>
<listitem><para>kdb with a keyboard</para>
<para><constant>kgdboc=kbd</constant></para>
</listitem>
</orderedlist>
</para>
</sect3>
<para>NOTE: Kgdboc does not support interrupting the target via the
gdb remote protocol. You must manually send a sysrq-g unless you
have a proxy that splits console output to a terminal program.
A console proxy has a separate TCP port for the debugger and a separate
TCP port for the "human" console. The proxy can take care of sending
the sysrq-g for you.
</para>
<para>When using kgdboc with no debugger proxy, you can end up
connecting the debugger at one of two entry points. If an
exception occurs after you have loaded kgdboc, a message should
print on the console stating it is waiting for the debugger. In
this case you disconnect your terminal program and then connect the
debugger in its place. If you want to interrupt the target system
and forcibly enter a debug session you have to issue a Sysrq
sequence and then type the letter <constant>g</constant>. Then
you disconnect the terminal session and connect gdb. Your options
if you don't like this are to hack gdb to send the sysrq-g for you
as well as on the initial connect, or to use a debugger proxy that
allows an unmodified gdb to do the debugging.
</para>
</sect2>
</sect1>
<sect1 id="kgdbwait">
<title>Kernel parameter: kgdbwait</title>
<para>
@ -162,103 +294,204 @@
</para>
<para>
The kernel will stop and wait as early as the I/O driver and
architecture will allow when you use this option. If you build the
kgdb I/O driver as a kernel module kgdbwait will not do anything.
architecture allows when you use this option. If you build the
kgdb I/O driver as a loadable kernel module kgdbwait will not do
anything.
</para>
</sect1>
<sect1 id="kgdboc">
<title>Kernel parameter: kgdboc</title>
<para>
The kgdboc driver was originally an abbreviation meant to stand for
"kgdb over console". Kgdboc is designed to work with a single
serial port. It was meant to cover the circumstance
where you wanted to use a serial console as your primary console as
well as using it to perform kernel debugging. Of course you can
also use kgdboc without assigning a console to the same port.
</para>
<sect2 id="UsingKgdboc">
<title>Using kgdboc</title>
<para>
You can configure kgdboc via sysfs or a module or kernel boot line
parameter depending on if you build with CONFIG_KGDBOC as a module
or built-in.
<orderedlist>
<listitem><para>From the module load or build-in</para>
<para><constant>kgdboc=&lt;tty-device&gt;,[baud]</constant></para>
<para>
The example here would be if your console port was typically ttyS0, you would use something like <constant>kgdboc=ttyS0,115200</constant> or on the ARM Versatile AB you would likely use <constant>kgdboc=ttyAMA0,115200</constant>
</para>
</listitem>
<listitem><para>From sysfs</para>
<para><constant>echo ttyS0 &gt; /sys/module/kgdboc/parameters/kgdboc</constant></para>
</listitem>
</orderedlist>
</para>
<para>
NOTE: Kgdboc does not support interrupting the target via the
gdb remote protocol. You must manually send a sysrq-g unless you
have a proxy that splits console output to a terminal problem and
has a separate port for the debugger to connect to that sends the
sysrq-g for you.
</para>
<para>When using kgdboc with no debugger proxy, you can end up
connecting the debugger for one of two entry points. If an
exception occurs after you have loaded kgdboc a message should print
on the console stating it is waiting for the debugger. In case you
disconnect your terminal program and then connect the debugger in
its place. If you want to interrupt the target system and forcibly
enter a debug session you have to issue a Sysrq sequence and then
type the letter <constant>g</constant>. Then you disconnect the
terminal session and connect gdb. Your options if you don't like
this are to hack gdb to send the sysrq-g for you as well as on the
initial connect, or to use a debugger proxy that allows an
unmodified gdb to do the debugging.
</para>
</sect2>
</sect1>
<sect1 id="kgdbcon">
<title>Kernel parameter: kgdbcon</title>
<para>
Kgdb supports using the gdb serial protocol to send console messages
to the debugger when the debugger is connected and running. There
are two ways to activate this feature.
<orderedlist>
<listitem><para>Activate with the kernel command line option:</para>
<para><constant>kgdbcon</constant></para>
</listitem>
<listitem><para>Use sysfs before configuring an io driver</para>
<para>
<constant>echo 1 &gt; /sys/module/kgdb/parameters/kgdb_use_con</constant>
</para>
<para>
NOTE: If you do this after you configure the kgdb I/O driver, the
setting will not take effect until the next point the I/O is
reconfigured.
</para>
</listitem>
</orderedlist>
</para>
<para>
IMPORTANT NOTE: Using this option with kgdb over the console
(kgdboc) is not supported.
<sect1 id="kgdbcon">
<title>Kernel parameter: kgdbcon</title>
<para> The kgdbcon feature allows you to see printk() messages
inside gdb while gdb is connected to the kernel. Kdb does not make
use of the kgdbcon feature.
</para>
<para>Kgdb supports using the gdb serial protocol to send console
messages to the debugger when the debugger is connected and running.
There are two ways to activate this feature.
<orderedlist>
<listitem><para>Activate with the kernel command line option:</para>
<para><constant>kgdbcon</constant></para>
</listitem>
<listitem><para>Use sysfs before configuring an I/O driver</para>
<para>
<constant>echo 1 &gt; /sys/module/kgdb/parameters/kgdb_use_con</constant>
</para>
<para>
NOTE: If you do this after you configure the kgdb I/O driver, the
setting will not take effect until the next point the I/O is
reconfigured.
</para>
</listitem>
</orderedlist>
<para>IMPORTANT NOTE: You cannot use kgdboc + kgdbcon on a tty that is an
active system console. An example incorrect usage is <constant>console=ttyS0,115200 kgdboc=ttyS0 kgdbcon</constant>
</para>
<para>It is possible to use this option with kgdboc on a tty that is not a system console.
</para>
</para>
</sect1>
</chapter>
<chapter id="ConnectingGDB">
<title>Connecting gdb</title>
<chapter id="usingKDB">
<title>Using kdb</title>
<para>
</para>
<sect1 id="quickKDBserial">
<title>Quick start for kdb on a serial port</title>
<para>This is a quick example of how to use kdb.</para>
<para><orderedlist>
<listitem><para>Boot kernel with arguments:
<itemizedlist>
<listitem><para><constant>console=ttyS0,115200 kgdboc=ttyS0,115200</constant></para></listitem>
</itemizedlist></para>
<para>OR</para>
<para>Configure kgdboc after the kernel booted; assuming you are using a serial port console:
<itemizedlist>
<listitem><para><constant>echo ttyS0 &gt; /sys/module/kgdboc/parameters/kgdboc</constant></para></listitem>
</itemizedlist>
</para>
</listitem>
<listitem><para>Enter the kernel debugger manually or by waiting for an oops or fault. There are several ways you can enter the kernel debugger manually; all involve using the sysrq-g, which means you must have enabled CONFIG_MAGIC_SYSRQ=y in your kernel config.</para>
<itemizedlist>
<listitem><para>When logged in as root or with a super user session you can run:</para>
<para><constant>echo g &gt; /proc/sysrq-trigger</constant></para></listitem>
<listitem><para>Example using minicom 2.2</para>
<para>Press: <constant>Control-a</constant></para>
<para>Press: <constant>f</constant></para>
<para>Press: <constant>g</constant></para>
</listitem>
<listitem><para>When you have telneted to a terminal server that supports sending a remote break</para>
<para>Press: <constant>Control-]</constant></para>
<para>Type in:<constant>send break</constant></para>
<para>Press: <constant>Enter</constant></para>
<para>Press: <constant>g</constant></para>
</listitem>
</itemizedlist>
</listitem>
<listitem><para>From the kdb prompt you can run the "help" command to see a complete list of the commands that are available.</para>
<para>Some useful commands in kdb include:
<itemizedlist>
<listitem><para>lsmod -- Shows where kernel modules are loaded</para></listitem>
<listitem><para>ps -- Displays only the active processes</para></listitem>
<listitem><para>ps A -- Shows all the processes</para></listitem>
<listitem><para>summary -- Shows kernel version info and memory usage</para></listitem>
<listitem><para>bt -- Get a backtrace of the current process using dump_stack()</para></listitem>
<listitem><para>dmesg -- View the kernel syslog buffer</para></listitem>
<listitem><para>go -- Continue the system</para></listitem>
</itemizedlist>
</para>
</listitem>
<listitem>
<para>When you are done using kdb you need to consider rebooting the
system or using the "go" command to resuming normal kernel
execution. If you have paused the kernel for a lengthy period of
time, applications that rely on timely networking or anything to do
with real wall clock time could be adversely affected, so you
should take this into consideration when using the kernel
debugger.</para>
</listitem>
</orderedlist></para>
</sect1>
<sect1 id="quickKDBkeyboard">
<title>Quick start for kdb using a keyboard connected console</title>
<para>This is a quick example of how to use kdb with a keyboard.</para>
<para><orderedlist>
<listitem><para>Boot kernel with arguments:
<itemizedlist>
<listitem><para><constant>kgdboc=kbd</constant></para></listitem>
</itemizedlist></para>
<para>OR</para>
<para>Configure kgdboc after the kernel booted:
<itemizedlist>
<listitem><para><constant>echo kbd &gt; /sys/module/kgdboc/parameters/kgdboc</constant></para></listitem>
</itemizedlist>
</para>
</listitem>
<listitem><para>Enter the kernel debugger manually or by waiting for an oops or fault. There are several ways you can enter the kernel debugger manually; all involve using the sysrq-g, which means you must have enabled CONFIG_MAGIC_SYSRQ=y in your kernel config.</para>
<itemizedlist>
<listitem><para>When logged in as root or with a super user session you can run:</para>
<para><constant>echo g &gt; /proc/sysrq-trigger</constant></para></listitem>
<listitem><para>Example using a laptop keyboard</para>
<para>Press and hold down: <constant>Alt</constant></para>
<para>Press and hold down: <constant>Fn</constant></para>
<para>Press and release the key with the label: <constant>SysRq</constant></para>
<para>Release: <constant>Fn</constant></para>
<para>Press and release: <constant>g</constant></para>
<para>Release: <constant>Alt</constant></para>
</listitem>
<listitem><para>Example using a PS/2 101-key keyboard</para>
<para>Press and hold down: <constant>Alt</constant></para>
<para>Press and release the key with the label: <constant>SysRq</constant></para>
<para>Press and release: <constant>g</constant></para>
<para>Release: <constant>Alt</constant></para>
</listitem>
</itemizedlist>
</listitem>
<listitem>
<para>Now type in a kdb command such as "help", "dmesg", "bt" or "go" to continue kernel execution.</para>
</listitem>
</orderedlist></para>
</sect1>
</chapter>
<chapter id="EnableKGDB">
<title>Using kgdb / gdb</title>
<para>In order to use kgdb you must activate it by passing
configuration information to one of the kgdb I/O drivers. If you
do not pass any configuration information kgdb will not do anything
at all. Kgdb will only actively hook up to the kernel trap hooks
if a kgdb I/O driver is loaded and configured. If you unconfigure
a kgdb I/O driver, kgdb will unregister all the kernel hook points.
</para>
<para> All kgdb I/O drivers can be reconfigured at run time, if
<symbol>CONFIG_SYSFS</symbol> and <symbol>CONFIG_MODULES</symbol>
are enabled, by echo'ing a new config string to
<constant>/sys/module/&lt;driver&gt;/parameter/&lt;option&gt;</constant>.
The driver can be unconfigured by passing an empty string. You cannot
change the configuration while the debugger is attached. Make sure
to detach the debugger with the <constant>detach</constant> command
prior to trying to unconfigure a kgdb I/O driver.
</para>
<sect1 id="ConnectingGDB">
<title>Connecting with gdb to a serial port</title>
<orderedlist>
<listitem><para>Configure kgdboc</para>
<para>Boot kernel with arguments:
<itemizedlist>
<listitem><para><constant>kgdboc=ttyS0,115200</constant></para></listitem>
</itemizedlist></para>
<para>OR</para>
<para>Configure kgdboc after the kernel booted:
<itemizedlist>
<listitem><para><constant>echo ttyS0 &gt; /sys/module/kgdboc/parameters/kgdboc</constant></para></listitem>
</itemizedlist></para>
</listitem>
<listitem>
<para>Stop kernel execution (break into the debugger)</para>
<para>In order to connect to gdb via kgdboc, the kernel must
first be stopped. There are several ways to stop the kernel which
include using kgdbwait as a boot argument, via a sysrq-g, or running
the kernel until it takes an exception where it waits for the
debugger to attach.
<itemizedlist>
<listitem><para>When logged in as root or with a super user session you can run:</para>
<para><constant>echo g &gt; /proc/sysrq-trigger</constant></para></listitem>
<listitem><para>Example using minicom 2.2</para>
<para>Press: <constant>Control-a</constant></para>
<para>Press: <constant>f</constant></para>
<para>Press: <constant>g</constant></para>
</listitem>
<listitem><para>When you have telneted to a terminal server that supports sending a remote break</para>
<para>Press: <constant>Control-]</constant></para>
<para>Type in:<constant>send break</constant></para>
<para>Press: <constant>Enter</constant></para>
<para>Press: <constant>g</constant></para>
</listitem>
</itemizedlist>
</para>
</listitem>
<listitem>
<para>Connect from from gdb</para>
<para>
If you are using kgdboc, you need to have used kgdbwait as a boot
argument, issued a sysrq-g, or the system you are going to debug
has already taken an exception and is waiting for the debugger to
attach before you can connect gdb.
</para>
<para>
If you are not using different kgdb I/O driver other than kgdboc,
you should be able to connect and the target will automatically
respond.
</para>
<para>
Example (using a serial port):
Example (using a directly connected port):
</para>
<programlisting>
% gdb ./vmlinux
@ -266,7 +499,7 @@
(gdb) target remote /dev/ttyS0
</programlisting>
<para>
Example (kgdb to a terminal server on tcp port 2012):
Example (kgdb to a terminal server on TCP port 2012):
</para>
<programlisting>
% gdb ./vmlinux
@ -283,6 +516,83 @@
communications. You do this prior to issuing the <constant>target
remote</constant> command by typing in: <constant>set debug remote 1</constant>
</para>
</listitem>
</orderedlist>
<para>Remember if you continue in gdb, and need to "break in" again,
you need to issue an other sysrq-g. It is easy to create a simple
entry point by putting a breakpoint at <constant>sys_sync</constant>
and then you can run "sync" from a shell or script to break into the
debugger.</para>
</sect1>
</chapter>
<chapter id="switchKdbKgdb">
<title>kgdb and kdb interoperability</title>
<para>It is possible to transition between kdb and kgdb dynamically.
The debug core will remember which you used the last time and
automatically start in the same mode.</para>
<sect1>
<title>Switching between kdb and kgdb</title>
<sect2>
<title>Switching from kgdb to kdb</title>
<para>
There are two ways to switch from kgdb to kdb: you can use gdb to
issue a maintenance packet, or you can blindly type the command $3#33.
Whenever kernel debugger stops in kgdb mode it will print the
message <constant>KGDB or $3#33 for KDB</constant>. It is important
to note that you have to type the sequence correctly in one pass.
You cannot type a backspace or delete because kgdb will interpret
that as part of the debug stream.
<orderedlist>
<listitem><para>Change from kgdb to kdb by blindly typing:</para>
<para><constant>$3#33</constant></para></listitem>
<listitem><para>Change from kgdb to kdb with gdb</para>
<para><constant>maintenance packet 3</constant></para>
<para>NOTE: Now you must kill gdb. Typically you press control-z and
issue the command: kill -9 %</para></listitem>
</orderedlist>
</para>
</sect2>
<sect2>
<title>Change from kdb to kgdb</title>
<para>There are two ways you can change from kdb to kgdb. You can
manually enter kgdb mode by issuing the kgdb command from the kdb
shell prompt, or you can connect gdb while the kdb shell prompt is
active. The kdb shell looks for the typical first commands that gdb
would issue with the gdb remote protocol and if it sees one of those
commands it automatically changes into kgdb mode.</para>
<orderedlist>
<listitem><para>From kdb issue the command:</para>
<para><constant>kgdb</constant></para>
<para>Now disconnect your terminal program and connect gdb in its place</para></listitem>
<listitem><para>At the kdb prompt, disconnect the terminal program and connect gdb in its place.</para></listitem>
</orderedlist>
</sect2>
</sect1>
<sect1>
<title>Running kdb commands from gdb</title>
<para>It is possible to run a limited set of kdb commands from gdb,
using the gdb monitor command. You don't want to execute any of the
run control or breakpoint operations, because it can disrupt the
state of the kernel debugger. You should be using gdb for
breakpoints and run control operations if you have gdb connected.
The more useful commands to run are things like lsmod, dmesg, ps or
possibly some of the memory information commands. To see all the kdb
commands you can run <constant>monitor help</constant>.</para>
<para>Example:
<informalexample><programlisting>
(gdb) monitor ps
1 idle process (state I) and
27 sleeping system daemon (state M) processes suppressed,
use 'ps A' to see all.
Task Addr Pid Parent [*] cpu State Thread Command
0xc78291d0 1 0 0 0 S 0xc7829404 init
0xc7954150 942 1 0 0 S 0xc7954384 dropbear
0xc78789c0 944 1 0 0 S 0xc7878bf4 sh
(gdb)
</programlisting></informalexample>
</para>
</sect1>
</chapter>
<chapter id="KGDBTestSuite">
<title>kgdb Test Suite</title>
@ -309,34 +619,36 @@
</para>
</chapter>
<chapter id="CommonBackEndReq">
<title>KGDB Internals</title>
<title>Kernel Debugger Internals</title>
<sect1 id="kgdbArchitecture">
<title>Architecture Specifics</title>
<para>
Kgdb is organized into three basic components:
The kernel debugger is organized into a number of components:
<orderedlist>
<listitem><para>kgdb core</para>
<listitem><para>The debug core</para>
<para>
The kgdb core is found in kernel/kgdb.c. It contains:
The debug core is found in kernel/debugger/debug_core.c. It contains:
<itemizedlist>
<listitem><para>All the logic to implement the gdb serial protocol</para></listitem>
<listitem><para>A generic OS exception handler which includes sync'ing the processors into a stopped state on an multi cpu system.</para></listitem>
<listitem><para>A generic OS exception handler which includes
sync'ing the processors into a stopped state on an multi-CPU
system.</para></listitem>
<listitem><para>The API to talk to the kgdb I/O drivers</para></listitem>
<listitem><para>The API to make calls to the arch specific kgdb implementation</para></listitem>
<listitem><para>The API to make calls to the arch-specific kgdb implementation</para></listitem>
<listitem><para>The logic to perform safe memory reads and writes to memory while using the debugger</para></listitem>
<listitem><para>A full implementation for software breakpoints unless overridden by the arch</para></listitem>
<listitem><para>The API to invoke either the kdb or kgdb frontend to the debug core.</para></listitem>
</itemizedlist>
</para>
</listitem>
<listitem><para>kgdb arch specific implementation</para>
<listitem><para>kgdb arch-specific implementation</para>
<para>
This implementation is generally found in arch/*/kernel/kgdb.c.
As an example, arch/x86/kernel/kgdb.c contains the specifics to
implement HW breakpoint as well as the initialization to
dynamically register and unregister for the trap handlers on
this architecture. The arch specific portion implements:
this architecture. The arch-specific portion implements:
<itemizedlist>
<listitem><para>contains an arch specific trap catcher which
<listitem><para>contains an arch-specific trap catcher which
invokes kgdb_handle_exception() to start kgdb about doing its
work</para></listitem>
<listitem><para>translation to and from gdb specific packet format to pt_regs</para></listitem>
@ -347,11 +659,35 @@
</itemizedlist>
</para>
</listitem>
<listitem><para>gdbstub frontend (aka kgdb)</para>
<para>The gdbstub is located in kernel/debug/gdbstub.c. It contains:</para>
<itemizedlist>
<listitem><para>All the logic to implement the gdb serial protocol</para></listitem>
</itemizedlist>
</listitem>
<listitem><para>kdb frontend</para>
<para>The kdb debugger shell is broken down into a number of
components. The kdb core is located in kernel/debug/kdb. There
are a number of helper functions in some of the other kernel
components to make it possible for kdb to examine and report
information about the kernel without taking locks that could
cause a kernel deadlock. The kdb core contains implements the following functionality.</para>
<itemizedlist>
<listitem><para>A simple shell</para></listitem>
<listitem><para>The kdb core command set</para></listitem>
<listitem><para>A registration API to register additional kdb shell commands.</para>
<para>A good example of a self-contained kdb module is the "ftdump" command for dumping the ftrace buffer. See: kernel/trace/trace_kdb.c</para></listitem>
<listitem><para>The implementation for kdb_printf() which
emits messages directly to I/O drivers, bypassing the kernel
log.</para></listitem>
<listitem><para>SW / HW breakpoint management for the kdb shell</para></listitem>
</itemizedlist>
</listitem>
<listitem><para>kgdb I/O driver</para>
<para>
Each kgdb I/O driver has to provide an implemenation for the following:
Each kgdb I/O driver has to provide an implementation for the following:
<itemizedlist>
<listitem><para>configuration via builtin or module</para></listitem>
<listitem><para>configuration via built-in or module</para></listitem>
<listitem><para>dynamic configuration and kgdb hook registration calls</para></listitem>
<listitem><para>read and write character interface</para></listitem>
<listitem><para>A cleanup handler for unconfiguring from the kgdb core</para></listitem>
@ -416,15 +752,15 @@
underlying low level to the hardware driver having "polling hooks"
which the to which the tty driver is attached. In the initial
implementation of kgdboc it the serial_core was changed to expose a
low level uart hook for doing polled mode reading and writing of a
low level UART hook for doing polled mode reading and writing of a
single character while in an atomic context. When kgdb makes an I/O
request to the debugger, kgdboc invokes a call back in the serial
core which in turn uses the call back in the uart driver. It is
certainly possible to extend kgdboc to work with non-uart based
core which in turn uses the call back in the UART driver. It is
certainly possible to extend kgdboc to work with non-UART based
consoles in the future.
</para>
<para>
When using kgdboc with a uart, the uart driver must implement two callbacks in the <constant>struct uart_ops</constant>. Example from drivers/8250.c:<programlisting>
When using kgdboc with a UART, the UART driver must implement two callbacks in the <constant>struct uart_ops</constant>. Example from drivers/8250.c:<programlisting>
#ifdef CONFIG_CONSOLE_POLL
.poll_get_char = serial8250_get_poll_char,
.poll_put_char = serial8250_put_poll_char,
@ -434,7 +770,7 @@
<constant>#ifdef CONFIG_CONSOLE_POLL</constant>, as shown above.
Keep in mind that polling hooks have to be implemented in such a way
that they can be called from an atomic context and have to restore
the state of the uart chip on return such that the system can return
the state of the UART chip on return such that the system can return
to normal when the debugger detaches. You need to be very careful
with any kind of lock you consider, because failing here is most
going to mean pressing the reset button.
@ -453,6 +789,10 @@
<itemizedlist>
<listitem><para>Jason Wessel<email>jason.wessel@windriver.com</email></para></listitem>
</itemizedlist>
In Jan 2010 this document was updated to include kdb.
<itemizedlist>
<listitem><para>Jason Wessel<email>jason.wessel@windriver.com</email></para></listitem>
</itemizedlist>
</para>
</chapter>
</book>

20
Documentation/DocBook/libata.tmpl
View File

@ -81,16 +81,14 @@ void (*port_disable) (struct ata_port *);
</programlisting>
<para>
Called from ata_bus_probe() and ata_bus_reset() error paths,
as well as when unregistering from the SCSI module (rmmod, hot
unplug).
Called from ata_bus_probe() error path, as well as when
unregistering from the SCSI module (rmmod, hot unplug).
This function should do whatever needs to be done to take the
port out of use. In most cases, ata_port_disable() can be used
as this hook.
</para>
<para>
Called from ata_bus_probe() on a failed probe.
Called from ata_bus_reset() on a failed bus reset.
Called from ata_scsi_release().
</para>
@ -227,6 +225,18 @@ u8 (*sff_check_altstatus)(struct ata_port *ap);
</sect2>
<sect2><title>Write specific ATA shadow register</title>
<programlisting>
void (*sff_set_devctl)(struct ata_port *ap, u8 ctl);
</programlisting>
<para>
Write the device control ATA shadow register to the hardware.
Most drivers don't need to define this.
</para>
</sect2>
<sect2><title>Select ATA device on bus</title>
<programlisting>
void (*sff_dev_select)(struct ata_port *ap, unsigned int device);
@ -477,7 +487,7 @@ void (*host_stop) (struct ata_host_set *host_set);
allocates space for a legacy IDE PRD table and returns.
</para>
<para>
->port_stop() is called after ->host_stop(). It's sole function
->port_stop() is called after ->host_stop(). Its sole function
is to release DMA/memory resources, now that they are no longer
actively being used. Many drivers also free driver-private
data from port at this time.

11
Documentation/DocBook/media-entities.tmpl
View File

@ -17,6 +17,7 @@
<!ENTITY VIDIOC-DBG-G-REGISTER "<link linkend='vidioc-dbg-g-register'><constant>VIDIOC_DBG_G_REGISTER</constant></link>">
<!ENTITY VIDIOC-DBG-S-REGISTER "<link linkend='vidioc-dbg-g-register'><constant>VIDIOC_DBG_S_REGISTER</constant></link>">
<!ENTITY VIDIOC-DQBUF "<link linkend='vidioc-qbuf'><constant>VIDIOC_DQBUF</constant></link>">
<!ENTITY VIDIOC-DQEVENT "<link linkend='vidioc-dqevent'><constant>VIDIOC_DQEVENT</constant></link>">
<!ENTITY VIDIOC-ENCODER-CMD "<link linkend='vidioc-encoder-cmd'><constant>VIDIOC_ENCODER_CMD</constant></link>">
<!ENTITY VIDIOC-ENUMAUDIO "<link linkend='vidioc-enumaudio'><constant>VIDIOC_ENUMAUDIO</constant></link>">
<!ENTITY VIDIOC-ENUMAUDOUT "<link linkend='vidioc-enumaudioout'><constant>VIDIOC_ENUMAUDOUT</constant></link>">
@ -60,6 +61,7 @@
<!ENTITY VIDIOC-REQBUFS "<link linkend='vidioc-reqbufs'><constant>VIDIOC_REQBUFS</constant></link>">
<!ENTITY VIDIOC-STREAMOFF "<link linkend='vidioc-streamon'><constant>VIDIOC_STREAMOFF</constant></link>">
<!ENTITY VIDIOC-STREAMON "<link linkend='vidioc-streamon'><constant>VIDIOC_STREAMON</constant></link>">
<!ENTITY VIDIOC-SUBSCRIBE-EVENT "<link linkend='vidioc-subscribe-event'><constant>VIDIOC_SUBSCRIBE_EVENT</constant></link>">
<!ENTITY VIDIOC-S-AUDIO "<link linkend='vidioc-g-audio'><constant>VIDIOC_S_AUDIO</constant></link>">
<!ENTITY VIDIOC-S-AUDOUT "<link linkend='vidioc-g-audioout'><constant>VIDIOC_S_AUDOUT</constant></link>">
<!ENTITY VIDIOC-S-CROP "<link linkend='vidioc-g-crop'><constant>VIDIOC_S_CROP</constant></link>">
@ -83,6 +85,7 @@
<!ENTITY VIDIOC-TRY-ENCODER-CMD "<link linkend='vidioc-encoder-cmd'><constant>VIDIOC_TRY_ENCODER_CMD</constant></link>">
<!ENTITY VIDIOC-TRY-EXT-CTRLS "<link linkend='vidioc-g-ext-ctrls'><constant>VIDIOC_TRY_EXT_CTRLS</constant></link>">
<!ENTITY VIDIOC-TRY-FMT "<link linkend='vidioc-g-fmt'><constant>VIDIOC_TRY_FMT</constant></link>">
<!ENTITY VIDIOC-UNSUBSCRIBE-EVENT "<link linkend='vidioc-subscribe-event'><constant>VIDIOC_UNSUBSCRIBE_EVENT</constant></link>">
<!-- Types -->
<!ENTITY v4l2-std-id "<link linkend='v4l2-std-id'>v4l2_std_id</link>">
@ -141,6 +144,9 @@
<!ENTITY v4l2-enc-idx "struct&nbsp;<link linkend='v4l2-enc-idx'>v4l2_enc_idx</link>">
<!ENTITY v4l2-enc-idx-entry "struct&nbsp;<link linkend='v4l2-enc-idx-entry'>v4l2_enc_idx_entry</link>">
<!ENTITY v4l2-encoder-cmd "struct&nbsp;<link linkend='v4l2-encoder-cmd'>v4l2_encoder_cmd</link>">
<!ENTITY v4l2-event "struct&nbsp;<link linkend='v4l2-event'>v4l2_event</link>">
<!ENTITY v4l2-event-subscription "struct&nbsp;<link linkend='v4l2-event-subscription'>v4l2_event_subscription</link>">
<!ENTITY v4l2-event-vsync "struct&nbsp;<link linkend='v4l2-event-vsync'>v4l2_event_vsync</link>">
<!ENTITY v4l2-ext-control "struct&nbsp;<link linkend='v4l2-ext-control'>v4l2_ext_control</link>">
<!ENTITY v4l2-ext-controls "struct&nbsp;<link linkend='v4l2-ext-controls'>v4l2_ext_controls</link>">
<!ENTITY v4l2-fmtdesc "struct&nbsp;<link linkend='v4l2-fmtdesc'>v4l2_fmtdesc</link>">
@ -200,6 +206,7 @@
<!ENTITY sub-controls SYSTEM "v4l/controls.xml">
<!ENTITY sub-dev-capture SYSTEM "v4l/dev-capture.xml">
<!ENTITY sub-dev-codec SYSTEM "v4l/dev-codec.xml">
<!ENTITY sub-dev-event SYSTEM "v4l/dev-event.xml">
<!ENTITY sub-dev-effect SYSTEM "v4l/dev-effect.xml">
<!ENTITY sub-dev-osd SYSTEM "v4l/dev-osd.xml">
<!ENTITY sub-dev-output SYSTEM "v4l/dev-output.xml">
@ -292,6 +299,8 @@
<!ENTITY sub-v4l2grab-c SYSTEM "v4l/v4l2grab.c.xml">
<!ENTITY sub-videodev2-h SYSTEM "v4l/videodev2.h.xml">
<!ENTITY sub-v4l2 SYSTEM "v4l/v4l2.xml">
<!ENTITY sub-dqevent SYSTEM "v4l/vidioc-dqevent.xml">
<!ENTITY sub-subscribe-event SYSTEM "v4l/vidioc-subscribe-event.xml">
<!ENTITY sub-intro SYSTEM "dvb/intro.xml">
<!ENTITY sub-frontend SYSTEM "dvb/frontend.xml">
<!ENTITY sub-dvbproperty SYSTEM "dvb/dvbproperty.xml">
@ -381,3 +390,5 @@
<!ENTITY reqbufs SYSTEM "v4l/vidioc-reqbufs.xml">
<!ENTITY s-hw-freq-seek SYSTEM "v4l/vidioc-s-hw-freq-seek.xml">
<!ENTITY streamon SYSTEM "v4l/vidioc-streamon.xml">
<!ENTITY dqevent SYSTEM "v4l/vidioc-dqevent.xml">
<!ENTITY subscribe_event SYSTEM "v4l/vidioc-subscribe-event.xml">

2
Documentation/DocBook/mtdnand.tmpl
View File

@ -269,7 +269,7 @@ static void board_hwcontrol(struct mtd_info *mtd, int cmd)
information about the device.
</para>
<programlisting>
int __init board_init (void)
static int __init board_init (void)
{
struct nand_chip *this;
int err = 0;

10
Documentation/DocBook/sh.tmpl
View File

@ -19,13 +19,17 @@
</authorgroup>
<copyright>
<year>2008</year>
<year>2008-2010</year>
<holder>Paul Mundt</holder>
</copyright>
<copyright>
<year>2008</year>
<year>2008-2010</year>
<holder>Renesas Technology Corp.</holder>
</copyright>
<copyright>
<year>2010</year>
<holder>Renesas Electronics Corp.</holder>
</copyright>
<legalnotice>
<para>
@ -77,7 +81,7 @@
</chapter>
<chapter id="clk">
<title>Clock Framework Extensions</title>
!Iarch/sh/include/asm/clock.h
!Iinclude/linux/sh_clk.h
</chapter>
<chapter id="mach">
<title>Machine Specific Interfaces</title>

130
Documentation/DocBook/v4l/compat.xml
View File

@ -2332,15 +2332,26 @@ more information.</para>
</listitem>
</orderedlist>
</section>
</section>
<section>
<title>V4L2 in Linux 2.6.34</title>
<orderedlist>
<listitem>
<para>Added
<constant>V4L2_CID_IRIS_ABSOLUTE</constant> and
<constant>V4L2_CID_IRIS_RELATIVE</constant> controls to the
<link linkend="camera-controls">Camera controls class</link>.
</para>
</listitem>
</orderedlist>
</section>
<section id="other">
<title>Relation of V4L2 to other Linux multimedia APIs</title>
<section id="other">
<title>Relation of V4L2 to other Linux multimedia APIs</title>
<section id="xvideo">
<title>X Video Extension</title>
<section id="xvideo">
<title>X Video Extension</title>
<para>The X Video Extension (abbreviated XVideo or just Xv) is
<para>The X Video Extension (abbreviated XVideo or just Xv) is
an extension of the X Window system, implemented for example by the
XFree86 project. Its scope is similar to V4L2, an API to video capture
and output devices for X clients. Xv allows applications to display
@ -2351,7 +2362,7 @@ capture or output still images in XPixmaps<footnote>
extension available across many operating systems and
architectures.</para>
<para>Because the driver is embedded into the X server Xv has a
<para>Because the driver is embedded into the X server Xv has a
number of advantages over the V4L2 <link linkend="overlay">video
overlay interface</link>. The driver can easily determine the overlay
target, &ie; visible graphics memory or off-screen buffers for a
@ -2360,16 +2371,16 @@ overlay, scaling or color-keying, or the clipping functions of the
video capture hardware, always in sync with drawing operations or
windows moving or changing their stacking order.</para>
<para>To combine the advantages of Xv and V4L a special Xv
<para>To combine the advantages of Xv and V4L a special Xv
driver exists in XFree86 and XOrg, just programming any overlay capable
Video4Linux device it finds. To enable it
<filename>/etc/X11/XF86Config</filename> must contain these lines:</para>
<para><screen>
<para><screen>
Section "Module"
Load "v4l"
EndSection</screen></para>
<para>As of XFree86 4.2 this driver still supports only V4L
<para>As of XFree86 4.2 this driver still supports only V4L
ioctls, however it should work just fine with all V4L2 devices through
the V4L2 backward-compatibility layer. Since V4L2 permits multiple
opens it is possible (if supported by the V4L2 driver) to capture
@ -2377,83 +2388,84 @@ video while an X client requested video overlay. Restrictions of
simultaneous capturing and overlay are discussed in <xref
linkend="overlay" /> apply.</para>
<para>Only marginally related to V4L2, XFree86 extended Xv to
<para>Only marginally related to V4L2, XFree86 extended Xv to
support hardware YUV to RGB conversion and scaling for faster video
playback, and added an interface to MPEG-2 decoding hardware. This API
is useful to display images captured with V4L2 devices.</para>
</section>
</section>
<section>
<title>Digital Video</title>
<section>
<title>Digital Video</title>
<para>V4L2 does not support digital terrestrial, cable or
<para>V4L2 does not support digital terrestrial, cable or
satellite broadcast. A separate project aiming at digital receivers
exists. You can find its homepage at <ulink
url="http://linuxtv.org">http://linuxtv.org</ulink>. The Linux DVB API
has no connection to the V4L2 API except that drivers for hybrid
hardware may support both.</para>
</section>
<section>
<title>Audio Interfaces</title>
<para>[to do - OSS/ALSA]</para>
</section>
</section>
<section>
<title>Audio Interfaces</title>
<section id="experimental">
<title>Experimental API Elements</title>
<para>[to do - OSS/ALSA]</para>
</section>
</section>
<section id="experimental">
<title>Experimental API Elements</title>
<para>The following V4L2 API elements are currently experimental
<para>The following V4L2 API elements are currently experimental
and may change in the future.</para>
<itemizedlist>
<listitem>
<para>Video Output Overlay (OSD) Interface, <xref
<itemizedlist>
<listitem>
<para>Video Output Overlay (OSD) Interface, <xref
linkend="osd" />.</para>
</listitem>
</listitem>
<listitem>
<para><constant>V4L2_BUF_TYPE_VIDEO_OUTPUT_OVERLAY</constant>,
<para><constant>V4L2_BUF_TYPE_VIDEO_OUTPUT_OVERLAY</constant>,
&v4l2-buf-type;, <xref linkend="v4l2-buf-type" />.</para>
</listitem>
<listitem>
<para><constant>V4L2_CAP_VIDEO_OUTPUT_OVERLAY</constant>,
</listitem>
<listitem>
<para><constant>V4L2_CAP_VIDEO_OUTPUT_OVERLAY</constant>,
&VIDIOC-QUERYCAP; ioctl, <xref linkend="device-capabilities" />.</para>
</listitem>
<listitem>
<para>&VIDIOC-ENUM-FRAMESIZES; and
</listitem>
<listitem>
<para>&VIDIOC-ENUM-FRAMESIZES; and
&VIDIOC-ENUM-FRAMEINTERVALS; ioctls.</para>
</listitem>
<listitem>
<para>&VIDIOC-G-ENC-INDEX; ioctl.</para>
</listitem>
<listitem>
<para>&VIDIOC-ENCODER-CMD; and &VIDIOC-TRY-ENCODER-CMD;
</listitem>
<listitem>
<para>&VIDIOC-G-ENC-INDEX; ioctl.</para>
</listitem>
<listitem>
<para>&VIDIOC-ENCODER-CMD; and &VIDIOC-TRY-ENCODER-CMD;
ioctls.</para>
</listitem>
<listitem>
<para>&VIDIOC-DBG-G-REGISTER; and &VIDIOC-DBG-S-REGISTER;
</listitem>
<listitem>
<para>&VIDIOC-DBG-G-REGISTER; and &VIDIOC-DBG-S-REGISTER;
ioctls.</para>
</listitem>
<listitem>
<para>&VIDIOC-DBG-G-CHIP-IDENT; ioctl.</para>
</listitem>
</itemizedlist>
</section>
</listitem>
<listitem>
<para>&VIDIOC-DBG-G-CHIP-IDENT; ioctl.</para>
</listitem>
</itemizedlist>
</section>
<section id="obsolete">
<title>Obsolete API Elements</title>
<section id="obsolete">
<title>Obsolete API Elements</title>
<para>The following V4L2 API elements were superseded by new
<para>The following V4L2 API elements were superseded by new
interfaces and should not be implemented in new drivers.</para>
<itemizedlist>
<listitem>
<para><constant>VIDIOC_G_MPEGCOMP</constant> and
<itemizedlist>
<listitem>
<para><constant>VIDIOC_G_MPEGCOMP</constant> and
<constant>VIDIOC_S_MPEGCOMP</constant> ioctls. Use Extended Controls,
<xref linkend="extended-controls" />.</para>
</listitem>
</itemizedlist>
</listitem>
</itemizedlist>
</section>
</section>
<!--

36
Documentation/DocBook/v4l/controls.xml
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@ -266,6 +266,12 @@ minimum value disables backlight compensation.</entry>
<entry>boolean</entry>
<entry>Chroma automatic gain control.</entry>
</row>
<row>
<entry><constant>V4L2_CID_CHROMA_GAIN</constant></entry>
<entry>integer</entry>
<entry>Adjusts the Chroma gain control (for use when chroma AGC
is disabled).</entry>
</row>
<row>
<entry><constant>V4L2_CID_COLOR_KILLER</constant></entry>
<entry>boolean</entry>
@ -277,8 +283,15 @@ minimum value disables backlight compensation.</entry>
<entry>Selects a color effect. Possible values for
<constant>enum v4l2_colorfx</constant> are:
<constant>V4L2_COLORFX_NONE</constant> (0),
<constant>V4L2_COLORFX_BW</constant> (1) and
<constant>V4L2_COLORFX_SEPIA</constant> (2).</entry>
<constant>V4L2_COLORFX_BW</constant> (1),
<constant>V4L2_COLORFX_SEPIA</constant> (2),
<constant>V4L2_COLORFX_NEGATIVE</constant> (3),
<constant>V4L2_COLORFX_EMBOSS</constant> (4),
<constant>V4L2_COLORFX_SKETCH</constant> (5),
<constant>V4L2_COLORFX_SKY_BLUE</constant> (6),
<constant>V4L2_COLORFX_GRASS_GREEN</constant> (7),
<constant>V4L2_COLORFX_SKIN_WHITEN</constant> (8) and
<constant>V4L2_COLORFX_VIVID</constant> (9).</entry>
</row>
<row>
<entry><constant>V4L2_CID_ROTATE</constant></entry>
@ -1824,6 +1837,25 @@ wide-angle direction. The zoom speed unit is driver-specific.</entry>
</row>
<row><entry></entry></row>
<row>
<entry spanname="id"><constant>V4L2_CID_IRIS_ABSOLUTE</constant>&nbsp;</entry>
<entry>integer</entry>
</row><row><entry spanname="descr">This control sets the
camera's aperture to the specified value. The unit is undefined.
Larger values open the iris wider, smaller values close it.</entry>
</row>
<row><entry></entry></row>
<row>
<entry spanname="id"><constant>V4L2_CID_IRIS_RELATIVE</constant>&nbsp;</entry>
<entry>integer</entry>
</row><row><entry spanname="descr">This control modifies the
camera's aperture by the specified amount. The unit is undefined.
Positive values open the iris one step further, negative values close
it one step further. This is a write-only control.</entry>
</row>
<row><entry></entry></row>
<row>
<entry spanname="id"><constant>V4L2_CID_PRIVACY</constant>&nbsp;</entry>
<entry>boolean</entry>

31
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@ -0,0 +1,31 @@
<title>Event Interface</title>
<para>The V4L2 event interface provides means for user to get
immediately notified on certain conditions taking place on a device.
This might include start of frame or loss of signal events, for
example.
</para>
<para>To receive events, the events the user is interested in first must
be subscribed using the &VIDIOC-SUBSCRIBE-EVENT; ioctl. Once an event is
subscribed, the events of subscribed types are dequeueable using the
&VIDIOC-DQEVENT; ioctl. Events may be unsubscribed using
VIDIOC_UNSUBSCRIBE_EVENT ioctl. The special event type V4L2_EVENT_ALL may
be used to unsubscribe all the events the driver supports.</para>
<para>The event subscriptions and event queues are specific to file
handles. Subscribing an event on one file handle does not affect
other file handles.
</para>
<para>The information on dequeueable events is obtained by using select or
poll system calls on video devices. The V4L2 events use POLLPRI events on
poll system call and exceptions on select system call. </para>
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18
Documentation/DocBook/v4l/io.xml
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@ -701,6 +701,16 @@ buffer cannot be on both queues at the same time, the
They can be both cleared however, then the buffer is in "dequeued"
state, in the application domain to say so.</entry>
</row>
<row>
<entry><constant>V4L2_BUF_FLAG_ERROR</constant></entry>
<entry>0x0040</entry>
<entry>When this flag is set, the buffer has been dequeued
successfully, although the data might have been corrupted.
This is recoverable, streaming may continue as normal and
the buffer may be reused normally.
Drivers set this flag when the <constant>VIDIOC_DQBUF</constant>
ioctl is called.</entry>
</row>
<row>
<entry><constant>V4L2_BUF_FLAG_KEYFRAME</constant></entry>
<entry>0x0008</entry>
@ -918,8 +928,8 @@ order</emphasis>.</para>
<para>When the driver provides or accepts images field by field
rather than interleaved, it is also important applications understand
how the fields combine to frames. We distinguish between top and
bottom fields, the <emphasis>spatial order</emphasis>: The first line
how the fields combine to frames. We distinguish between top (aka odd) and
bottom (aka even) fields, the <emphasis>spatial order</emphasis>: The first line
of the top field is the first line of an interlaced frame, the first
line of the bottom field is the second line of that frame.</para>
@ -972,12 +982,12 @@ between <constant>V4L2_FIELD_TOP</constant> and
<row>
<entry><constant>V4L2_FIELD_TOP</constant></entry>
<entry>2</entry>
<entry>Images consist of the top field only.</entry>
<entry>Images consist of the top (aka odd) field only.</entry>
</row>
<row>
<entry><constant>V4L2_FIELD_BOTTOM</constant></entry>
<entry>3</entry>
<entry>Images consist of the bottom field only.
<entry>Images consist of the bottom (aka even) field only.
Applications may wish to prevent a device from capturing interlaced
images because they will have "comb" or "feathering" artefacts around
moving objects.</entry>

12
Documentation/DocBook/v4l/pixfmt.xml
View File

@ -792,6 +792,18 @@ http://www.thedirks.org/winnov/</ulink></para></entry>
<entry>'YYUV'</entry>
<entry>unknown</entry>
</row>
<row id="V4L2-PIX-FMT-Y4">
<entry><constant>V4L2_PIX_FMT_Y4</constant></entry>
<entry>'Y04 '</entry>
<entry>Old 4-bit greyscale format. Only the least significant 4 bits of each byte are used,
the other bits are set to 0.</entry>
</row>
<row id="V4L2-PIX-FMT-Y6">
<entry><constant>V4L2_PIX_FMT_Y6</constant></entry>
<entry>'Y06 '</entry>
<entry>Old 6-bit greyscale format. Only the least significant 6 bits of each byte are used,
the other bits are set to 0.</entry>
</row>
</tbody>
</tgroup>
</table>

3
Documentation/DocBook/v4l/v4l2.xml
View File

@ -401,6 +401,7 @@ and discussions on the V4L mailing list.</revremark>
<section id="ttx"> &sub-dev-teletext; </section>
<section id="radio"> &sub-dev-radio; </section>
<section id="rds"> &sub-dev-rds; </section>
<section id="event"> &sub-dev-event; </section>
</chapter>
<chapter id="driver">
@ -426,6 +427,7 @@ and discussions on the V4L mailing list.</revremark>
&sub-cropcap;
&sub-dbg-g-chip-ident;
&sub-dbg-g-register;
&sub-dqevent;
&sub-encoder-cmd;
&sub-enumaudio;
&sub-enumaudioout;
@ -467,6 +469,7 @@ and discussions on the V4L mailing list.</revremark>
&sub-reqbufs;
&sub-s-hw-freq-seek;
&sub-streamon;
&sub-subscribe-event;
<!-- End of ioctls. -->
&sub-mmap;
&sub-munmap;

10
Documentation/DocBook/v4l/videodev2.h.xml
View File

@ -1018,6 +1018,13 @@ enum <link linkend="v4l2-colorfx">v4l2_colorfx</link> {
V4L2_COLORFX_NONE = 0,
V4L2_COLORFX_BW = 1,
V4L2_COLORFX_SEPIA = 2,
V4L2_COLORFX_NEGATIVE = 3,
V4L2_COLORFX_EMBOSS = 4,
V4L2_COLORFX_SKETCH = 5,
V4L2_COLORFX_SKY_BLUE = 6,
V4L2_COLORFX_GRASS_GREEN = 7,
V4L2_COLORFX_SKIN_WHITEN = 8,
V4L2_COLORFX_VIVID = 9.
};
#define V4L2_CID_AUTOBRIGHTNESS (V4L2_CID_BASE+32)
#define V4L2_CID_BAND_STOP_FILTER (V4L2_CID_BASE+33)
@ -1271,6 +1278,9 @@ enum <link linkend="v4l2-exposure-auto-type">v4l2_exposure_auto_type</link> {
#define V4L2_CID_PRIVACY (V4L2_CID_CAMERA_CLASS_BASE+16)
#define V4L2_CID_IRIS_ABSOLUTE (V4L2_CID_CAMERA_CLASS_BASE+17)
#define V4L2_CID_IRIS_RELATIVE (V4L2_CID_CAMERA_CLASS_BASE+18)
/* FM Modulator class control IDs */
#define V4L2_CID_FM_TX_CLASS_BASE (V4L2_CTRL_CLASS_FM_TX | 0x900)
#define V4L2_CID_FM_TX_CLASS (V4L2_CTRL_CLASS_FM_TX | 1)

131
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@ -0,0 +1,131 @@
<refentry id="vidioc-dqevent">
<refmeta>
<refentrytitle>ioctl VIDIOC_DQEVENT</refentrytitle>
&manvol;
</refmeta>
<refnamediv>
<refname>VIDIOC_DQEVENT</refname>
<refpurpose>Dequeue event</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcprototype>
<funcdef>int <function>ioctl</function></funcdef>
<paramdef>int <parameter>fd</parameter></paramdef>
<paramdef>int <parameter>request</parameter></paramdef>
<paramdef>struct v4l2_event
*<parameter>argp</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>fd</parameter></term>
<listitem>
<para>&fd;</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>request</parameter></term>
<listitem>
<para>VIDIOC_DQEVENT</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>argp</parameter></term>
<listitem>
<para></para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>Dequeue an event from a video device. No input is required
for this ioctl. All the fields of the &v4l2-event; structure are
filled by the driver. The file handle will also receive exceptions
which the application may get by e.g. using the select system
call.</para>
<table frame="none" pgwide="1" id="v4l2-event">
<title>struct <structname>v4l2_event</structname></title>
<tgroup cols="4">
&cs-str;
<tbody valign="top">
<row>
<entry>__u32</entry>
<entry><structfield>type</structfield></entry>
<entry></entry>
<entry>Type of the event.</entry>
</row>
<row>
<entry>union</entry>
<entry><structfield>u</structfield></entry>
<entry></entry>
<entry></entry>
</row>
<row>
<entry></entry>
<entry>&v4l2-event-vsync;</entry>
<entry><structfield>vsync</structfield></entry>
<entry>Event data for event V4L2_EVENT_VSYNC.
</entry>
</row>
<row>
<entry></entry>
<entry>__u8</entry>
<entry><structfield>data</structfield>[64]</entry>
<entry>Event data. Defined by the event type. The union
should be used to define easily accessible type for
events.</entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>pending</structfield></entry>
<entry></entry>
<entry>Number of pending events excluding this one.</entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>sequence</structfield></entry>
<entry></entry>
<entry>Event sequence number. The sequence number is
incremented for every subscribed event that takes place.
If sequence numbers are not contiguous it means that
events have been lost.
</entry>
</row>
<row>
<entry>struct timespec</entry>
<entry><structfield>timestamp</structfield></entry>
<entry></entry>
<entry>Event timestamp.</entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>reserved</structfield>[9]</entry>
<entry></entry>
<entry>Reserved for future extensions. Drivers must set
the array to zero.</entry>
</row>
</tbody>
</tgroup>
</table>
</refsect1>
</refentry>
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2
Documentation/DocBook/v4l/vidioc-enuminput.xml
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@ -283,7 +283,7 @@ input/output interface to linux-media@vger.kernel.org on 19 Oct 2009.
<entry>This input supports setting DV presets by using VIDIOC_S_DV_PRESET.</entry>
</row>
<row>
<entry><constant>V4L2_OUT_CAP_CUSTOM_TIMINGS</constant></entry>
<entry><constant>V4L2_IN_CAP_CUSTOM_TIMINGS</constant></entry>
<entry>0x00000002</entry>
<entry>This input supports setting custom video timings by using VIDIOC_S_DV_TIMINGS.</entry>
</row>

14
Documentation/DocBook/v4l/vidioc-qbuf.xml
View File

@ -111,7 +111,11 @@ from the driver's outgoing queue. They just set the
and <structfield>reserved</structfield>
fields of a &v4l2-buffer; as above, when <constant>VIDIOC_DQBUF</constant>
is called with a pointer to this structure the driver fills the
remaining fields or returns an error code.</para>
remaining fields or returns an error code. The driver may also set
<constant>V4L2_BUF_FLAG_ERROR</constant> in the <structfield>flags</structfield>
field. It indicates a non-critical (recoverable) streaming error. In such case
the application may continue as normal, but should be aware that data in the
dequeued buffer might be corrupted.</para>
<para>By default <constant>VIDIOC_DQBUF</constant> blocks when no
buffer is in the outgoing queue. When the
@ -158,7 +162,13 @@ enqueue a user pointer buffer.</para>
<para><constant>VIDIOC_DQBUF</constant> failed due to an
internal error. Can also indicate temporary problems like signal
loss. Note the driver might dequeue an (empty) buffer despite
returning an error, or even stop capturing.</para>
returning an error, or even stop capturing. Reusing such buffer may be unsafe
though and its details (e.g. <structfield>index</structfield>) may not be
returned either. It is recommended that drivers indicate recoverable errors
by setting the <constant>V4L2_BUF_FLAG_ERROR</constant> and returning 0 instead.
In that case the application should be able to safely reuse the buffer and
continue streaming.
</para>
</listitem>
</varlistentry>
</variablelist>

2
Documentation/DocBook/v4l/vidioc-queryctrl.xml
View File

@ -325,7 +325,7 @@ should be part of the control documentation.</entry>
<entry>n/a</entry>
<entry>This is not a control. When
<constant>VIDIOC_QUERYCTRL</constant> is called with a control ID
equal to a control class code (see <xref linkend="ctrl-class" />), the
equal to a control class code (see <xref linkend="ctrl-class" />) + 1, the
ioctl returns the name of the control class and this control type.
Older drivers which do not support this feature return an
&EINVAL;.</entry>

2
Documentation/DocBook/v4l/vidioc-reqbufs.xml
View File

@ -61,7 +61,7 @@ fields of the <structname>v4l2_requestbuffers</structname> structure.
They set the <structfield>type</structfield> field to the respective
stream or buffer type, the <structfield>count</structfield> field to
the desired number of buffers, <structfield>memory</structfield>
must be set to the requested I/O method and the reserved array
must be set to the requested I/O method and the <structfield>reserved</structfield> array
must be zeroed. When the ioctl
is called with a pointer to this structure the driver will attempt to allocate
the requested number of buffers and it stores the actual number

133
Documentation/DocBook/v4l/vidioc-subscribe-event.xml Normal file
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@ -0,0 +1,133 @@
<refentry id="vidioc-subscribe-event">
<refmeta>
<refentrytitle>ioctl VIDIOC_SUBSCRIBE_EVENT, VIDIOC_UNSUBSCRIBE_EVENT</refentrytitle>
&manvol;
</refmeta>
<refnamediv>
<refname>VIDIOC_SUBSCRIBE_EVENT, VIDIOC_UNSUBSCRIBE_EVENT</refname>
<refpurpose>Subscribe or unsubscribe event</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcprototype>
<funcdef>int <function>ioctl</function></funcdef>
<paramdef>int <parameter>fd</parameter></paramdef>
<paramdef>int <parameter>request</parameter></paramdef>
<paramdef>struct v4l2_event_subscription
*<parameter>argp</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>fd</parameter></term>
<listitem>
<para>&fd;</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>request</parameter></term>
<listitem>
<para>VIDIOC_SUBSCRIBE_EVENT, VIDIOC_UNSUBSCRIBE_EVENT</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>argp</parameter></term>
<listitem>
<para></para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>Subscribe or unsubscribe V4L2 event. Subscribed events are
dequeued by using the &VIDIOC-DQEVENT; ioctl.</para>
<table frame="none" pgwide="1" id="v4l2-event-subscription">
<title>struct <structname>v4l2_event_subscription</structname></title>
<tgroup cols="3">
&cs-str;
<tbody valign="top">
<row>
<entry>__u32</entry>
<entry><structfield>type</structfield></entry>
<entry>Type of the event.</entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>reserved</structfield>[7]</entry>
<entry>Reserved for future extensions. Drivers and applications
must set the array to zero.</entry>
</row>
</tbody>
</tgroup>
</table>
<table frame="none" pgwide="1" id="event-type">
<title>Event Types</title>
<tgroup cols="3">
&cs-def;
<tbody valign="top">
<row>
<entry><constant>V4L2_EVENT_ALL</constant></entry>
<entry>0</entry>
<entry>All events. V4L2_EVENT_ALL is valid only for
VIDIOC_UNSUBSCRIBE_EVENT for unsubscribing all events at once.
</entry>
</row>
<row>
<entry><constant>V4L2_EVENT_VSYNC</constant></entry>
<entry>1</entry>
<entry>This event is triggered on the vertical sync.
This event has &v4l2-event-vsync; associated with it.
</entry>
</row>
<row>
<entry><constant>V4L2_EVENT_EOS</constant></entry>
<entry>2</entry>
<entry>This event is triggered when the end of a stream is reached.
This is typically used with MPEG decoders to report to the application
when the last of the MPEG stream has been decoded.
</entry>
</row>
<row>
<entry><constant>V4L2_EVENT_PRIVATE_START</constant></entry>
<entry>0x08000000</entry>
<entry>Base event number for driver-private events.</entry>
</row>
</tbody>
</tgroup>
</table>
<table frame="none" pgwide="1" id="v4l2-event-vsync">
<title>struct <structname>v4l2_event_vsync</structname></title>
<tgroup cols="3">
&cs-str;
<tbody valign="top">
<row>
<entry>__u8</entry>
<entry><structfield>field</structfield></entry>
<entry>The upcoming field. See &v4l2-field;.</entry>
</row>
</tbody>
</tgroup>
</table>
</refsect1>
</refentry>
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27
Documentation/DocBook/writing-an-alsa-driver.tmpl
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@ -5518,34 +5518,41 @@ struct _snd_pcm_runtime {
]]>
</programlisting>
</informalexample>
For the raw data, <structfield>size</structfield> field must be
set properly. This specifies the maximum size of the proc file access.
</para>
<para>
The callback is much more complicated than the text-file
version. You need to use a low-level I/O functions such as
The read/write callbacks of raw mode are more direct than the text mode.
You need to use a low-level I/O functions such as
<function>copy_from/to_user()</function> to transfer the
data.
<informalexample>
<programlisting>
<![CDATA[
static long my_file_io_read(struct snd_info_entry *entry,
static ssize_t my_file_io_read(struct snd_info_entry *entry,
void *file_private_data,
struct file *file,
char *buf,
unsigned long count,
unsigned long pos)
size_t count,
loff_t pos)
{
long size = count;
if (pos + size > local_max_size)
size = local_max_size - pos;
if (copy_to_user(buf, local_data + pos, size))
if (copy_to_user(buf, local_data + pos, count))
return -EFAULT;
return size;
return count;
}
]]>
</programlisting>
</informalexample>
If the size of the info entry has been set up properly,
<structfield>count</structfield> and <structfield>pos</structfield> are
guaranteed to fit within 0 and the given size.
You don't have to check the range in the callbacks unless any
other condition is required.
</para>
</chapter>

2
Documentation/DocBook/writing_usb_driver.tmpl
View File

@ -342,7 +342,7 @@ static inline void skel_delete (struct usb_skel *dev)
{
kfree (dev->bulk_in_buffer);
if (dev->bulk_out_buffer != NULL)
usb_buffer_free (dev->udev, dev->bulk_out_size,
usb_free_coherent (dev->udev, dev->bulk_out_size,
dev->bulk_out_buffer,
dev->write_urb->transfer_dma);
usb_free_urb (dev->write_urb);

4
Documentation/PCI/pci-error-recovery.txt
View File

@ -216,7 +216,7 @@ The driver should return one of the following result codes:
- PCI_ERS_RESULT_NEED_RESET
Driver returns this if it thinks the device is not
recoverable in it's current state and it needs a slot
recoverable in its current state and it needs a slot
reset to proceed.
- PCI_ERS_RESULT_DISCONNECT
@ -241,7 +241,7 @@ in working condition.
The driver is not supposed to restart normal driver I/O operations
at this point. It should limit itself to "probing" the device to
check it's recoverability status. If all is right, then the platform
check its recoverability status. If all is right, then the platform
will call resume() once all drivers have ack'd link_reset().
Result codes:

29
Documentation/PCI/pcieaer-howto.txt
View File

@ -13,7 +13,7 @@ Reporting (AER) driver and provides information on how to use it, as
well as how to enable the drivers of endpoint devices to conform with
PCI Express AER driver.
1.2 Copyright © Intel Corporation 2006.
1.2 Copyright (C) Intel Corporation 2006.
1.3 What is the PCI Express AER Driver?
@ -71,15 +71,11 @@ console. If it's a correctable error, it is outputed as a warning.
Otherwise, it is printed as an error. So users could choose different
log level to filter out correctable error messages.
Below shows an example.
+------ PCI-Express Device Error -----+
Error Severity : Uncorrected (Fatal)
PCIE Bus Error type : Transaction Layer
Unsupported Request : First
Requester ID : 0500
VendorID=8086h, DeviceID=0329h, Bus=05h, Device=00h, Function=00h
TLB Header:
04000001 00200a03 05010000 00050100
Below shows an example:
0000:50:00.0: PCIe Bus Error: severity=Uncorrected (Fatal), type=Transaction Layer, id=0500(Requester ID)
0000:50:00.0: device [8086:0329] error status/mask=00100000/00000000
0000:50:00.0: [20] Unsupported Request (First)
0000:50:00.0: TLP Header: 04000001 00200a03 05010000 00050100
In the example, 'Requester ID' means the ID of the device who sends
the error message to root port. Pls. refer to pci express specs for
@ -112,7 +108,7 @@ but the PCI Express link itself is fully functional. Fatal errors, on
the other hand, cause the link to be unreliable.
When AER is enabled, a PCI Express device will automatically send an
error message to the PCIE root port above it when the device captures
error message to the PCIe root port above it when the device captures
an error. The Root Port, upon receiving an error reporting message,
internally processes and logs the error message in its PCI Express
capability structure. Error information being logged includes storing
@ -198,8 +194,9 @@ to reset link, AER port service driver is required to provide the
function to reset link. Firstly, kernel looks for if the upstream
component has an aer driver. If it has, kernel uses the reset_link
callback of the aer driver. If the upstream component has no aer driver
and the port is downstream port, we will use the aer driver of the
root port who reports the AER error. As for upstream ports,
and the port is downstream port, we will perform a hot reset as the
default by setting the Secondary Bus Reset bit of the Bridge Control
register associated with the downstream port. As for upstream ports,
they should provide their own aer service drivers with reset_link
function. If error_detected returns PCI_ERS_RESULT_CAN_RECOVER and
reset_link returns PCI_ERS_RESULT_RECOVERED, the error handling goes
@ -253,11 +250,11 @@ cleanup uncorrectable status register. Pls. refer to section 3.3.
4. Software error injection
Debugging PCIE AER error recovery code is quite difficult because it
Debugging PCIe AER error recovery code is quite difficult because it
is hard to trigger real hardware errors. Software based error
injection can be used to fake various kinds of PCIE errors.
injection can be used to fake various kinds of PCIe errors.
First you should enable PCIE AER software error injection in kernel
First you should enable PCIe AER software error injection in kernel
configuration, that is, following item should be in your .config.
CONFIG_PCIEAER_INJECT=y or CONFIG_PCIEAER_INJECT=m

92
Documentation/RCU/stallwarn.txt
View File

@ -3,35 +3,79 @@ Using RCU's CPU Stall Detector
The CONFIG_RCU_CPU_STALL_DETECTOR kernel config parameter enables
RCU's CPU stall detector, which detects conditions that unduly delay
RCU grace periods. The stall detector's idea of what constitutes
"unduly delayed" is controlled by a pair of C preprocessor macros:
"unduly delayed" is controlled by a set of C preprocessor macros:
RCU_SECONDS_TILL_STALL_CHECK
This macro defines the period of time that RCU will wait from
the beginning of a grace period until it issues an RCU CPU
stall warning. It is normally ten seconds.
stall warning. This time period is normally ten seconds.
RCU_SECONDS_TILL_STALL_RECHECK
This macro defines the period of time that RCU will wait after
issuing a stall warning until it issues another stall warning.
It is normally set to thirty seconds.
issuing a stall warning until it issues another stall warning
for the same stall. This time period is normally set to thirty
seconds.
RCU_STALL_RAT_DELAY
The CPU stall detector tries to make the offending CPU rat on itself,
as this often gives better-quality stack traces. However, if
the offending CPU does not detect its own stall in the number
of jiffies specified by RCU_STALL_RAT_DELAY, then other CPUs will
complain. This is normally set to two jiffies.
The CPU stall detector tries to make the offending CPU print its
own warnings, as this often gives better-quality stack traces.
However, if the offending CPU does not detect its own stall in
the number of jiffies specified by RCU_STALL_RAT_DELAY, then
some other CPU will complain. This delay is normally set to
two jiffies.
The following problems can result in an RCU CPU stall warning:
When a CPU detects that it is stalling, it will print a message similar
to the following:
INFO: rcu_sched_state detected stall on CPU 5 (t=2500 jiffies)
This message indicates that CPU 5 detected that it was causing a stall,
and that the stall was affecting RCU-sched. This message will normally be
followed by a stack dump of the offending CPU. On TREE_RCU kernel builds,
RCU and RCU-sched are implemented by the same underlying mechanism,
while on TREE_PREEMPT_RCU kernel builds, RCU is instead implemented
by rcu_preempt_state.
On the other hand, if the offending CPU fails to print out a stall-warning
message quickly enough, some other CPU will print a message similar to
the following:
INFO: rcu_bh_state detected stalls on CPUs/tasks: { 3 5 } (detected by 2, 2502 jiffies)
This message indicates that CPU 2 detected that CPUs 3 and 5 were both
causing stalls, and that the stall was affecting RCU-bh. This message
will normally be followed by stack dumps for each CPU. Please note that
TREE_PREEMPT_RCU builds can be stalled by tasks as well as by CPUs,
and that the tasks will be indicated by PID, for example, "P3421".
It is even possible for a rcu_preempt_state stall to be caused by both
CPUs -and- tasks, in which case the offending CPUs and tasks will all
be called out in the list.
Finally, if the grace period ends just as the stall warning starts
printing, there will be a spurious stall-warning message:
INFO: rcu_bh_state detected stalls on CPUs/tasks: { } (detected by 4, 2502 jiffies)
This is rare, but does happen from time to time in real life.
So your kernel printed an RCU CPU stall warning. The next question is
"What caused it?" The following problems can result in RCU CPU stall
warnings:
o A CPU looping in an RCU read-side critical section.
o A CPU looping with interrupts disabled.
o A CPU looping with interrupts disabled. This condition can
result in RCU-sched and RCU-bh stalls.
o A CPU looping with preemption disabled.
o A CPU looping with preemption disabled. This condition can
result in RCU-sched stalls and, if ksoftirqd is in use, RCU-bh
stalls.
o A CPU looping with bottom halves disabled. This condition can
result in RCU-sched and RCU-bh stalls.
o For !CONFIG_PREEMPT kernels, a CPU looping anywhere in the kernel
without invoking schedule().
@ -39,20 +83,24 @@ o For !CONFIG_PREEMPT kernels, a CPU looping anywhere in the kernel
o A bug in the RCU implementation.
o A hardware failure. This is quite unlikely, but has occurred
at least once in a former life. A CPU failed in a running system,
at least once in real life. A CPU failed in a running system,
becoming unresponsive, but not causing an immediate crash.
This resulted in a series of RCU CPU stall warnings, eventually
leading the realization that the CPU had failed.
The RCU, RCU-sched, and RCU-bh implementations have CPU stall warning.
SRCU does not do so directly, but its calls to synchronize_sched() will
result in RCU-sched detecting any CPU stalls that might be occurring.
The RCU, RCU-sched, and RCU-bh implementations have CPU stall
warning. SRCU does not have its own CPU stall warnings, but its
calls to synchronize_sched() will result in RCU-sched detecting
RCU-sched-related CPU stalls. Please note that RCU only detects
CPU stalls when there is a grace period in progress. No grace period,
no CPU stall warnings.
To diagnose the cause of the stall, inspect the stack traces. The offending
function will usually be near the top of the stack. If you have a series
of stall warnings from a single extended stall, comparing the stack traces
can often help determine where the stall is occurring, which will usually
be in the function nearest the top of the stack that stays the same from
trace to trace.
To diagnose the cause of the stall, inspect the stack traces.
The offending function will usually be near the top of the stack.
If you have a series of stall warnings from a single extended stall,
comparing the stack traces can often help determine where the stall
is occurring, which will usually be in the function nearest the top of
that portion of the stack which remains the same from trace to trace.
If you can reliably trigger the stall, ftrace can be quite helpful.
RCU bugs can often be debugged with the help of CONFIG_RCU_TRACE.

10
Documentation/RCU/torture.txt
View File

@ -182,16 +182,6 @@ Similarly, sched_expedited RCU provides the following:
sched_expedited-torture: Reader Pipe: 12660320201 95875 0 0 0 0 0 0 0 0 0
sched_expedited-torture: Reader Batch: 12660424885 0 0 0 0 0 0 0 0 0 0
sched_expedited-torture: Free-Block Circulation: 1090795 1090795 1090794 1090793 1090792 1090791 1090790 1090789 1090788 1090787 0
state: -1 / 0:0 3:0 4:0
As before, the first four lines are similar to those for RCU.
The last line shows the task-migration state. The first number is
-1 if synchronize_sched_expedited() is idle, -2 if in the process of
posting wakeups to the migration kthreads, and N when waiting on CPU N.
Each of the colon-separated fields following the "/" is a CPU:state pair.
Valid states are "0" for idle, "1" for waiting for quiescent state,
"2" for passed through quiescent state, and "3" when a race with a
CPU-hotplug event forces use of the synchronize_sched() primitive.
USAGE

35
Documentation/RCU/trace.txt
View File

@ -256,23 +256,23 @@ o Each element of the form "1/1 0:127 ^0" represents one struct
The output of "cat rcu/rcu_pending" looks as follows:
rcu_sched:
0 np=255892 qsp=53936 cbr=0 cng=14417 gpc=10033 gps=24320 nf=6445 nn=146741
1 np=261224 qsp=54638 cbr=0 cng=25723 gpc=16310 gps=2849 nf=5912 nn=155792
2 np=237496 qsp=49664 cbr=0 cng=2762 gpc=45478 gps=1762 nf=1201 nn=136629
3 np=236249 qsp=48766 cbr=0 cng=286 gpc=48049 gps=1218 nf=207 nn=137723
4 np=221310 qsp=46850 cbr=0 cng=26 gpc=43161 gps=4634 nf=3529 nn=123110
5 np=237332 qsp=48449 cbr=0 cng=54 gpc=47920 gps=3252 nf=201 nn=137456
6 np=219995 qsp=46718 cbr=0 cng=50 gpc=42098 gps=6093 nf=4202 nn=120834
7 np=249893 qsp=49390 cbr=0 cng=72 gpc=38400 gps=17102 nf=41 nn=144888
0 np=255892 qsp=53936 rpq=85 cbr=0 cng=14417 gpc=10033 gps=24320 nf=6445 nn=146741
1 np=261224 qsp=54638 rpq=33 cbr=0 cng=25723 gpc=16310 gps=2849 nf=5912 nn=155792
2 np=237496 qsp=49664 rpq=23 cbr=0 cng=2762 gpc=45478 gps=1762 nf=1201 nn=136629
3 np=236249 qsp=48766 rpq=98 cbr=0 cng=286 gpc=48049 gps=1218 nf=207 nn=137723
4 np=221310 qsp=46850 rpq=7 cbr=0 cng=26 gpc=43161 gps=4634 nf=3529 nn=123110
5 np=237332 qsp=48449 rpq=9 cbr=0 cng=54 gpc=47920 gps=3252 nf=201 nn=137456
6 np=219995 qsp=46718 rpq=12 cbr=0 cng=50 gpc=42098 gps=6093 nf=4202 nn=120834
7 np=249893 qsp=49390 rpq=42 cbr=0 cng=72 gpc=38400 gps=17102 nf=41 nn=144888
rcu_bh:
0 np=146741 qsp=1419 cbr=0 cng=6 gpc=0 gps=0 nf=2 nn=145314
1 np=155792 qsp=12597 cbr=0 cng=0 gpc=4 gps=8 nf=3 nn=143180
2 np=136629 qsp=18680 cbr=0 cng=0 gpc=7 gps=6 nf=0 nn=117936
3 np=137723 qsp=2843 cbr=0 cng=0 gpc=10 gps=7 nf=0 nn=134863
4 np=123110 qsp=12433 cbr=0 cng=0 gpc=4 gps=2 nf=0 nn=110671
5 np=137456 qsp=4210 cbr=0 cng=0 gpc=6 gps=5 nf=0 nn=133235
6 np=120834 qsp=9902 cbr=0 cng=0 gpc=6 gps=3 nf=2 nn=110921
7 np=144888 qsp=26336 cbr=0 cng=0 gpc=8 gps=2 nf=0 nn=118542
0 np=146741 qsp=1419 rpq=6 cbr=0 cng=6 gpc=0 gps=0 nf=2 nn=145314
1 np=155792 qsp=12597 rpq=3 cbr=0 cng=0 gpc=4 gps=8 nf=3 nn=143180
2 np=136629 qsp=18680 rpq=1 cbr=0 cng=0 gpc=7 gps=6 nf=0 nn=117936
3 np=137723 qsp=2843 rpq=0 cbr=0 cng=0 gpc=10 gps=7 nf=0 nn=134863
4 np=123110 qsp=12433 rpq=0 cbr=0 cng=0 gpc=4 gps=2 nf=0 nn=110671
5 np=137456 qsp=4210 rpq=1 cbr=0 cng=0 gpc=6 gps=5 nf=0 nn=133235
6 np=120834 qsp=9902 rpq=2 cbr=0 cng=0 gpc=6 gps=3 nf=2 nn=110921
7 np=144888 qsp=26336 rpq=0 cbr=0 cng=0 gpc=8 gps=2 nf=0 nn=118542
As always, this is once again split into "rcu_sched" and "rcu_bh"
portions, with CONFIG_TREE_PREEMPT_RCU kernels having an additional
@ -284,6 +284,9 @@ o "np" is the number of times that __rcu_pending() has been invoked
o "qsp" is the number of times that the RCU was waiting for a
quiescent state from this CPU.
o "rpq" is the number of times that the CPU had passed through
a quiescent state, but not yet reported it to RCU.
o "cbr" is the number of times that this CPU had RCU callbacks
that had passed through a grace period, and were thus ready
to be invoked.

2
Documentation/Smack.txt
View File

@ -73,7 +73,7 @@ NOTE: Smack labels are limited to 23 characters. The attr command
If you don't do anything special all users will get the floor ("_")
label when they log in. If you do want to log in via the hacked ssh
at other labels use the attr command to set the smack value on the
home directory and it's contents.
home directory and its contents.
You can add access rules in /etc/smack/accesses. They take the form:

12
Documentation/SubmitChecklist
View File

@ -18,6 +18,8 @@ kernel patches.
2b: Passes allnoconfig, allmodconfig
2c: Builds successfully when using O=builddir
3: Builds on multiple CPU architectures by using local cross-compile tools
or some other build farm.
@ -95,3 +97,13 @@ kernel patches.
25: If any ioctl's are added by the patch, then also update
Documentation/ioctl/ioctl-number.txt.
26: If your modified source code depends on or uses any of the kernel
APIs or features that are related to the following kconfig symbols,
then test multiple builds with the related kconfig symbols disabled
and/or =m (if that option is available) [not all of these at the
same time, just various/random combinations of them]:
CONFIG_SMP, CONFIG_SYSFS, CONFIG_PROC_FS, CONFIG_INPUT, CONFIG_PCI,
CONFIG_BLOCK, CONFIG_PM, CONFIG_HOTPLUG, CONFIG_MAGIC_SYSRQ,
CONFIG_NET, CONFIG_INET=n (but latter with CONFIG_NET=y)

5
Documentation/SubmittingDrivers
View File

@ -130,6 +130,8 @@ Linux kernel master tree:
ftp.??.kernel.org:/pub/linux/kernel/...
?? == your country code, such as "us", "uk", "fr", etc.
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git
Linux kernel mailing list:
linux-kernel@vger.kernel.org
[mail majordomo@vger.kernel.org to subscribe]
@ -160,3 +162,6 @@ How to NOT write kernel driver by Arjan van de Ven:
Kernel Janitor:
http://janitor.kernelnewbies.org/
GIT, Fast Version Control System:
http://git-scm.com/

59
Documentation/acpi/apei/einj.txt Normal file
View File

@ -0,0 +1,59 @@
APEI Error INJection
~~~~~~~~~~~~~~~~~~~~
EINJ provides a hardware error injection mechanism
It is very useful for debugging and testing of other APEI and RAS features.
To use EINJ, make sure the following are enabled in your kernel
configuration:
CONFIG_DEBUG_FS
CONFIG_ACPI_APEI
CONFIG_ACPI_APEI_EINJ
The user interface of EINJ is debug file system, under the
directory apei/einj. The following files are provided.
- available_error_type
Reading this file returns the error injection capability of the
platform, that is, which error types are supported. The error type
definition is as follow, the left field is the error type value, the
right field is error description.
0x00000001 Processor Correctable
0x00000002 Processor Uncorrectable non-fatal
0x00000004 Processor Uncorrectable fatal
0x00000008 Memory Correctable
0x00000010 Memory Uncorrectable non-fatal
0x00000020 Memory Uncorrectable fatal
0x00000040 PCI Express Correctable
0x00000080 PCI Express Uncorrectable fatal
0x00000100 PCI Express Uncorrectable non-fatal
0x00000200 Platform Correctable
0x00000400 Platform Uncorrectable non-fatal
0x00000800 Platform Uncorrectable fatal
The format of file contents are as above, except there are only the
available error type lines.
- error_type
This file is used to set the error type value. The error type value
is defined in "available_error_type" description.
- error_inject
Write any integer to this file to trigger the error
injection. Before this, please specify all necessary error
parameters.
- param1
This file is used to set the first error parameter value. Effect of
parameter depends on error_type specified. For memory error, this is
physical memory address.
- param2
This file is used to set the second error parameter value. Effect of
parameter depends on error_type specified. For memory error, this is
physical memory address mask.
For more information about EINJ, please refer to ACPI specification
version 4.0, section 17.5.

2
Documentation/arm/00-INDEX
View File

@ -20,6 +20,8 @@ Samsung-S3C24XX
- S3C24XX ARM Linux Overview
Sharp-LH
- Linux on Sharp LH79524 and LH7A40X System On a Chip (SOC)
SPEAr
- ST SPEAr platform Linux Overview
VFP/
- Release notes for Linux Kernel Vector Floating Point support code
empeg/

2
Documentation/arm/SA1100/ADSBitsy
View File

@ -32,7 +32,7 @@ Notes:
- The flash on board is divided into 3 partitions.
You should be careful to use flash on board.
It's partition is different from GraphicsClient Plus and GraphicsMaster
Its partition is different from GraphicsClient Plus and GraphicsMaster
- 16bpp mode requires a different cable than what ships with the board.
Contact ADS or look through the manual to wire your own. Currently,

60
Documentation/arm/SPEAr/overview.txt Normal file
View File

@ -0,0 +1,60 @@
SPEAr ARM Linux Overview
==========================
Introduction
------------
SPEAr (Structured Processor Enhanced Architecture).
weblink : http://www.st.com/spear
The ST Microelectronics SPEAr range of ARM9/CortexA9 System-on-Chip CPUs are
supported by the 'spear' platform of ARM Linux. Currently SPEAr300,
SPEAr310, SPEAr320 and SPEAr600 SOCs are supported. Support for the SPEAr13XX
series is in progress.
Hierarchy in SPEAr is as follows:
SPEAr (Platform)
- SPEAr3XX (3XX SOC series, based on ARM9)
- SPEAr300 (SOC)
- SPEAr300_EVB (Evaluation Board)
- SPEAr310 (SOC)
- SPEAr310_EVB (Evaluation Board)
- SPEAr320 (SOC)
- SPEAr320_EVB (Evaluation Board)
- SPEAr6XX (6XX SOC series, based on ARM9)
- SPEAr600 (SOC)
- SPEAr600_EVB (Evaluation Board)
- SPEAr13XX (13XX SOC series, based on ARM CORTEXA9)
- SPEAr1300 (SOC)
Configuration
-------------
A generic configuration is provided for each machine, and can be used as the
default by
make spear600_defconfig
make spear300_defconfig
make spear310_defconfig
make spear320_defconfig
Layout
------
The common files for multiple machine families (SPEAr3XX, SPEAr6XX and
SPEAr13XX) are located in the platform code contained in arch/arm/plat-spear
with headers in plat/.
Each machine series have a directory with name arch/arm/mach-spear followed by
series name. Like mach-spear3xx, mach-spear6xx and mach-spear13xx.
Common file for machines of spear3xx family is mach-spear3xx/spear3xx.c and for
spear6xx is mach-spear6xx/spear6xx.c. mach-spear* also contain soc/machine
specific files, like spear300.c, spear310.c, spear320.c and spear600.c.
mach-spear* also contains board specific files for each machine type.
Document Author
---------------
Viresh Kumar, (c) 2010 ST Microelectronics

81
Documentation/arm/Samsung-S3C24XX/GPIO.txt
View File

@ -12,6 +12,8 @@ Introduction
of the s3c2410 GPIO system, please read the Samsung provided
data-sheet/users manual to find out the complete list.
See Documentation/arm/Samsung/GPIO.txt for the core implemetation.
GPIOLIB
-------
@ -24,8 +26,60 @@ GPIOLIB
listed below will be removed (they may be marked as __deprecated
in the near future).
- s3c2410_gpio_getpin
- s3c2410_gpio_setpin
The following functions now either have a s3c_ specific variant
or are merged into gpiolib. See the definitions in
arch/arm/plat-samsung/include/plat/gpio-cfg.h:
s3c2410_gpio_setpin() gpio_set_value() or gpio_direction_output()
s3c2410_gpio_getpin() gpio_get_value() or gpio_direction_input()
s3c2410_gpio_getirq() gpio_to_irq()
s3c2410_gpio_cfgpin() s3c_gpio_cfgpin()
s3c2410_gpio_getcfg() s3c_gpio_getcfg()
s3c2410_gpio_pullup() s3c_gpio_setpull()
GPIOLIB conversion
------------------
If you need to convert your board or driver to use gpiolib from the exiting
s3c2410 api, then here are some notes on the process.
1) If your board is exclusively using an GPIO, say to control peripheral
power, then it will require to claim the gpio with gpio_request() before
it can use it.
It is recommended to check the return value, with at least WARN_ON()
during initialisation.
2) The s3c2410_gpio_cfgpin() can be directly replaced with s3c_gpio_cfgpin()
as they have the same arguments, and can either take the pin specific
values, or the more generic special-function-number arguments.
3) s3c2410_gpio_pullup() changs have the problem that whilst the
s3c2410_gpio_pullup(x, 1) can be easily translated to the
s3c_gpio_setpull(x, S3C_GPIO_PULL_NONE), the s3c2410_gpio_pullup(x, 0)
are not so easy.
The s3c2410_gpio_pullup(x, 0) case enables the pull-up (or in the case
of some of the devices, a pull-down) and as such the new API distinguishes
between the UP and DOWN case. There is currently no 'just turn on' setting
which may be required if this becomes a problem.
4) s3c2410_gpio_setpin() can be replaced by gpio_set_value(), the old call
does not implicitly configure the relevant gpio to output. The gpio
direction should be changed before using gpio_set_value().
5) s3c2410_gpio_getpin() is replaceable by gpio_get_value() if the pin
has been set to input. It is currently unknown what the behaviour is
when using gpio_get_value() on an output pin (s3c2410_gpio_getpin
would return the value the pin is supposed to be outputting).
6) s3c2410_gpio_getirq() should be directly replacable with the
gpio_to_irq() call.
The s3c2410_gpio and gpio_ calls have always operated on the same gpio
numberspace, so there is no problem with converting the gpio numbering
between the calls.
Headers
@ -54,6 +108,11 @@ PIN Numbers
eg S3C2410_GPA(0) or S3C2410_GPF(1). These defines are used to tell
the GPIO functions which pin is to be used.
With the conversion to gpiolib, there is no longer a direct conversion
from gpio pin number to register base address as in earlier kernels. This
is due to the number space required for newer SoCs where the later
GPIOs are not contiguous.
Configuring a pin
-----------------
@ -71,6 +130,8 @@ Configuring a pin
which would turn GPA(0) into the lowest Address line A0, and set
GPE(8) to be connected to the SDIO/MMC controller's SDDAT1 line.
The s3c_gpio_cfgpin() call is a functional replacement for this call.
Reading the current configuration
---------------------------------
@ -82,6 +143,9 @@ Reading the current configuration
The return value will be from the same set of values which can be
passed to s3c2410_gpio_cfgpin().
The s3c_gpio_getcfg() call should be a functional replacement for
this call.
Configuring a pull-up resistor
------------------------------
@ -95,6 +159,10 @@ Configuring a pull-up resistor
Where the to value is zero to set the pull-up off, and 1 to enable
the specified pull-up. Any other values are currently undefined.
The s3c_gpio_setpull() offers similar functionality, but with the
ability to encode whether the pull is up or down. Currently there
is no 'just on' state, so up or down must be selected.
Getting the state of a PIN
--------------------------
@ -106,6 +174,9 @@ Getting the state of a PIN
This will return either zero or non-zero. Do not count on this
function returning 1 if the pin is set.
This call is now implemented by the relevant gpiolib calls, convert
your board or driver to use gpiolib.
Setting the state of a PIN
--------------------------
@ -117,6 +188,9 @@ Setting the state of a PIN
Which sets the given pin to the value. Use 0 to write 0, and 1 to
set the output to 1.
This call is now implemented by the relevant gpiolib calls, convert
your board or driver to use gpiolib.
Getting the IRQ number associated with a PIN
--------------------------------------------
@ -128,6 +202,9 @@ Getting the IRQ number associated with a PIN
Note, not all pins have an IRQ.
This call is now implemented by the relevant gpiolib calls, convert
your board or driver to use gpiolib.
Authour
-------

15
Documentation/arm/Samsung-S3C24XX/Overview.txt
View File

@ -8,10 +8,16 @@ Introduction
The Samsung S3C24XX range of ARM9 System-on-Chip CPUs are supported
by the 's3c2410' architecture of ARM Linux. Currently the S3C2410,
S3C2412, S3C2413, S3C2440, S3C2442 and S3C2443 devices are supported.
S3C2412, S3C2413, S3C2416 S3C2440, S3C2442, S3C2443 and S3C2450 devices
are supported.
Support for the S3C2400 and S3C24A0 series are in progress.
The S3C2416 and S3C2450 devices are very similar and S3C2450 support is
included under the arch/arm/mach-s3c2416 directory. Note, whilst core
support for these SoCs is in, work on some of the extra peripherals
and extra interrupts is still ongoing.
Configuration
-------------
@ -209,6 +215,13 @@ GPIO
Newer kernels carry GPIOLIB, and support is being moved towards
this with some of the older support in line to be removed.
As of v2.6.34, the move towards using gpiolib support is almost
complete, and very little of the old calls are left.
See Documentation/arm/Samsung-S3C24XX/GPIO.txt for the S3C24XX specific
support and Documentation/arm/Samsung/GPIO.txt for the core Samsung
implementation.
Clock Management
----------------

42
Documentation/arm/Samsung/GPIO.txt Normal file
View File

@ -0,0 +1,42 @@
Samsung GPIO implementation
===========================
Introduction
------------
This outlines the Samsung GPIO implementation and the architecture
specfic calls provided alongisde the drivers/gpio core.
S3C24XX (Legacy)
----------------
See Documentation/arm/Samsung-S3C24XX/GPIO.txt for more information
about these devices. Their implementation is being brought into line
with the core samsung implementation described in this document.
GPIOLIB integration
-------------------
The gpio implementation uses gpiolib as much as possible, only providing
specific calls for the items that require Samsung specific handling, such
as pin special-function or pull resistor control.
GPIO numbering is synchronised between the Samsung and gpiolib system.
PIN configuration
-----------------
Pin configuration is specific to the Samsung architecutre, with each SoC
registering the necessary information for the core gpio configuration
implementation to configure pins as necessary.
The s3c_gpio_cfgpin() and s3c_gpio_setpull() provide the means for a
driver or machine to change gpio configuration.
See arch/arm/plat-samsung/include/plat/gpio-cfg.h for more information
on these functions.

35
Documentation/arm/Samsung/Overview.txt
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@ -13,9 +13,10 @@ Introduction
- S3C24XX: See Documentation/arm/Samsung-S3C24XX/Overview.txt for full list
- S3C64XX: S3C6400 and S3C6410
- S5PC6440
S5PC100 and S5PC110 support is currently being merged
- S5P6440
- S5P6442
- S5PC100
- S5PC110 / S5PV210
S3C24XX Systems
@ -35,7 +36,10 @@ Configuration
unifying all the SoCs into one kernel.
s5p6440_defconfig - S5P6440 specific default configuration
s5p6442_defconfig - S5P6442 specific default configuration
s5pc100_defconfig - S5PC100 specific default configuration
s5pc110_defconfig - S5PC110 specific default configuration
s5pv210_defconfig - S5PV210 specific default configuration
Layout
@ -50,18 +54,27 @@ Layout
specific information. It contains the base clock, GPIO and device definitions
to get the system running.
plat-s3c is the s3c24xx/s3c64xx platform directory, although it is currently
involved in other builds this will be phased out once the relevant code is
moved elsewhere.
plat-s3c24xx is for s3c24xx specific builds, see the S3C24XX docs.
plat-s3c64xx is for the s3c64xx specific bits, see the S3C24XX docs.
plat-s5p is for s5p specific builds, more to be added.
plat-s5p is for s5p specific builds, and contains common support for the
S5P specific systems. Not all S5Ps use all the features in this directory
due to differences in the hardware.
Layout changes
--------------
The old plat-s3c and plat-s5pc1xx directories have been removed, with
support moved to either plat-samsung or plat-s5p as necessary. These moves
where to simplify the include and dependency issues involved with having
so many different platform directories.
It was decided to remove plat-s5pc1xx as some of the support was already
in plat-s5p or plat-samsung, with the S5PC110 support added with S5PV210
the only user was the S5PC100. The S5PC100 specific items where moved to
arch/arm/mach-s5pc100.
[ to finish ]
Port Contributors

2
Documentation/arm/Sharp-LH/ADC-LH7-Touchscreen
View File

@ -7,7 +7,7 @@ The driver only implements a four-wire touch panel protocol.
The touchscreen driver is maintenance free except for the pen-down or
touch threshold. Some resistive displays and board combinations may
require tuning of this threshold. The driver exposes some of it's
require tuning of this threshold. The driver exposes some of its
internal state in the sys filesystem. If the kernel is configured
with it, CONFIG_SYSFS, and sysfs is mounted at /sys, there will be a
directory

2
Documentation/atomic_ops.txt
View File

@ -320,7 +320,7 @@ counter decrement would not become globally visible until the
obj->active update does.
As a historical note, 32-bit Sparc used to only allow usage of
24-bits of it's atomic_t type. This was because it used 8 bits
24-bits of its atomic_t type. This was because it used 8 bits
as a spinlock for SMP safety. Sparc32 lacked a "compare and swap"
type instruction. However, 32-bit Sparc has since been moved over
to a "hash table of spinlocks" scheme, that allows the full 32-bit

2
Documentation/blackfin/bfin-gpio-notes.txt
View File

@ -43,7 +43,7 @@
void bfin_gpio_irq_free(unsigned gpio);
The request functions will record the function state for a certain pin,
the free functions will clear it's function state.
the free functions will clear its function state.
Once a pin is requested, it can't be requested again before it is freed by
previous caller, otherwise kernel will dump stacks, and the request
function fail.

6
Documentation/cachetlb.txt
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@ -5,7 +5,7 @@
This document describes the cache/tlb flushing interfaces called
by the Linux VM subsystem. It enumerates over each interface,
describes it's intended purpose, and what side effect is expected
describes its intended purpose, and what side effect is expected
after the interface is invoked.
The side effects described below are stated for a uniprocessor
@ -231,7 +231,7 @@ require a whole different set of interfaces to handle properly.
The biggest problem is that of virtual aliasing in the data cache
of a processor.
Is your port susceptible to virtual aliasing in it's D-cache?
Is your port susceptible to virtual aliasing in its D-cache?
Well, if your D-cache is virtually indexed, is larger in size than
PAGE_SIZE, and does not prevent multiple cache lines for the same
physical address from existing at once, you have this problem.
@ -249,7 +249,7 @@ one way to solve this (in particular SPARC_FLAG_MMAPSHARED).
Next, you have to solve the D-cache aliasing issue for all
other cases. Please keep in mind that fact that, for a given page
mapped into some user address space, there is always at least one more
mapping, that of the kernel in it's linear mapping starting at
mapping, that of the kernel in its linear mapping starting at
PAGE_OFFSET. So immediately, once the first user maps a given
physical page into its address space, by implication the D-cache
aliasing problem has the potential to exist since the kernel already

151
Documentation/cgroups/blkio-controller.txt
View File

@ -17,6 +17,9 @@ HOWTO
You can do a very simple testing of running two dd threads in two different
cgroups. Here is what you can do.
- Enable Block IO controller
CONFIG_BLK_CGROUP=y
- Enable group scheduling in CFQ
CONFIG_CFQ_GROUP_IOSCHED=y
@ -54,32 +57,52 @@ cgroups. Here is what you can do.
Various user visible config options
===================================
CONFIG_BLK_CGROUP
- Block IO controller.
CONFIG_DEBUG_BLK_CGROUP
- Debug help. Right now some additional stats file show up in cgroup
if this option is enabled.
CONFIG_CFQ_GROUP_IOSCHED
- Enables group scheduling in CFQ. Currently only 1 level of group
creation is allowed.
CONFIG_DEBUG_CFQ_IOSCHED
- Enables some debugging messages in blktrace. Also creates extra
cgroup file blkio.dequeue.
Config options selected automatically
=====================================
These config options are not user visible and are selected/deselected
automatically based on IO scheduler configuration.
CONFIG_BLK_CGROUP
- Block IO controller. Selected by CONFIG_CFQ_GROUP_IOSCHED.
CONFIG_DEBUG_BLK_CGROUP
- Debug help. Selected by CONFIG_DEBUG_CFQ_IOSCHED.
Details of cgroup files
=======================
- blkio.weight
- Specifies per cgroup weight.
- Specifies per cgroup weight. This is default weight of the group
on all the devices until and unless overridden by per device rule.
(See blkio.weight_device).
Currently allowed range of weights is from 100 to 1000.
- blkio.weight_device
- One can specify per cgroup per device rules using this interface.
These rules override the default value of group weight as specified
by blkio.weight.
Following is the format.
#echo dev_maj:dev_minor weight > /path/to/cgroup/blkio.weight_device
Configure weight=300 on /dev/sdb (8:16) in this cgroup
# echo 8:16 300 > blkio.weight_device
# cat blkio.weight_device
dev weight
8:16 300
Configure weight=500 on /dev/sda (8:0) in this cgroup
# echo 8:0 500 > blkio.weight_device
# cat blkio.weight_device
dev weight
8:0 500
8:16 300
Remove specific weight for /dev/sda in this cgroup
# echo 8:0 0 > blkio.weight_device
# cat blkio.weight_device
dev weight
8:16 300
- blkio.time
- disk time allocated to cgroup per device in milliseconds. First
two fields specify the major and minor number of the device and
@ -92,13 +115,105 @@ Details of cgroup files
third field specifies the number of sectors transferred by the
group to/from the device.
- blkio.io_service_bytes
- Number of bytes transferred to/from the disk by the group. These
are further divided by the type of operation - read or write, sync
or async. First two fields specify the major and minor number of the
device, third field specifies the operation type and the fourth field
specifies the number of bytes.
- blkio.io_serviced
- Number of IOs completed to/from the disk by the group. These
are further divided by the type of operation - read or write, sync
or async. First two fields specify the major and minor number of the
device, third field specifies the operation type and the fourth field
specifies the number of IOs.
- blkio.io_service_time
- Total amount of time between request dispatch and request completion
for the IOs done by this cgroup. This is in nanoseconds to make it
meaningful for flash devices too. For devices with queue depth of 1,
this time represents the actual service time. When queue_depth > 1,
that is no longer true as requests may be served out of order. This
may cause the service time for a given IO to include the service time
of multiple IOs when served out of order which may result in total
io_service_time > actual time elapsed. This time is further divided by
the type of operation - read or write, sync or async. First two fields
specify the major and minor number of the device, third field
specifies the operation type and the fourth field specifies the
io_service_time in ns.
- blkio.io_wait_time
- Total amount of time the IOs for this cgroup spent waiting in the
scheduler queues for service. This can be greater than the total time
elapsed since it is cumulative io_wait_time for all IOs. It is not a
measure of total time the cgroup spent waiting but rather a measure of
the wait_time for its individual IOs. For devices with queue_depth > 1
this metric does not include the time spent waiting for service once
the IO is dispatched to the device but till it actually gets serviced
(there might be a time lag here due to re-ordering of requests by the
device). This is in nanoseconds to make it meaningful for flash
devices too. This time is further divided by the type of operation -
read or write, sync or async. First two fields specify the major and
minor number of the device, third field specifies the operation type
and the fourth field specifies the io_wait_time in ns.
- blkio.io_merged
- Total number of bios/requests merged into requests belonging to this
cgroup. This is further divided by the type of operation - read or
write, sync or async.
- blkio.io_queued
- Total number of requests queued up at any given instant for this
cgroup. This is further divided by the type of operation - read or
write, sync or async.
- blkio.avg_queue_size
- Debugging aid only enabled if CONFIG_DEBUG_BLK_CGROUP=y.
The average queue size for this cgroup over the entire time of this
cgroup's existence. Queue size samples are taken each time one of the
queues of this cgroup gets a timeslice.
- blkio.group_wait_time
- Debugging aid only enabled if CONFIG_DEBUG_BLK_CGROUP=y.
This is the amount of time the cgroup had to wait since it became busy
(i.e., went from 0 to 1 request queued) to get a timeslice for one of
its queues. This is different from the io_wait_time which is the
cumulative total of the amount of time spent by each IO in that cgroup
waiting in the scheduler queue. This is in nanoseconds. If this is
read when the cgroup is in a waiting (for timeslice) state, the stat
will only report the group_wait_time accumulated till the last time it
got a timeslice and will not include the current delta.
- blkio.empty_time
- Debugging aid only enabled if CONFIG_DEBUG_BLK_CGROUP=y.
This is the amount of time a cgroup spends without any pending
requests when not being served, i.e., it does not include any time
spent idling for one of the queues of the cgroup. This is in
nanoseconds. If this is read when the cgroup is in an empty state,
the stat will only report the empty_time accumulated till the last
time it had a pending request and will not include the current delta.
- blkio.idle_time
- Debugging aid only enabled if CONFIG_DEBUG_BLK_CGROUP=y.
This is the amount of time spent by the IO scheduler idling for a
given cgroup in anticipation of a better request than the exising ones
from other queues/cgroups. This is in nanoseconds. If this is read
when the cgroup is in an idling state, the stat will only report the
idle_time accumulated till the last idle period and will not include
the current delta.
- blkio.dequeue
- Debugging aid only enabled if CONFIG_DEBUG_CFQ_IOSCHED=y. This
- Debugging aid only enabled if CONFIG_DEBUG_BLK_CGROUP=y. This
gives the statistics about how many a times a group was dequeued
from service tree of the device. First two fields specify the major
and minor number of the device and third field specifies the number
of times a group was dequeued from a particular device.
- blkio.reset_stats
- Writing an int to this file will result in resetting all the stats
for that cgroup.
CFQ sysfs tunable
=================
/sys/block/<disk>/queue/iosched/group_isolation

4
Documentation/cgroups/cgroups.txt
View File

@ -339,7 +339,7 @@ To mount a cgroup hierarchy with all available subsystems, type:
The "xxx" is not interpreted by the cgroup code, but will appear in
/proc/mounts so may be any useful identifying string that you like.
To mount a cgroup hierarchy with just the cpuset and numtasks
To mount a cgroup hierarchy with just the cpuset and memory
subsystems, type:
# mount -t cgroup -o cpuset,memory hier1 /dev/cgroup
@ -572,7 +572,7 @@ void cancel_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
Called when a task attach operation has failed after can_attach() has succeeded.
A subsystem whose can_attach() has some side-effects should provide this
function, so that the subsytem can implement a rollback. If not, not necessary.
function, so that the subsystem can implement a rollback. If not, not necessary.
This will be called only about subsystems whose can_attach() operation have
succeeded.

38
Documentation/cgroups/cpusets.txt
View File

@ -42,7 +42,7 @@ Nodes to a set of tasks. In this document "Memory Node" refers to
an on-line node that contains memory.
Cpusets constrain the CPU and Memory placement of tasks to only
the resources within a tasks current cpuset. They form a nested
the resources within a task's current cpuset. They form a nested
hierarchy visible in a virtual file system. These are the essential
hooks, beyond what is already present, required to manage dynamic
job placement on large systems.
@ -53,11 +53,11 @@ Documentation/cgroups/cgroups.txt.
Requests by a task, using the sched_setaffinity(2) system call to
include CPUs in its CPU affinity mask, and using the mbind(2) and
set_mempolicy(2) system calls to include Memory Nodes in its memory
policy, are both filtered through that tasks cpuset, filtering out any
policy, are both filtered through that task's cpuset, filtering out any
CPUs or Memory Nodes not in that cpuset. The scheduler will not
schedule a task on a CPU that is not allowed in its cpus_allowed
vector, and the kernel page allocator will not allocate a page on a
node that is not allowed in the requesting tasks mems_allowed vector.
node that is not allowed in the requesting task's mems_allowed vector.
User level code may create and destroy cpusets by name in the cgroup
virtual file system, manage the attributes and permissions of these
@ -121,9 +121,9 @@ Cpusets extends these two mechanisms as follows:
- Each task in the system is attached to a cpuset, via a pointer
in the task structure to a reference counted cgroup structure.
- Calls to sched_setaffinity are filtered to just those CPUs
allowed in that tasks cpuset.
allowed in that task's cpuset.
- Calls to mbind and set_mempolicy are filtered to just
those Memory Nodes allowed in that tasks cpuset.
those Memory Nodes allowed in that task's cpuset.
- The root cpuset contains all the systems CPUs and Memory
Nodes.
- For any cpuset, one can define child cpusets containing a subset
@ -141,11 +141,11 @@ into the rest of the kernel, none in performance critical paths:
- in init/main.c, to initialize the root cpuset at system boot.
- in fork and exit, to attach and detach a task from its cpuset.
- in sched_setaffinity, to mask the requested CPUs by what's
allowed in that tasks cpuset.
allowed in that task's cpuset.
- in sched.c migrate_live_tasks(), to keep migrating tasks within
the CPUs allowed by their cpuset, if possible.
- in the mbind and set_mempolicy system calls, to mask the requested
Memory Nodes by what's allowed in that tasks cpuset.
Memory Nodes by what's allowed in that task's cpuset.
- in page_alloc.c, to restrict memory to allowed nodes.
- in vmscan.c, to restrict page recovery to the current cpuset.
@ -155,7 +155,7 @@ new system calls are added for cpusets - all support for querying and
modifying cpusets is via this cpuset file system.
The /proc/<pid>/status file for each task has four added lines,
displaying the tasks cpus_allowed (on which CPUs it may be scheduled)
displaying the task's cpus_allowed (on which CPUs it may be scheduled)
and mems_allowed (on which Memory Nodes it may obtain memory),
in the two formats seen in the following example:
@ -323,17 +323,17 @@ stack segment pages of a task.
By default, both kinds of memory spreading are off, and memory
pages are allocated on the node local to where the task is running,
except perhaps as modified by the tasks NUMA mempolicy or cpuset
except perhaps as modified by the task's NUMA mempolicy or cpuset
configuration, so long as sufficient free memory pages are available.
When new cpusets are created, they inherit the memory spread settings
of their parent.
Setting memory spreading causes allocations for the affected page
or slab caches to ignore the tasks NUMA mempolicy and be spread
or slab caches to ignore the task's NUMA mempolicy and be spread
instead. Tasks using mbind() or set_mempolicy() calls to set NUMA
mempolicies will not notice any change in these calls as a result of
their containing tasks memory spread settings. If memory spreading
their containing task's memory spread settings. If memory spreading
is turned off, then the currently specified NUMA mempolicy once again
applies to memory page allocations.
@ -357,7 +357,7 @@ pages from the node returned by cpuset_mem_spread_node().
The cpuset_mem_spread_node() routine is also simple. It uses the
value of a per-task rotor cpuset_mem_spread_rotor to select the next
node in the current tasks mems_allowed to prefer for the allocation.
node in the current task's mems_allowed to prefer for the allocation.
This memory placement policy is also known (in other contexts) as
round-robin or interleave.
@ -594,7 +594,7 @@ is attached, is subtle.
If a cpuset has its Memory Nodes modified, then for each task attached
to that cpuset, the next time that the kernel attempts to allocate
a page of memory for that task, the kernel will notice the change
in the tasks cpuset, and update its per-task memory placement to
in the task's cpuset, and update its per-task memory placement to
remain within the new cpusets memory placement. If the task was using
mempolicy MPOL_BIND, and the nodes to which it was bound overlap with
its new cpuset, then the task will continue to use whatever subset
@ -603,13 +603,13 @@ was using MPOL_BIND and now none of its MPOL_BIND nodes are allowed
in the new cpuset, then the task will be essentially treated as if it
was MPOL_BIND bound to the new cpuset (even though its NUMA placement,
as queried by get_mempolicy(), doesn't change). If a task is moved
from one cpuset to another, then the kernel will adjust the tasks
from one cpuset to another, then the kernel will adjust the task's
memory placement, as above, the next time that the kernel attempts
to allocate a page of memory for that task.
If a cpuset has its 'cpuset.cpus' modified, then each task in that cpuset
will have its allowed CPU placement changed immediately. Similarly,
if a tasks pid is written to another cpusets 'cpuset.tasks' file, then its
if a task's pid is written to another cpusets 'cpuset.tasks' file, then its
allowed CPU placement is changed immediately. If such a task had been
bound to some subset of its cpuset using the sched_setaffinity() call,
the task will be allowed to run on any CPU allowed in its new cpuset,
@ -626,16 +626,16 @@ cpusets memory placement policy 'cpuset.mems' subsequently changes.
If the cpuset flag file 'cpuset.memory_migrate' is set true, then when
tasks are attached to that cpuset, any pages that task had
allocated to it on nodes in its previous cpuset are migrated
to the tasks new cpuset. The relative placement of the page within
to the task's new cpuset. The relative placement of the page within
the cpuset is preserved during these migration operations if possible.
For example if the page was on the second valid node of the prior cpuset
then the page will be placed on the second valid node of the new cpuset.
Also if 'cpuset.memory_migrate' is set true, then if that cpusets
Also if 'cpuset.memory_migrate' is set true, then if that cpuset's
'cpuset.mems' file is modified, pages allocated to tasks in that
cpuset, that were on nodes in the previous setting of 'cpuset.mems',
will be moved to nodes in the new setting of 'mems.'
Pages that were not in the tasks prior cpuset, or in the cpusets
Pages that were not in the task's prior cpuset, or in the cpuset's
prior 'cpuset.mems' setting, will not be moved.
There is an exception to the above. If hotplug functionality is used
@ -655,7 +655,7 @@ There is a second exception to the above. GFP_ATOMIC requests are
kernel internal allocations that must be satisfied, immediately.
The kernel may drop some request, in rare cases even panic, if a
GFP_ATOMIC alloc fails. If the request cannot be satisfied within
the current tasks cpuset, then we relax the cpuset, and look for
the current task's cpuset, then we relax the cpuset, and look for
memory anywhere we can find it. It's better to violate the cpuset
than stress the kernel.

2
Documentation/cgroups/memcg_test.txt
View File

@ -244,7 +244,7 @@ Under below explanation, we assume CONFIG_MEM_RES_CTRL_SWAP=y.
we have to check if OLDPAGE/NEWPAGE is a valid page after commit().
8. LRU
Each memcg has its own private LRU. Now, it's handling is under global
Each memcg has its own private LRU. Now, its handling is under global
VM's control (means that it's handled under global zone->lru_lock).
Almost all routines around memcg's LRU is called by global LRU's
list management functions under zone->lru_lock().

328
Documentation/cgroups/memory.txt
View File

@ -1,18 +1,15 @@
Memory Resource Controller
NOTE: The Memory Resource Controller has been generically been referred
to as the memory controller in this document. Do not confuse memory controller
used here with the memory controller that is used in hardware.
to as the memory controller in this document. Do not confuse memory
controller used here with the memory controller that is used in hardware.
Salient features
a. Enable control of Anonymous, Page Cache (mapped and unmapped) and
Swap Cache memory pages.
b. The infrastructure allows easy addition of other types of memory to control
c. Provides *zero overhead* for non memory controller users
d. Provides a double LRU: global memory pressure causes reclaim from the
global LRU; a cgroup on hitting a limit, reclaims from the per
cgroup LRU
(For editors)
In this document:
When we mention a cgroup (cgroupfs's directory) with memory controller,
we call it "memory cgroup". When you see git-log and source code, you'll
see patch's title and function names tend to use "memcg".
In this document, we avoid using it.
Benefits and Purpose of the memory controller
@ -33,6 +30,45 @@ d. A CD/DVD burner could control the amount of memory used by the
e. There are several other use cases, find one or use the controller just
for fun (to learn and hack on the VM subsystem).
Current Status: linux-2.6.34-mmotm(development version of 2010/April)
Features:
- accounting anonymous pages, file caches, swap caches usage and limiting them.
- private LRU and reclaim routine. (system's global LRU and private LRU
work independently from each other)
- optionally, memory+swap usage can be accounted and limited.
- hierarchical accounting
- soft limit
- moving(recharging) account at moving a task is selectable.
- usage threshold notifier
- oom-killer disable knob and oom-notifier
- Root cgroup has no limit controls.
Kernel memory and Hugepages are not under control yet. We just manage
pages on LRU. To add more controls, we have to take care of performance.
Brief summary of control files.
tasks # attach a task(thread) and show list of threads
cgroup.procs # show list of processes
cgroup.event_control # an interface for event_fd()
memory.usage_in_bytes # show current memory(RSS+Cache) usage.
memory.memsw.usage_in_bytes # show current memory+Swap usage
memory.limit_in_bytes # set/show limit of memory usage
memory.memsw.limit_in_bytes # set/show limit of memory+Swap usage
memory.failcnt # show the number of memory usage hits limits
memory.memsw.failcnt # show the number of memory+Swap hits limits
memory.max_usage_in_bytes # show max memory usage recorded
memory.memsw.usage_in_bytes # show max memory+Swap usage recorded
memory.soft_limit_in_bytes # set/show soft limit of memory usage
memory.stat # show various statistics
memory.use_hierarchy # set/show hierarchical account enabled
memory.force_empty # trigger forced move charge to parent
memory.swappiness # set/show swappiness parameter of vmscan
(See sysctl's vm.swappiness)
memory.move_charge_at_immigrate # set/show controls of moving charges
memory.oom_control # set/show oom controls.
1. History
The memory controller has a long history. A request for comments for the memory
@ -106,14 +142,14 @@ the necessary data structures and check if the cgroup that is being charged
is over its limit. If it is then reclaim is invoked on the cgroup.
More details can be found in the reclaim section of this document.
If everything goes well, a page meta-data-structure called page_cgroup is
allocated and associated with the page. This routine also adds the page to
the per cgroup LRU.
updated. page_cgroup has its own LRU on cgroup.
(*) page_cgroup structure is allocated at boot/memory-hotplug time.
2.2.1 Accounting details
All mapped anon pages (RSS) and cache pages (Page Cache) are accounted.
(some pages which never be reclaimable and will not be on global LRU
are not accounted. we just accounts pages under usual vm management.)
Some pages which are never reclaimable and will not be on the global LRU
are not accounted. We just account pages under usual VM management.
RSS pages are accounted at page_fault unless they've already been accounted
for earlier. A file page will be accounted for as Page Cache when it's
@ -121,12 +157,19 @@ inserted into inode (radix-tree). While it's mapped into the page tables of
processes, duplicate accounting is carefully avoided.
A RSS page is unaccounted when it's fully unmapped. A PageCache page is
unaccounted when it's removed from radix-tree.
unaccounted when it's removed from radix-tree. Even if RSS pages are fully
unmapped (by kswapd), they may exist as SwapCache in the system until they
are really freed. Such SwapCaches also also accounted.
A swapped-in page is not accounted until it's mapped.
Note: The kernel does swapin-readahead and read multiple swaps at once.
This means swapped-in pages may contain pages for other tasks than a task
causing page fault. So, we avoid accounting at swap-in I/O.
At page migration, accounting information is kept.
Note: we just account pages-on-lru because our purpose is to control amount
of used pages. not-on-lru pages are tend to be out-of-control from vm view.
Note: we just account pages-on-LRU because our purpose is to control amount
of used pages; not-on-LRU pages tend to be out-of-control from VM view.
2.3 Shared Page Accounting
@ -143,6 +186,7 @@ caller of swapoff rather than the users of shmem.
2.4 Swap Extension (CONFIG_CGROUP_MEM_RES_CTLR_SWAP)
Swap Extension allows you to record charge for swap. A swapped-in page is
charged back to original page allocator if possible.
@ -150,13 +194,20 @@ When swap is accounted, following files are added.
- memory.memsw.usage_in_bytes.
- memory.memsw.limit_in_bytes.
usage of mem+swap is limited by memsw.limit_in_bytes.
memsw means memory+swap. Usage of memory+swap is limited by
memsw.limit_in_bytes.
* why 'mem+swap' rather than swap.
Example: Assume a system with 4G of swap. A task which allocates 6G of memory
(by mistake) under 2G memory limitation will use all swap.
In this case, setting memsw.limit_in_bytes=3G will prevent bad use of swap.
By using memsw limit, you can avoid system OOM which can be caused by swap
shortage.
* why 'memory+swap' rather than swap.
The global LRU(kswapd) can swap out arbitrary pages. Swap-out means
to move account from memory to swap...there is no change in usage of
mem+swap. In other words, when we want to limit the usage of swap without
affecting global LRU, mem+swap limit is better than just limiting swap from
memory+swap. In other words, when we want to limit the usage of swap without
affecting global LRU, memory+swap limit is better than just limiting swap from
OS point of view.
* What happens when a cgroup hits memory.memsw.limit_in_bytes
@ -168,12 +219,12 @@ it by cgroup.
2.5 Reclaim
Each cgroup maintains a per cgroup LRU that consists of an active
and inactive list. When a cgroup goes over its limit, we first try
Each cgroup maintains a per cgroup LRU which has the same structure as
global VM. When a cgroup goes over its limit, we first try
to reclaim memory from the cgroup so as to make space for the new
pages that the cgroup has touched. If the reclaim is unsuccessful,
an OOM routine is invoked to select and kill the bulkiest task in the
cgroup.
cgroup. (See 10. OOM Control below.)
The reclaim algorithm has not been modified for cgroups, except that
pages that are selected for reclaiming come from the per cgroup LRU
@ -184,13 +235,22 @@ limits on the root cgroup.
Note2: When panic_on_oom is set to "2", the whole system will panic.
2. Locking
When oom event notifier is registered, event will be delivered.
(See oom_control section)
The memory controller uses the following hierarchy
2.6 Locking
1. zone->lru_lock is used for selecting pages to be isolated
2. mem->per_zone->lru_lock protects the per cgroup LRU (per zone)
3. lock_page_cgroup() is used to protect page->page_cgroup
lock_page_cgroup()/unlock_page_cgroup() should not be called under
mapping->tree_lock.
Other lock order is following:
PG_locked.
mm->page_table_lock
zone->lru_lock
lock_page_cgroup.
In many cases, just lock_page_cgroup() is called.
per-zone-per-cgroup LRU (cgroup's private LRU) is just guarded by
zone->lru_lock, it has no lock of its own.
3. User Interface
@ -199,6 +259,7 @@ The memory controller uses the following hierarchy
a. Enable CONFIG_CGROUPS
b. Enable CONFIG_RESOURCE_COUNTERS
c. Enable CONFIG_CGROUP_MEM_RES_CTLR
d. Enable CONFIG_CGROUP_MEM_RES_CTLR_SWAP (to use swap extension)
1. Prepare the cgroups
# mkdir -p /cgroups
@ -206,31 +267,28 @@ c. Enable CONFIG_CGROUP_MEM_RES_CTLR
2. Make the new group and move bash into it
# mkdir /cgroups/0
# echo $$ > /cgroups/0/tasks
# echo $$ > /cgroups/0/tasks
Since now we're in the 0 cgroup,
We can alter the memory limit:
Since now we're in the 0 cgroup, we can alter the memory limit:
# echo 4M > /cgroups/0/memory.limit_in_bytes
NOTE: We can use a suffix (k, K, m, M, g or G) to indicate values in kilo,
mega or gigabytes.
mega or gigabytes. (Here, Kilo, Mega, Giga are Kibibytes, Mebibytes, Gibibytes.)
NOTE: We can write "-1" to reset the *.limit_in_bytes(unlimited).
NOTE: We cannot set limits on the root cgroup any more.
# cat /cgroups/0/memory.limit_in_bytes
4194304
NOTE: The interface has now changed to display the usage in bytes
instead of pages
We can check the usage:
# cat /cgroups/0/memory.usage_in_bytes
1216512
A successful write to this file does not guarantee a successful set of
this limit to the value written into the file. This can be due to a
this limit to the value written into the file. This can be due to a
number of factors, such as rounding up to page boundaries or the total
availability of memory on the system. The user is required to re-read
availability of memory on the system. The user is required to re-read
this file after a write to guarantee the value committed by the kernel.
# echo 1 > memory.limit_in_bytes
@ -245,15 +303,23 @@ caches, RSS and Active pages/Inactive pages are shown.
4. Testing
Balbir posted lmbench, AIM9, LTP and vmmstress results [10] and [11].
Apart from that v6 has been tested with several applications and regular
daily use. The controller has also been tested on the PPC64, x86_64 and
UML platforms.
For testing features and implementation, see memcg_test.txt.
Performance test is also important. To see pure memory controller's overhead,
testing on tmpfs will give you good numbers of small overheads.
Example: do kernel make on tmpfs.
Page-fault scalability is also important. At measuring parallel
page fault test, multi-process test may be better than multi-thread
test because it has noise of shared objects/status.
But the above two are testing extreme situations.
Trying usual test under memory controller is always helpful.
4.1 Troubleshooting
Sometimes a user might find that the application under a cgroup is
terminated. There are several causes for this:
terminated by OOM killer. There are several causes for this:
1. The cgroup limit is too low (just too low to do anything useful)
2. The user is using anonymous memory and swap is turned off or too low
@ -261,23 +327,29 @@ terminated. There are several causes for this:
A sync followed by echo 1 > /proc/sys/vm/drop_caches will help get rid of
some of the pages cached in the cgroup (page cache pages).
To know what happens, disable OOM_Kill by 10. OOM Control(see below) and
seeing what happens will be helpful.
4.2 Task migration
When a task migrates from one cgroup to another, it's charge is not
When a task migrates from one cgroup to another, its charge is not
carried forward by default. The pages allocated from the original cgroup still
remain charged to it, the charge is dropped when the page is freed or
reclaimed.
Note: You can move charges of a task along with task migration. See 8.
You can move charges of a task along with task migration.
See 8. "Move charges at task migration"
4.3 Removing a cgroup
A cgroup can be removed by rmdir, but as discussed in sections 4.1 and 4.2, a
cgroup might have some charge associated with it, even though all
tasks have migrated away from it.
Such charges are freed(at default) or moved to its parent. When moved,
both of RSS and CACHES are moved to parent.
If both of them are busy, rmdir() returns -EBUSY. See 5.1 Also.
tasks have migrated away from it. (because we charge against pages, not
against tasks.)
Such charges are freed or moved to their parent. At moving, both of RSS
and CACHES are moved to parent.
rmdir() may return -EBUSY if freeing/moving fails. See 5.1 also.
Charges recorded in swap information is not updated at removal of cgroup.
Recorded information is discarded and a cgroup which uses swap (swapcache)
@ -293,10 +365,10 @@ will be charged as a new owner of it.
# echo 0 > memory.force_empty
Almost all pages tracked by this memcg will be unmapped and freed. Some of
pages cannot be freed because it's locked or in-use. Such pages are moved
to parent and this cgroup will be empty. But this may return -EBUSY in
some too busy case.
Almost all pages tracked by this memory cgroup will be unmapped and freed.
Some pages cannot be freed because they are locked or in-use. Such pages are
moved to parent and this cgroup will be empty. This may return -EBUSY if
VM is too busy to free/move all pages immediately.
Typical use case of this interface is that calling this before rmdir().
Because rmdir() moves all pages to parent, some out-of-use page caches can be
@ -306,19 +378,41 @@ will be charged as a new owner of it.
memory.stat file includes following statistics
# per-memory cgroup local status
cache - # of bytes of page cache memory.
rss - # of bytes of anonymous and swap cache memory.
mapped_file - # of bytes of mapped file (includes tmpfs/shmem)
pgpgin - # of pages paged in (equivalent to # of charging events).
pgpgout - # of pages paged out (equivalent to # of uncharging events).
active_anon - # of bytes of anonymous and swap cache memory on active
lru list.
swap - # of bytes of swap usage
inactive_anon - # of bytes of anonymous memory and swap cache memory on
inactive lru list.
active_file - # of bytes of file-backed memory on active lru list.
inactive_file - # of bytes of file-backed memory on inactive lru list.
LRU list.
active_anon - # of bytes of anonymous and swap cache memory on active
inactive LRU list.
inactive_file - # of bytes of file-backed memory on inactive LRU list.
active_file - # of bytes of file-backed memory on active LRU list.
unevictable - # of bytes of memory that cannot be reclaimed (mlocked etc).
The following additional stats are dependent on CONFIG_DEBUG_VM.
# status considering hierarchy (see memory.use_hierarchy settings)
hierarchical_memory_limit - # of bytes of memory limit with regard to hierarchy
under which the memory cgroup is
hierarchical_memsw_limit - # of bytes of memory+swap limit with regard to
hierarchy under which memory cgroup is.
total_cache - sum of all children's "cache"
total_rss - sum of all children's "rss"
total_mapped_file - sum of all children's "cache"
total_pgpgin - sum of all children's "pgpgin"
total_pgpgout - sum of all children's "pgpgout"
total_swap - sum of all children's "swap"
total_inactive_anon - sum of all children's "inactive_anon"
total_active_anon - sum of all children's "active_anon"
total_inactive_file - sum of all children's "inactive_file"
total_active_file - sum of all children's "active_file"
total_unevictable - sum of all children's "unevictable"
# The following additional stats are dependent on CONFIG_DEBUG_VM.
inactive_ratio - VM internal parameter. (see mm/page_alloc.c)
recent_rotated_anon - VM internal parameter. (see mm/vmscan.c)
@ -327,24 +421,37 @@ recent_scanned_anon - VM internal parameter. (see mm/vmscan.c)
recent_scanned_file - VM internal parameter. (see mm/vmscan.c)
Memo:
recent_rotated means recent frequency of lru rotation.
recent_scanned means recent # of scans to lru.
recent_rotated means recent frequency of LRU rotation.
recent_scanned means recent # of scans to LRU.
showing for better debug please see the code for meanings.
Note:
Only anonymous and swap cache memory is listed as part of 'rss' stat.
This should not be confused with the true 'resident set size' or the
amount of physical memory used by the cgroup. Per-cgroup rss
accounting is not done yet.
amount of physical memory used by the cgroup.
'rss + file_mapped" will give you resident set size of cgroup.
(Note: file and shmem may be shared among other cgroups. In that case,
file_mapped is accounted only when the memory cgroup is owner of page
cache.)
5.3 swappiness
Similar to /proc/sys/vm/swappiness, but affecting a hierarchy of groups only.
Following cgroups' swappiness can't be changed.
- root cgroup (uses /proc/sys/vm/swappiness).
- a cgroup which uses hierarchy and it has child cgroup.
- a cgroup which uses hierarchy and not the root of hierarchy.
Similar to /proc/sys/vm/swappiness, but affecting a hierarchy of groups only.
Following cgroups' swappiness can't be changed.
- root cgroup (uses /proc/sys/vm/swappiness).
- a cgroup which uses hierarchy and it has other cgroup(s) below it.
- a cgroup which uses hierarchy and not the root of hierarchy.
5.4 failcnt
A memory cgroup provides memory.failcnt and memory.memsw.failcnt files.
This failcnt(== failure count) shows the number of times that a usage counter
hit its limit. When a memory cgroup hits a limit, failcnt increases and
memory under it will be reclaimed.
You can reset failcnt by writing 0 to failcnt file.
# echo 0 > .../memory.failcnt
6. Hierarchy support
@ -363,13 +470,13 @@ hierarchy
In the diagram above, with hierarchical accounting enabled, all memory
usage of e, is accounted to its ancestors up until the root (i.e, c and root),
that has memory.use_hierarchy enabled. If one of the ancestors goes over its
that has memory.use_hierarchy enabled. If one of the ancestors goes over its
limit, the reclaim algorithm reclaims from the tasks in the ancestor and the
children of the ancestor.
6.1 Enabling hierarchical accounting and reclaim
The memory controller by default disables the hierarchy feature. Support
A memory cgroup by default disables the hierarchy feature. Support
can be enabled by writing 1 to memory.use_hierarchy file of the root cgroup
# echo 1 > memory.use_hierarchy
@ -379,10 +486,10 @@ The feature can be disabled by
# echo 0 > memory.use_hierarchy
NOTE1: Enabling/disabling will fail if the cgroup already has other
cgroups created below it.
cgroups created below it.
NOTE2: When panic_on_oom is set to "2", the whole system will panic in
case of an oom event in any cgroup.
case of an OOM event in any cgroup.
7. Soft limits
@ -392,7 +499,7 @@ is to allow control groups to use as much of the memory as needed, provided
a. There is no memory contention
b. They do not exceed their hard limit
When the system detects memory contention or low memory control groups
When the system detects memory contention or low memory, control groups
are pushed back to their soft limits. If the soft limit of each control
group is very high, they are pushed back as much as possible to make
sure that one control group does not starve the others of memory.
@ -406,7 +513,7 @@ it gets invoked from balance_pgdat (kswapd).
7.1 Interface
Soft limits can be setup by using the following commands (in this example we
assume a soft limit of 256 megabytes)
assume a soft limit of 256 MiB)
# echo 256M > memory.soft_limit_in_bytes
@ -442,7 +549,7 @@ Note: Charges are moved only when you move mm->owner, IOW, a leader of a thread
Note: If we cannot find enough space for the task in the destination cgroup, we
try to make space by reclaiming memory. Task migration may fail if we
cannot make enough space.
Note: It can take several seconds if you move charges in giga bytes order.
Note: It can take several seconds if you move charges much.
And if you want disable it again:
@ -451,21 +558,27 @@ And if you want disable it again:
8.2 Type of charges which can be move
Each bits of move_charge_at_immigrate has its own meaning about what type of
charges should be moved.
charges should be moved. But in any cases, it must be noted that an account of
a page or a swap can be moved only when it is charged to the task's current(old)
memory cgroup.
bit | what type of charges would be moved ?
-----+------------------------------------------------------------------------
0 | A charge of an anonymous page(or swap of it) used by the target task.
| Those pages and swaps must be used only by the target task. You must
| enable Swap Extension(see 2.4) to enable move of swap charges.
Note: Those pages and swaps must be charged to the old cgroup.
Note: More type of pages(e.g. file cache, shmem,) will be supported by other
bits in future.
-----+------------------------------------------------------------------------
1 | A charge of file pages(normal file, tmpfs file(e.g. ipc shared memory)
| and swaps of tmpfs file) mmapped by the target task. Unlike the case of
| anonymous pages, file pages(and swaps) in the range mmapped by the task
| will be moved even if the task hasn't done page fault, i.e. they might
| not be the task's "RSS", but other task's "RSS" that maps the same file.
| And mapcount of the page is ignored(the page can be moved even if
| page_mapcount(page) > 1). You must enable Swap Extension(see 2.4) to
| enable move of swap charges.
8.3 TODO
- Add support for other types of pages(e.g. file cache, shmem, etc.).
- Implement madvise(2) to let users decide the vma to be moved or not to be
moved.
- All of moving charge operations are done under cgroup_mutex. It's not good
@ -473,22 +586,61 @@ Note: More type of pages(e.g. file cache, shmem,) will be supported by other
9. Memory thresholds
Memory controler implements memory thresholds using cgroups notification
Memory cgroup implements memory thresholds using cgroups notification
API (see cgroups.txt). It allows to register multiple memory and memsw
thresholds and gets notifications when it crosses.
To register a threshold application need:
- create an eventfd using eventfd(2);
- open memory.usage_in_bytes or memory.memsw.usage_in_bytes;
- write string like "<event_fd> <memory.usage_in_bytes> <threshold>" to
cgroup.event_control.
- create an eventfd using eventfd(2);
- open memory.usage_in_bytes or memory.memsw.usage_in_bytes;
- write string like "<event_fd> <fd of memory.usage_in_bytes> <threshold>" to
cgroup.event_control.
Application will be notified through eventfd when memory usage crosses
threshold in any direction.
It's applicable for root and non-root cgroup.
10. TODO
10. OOM Control
memory.oom_control file is for OOM notification and other controls.
Memory cgroup implements OOM notifier using cgroup notification
API (See cgroups.txt). It allows to register multiple OOM notification
delivery and gets notification when OOM happens.
To register a notifier, application need:
- create an eventfd using eventfd(2)
- open memory.oom_control file
- write string like "<event_fd> <fd of memory.oom_control>" to
cgroup.event_control
Application will be notified through eventfd when OOM happens.
OOM notification doesn't work for root cgroup.
You can disable OOM-killer by writing "1" to memory.oom_control file, as:
#echo 1 > memory.oom_control
This operation is only allowed to the top cgroup of sub-hierarchy.
If OOM-killer is disabled, tasks under cgroup will hang/sleep
in memory cgroup's OOM-waitqueue when they request accountable memory.
For running them, you have to relax the memory cgroup's OOM status by
* enlarge limit or reduce usage.
To reduce usage,
* kill some tasks.
* move some tasks to other group with account migration.
* remove some files (on tmpfs?)
Then, stopped tasks will work again.
At reading, current status of OOM is shown.
oom_kill_disable 0 or 1 (if 1, oom-killer is disabled)
under_oom 0 or 1 (if 1, the memory cgroup is under OOM, tasks may
be stopped.)
11. TODO
1. Add support for accounting huge pages (as a separate controller)
2. Make per-cgroup scanner reclaim not-shared pages first

2
Documentation/connector/connector.txt
View File

@ -88,7 +88,7 @@ int cn_netlink_send(struct cn_msg *msg, u32 __groups, int gfp_mask);
int gfp_mask - GFP mask.
Note: When registering new callback user, connector core assigns
netlink group to the user which is equal to it's id.idx.
netlink group to the user which is equal to its id.idx.
/*****************************************/
Protocol description.

14
Documentation/credentials.txt
View File

@ -408,9 +408,6 @@ This should be used inside the RCU read lock, as in the following example:
...
}
A function need not get RCU read lock to use __task_cred() if it is holding a
spinlock at the time as this implicitly holds the RCU read lock.
Should it be necessary to hold another task's credentials for a long period of
time, and possibly to sleep whilst doing so, then the caller should get a
reference on them using:
@ -426,17 +423,16 @@ credentials, hiding the RCU magic from the caller:
uid_t task_uid(task) Task's real UID
uid_t task_euid(task) Task's effective UID
If the caller is holding a spinlock or the RCU read lock at the time anyway,
then:
If the caller is holding the RCU read lock at the time anyway, then:
__task_cred(task)->uid
__task_cred(task)->euid
should be used instead. Similarly, if multiple aspects of a task's credentials
need to be accessed, RCU read lock or a spinlock should be used, __task_cred()
called, the result stored in a temporary pointer and then the credential
aspects called from that before dropping the lock. This prevents the
potentially expensive RCU magic from being invoked multiple times.
need to be accessed, RCU read lock should be used, __task_cred() called, the
result stored in a temporary pointer and then the credential aspects called
from that before dropping the lock. This prevents the potentially expensive
RCU magic from being invoked multiple times.
Should some other single aspect of another task's credentials need to be
accessed, then this can be used:

29
Documentation/development-process/2.Process
View File

@ -151,7 +151,7 @@ The stages that a patch goes through are, generally:
well.
- Wider review. When the patch is getting close to ready for mainline
inclusion, it will be accepted by a relevant subsystem maintainer -
inclusion, it should be accepted by a relevant subsystem maintainer -
though this acceptance is not a guarantee that the patch will make it
all the way to the mainline. The patch will show up in the maintainer's
subsystem tree and into the staging trees (described below). When the
@ -159,6 +159,15 @@ The stages that a patch goes through are, generally:
the discovery of any problems resulting from the integration of this
patch with work being done by others.
- Please note that most maintainers also have day jobs, so merging
your patch may not be their highest priority. If your patch is
getting feedback about changes that are needed, you should either
make those changes or justify why they should not be made. If your
patch has no review complaints but is not being merged by its
appropriate subsystem or driver maintainer, you should be persistent
in updating the patch to the current kernel so that it applies cleanly
and keep sending it for review and merging.
- Merging into the mainline. Eventually, a successful patch will be
merged into the mainline repository managed by Linus Torvalds. More
comments and/or problems may surface at this time; it is important that
@ -258,12 +267,8 @@ an appropriate subsystem tree or be sent directly to Linus. In a typical
development cycle, approximately 10% of the patches going into the mainline
get there via -mm.
The current -mm patch can always be found from the front page of
http://kernel.org/
Those who want to see the current state of -mm can get the "-mm of the
moment" tree, found at:
The current -mm patch is available in the "mmotm" (-mm of the moment)
directory at:
http://userweb.kernel.org/~akpm/mmotm/
@ -298,6 +303,12 @@ volatility of linux-next tends to make it a difficult development target.
See http://lwn.net/Articles/289013/ for more information on this topic, and
stay tuned; much is still in flux where linux-next is involved.
Besides the mmotm and linux-next trees, the kernel source tree now contains
the drivers/staging/ directory and many sub-directories for drivers or
filesystems that are on their way to being added to the kernel tree
proper, but they remain in drivers/staging/ while they still need more
work.
2.5: TOOLS
@ -319,9 +330,9 @@ developers; even if they do not use it for their own work, they'll need git
to keep up with what other developers (and the mainline) are doing.
Git is now packaged by almost all Linux distributions. There is a home
page at
page at:
http://git.or.cz/
http://git-scm.com/
That page has pointers to documentation and tutorials. One should be
aware, in particular, of the Kernel Hacker's Guide to git, which has

2
Documentation/development-process/7.AdvancedTopics
View File

@ -25,7 +25,7 @@ long document in its own right. Instead, the focus here will be on how git
fits into the kernel development process in particular. Developers who
wish to come up to speed with git will find more information at:
http://git.or.cz/
http://git-scm.com/
http://www.kernel.org/pub/software/scm/git/docs/user-manual.html

2
Documentation/devices.txt
View File

@ -443,6 +443,8 @@ Your cooperation is appreciated.
231 = /dev/snapshot System memory snapshot device
232 = /dev/kvm Kernel-based virtual machine (hardware virtualization extensions)
233 = /dev/kmview View-OS A process with a view
234 = /dev/btrfs-control Btrfs control device
235 = /dev/autofs Autofs control device
240-254 Reserved for local use
255 Reserved for MISC_DYNAMIC_MINOR

2
Documentation/dvb/ci.txt
View File

@ -41,7 +41,7 @@ This application requires the following to function properly as of now.
* Cards that fall in this category
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
At present the cards that fall in this category are the Twinhan and it's
At present the cards that fall in this category are the Twinhan and its
clones, these cards are available as VVMER, Tomato, Hercules, Orange and
so on.

2
Documentation/dvb/contributors.txt
View File

@ -1,7 +1,7 @@
Thanks go to the following people for patches and contributions:
Michael Hunold <m.hunold@gmx.de>
for the initial saa7146 driver and it's recent overhaul
for the initial saa7146 driver and its recent overhaul
Christian Theiss
for his work on the initial Linux DVB driver

101
Documentation/feature-removal-schedule.txt
View File

@ -241,16 +241,6 @@ Who: Thomas Gleixner <tglx@linutronix.de>
---------------------------
What (Why):
- xt_recent: the old ipt_recent proc dir
(superseded by /proc/net/xt_recent)
When: January 2009 or Linux 2.7.0, whichever comes first
Why: Superseded by newer revisions or modules
Who: Jan Engelhardt <jengelh@computergmbh.de>
---------------------------
What: GPIO autorequest on gpio_direction_{input,output}() in gpiolib
When: February 2010
Why: All callers should use explicit gpio_request()/gpio_free().
@ -520,26 +510,21 @@ Who: Hans de Goede <hdegoede@redhat.com>
----------------------------
What: corgikbd, spitzkbd, tosakbd driver
When: 2.6.35
Files: drivers/input/keyboard/{corgi,spitz,tosa}kbd.c
Why: We now have a generic GPIO based matrix keyboard driver that
are fully capable of handling all the keys on these devices.
The original drivers manipulate the GPIO registers directly
and so are difficult to maintain.
Who: Eric Miao <eric.y.miao@gmail.com>
What: sysfs-class-rfkill state file
When: Feb 2014
Files: net/rfkill/core.c
Why: Documented as obsolete since Feb 2010. This file is limited to 3
states while the rfkill drivers can have 4 states.
Who: anybody or Florian Mickler <florian@mickler.org>
----------------------------
What: corgi_ssp and corgi_ts driver
When: 2.6.35
Files: arch/arm/mach-pxa/corgi_ssp.c, drivers/input/touchscreen/corgi_ts.c
Why: The corgi touchscreen is now deprecated in favour of the generic
ads7846.c driver. The noise reduction technique used in corgi_ts.c,
that's to wait till vsync before ADC sampling, is also integrated into
ads7846 driver now. Provided that the original driver is not generic
and is difficult to maintain, it will be removed later.
Who: Eric Miao <eric.y.miao@gmail.com>
What: sysfs-class-rfkill claim file
When: Feb 2012
Files: net/rfkill/core.c
Why: It is not possible to claim an rfkill driver since 2007. This is
Documented as obsolete since Feb 2010.
Who: anybody or Florian Mickler <florian@mickler.org>
----------------------------
@ -564,6 +549,16 @@ Who: Avi Kivity <avi@redhat.com>
----------------------------
What: xtime, wall_to_monotonic
When: 2.6.36+
Files: kernel/time/timekeeping.c include/linux/time.h
Why: Cleaning up timekeeping internal values. Please use
existing timekeeping accessor functions to access
the equivalent functionality.
Who: John Stultz <johnstul@us.ibm.com>
----------------------------
What: KVM kernel-allocated memory slots
When: July 2010
Why: Since 2.6.25, kvm supports user-allocated memory slots, which are
@ -583,15 +578,35 @@ Who: Avi Kivity <avi@redhat.com>
----------------------------
What: "acpi=ht" boot option
When: 2.6.35
Why: Useful in 2003, implementation is a hack.
Generally invoked by accident today.
Seen as doing more harm than good.
Who: Len Brown <len.brown@intel.com>
What: iwlwifi 50XX module parameters
When: 2.6.40
Why: The "..50" modules parameters were used to configure 5000 series and
up devices; different set of module parameters also available for 4965
with same functionalities. Consolidate both set into single place
in drivers/net/wireless/iwlwifi/iwl-agn.c
Who: Wey-Yi Guy <wey-yi.w.guy@intel.com>
----------------------------
What: iwl4965 alias support
When: 2.6.40
Why: Internal alias support has been present in module-init-tools for some
time, the MODULE_ALIAS("iwl4965") boilerplate aliases can be removed
with no impact.
Who: Wey-Yi Guy <wey-yi.w.guy@intel.com>
---------------------------
What: xt_NOTRACK
Files: net/netfilter/xt_NOTRACK.c
When: April 2011
Why: Superseded by xt_CT
Who: Netfilter developer team <netfilter-devel@vger.kernel.org>
---------------------------
What: video4linux /dev/vtx teletext API support
When: 2.6.35
Files: drivers/media/video/saa5246a.c drivers/media/video/saa5249.c
@ -612,3 +627,23 @@ Why: The vtx device nodes have been superseded by vbi device nodes
provided by the vtx API, then that functionality should be build
around the sliced VBI API instead.
Who: Hans Verkuil <hverkuil@xs4all.nl>
----------------------------
What: IRQF_DISABLED
When: 2.6.36
Why: The flag is a NOOP as we run interrupt handlers with interrupts disabled
Who: Thomas Gleixner <tglx@linutronix.de>
----------------------------
What: old ieee1394 subsystem (CONFIG_IEEE1394)
When: 2.6.37
Files: drivers/ieee1394/ except init_ohci1394_dma.c
Why: superseded by drivers/firewire/ (CONFIG_FIREWIRE) which offers more
features, better performance, and better security, all with smaller
and more modern code base
Who: Stefan Richter <stefanr@s5r6.in-berlin.de>
----------------------------

9
Documentation/filesystems/Locking
View File

@ -178,7 +178,7 @@ prototypes:
locking rules:
All except set_page_dirty may block
BKL PageLocked(page) i_sem
BKL PageLocked(page) i_mutex
writepage: no yes, unlocks (see below)
readpage: no yes, unlocks
sync_page: no maybe
@ -380,7 +380,7 @@ prototypes:
int (*open) (struct inode *, struct file *);
int (*flush) (struct file *);
int (*release) (struct inode *, struct file *);
int (*fsync) (struct file *, struct dentry *, int datasync);
int (*fsync) (struct file *, int datasync);
int (*aio_fsync) (struct kiocb *, int datasync);
int (*fasync) (int, struct file *, int);
int (*lock) (struct file *, int, struct file_lock *);
@ -429,8 +429,9 @@ check_flags: no
implementations. If your fs is not using generic_file_llseek, you
need to acquire and release the appropriate locks in your ->llseek().
For many filesystems, it is probably safe to acquire the inode
semaphore. Note some filesystems (i.e. remote ones) provide no
protection for i_size so you will need to use the BKL.
mutex or just to use i_size_read() instead.
Note: this does not protect the file->f_pos against concurrent modifications
since this is something the userspace has to take care about.
Note: ext2_release() was *the* source of contention on fs-intensive
loads and dropping BKL on ->release() helps to get rid of that (we still

2
Documentation/filesystems/autofs4-mount-control.txt
View File

@ -146,7 +146,7 @@ found to be inadequate, in this case. The Generic Netlink system was
used for this as raw Netlink would lead to a significant increase in
complexity. There's no question that the Generic Netlink system is an
elegant solution for common case ioctl functions but it's not a complete
replacement probably because it's primary purpose in life is to be a
replacement probably because its primary purpose in life is to be a
message bus implementation rather than specifically an ioctl replacement.
While it would be possible to work around this there is one concern
that lead to the decision to not use it. This is that the autofs

2
Documentation/filesystems/ceph.txt
View File

@ -90,7 +90,7 @@ Mount Options
Specify the IP and/or port the client should bind to locally.
There is normally not much reason to do this. If the IP is not
specified, the client's IP address is determined by looking at the
address it's connection to the monitor originates from.
address its connection to the monitor originates from.
wsize=X
Specify the maximum write size in bytes. By default there is no

2
Documentation/filesystems/dlmfs.txt
View File

@ -47,7 +47,7 @@ You'll want to start heartbeating on a volume which all the nodes in
your lockspace can access. The easiest way to do this is via
ocfs2_hb_ctl (distributed with ocfs2-tools). Right now it requires
that an OCFS2 file system be in place so that it can automatically
find it's heartbeat area, though it will eventually support heartbeat
find its heartbeat area, though it will eventually support heartbeat
against raw disks.
Please see the ocfs2_hb_ctl and mkfs.ocfs2 manual pages distributed

15
Documentation/filesystems/ext3.txt
View File

@ -59,8 +59,19 @@ commit=nrsec (*) Ext3 can be told to sync all its data and metadata
Setting it to very large values will improve
performance.
barrier=1 This enables/disables barriers. barrier=0 disables
it, barrier=1 enables it.
barrier=<0(*)|1> This enables/disables the use of write barriers in
barrier the jbd code. barrier=0 disables, barrier=1 enables.
nobarrier (*) This also requires an IO stack which can support
barriers, and if jbd gets an error on a barrier
write, it will disable again with a warning.
Write barriers enforce proper on-disk ordering
of journal commits, making volatile disk write caches
safe to use, at some performance penalty. If
your disks are battery-backed in one way or another,
disabling barriers may safely improve performance.
The mount options "barrier" and "nobarrier" can
also be used to enable or disable barriers, for
consistency with other ext3 mount options.
orlov (*) This enables the new Orlov block allocator. It is
enabled by default.

12
Documentation/filesystems/fiemap.txt
View File

@ -38,7 +38,7 @@ flags, it will return EBADR and the contents of fm_flags will contain
the set of flags which caused the error. If the kernel is compatible
with all flags passed, the contents of fm_flags will be unmodified.
It is up to userspace to determine whether rejection of a particular
flag is fatal to it's operation. This scheme is intended to allow the
flag is fatal to its operation. This scheme is intended to allow the
fiemap interface to grow in the future but without losing
compatibility with old software.
@ -56,7 +56,7 @@ If this flag is set, the kernel will sync the file before mapping extents.
* FIEMAP_FLAG_XATTR
If this flag is set, the extents returned will describe the inodes
extended attribute lookup tree, instead of it's data tree.
extended attribute lookup tree, instead of its data tree.
Extent Mapping
@ -89,7 +89,7 @@ struct fiemap_extent {
};
All offsets and lengths are in bytes and mirror those on disk. It is valid
for an extents logical offset to start before the request or it's logical
for an extents logical offset to start before the request or its logical
length to extend past the request. Unless FIEMAP_EXTENT_NOT_ALIGNED is
returned, fe_logical, fe_physical, and fe_length will be aligned to the
block size of the file system. With the exception of extents flagged as
@ -125,7 +125,7 @@ been allocated for the file yet.
* FIEMAP_EXTENT_DELALLOC
- This will also set FIEMAP_EXTENT_UNKNOWN.
Delayed allocation - while there is data for this extent, it's
Delayed allocation - while there is data for this extent, its
physical location has not been allocated yet.
* FIEMAP_EXTENT_ENCODED
@ -159,7 +159,7 @@ Data is located within a meta data block.
Data is packed into a block with data from other files.
* FIEMAP_EXTENT_UNWRITTEN
Unwritten extent - the extent is allocated but it's data has not been
Unwritten extent - the extent is allocated but its data has not been
initialized. This indicates the extent's data will be all zero if read
through the filesystem but the contents are undefined if read directly from
the device.
@ -176,7 +176,7 @@ VFS -> File System Implementation
File systems wishing to support fiemap must implement a ->fiemap callback on
their inode_operations structure. The fs ->fiemap call is responsible for
defining it's set of supported fiemap flags, and calling a helper function on
defining its set of supported fiemap flags, and calling a helper function on
each discovered extent:
struct inode_operations {

4
Documentation/filesystems/fuse.txt
View File

@ -91,7 +91,7 @@ Mount options
'default_permissions'
By default FUSE doesn't check file access permissions, the
filesystem is free to implement it's access policy or leave it to
filesystem is free to implement its access policy or leave it to
the underlying file access mechanism (e.g. in case of network
filesystems). This option enables permission checking, restricting
access based on file mode. It is usually useful together with the
@ -171,7 +171,7 @@ or may honor them by sending a reply to the _original_ request, with
the error set to EINTR.
It is also possible that there's a race between processing the
original request and it's INTERRUPT request. There are two possibilities:
original request and its INTERRUPT request. There are two possibilities:
1) The INTERRUPT request is processed before the original request is
processed

12
Documentation/filesystems/gfs2.txt
View File

@ -1,7 +1,7 @@
Global File System
------------------
http://sources.redhat.com/cluster/
http://sources.redhat.com/cluster/wiki/
GFS is a cluster file system. It allows a cluster of computers to
simultaneously use a block device that is shared between them (with FC,
@ -36,11 +36,11 @@ GFS2 is not on-disk compatible with previous versions of GFS, but it
is pretty close.
The following man pages can be found at the URL above:
fsck.gfs2 to repair a filesystem
gfs2_grow to expand a filesystem online
gfs2_jadd to add journals to a filesystem online
gfs2_tool to manipulate, examine and tune a filesystem
fsck.gfs2 to repair a filesystem
gfs2_grow to expand a filesystem online
gfs2_jadd to add journals to a filesystem online
gfs2_tool to manipulate, examine and tune a filesystem
gfs2_quota to examine and change quota values in a filesystem
gfs2_convert to convert a gfs filesystem to gfs2 in-place
mount.gfs2 to help mount(8) mount a filesystem
mkfs.gfs2 to make a filesystem
mkfs.gfs2 to make a filesystem

2
Documentation/filesystems/hpfs.txt
View File

@ -103,7 +103,7 @@ to analyze or change OS2SYS.INI.
Codepages
HPFS can contain several uppercasing tables for several codepages and each
file has a pointer to codepage it's name is in. However OS/2 was created in
file has a pointer to codepage its name is in. However OS/2 was created in
America where people don't care much about codepages and so multiple codepages
support is quite buggy. I have Czech OS/2 working in codepage 852 on my disk.
Once I booted English OS/2 working in cp 850 and I created a file on my 852

8
Documentation/filesystems/logfs.txt
View File

@ -59,7 +59,7 @@ Levels
------
Garbage collection (GC) may fail if all data is written
indiscriminately. One requirement of GC is that data is seperated
indiscriminately. One requirement of GC is that data is separated
roughly according to the distance between the tree root and the data.
Effectively that means all file data is on level 0, indirect blocks
are on levels 1, 2, 3 4 or 5 for 1x, 2x, 3x, 4x or 5x indirect blocks,
@ -67,7 +67,7 @@ respectively. Inode file data is on level 6 for the inodes and 7-11
for indirect blocks.
Each segment contains objects of a single level only. As a result,
each level requires its own seperate segment to be open for writing.
each level requires its own separate segment to be open for writing.
Inode File
----------
@ -106,9 +106,9 @@ Vim
---
By cleverly predicting the life time of data, it is possible to
seperate long-living data from short-living data and thereby reduce
separate long-living data from short-living data and thereby reduce
the GC overhead later. Each type of distinc life expectency (vim) can
have a seperate segment open for writing. Each (level, vim) tupel can
have a separate segment open for writing. Each (level, vim) tupel can
be open just once. If an open segment with unknown vim is encountered
at mount time, it is closed and ignored henceforth.

2
Documentation/filesystems/nfs/nfs41-server.txt
View File

@ -137,7 +137,7 @@ NS*| OPENATTR | OPT | | Section 18.17 |
| READ | REQ | | Section 18.22 |
| READDIR | REQ | | Section 18.23 |
| READLINK | OPT | | Section 18.24 |
NS | RECLAIM_COMPLETE | REQ | | Section 18.51 |
| RECLAIM_COMPLETE | REQ | | Section 18.51 |
| RELEASE_LOCKOWNER | MNI | | N/A |
| REMOVE | REQ | | Section 18.25 |
| RENAME | REQ | | Section 18.26 |

2
Documentation/filesystems/nfs/rpc-cache.txt
View File

@ -185,7 +185,7 @@ failed lookup meant a definite 'no'.
request/response format
-----------------------
While each cache is free to use it's own format for requests
While each cache is free to use its own format for requests
and responses over channel, the following is recommended as
appropriate and support routines are available to help:
Each request or response record should be printable ASCII

4
Documentation/filesystems/nilfs2.txt
View File

@ -50,8 +50,8 @@ NILFS2 supports the following mount options:
(*) == default
nobarrier Disables barriers.
errors=continue(*) Keep going on a filesystem error.
errors=remount-ro Remount the filesystem read-only on an error.
errors=continue Keep going on a filesystem error.
errors=remount-ro(*) Remount the filesystem read-only on an error.
errors=panic Panic and halt the machine if an error occurs.
cp=n Specify the checkpoint-number of the snapshot to be
mounted. Checkpoints and snapshots are listed by lscp

7
Documentation/filesystems/ocfs2.txt
View File

@ -80,3 +80,10 @@ user_xattr (*) Enables Extended User Attributes.
nouser_xattr Disables Extended User Attributes.
acl Enables POSIX Access Control Lists support.
noacl (*) Disables POSIX Access Control Lists support.
resv_level=2 (*) Set how agressive allocation reservations will be.
Valid values are between 0 (reservations off) to 8
(maximum space for reservations).
dir_resv_level= (*) By default, directory reservations will scale with file
reservations - users should rarely need to change this
value. If allocation reservations are turned off, this
option will have no effect.

10
Documentation/filesystems/proc.txt
View File

@ -305,7 +305,7 @@ Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
cgtime guest time of the task children in jiffies
..............................................................................
The /proc/PID/map file containing the currently mapped memory regions and
The /proc/PID/maps file containing the currently mapped memory regions and
their access permissions.
The format is:
@ -565,6 +565,10 @@ The default_smp_affinity mask applies to all non-active IRQs, which are the
IRQs which have not yet been allocated/activated, and hence which lack a
/proc/irq/[0-9]* directory.
The node file on an SMP system shows the node to which the device using the IRQ
reports itself as being attached. This hardware locality information does not
include information about any possible driver locality preference.
prof_cpu_mask specifies which CPUs are to be profiled by the system wide
profiler. Default value is ffffffff (all cpus).
@ -964,7 +968,7 @@ your system and how much traffic was routed over those devices:
...] 1375103 17405 0 0 0 0 0 0
...] 1703981 5535 0 0 0 3 0 0
In addition, each Channel Bond interface has it's own directory. For
In addition, each Channel Bond interface has its own directory. For
example, the bond0 device will have a directory called /proc/net/bond0/.
It will contain information that is specific to that bond, such as the
current slaves of the bond, the link status of the slaves, and how
@ -1361,7 +1365,7 @@ been accounted as having caused 1MB of write.
In other words: The number of bytes which this process caused to not happen,
by truncating pagecache. A task can cause "negative" IO too. If this task
truncates some dirty pagecache, some IO which another task has been accounted
for (in it's write_bytes) will not be happening. We _could_ just subtract that
for (in its write_bytes) will not be happening. We _could_ just subtract that
from the truncating task's write_bytes, but there is information loss in doing
that.

2
Documentation/filesystems/smbfs.txt
View File

@ -3,6 +3,6 @@ protocol used by Windows for Workgroups, Windows 95 and Windows NT.
Smbfs was inspired by Samba, the program written by Andrew Tridgell
that turns any Unix host into a file server for DOS or Windows clients.
Smbfs is a SMB client, but uses parts of samba for it's operation. For
Smbfs is a SMB client, but uses parts of samba for its operation. For
more info on samba, including documentation, please go to
http://www.samba.org/ and then on to your nearest mirror.

32
Documentation/filesystems/squashfs.txt
View File

@ -38,7 +38,8 @@ Hard link support: yes no
Real inode numbers: yes no
32-bit uids/gids: yes no
File creation time: yes no
Xattr and ACL support: no no
Xattr support: yes no
ACL support: no no
Squashfs compresses data, inodes and directories. In addition, inode and
directory data are highly compacted, and packed on byte boundaries. Each
@ -58,7 +59,7 @@ obtained from this site also.
3. SQUASHFS FILESYSTEM DESIGN
-----------------------------
A squashfs filesystem consists of seven parts, packed together on a byte
A squashfs filesystem consists of a maximum of eight parts, packed together on a byte
alignment:
---------------
@ -80,6 +81,9 @@ alignment:
|---------------|
| uid/gid |
| lookup table |
|---------------|
| xattr |
| table |
---------------
Compressed data blocks are written to the filesystem as files are read from
@ -192,6 +196,26 @@ This table is stored compressed into metadata blocks. A second index table is
used to locate these. This second index table for speed of access (and because
it is small) is read at mount time and cached in memory.
3.7 Xattr table
---------------
The xattr table contains extended attributes for each inode. The xattrs
for each inode are stored in a list, each list entry containing a type,
name and value field. The type field encodes the xattr prefix
("user.", "trusted." etc) and it also encodes how the name/value fields
should be interpreted. Currently the type indicates whether the value
is stored inline (in which case the value field contains the xattr value),
or if it is stored out of line (in which case the value field stores a
reference to where the actual value is stored). This allows large values
to be stored out of line improving scanning and lookup performance and it
also allows values to be de-duplicated, the value being stored once, and
all other occurences holding an out of line reference to that value.
The xattr lists are packed into compressed 8K metadata blocks.
To reduce overhead in inodes, rather than storing the on-disk
location of the xattr list inside each inode, a 32-bit xattr id
is stored. This xattr id is mapped into the location of the xattr
list using a second xattr id lookup table.
4. TODOS AND OUTSTANDING ISSUES
-------------------------------
@ -199,9 +223,7 @@ it is small) is read at mount time and cached in memory.
4.1 Todo list
-------------
Implement Xattr and ACL support. The Squashfs 4.0 filesystem layout has hooks
for these but the code has not been written. Once the code has been written
the existing layout should not require modification.
Implement ACL support.
4.2 Squashfs internal cache
---------------------------

42
Documentation/filesystems/sysfs-tagging.txt Normal file
View File

@ -0,0 +1,42 @@
Sysfs tagging
-------------
(Taken almost verbatim from Eric Biederman's netns tagging patch
commit msg)
The problem. Network devices show up in sysfs and with the network
namespace active multiple devices with the same name can show up in
the same directory, ouch!
To avoid that problem and allow existing applications in network
namespaces to see the same interface that is currently presented in
sysfs, sysfs now has tagging directory support.
By using the network namespace pointers as tags to separate out the
the sysfs directory entries we ensure that we don't have conflicts
in the directories and applications only see a limited set of
the network devices.
Each sysfs directory entry may be tagged with zero or one
namespaces. A sysfs_dirent is augmented with a void *s_ns. If a
directory entry is tagged, then sysfs_dirent->s_flags will have a
flag between KOBJ_NS_TYPE_NONE and KOBJ_NS_TYPES, and s_ns will
point to the namespace to which it belongs.
Each sysfs superblock's sysfs_super_info contains an array void
*ns[KOBJ_NS_TYPES]. When a a task in a tagging namespace
kobj_nstype first mounts sysfs, a new superblock is created. It
will be differentiated from other sysfs mounts by having its
s_fs_info->ns[kobj_nstype] set to the new namespace. Note that
through bind mounting and mounts propagation, a task can easily view
the contents of other namespaces' sysfs mounts. Therefore, when a
namespace exits, it will call kobj_ns_exit() to invalidate any
sysfs_dirent->s_ns pointers pointing to it.
Users of this interface:
- define a type in the kobj_ns_type enumeration.
- call kobj_ns_type_register() with its kobj_ns_type_operations which has
- current_ns() which returns current's namespace
- netlink_ns() which returns a socket's namespace
- initial_ns() which returns the initial namesapce
- call kobj_ns_exit() when an individual tag is no longer valid

10
Documentation/filesystems/tmpfs.txt
View File

@ -94,11 +94,19 @@ NodeList format is a comma-separated list of decimal numbers and ranges,
a range being two hyphen-separated decimal numbers, the smallest and
largest node numbers in the range. For example, mpol=bind:0-3,5,7,9-15
A memory policy with a valid NodeList will be saved, as specified, for
use at file creation time. When a task allocates a file in the file
system, the mount option memory policy will be applied with a NodeList,
if any, modified by the calling task's cpuset constraints
[See Documentation/cgroups/cpusets.txt] and any optional flags, listed
below. If the resulting NodeLists is the empty set, the effective memory
policy for the file will revert to "default" policy.
NUMA memory allocation policies have optional flags that can be used in
conjunction with their modes. These optional flags can be specified
when tmpfs is mounted by appending them to the mode before the NodeList.
See Documentation/vm/numa_memory_policy.txt for a list of all available
memory allocation policy mode flags.
memory allocation policy mode flags and their effect on memory policy.
=static is equivalent to MPOL_F_STATIC_NODES
=relative is equivalent to MPOL_F_RELATIVE_NODES

11
Documentation/filesystems/vfs.txt
View File

@ -72,7 +72,7 @@ structure (this is the kernel-side implementation of file
descriptors). The freshly allocated file structure is initialized with
a pointer to the dentry and a set of file operation member functions.
These are taken from the inode data. The open() file method is then
called so the specific filesystem implementation can do it's work. You
called so the specific filesystem implementation can do its work. You
can see that this is another switch performed by the VFS. The file
structure is placed into the file descriptor table for the process.
@ -401,11 +401,16 @@ otherwise noted.
started might not be in the page cache at the end of the
walk).
truncate: called by the VFS to change the size of a file. The
truncate: Deprecated. This will not be called if ->setsize is defined.
Called by the VFS to change the size of a file. The
i_size field of the inode is set to the desired size by the
VFS before this method is called. This method is called by
the truncate(2) system call and related functionality.
Note: ->truncate and vmtruncate are deprecated. Do not add new
instances/calls of these. Filesystems should be converted to do their
truncate sequence via ->setattr().
permission: called by the VFS to check for access rights on a POSIX-like
filesystem.
@ -729,7 +734,7 @@ struct file_operations {
int (*open) (struct inode *, struct file *);
int (*flush) (struct file *);
int (*release) (struct inode *, struct file *);
int (*fsync) (struct file *, struct dentry *, int datasync);
int (*fsync) (struct file *, int datasync);
int (*aio_fsync) (struct kiocb *, int datasync);
int (*fasync) (int, struct file *, int);
int (*lock) (struct file *, int, struct file_lock *);

816
Documentation/filesystems/xfs-delayed-logging-design.txt Normal file
View File

@ -0,0 +1,816 @@
XFS Delayed Logging Design
--------------------------
Introduction to Re-logging in XFS
---------------------------------
XFS logging is a combination of logical and physical logging. Some objects,
such as inodes and dquots, are logged in logical format where the details
logged are made up of the changes to in-core structures rather than on-disk
structures. Other objects - typically buffers - have their physical changes
logged. The reason for these differences is to reduce the amount of log space
required for objects that are frequently logged. Some parts of inodes are more
frequently logged than others, and inodes are typically more frequently logged
than any other object (except maybe the superblock buffer) so keeping the
amount of metadata logged low is of prime importance.
The reason that this is such a concern is that XFS allows multiple separate
modifications to a single object to be carried in the log at any given time.
This allows the log to avoid needing to flush each change to disk before
recording a new change to the object. XFS does this via a method called
"re-logging". Conceptually, this is quite simple - all it requires is that any
new change to the object is recorded with a *new copy* of all the existing
changes in the new transaction that is written to the log.
That is, if we have a sequence of changes A through to F, and the object was
written to disk after change D, we would see in the log the following series
of transactions, their contents and the log sequence number (LSN) of the
transaction:
Transaction Contents LSN
A A X
B A+B X+n
C A+B+C X+n+m
D A+B+C+D X+n+m+o
<object written to disk>
E E Y (> X+n+m+o)
F E+F Yٍ+p
In other words, each time an object is relogged, the new transaction contains
the aggregation of all the previous changes currently held only in the log.
This relogging technique also allows objects to be moved forward in the log so
that an object being relogged does not prevent the tail of the log from ever
moving forward. This can be seen in the table above by the changing
(increasing) LSN of each subsquent transaction - the LSN is effectively a
direct encoding of the location in the log of the transaction.
This relogging is also used to implement long-running, multiple-commit
transactions. These transaction are known as rolling transactions, and require
a special log reservation known as a permanent transaction reservation. A
typical example of a rolling transaction is the removal of extents from an
inode which can only be done at a rate of two extents per transaction because
of reservation size limitations. Hence a rolling extent removal transaction
keeps relogging the inode and btree buffers as they get modified in each
removal operation. This keeps them moving forward in the log as the operation
progresses, ensuring that current operation never gets blocked by itself if the
log wraps around.
Hence it can be seen that the relogging operation is fundamental to the correct
working of the XFS journalling subsystem. From the above description, most
people should be able to see why the XFS metadata operations writes so much to
the log - repeated operations to the same objects write the same changes to
the log over and over again. Worse is the fact that objects tend to get
dirtier as they get relogged, so each subsequent transaction is writing more
metadata into the log.
Another feature of the XFS transaction subsystem is that most transactions are
asynchronous. That is, they don't commit to disk until either a log buffer is
filled (a log buffer can hold multiple transactions) or a synchronous operation
forces the log buffers holding the transactions to disk. This means that XFS is
doing aggregation of transactions in memory - batching them, if you like - to
minimise the impact of the log IO on transaction throughput.
The limitation on asynchronous transaction throughput is the number and size of
log buffers made available by the log manager. By default there are 8 log
buffers available and the size of each is 32kB - the size can be increased up
to 256kB by use of a mount option.
Effectively, this gives us the maximum bound of outstanding metadata changes
that can be made to the filesystem at any point in time - if all the log
buffers are full and under IO, then no more transactions can be committed until
the current batch completes. It is now common for a single current CPU core to
be to able to issue enough transactions to keep the log buffers full and under
IO permanently. Hence the XFS journalling subsystem can be considered to be IO
bound.
Delayed Logging: Concepts
-------------------------
The key thing to note about the asynchronous logging combined with the
relogging technique XFS uses is that we can be relogging changed objects
multiple times before they are committed to disk in the log buffers. If we
return to the previous relogging example, it is entirely possible that
transactions A through D are committed to disk in the same log buffer.
That is, a single log buffer may contain multiple copies of the same object,
but only one of those copies needs to be there - the last one "D", as it
contains all the changes from the previous changes. In other words, we have one
necessary copy in the log buffer, and three stale copies that are simply
wasting space. When we are doing repeated operations on the same set of
objects, these "stale objects" can be over 90% of the space used in the log
buffers. It is clear that reducing the number of stale objects written to the
log would greatly reduce the amount of metadata we write to the log, and this
is the fundamental goal of delayed logging.
From a conceptual point of view, XFS is already doing relogging in memory (where
memory == log buffer), only it is doing it extremely inefficiently. It is using
logical to physical formatting to do the relogging because there is no
infrastructure to keep track of logical changes in memory prior to physically
formatting the changes in a transaction to the log buffer. Hence we cannot avoid
accumulating stale objects in the log buffers.
Delayed logging is the name we've given to keeping and tracking transactional
changes to objects in memory outside the log buffer infrastructure. Because of
the relogging concept fundamental to the XFS journalling subsystem, this is
actually relatively easy to do - all the changes to logged items are already
tracked in the current infrastructure. The big problem is how to accumulate
them and get them to the log in a consistent, recoverable manner.
Describing the problems and how they have been solved is the focus of this
document.
One of the key changes that delayed logging makes to the operation of the
journalling subsystem is that it disassociates the amount of outstanding
metadata changes from the size and number of log buffers available. In other
words, instead of there only being a maximum of 2MB of transaction changes not
written to the log at any point in time, there may be a much greater amount
being accumulated in memory. Hence the potential for loss of metadata on a
crash is much greater than for the existing logging mechanism.
It should be noted that this does not change the guarantee that log recovery
will result in a consistent filesystem. What it does mean is that as far as the
recovered filesystem is concerned, there may be many thousands of transactions
that simply did not occur as a result of the crash. This makes it even more
important that applications that care about their data use fsync() where they
need to ensure application level data integrity is maintained.
It should be noted that delayed logging is not an innovative new concept that
warrants rigorous proofs to determine whether it is correct or not. The method
of accumulating changes in memory for some period before writing them to the
log is used effectively in many filesystems including ext3 and ext4. Hence
no time is spent in this document trying to convince the reader that the
concept is sound. Instead it is simply considered a "solved problem" and as
such implementing it in XFS is purely an exercise in software engineering.
The fundamental requirements for delayed logging in XFS are simple:
1. Reduce the amount of metadata written to the log by at least
an order of magnitude.
2. Supply sufficient statistics to validate Requirement #1.
3. Supply sufficient new tracing infrastructure to be able to debug
problems with the new code.
4. No on-disk format change (metadata or log format).
5. Enable and disable with a mount option.
6. No performance regressions for synchronous transaction workloads.
Delayed Logging: Design
-----------------------
Storing Changes
The problem with accumulating changes at a logical level (i.e. just using the
existing log item dirty region tracking) is that when it comes to writing the
changes to the log buffers, we need to ensure that the object we are formatting
is not changing while we do this. This requires locking the object to prevent
concurrent modification. Hence flushing the logical changes to the log would
require us to lock every object, format them, and then unlock them again.
This introduces lots of scope for deadlocks with transactions that are already
running. For example, a transaction has object A locked and modified, but needs
the delayed logging tracking lock to commit the transaction. However, the
flushing thread has the delayed logging tracking lock already held, and is
trying to get the lock on object A to flush it to the log buffer. This appears
to be an unsolvable deadlock condition, and it was solving this problem that
was the barrier to implementing delayed logging for so long.
The solution is relatively simple - it just took a long time to recognise it.
Put simply, the current logging code formats the changes to each item into an
vector array that points to the changed regions in the item. The log write code
simply copies the memory these vectors point to into the log buffer during
transaction commit while the item is locked in the transaction. Instead of
using the log buffer as the destination of the formatting code, we can use an
allocated memory buffer big enough to fit the formatted vector.
If we then copy the vector into the memory buffer and rewrite the vector to
point to the memory buffer rather than the object itself, we now have a copy of
the changes in a format that is compatible with the log buffer writing code.
that does not require us to lock the item to access. This formatting and
rewriting can all be done while the object is locked during transaction commit,
resulting in a vector that is transactionally consistent and can be accessed
without needing to lock the owning item.
Hence we avoid the need to lock items when we need to flush outstanding
asynchronous transactions to the log. The differences between the existing
formatting method and the delayed logging formatting can be seen in the
diagram below.
Current format log vector:
Object +---------------------------------------------+
Vector 1 +----+
Vector 2 +----+
Vector 3 +----------+
After formatting:
Log Buffer +-V1-+-V2-+----V3----+
Delayed logging vector:
Object +---------------------------------------------+
Vector 1 +----+
Vector 2 +----+
Vector 3 +----------+
After formatting:
Memory Buffer +-V1-+-V2-+----V3----+
Vector 1 +----+
Vector 2 +----+
Vector 3 +----------+
The memory buffer and associated vector need to be passed as a single object,
but still need to be associated with the parent object so if the object is
relogged we can replace the current memory buffer with a new memory buffer that
contains the latest changes.
The reason for keeping the vector around after we've formatted the memory
buffer is to support splitting vectors across log buffer boundaries correctly.
If we don't keep the vector around, we do not know where the region boundaries
are in the item, so we'd need a new encapsulation method for regions in the log
buffer writing (i.e. double encapsulation). This would be an on-disk format
change and as such is not desirable. It also means we'd have to write the log
region headers in the formatting stage, which is problematic as there is per
region state that needs to be placed into the headers during the log write.
Hence we need to keep the vector, but by attaching the memory buffer to it and
rewriting the vector addresses to point at the memory buffer we end up with a
self-describing object that can be passed to the log buffer write code to be
handled in exactly the same manner as the existing log vectors are handled.
Hence we avoid needing a new on-disk format to handle items that have been
relogged in memory.
Tracking Changes
Now that we can record transactional changes in memory in a form that allows
them to be used without limitations, we need to be able to track and accumulate
them so that they can be written to the log at some later point in time. The
log item is the natural place to store this vector and buffer, and also makes sense
to be the object that is used to track committed objects as it will always
exist once the object has been included in a transaction.
The log item is already used to track the log items that have been written to
the log but not yet written to disk. Such log items are considered "active"
and as such are stored in the Active Item List (AIL) which is a LSN-ordered
double linked list. Items are inserted into this list during log buffer IO
completion, after which they are unpinned and can be written to disk. An object
that is in the AIL can be relogged, which causes the object to be pinned again
and then moved forward in the AIL when the log buffer IO completes for that
transaction.
Essentially, this shows that an item that is in the AIL can still be modified
and relogged, so any tracking must be separate to the AIL infrastructure. As
such, we cannot reuse the AIL list pointers for tracking committed items, nor
can we store state in any field that is protected by the AIL lock. Hence the
committed item tracking needs it's own locks, lists and state fields in the log
item.
Similar to the AIL, tracking of committed items is done through a new list
called the Committed Item List (CIL). The list tracks log items that have been
committed and have formatted memory buffers attached to them. It tracks objects
in transaction commit order, so when an object is relogged it is removed from
it's place in the list and re-inserted at the tail. This is entirely arbitrary
and done to make it easy for debugging - the last items in the list are the
ones that are most recently modified. Ordering of the CIL is not necessary for
transactional integrity (as discussed in the next section) so the ordering is
done for convenience/sanity of the developers.
Delayed Logging: Checkpoints
When we have a log synchronisation event, commonly known as a "log force",
all the items in the CIL must be written into the log via the log buffers.
We need to write these items in the order that they exist in the CIL, and they
need to be written as an atomic transaction. The need for all the objects to be
written as an atomic transaction comes from the requirements of relogging and
log replay - all the changes in all the objects in a given transaction must
either be completely replayed during log recovery, or not replayed at all. If
a transaction is not replayed because it is not complete in the log, then
no later transactions should be replayed, either.
To fulfill this requirement, we need to write the entire CIL in a single log
transaction. Fortunately, the XFS log code has no fixed limit on the size of a
transaction, nor does the log replay code. The only fundamental limit is that
the transaction cannot be larger than just under half the size of the log. The
reason for this limit is that to find the head and tail of the log, there must
be at least one complete transaction in the log at any given time. If a
transaction is larger than half the log, then there is the possibility that a
crash during the write of a such a transaction could partially overwrite the
only complete previous transaction in the log. This will result in a recovery
failure and an inconsistent filesystem and hence we must enforce the maximum
size of a checkpoint to be slightly less than a half the log.
Apart from this size requirement, a checkpoint transaction looks no different
to any other transaction - it contains a transaction header, a series of
formatted log items and a commit record at the tail. From a recovery
perspective, the checkpoint transaction is also no different - just a lot
bigger with a lot more items in it. The worst case effect of this is that we
might need to tune the recovery transaction object hash size.
Because the checkpoint is just another transaction and all the changes to log
items are stored as log vectors, we can use the existing log buffer writing
code to write the changes into the log. To do this efficiently, we need to
minimise the time we hold the CIL locked while writing the checkpoint
transaction. The current log write code enables us to do this easily with the
way it separates the writing of the transaction contents (the log vectors) from
the transaction commit record, but tracking this requires us to have a
per-checkpoint context that travels through the log write process through to
checkpoint completion.
Hence a checkpoint has a context that tracks the state of the current
checkpoint from initiation to checkpoint completion. A new context is initiated
at the same time a checkpoint transaction is started. That is, when we remove
all the current items from the CIL during a checkpoint operation, we move all
those changes into the current checkpoint context. We then initialise a new
context and attach that to the CIL for aggregation of new transactions.
This allows us to unlock the CIL immediately after transfer of all the
committed items and effectively allow new transactions to be issued while we
are formatting the checkpoint into the log. It also allows concurrent
checkpoints to be written into the log buffers in the case of log force heavy
workloads, just like the existing transaction commit code does. This, however,
requires that we strictly order the commit records in the log so that
checkpoint sequence order is maintained during log replay.
To ensure that we can be writing an item into a checkpoint transaction at
the same time another transaction modifies the item and inserts the log item
into the new CIL, then checkpoint transaction commit code cannot use log items
to store the list of log vectors that need to be written into the transaction.
Hence log vectors need to be able to be chained together to allow them to be
detatched from the log items. That is, when the CIL is flushed the memory
buffer and log vector attached to each log item needs to be attached to the
checkpoint context so that the log item can be released. In diagrammatic form,
the CIL would look like this before the flush:
CIL Head
|
V
Log Item <-> log vector 1 -> memory buffer
| -> vector array
V
Log Item <-> log vector 2 -> memory buffer
| -> vector array
V
......
|
V
Log Item <-> log vector N-1 -> memory buffer
| -> vector array
V
Log Item <-> log vector N -> memory buffer
-> vector array
And after the flush the CIL head is empty, and the checkpoint context log
vector list would look like:
Checkpoint Context
|
V
log vector 1 -> memory buffer
| -> vector array
| -> Log Item
V
log vector 2 -> memory buffer
| -> vector array
| -> Log Item
V
......
|
V
log vector N-1 -> memory buffer
| -> vector array
| -> Log Item
V
log vector N -> memory buffer
-> vector array
-> Log Item
Once this transfer is done, the CIL can be unlocked and new transactions can
start, while the checkpoint flush code works over the log vector chain to
commit the checkpoint.
Once the checkpoint is written into the log buffers, the checkpoint context is
attached to the log buffer that the commit record was written to along with a
completion callback. Log IO completion will call that callback, which can then
run transaction committed processing for the log items (i.e. insert into AIL
and unpin) in the log vector chain and then free the log vector chain and
checkpoint context.
Discussion Point: I am uncertain as to whether the log item is the most
efficient way to track vectors, even though it seems like the natural way to do
it. The fact that we walk the log items (in the CIL) just to chain the log
vectors and break the link between the log item and the log vector means that
we take a cache line hit for the log item list modification, then another for
the log vector chaining. If we track by the log vectors, then we only need to
break the link between the log item and the log vector, which means we should
dirty only the log item cachelines. Normally I wouldn't be concerned about one
vs two dirty cachelines except for the fact I've seen upwards of 80,000 log
vectors in one checkpoint transaction. I'd guess this is a "measure and
compare" situation that can be done after a working and reviewed implementation
is in the dev tree....
Delayed Logging: Checkpoint Sequencing
One of the key aspects of the XFS transaction subsystem is that it tags
committed transactions with the log sequence number of the transaction commit.
This allows transactions to be issued asynchronously even though there may be
future operations that cannot be completed until that transaction is fully
committed to the log. In the rare case that a dependent operation occurs (e.g.
re-using a freed metadata extent for a data extent), a special, optimised log
force can be issued to force the dependent transaction to disk immediately.
To do this, transactions need to record the LSN of the commit record of the
transaction. This LSN comes directly from the log buffer the transaction is
written into. While this works just fine for the existing transaction
mechanism, it does not work for delayed logging because transactions are not
written directly into the log buffers. Hence some other method of sequencing
transactions is required.
As discussed in the checkpoint section, delayed logging uses per-checkpoint
contexts, and as such it is simple to assign a sequence number to each
checkpoint. Because the switching of checkpoint contexts must be done
atomically, it is simple to ensure that each new context has a monotonically
increasing sequence number assigned to it without the need for an external
atomic counter - we can just take the current context sequence number and add
one to it for the new context.
Then, instead of assigning a log buffer LSN to the transaction commit LSN
during the commit, we can assign the current checkpoint sequence. This allows
operations that track transactions that have not yet completed know what
checkpoint sequence needs to be committed before they can continue. As a
result, the code that forces the log to a specific LSN now needs to ensure that
the log forces to a specific checkpoint.
To ensure that we can do this, we need to track all the checkpoint contexts
that are currently committing to the log. When we flush a checkpoint, the
context gets added to a "committing" list which can be searched. When a
checkpoint commit completes, it is removed from the committing list. Because
the checkpoint context records the LSN of the commit record for the checkpoint,
we can also wait on the log buffer that contains the commit record, thereby
using the existing log force mechanisms to execute synchronous forces.
It should be noted that the synchronous forces may need to be extended with
mitigation algorithms similar to the current log buffer code to allow
aggregation of multiple synchronous transactions if there are already
synchronous transactions being flushed. Investigation of the performance of the
current design is needed before making any decisions here.
The main concern with log forces is to ensure that all the previous checkpoints
are also committed to disk before the one we need to wait for. Therefore we
need to check that all the prior contexts in the committing list are also
complete before waiting on the one we need to complete. We do this
synchronisation in the log force code so that we don't need to wait anywhere
else for such serialisation - it only matters when we do a log force.
The only remaining complexity is that a log force now also has to handle the
case where the forcing sequence number is the same as the current context. That
is, we need to flush the CIL and potentially wait for it to complete. This is a
simple addition to the existing log forcing code to check the sequence numbers
and push if required. Indeed, placing the current sequence checkpoint flush in
the log force code enables the current mechanism for issuing synchronous
transactions to remain untouched (i.e. commit an asynchronous transaction, then
force the log at the LSN of that transaction) and so the higher level code
behaves the same regardless of whether delayed logging is being used or not.
Delayed Logging: Checkpoint Log Space Accounting
The big issue for a checkpoint transaction is the log space reservation for the
transaction. We don't know how big a checkpoint transaction is going to be
ahead of time, nor how many log buffers it will take to write out, nor the
number of split log vector regions are going to be used. We can track the
amount of log space required as we add items to the commit item list, but we
still need to reserve the space in the log for the checkpoint.
A typical transaction reserves enough space in the log for the worst case space
usage of the transaction. The reservation accounts for log record headers,
transaction and region headers, headers for split regions, buffer tail padding,
etc. as well as the actual space for all the changed metadata in the
transaction. While some of this is fixed overhead, much of it is dependent on
the size of the transaction and the number of regions being logged (the number
of log vectors in the transaction).
An example of the differences would be logging directory changes versus logging
inode changes. If you modify lots of inode cores (e.g. chmod -R g+w *), then
there are lots of transactions that only contain an inode core and an inode log
format structure. That is, two vectors totaling roughly 150 bytes. If we modify
10,000 inodes, we have about 1.5MB of metadata to write in 20,000 vectors. Each
vector is 12 bytes, so the total to be logged is approximately 1.75MB. In
comparison, if we are logging full directory buffers, they are typically 4KB
each, so we in 1.5MB of directory buffers we'd have roughly 400 buffers and a
buffer format structure for each buffer - roughly 800 vectors or 1.51MB total
space. From this, it should be obvious that a static log space reservation is
not particularly flexible and is difficult to select the "optimal value" for
all workloads.
Further, if we are going to use a static reservation, which bit of the entire
reservation does it cover? We account for space used by the transaction
reservation by tracking the space currently used by the object in the CIL and
then calculating the increase or decrease in space used as the object is
relogged. This allows for a checkpoint reservation to only have to account for
log buffer metadata used such as log header records.
However, even using a static reservation for just the log metadata is
problematic. Typically log record headers use at least 16KB of log space per
1MB of log space consumed (512 bytes per 32k) and the reservation needs to be
large enough to handle arbitrary sized checkpoint transactions. This
reservation needs to be made before the checkpoint is started, and we need to
be able to reserve the space without sleeping. For a 8MB checkpoint, we need a
reservation of around 150KB, which is a non-trivial amount of space.
A static reservation needs to manipulate the log grant counters - we can take a
permanent reservation on the space, but we still need to make sure we refresh
the write reservation (the actual space available to the transaction) after
every checkpoint transaction completion. Unfortunately, if this space is not
available when required, then the regrant code will sleep waiting for it.
The problem with this is that it can lead to deadlocks as we may need to commit
checkpoints to be able to free up log space (refer back to the description of
rolling transactions for an example of this). Hence we *must* always have
space available in the log if we are to use static reservations, and that is
very difficult and complex to arrange. It is possible to do, but there is a
simpler way.
The simpler way of doing this is tracking the entire log space used by the
items in the CIL and using this to dynamically calculate the amount of log
space required by the log metadata. If this log metadata space changes as a
result of a transaction commit inserting a new memory buffer into the CIL, then
the difference in space required is removed from the transaction that causes
the change. Transactions at this level will *always* have enough space
available in their reservation for this as they have already reserved the
maximal amount of log metadata space they require, and such a delta reservation
will always be less than or equal to the maximal amount in the reservation.
Hence we can grow the checkpoint transaction reservation dynamically as items
are added to the CIL and avoid the need for reserving and regranting log space
up front. This avoids deadlocks and removes a blocking point from the
checkpoint flush code.
As mentioned early, transactions can't grow to more than half the size of the
log. Hence as part of the reservation growing, we need to also check the size
of the reservation against the maximum allowed transaction size. If we reach
the maximum threshold, we need to push the CIL to the log. This is effectively
a "background flush" and is done on demand. This is identical to
a CIL push triggered by a log force, only that there is no waiting for the
checkpoint commit to complete. This background push is checked and executed by
transaction commit code.
If the transaction subsystem goes idle while we still have items in the CIL,
they will be flushed by the periodic log force issued by the xfssyncd. This log
force will push the CIL to disk, and if the transaction subsystem stays idle,
allow the idle log to be covered (effectively marked clean) in exactly the same
manner that is done for the existing logging method. A discussion point is
whether this log force needs to be done more frequently than the current rate
which is once every 30s.
Delayed Logging: Log Item Pinning
Currently log items are pinned during transaction commit while the items are
still locked. This happens just after the items are formatted, though it could
be done any time before the items are unlocked. The result of this mechanism is
that items get pinned once for every transaction that is committed to the log
buffers. Hence items that are relogged in the log buffers will have a pin count
for every outstanding transaction they were dirtied in. When each of these
transactions is completed, they will unpin the item once. As a result, the item
only becomes unpinned when all the transactions complete and there are no
pending transactions. Thus the pinning and unpinning of a log item is symmetric
as there is a 1:1 relationship with transaction commit and log item completion.
For delayed logging, however, we have an assymetric transaction commit to
completion relationship. Every time an object is relogged in the CIL it goes
through the commit process without a corresponding completion being registered.
That is, we now have a many-to-one relationship between transaction commit and
log item completion. The result of this is that pinning and unpinning of the
log items becomes unbalanced if we retain the "pin on transaction commit, unpin
on transaction completion" model.
To keep pin/unpin symmetry, the algorithm needs to change to a "pin on
insertion into the CIL, unpin on checkpoint completion". In other words, the
pinning and unpinning becomes symmetric around a checkpoint context. We have to
pin the object the first time it is inserted into the CIL - if it is already in
the CIL during a transaction commit, then we do not pin it again. Because there
can be multiple outstanding checkpoint contexts, we can still see elevated pin
counts, but as each checkpoint completes the pin count will retain the correct
value according to it's context.
Just to make matters more slightly more complex, this checkpoint level context
for the pin count means that the pinning of an item must take place under the
CIL commit/flush lock. If we pin the object outside this lock, we cannot
guarantee which context the pin count is associated with. This is because of
the fact pinning the item is dependent on whether the item is present in the
current CIL or not. If we don't pin the CIL first before we check and pin the
object, we have a race with CIL being flushed between the check and the pin
(or not pinning, as the case may be). Hence we must hold the CIL flush/commit
lock to guarantee that we pin the items correctly.
Delayed Logging: Concurrent Scalability
A fundamental requirement for the CIL is that accesses through transaction
commits must scale to many concurrent commits. The current transaction commit
code does not break down even when there are transactions coming from 2048
processors at once. The current transaction code does not go any faster than if
there was only one CPU using it, but it does not slow down either.
As a result, the delayed logging transaction commit code needs to be designed
for concurrency from the ground up. It is obvious that there are serialisation
points in the design - the three important ones are:
1. Locking out new transaction commits while flushing the CIL
2. Adding items to the CIL and updating item space accounting
3. Checkpoint commit ordering
Looking at the transaction commit and CIL flushing interactions, it is clear
that we have a many-to-one interaction here. That is, the only restriction on
the number of concurrent transactions that can be trying to commit at once is
the amount of space available in the log for their reservations. The practical
limit here is in the order of several hundred concurrent transactions for a
128MB log, which means that it is generally one per CPU in a machine.
The amount of time a transaction commit needs to hold out a flush is a
relatively long period of time - the pinning of log items needs to be done
while we are holding out a CIL flush, so at the moment that means it is held
across the formatting of the objects into memory buffers (i.e. while memcpy()s
are in progress). Ultimately a two pass algorithm where the formatting is done
separately to the pinning of objects could be used to reduce the hold time of
the transaction commit side.
Because of the number of potential transaction commit side holders, the lock
really needs to be a sleeping lock - if the CIL flush takes the lock, we do not
want every other CPU in the machine spinning on the CIL lock. Given that
flushing the CIL could involve walking a list of tens of thousands of log
items, it will get held for a significant time and so spin contention is a
significant concern. Preventing lots of CPUs spinning doing nothing is the
main reason for choosing a sleeping lock even though nothing in either the
transaction commit or CIL flush side sleeps with the lock held.
It should also be noted that CIL flushing is also a relatively rare operation
compared to transaction commit for asynchronous transaction workloads - only
time will tell if using a read-write semaphore for exclusion will limit
transaction commit concurrency due to cache line bouncing of the lock on the
read side.
The second serialisation point is on the transaction commit side where items
are inserted into the CIL. Because transactions can enter this code
concurrently, the CIL needs to be protected separately from the above
commit/flush exclusion. It also needs to be an exclusive lock but it is only
held for a very short time and so a spin lock is appropriate here. It is
possible that this lock will become a contention point, but given the short
hold time once per transaction I think that contention is unlikely.
The final serialisation point is the checkpoint commit record ordering code
that is run as part of the checkpoint commit and log force sequencing. The code
path that triggers a CIL flush (i.e. whatever triggers the log force) will enter
an ordering loop after writing all the log vectors into the log buffers but
before writing the commit record. This loop walks the list of committing
checkpoints and needs to block waiting for checkpoints to complete their commit
record write. As a result it needs a lock and a wait variable. Log force
sequencing also requires the same lock, list walk, and blocking mechanism to
ensure completion of checkpoints.
These two sequencing operations can use the mechanism even though the
events they are waiting for are different. The checkpoint commit record
sequencing needs to wait until checkpoint contexts contain a commit LSN
(obtained through completion of a commit record write) while log force
sequencing needs to wait until previous checkpoint contexts are removed from
the committing list (i.e. they've completed). A simple wait variable and
broadcast wakeups (thundering herds) has been used to implement these two
serialisation queues. They use the same lock as the CIL, too. If we see too
much contention on the CIL lock, or too many context switches as a result of
the broadcast wakeups these operations can be put under a new spinlock and
given separate wait lists to reduce lock contention and the number of processes
woken by the wrong event.
Lifecycle Changes
The existing log item life cycle is as follows:
1. Transaction allocate
2. Transaction reserve
3. Lock item
4. Join item to transaction
If not already attached,
Allocate log item
Attach log item to owner item
Attach log item to transaction
5. Modify item
Record modifications in log item
6. Transaction commit
Pin item in memory
Format item into log buffer
Write commit LSN into transaction
Unlock item
Attach transaction to log buffer
<log buffer IO dispatched>
<log buffer IO completes>
7. Transaction completion
Mark log item committed
Insert log item into AIL
Write commit LSN into log item
Unpin log item
8. AIL traversal
Lock item
Mark log item clean
Flush item to disk
<item IO completion>
9. Log item removed from AIL
Moves log tail
Item unlocked
Essentially, steps 1-6 operate independently from step 7, which is also
independent of steps 8-9. An item can be locked in steps 1-6 or steps 8-9
at the same time step 7 is occurring, but only steps 1-6 or 8-9 can occur
at the same time. If the log item is in the AIL or between steps 6 and 7
and steps 1-6 are re-entered, then the item is relogged. Only when steps 8-9
are entered and completed is the object considered clean.
With delayed logging, there are new steps inserted into the life cycle:
1. Transaction allocate
2. Transaction reserve
3. Lock item
4. Join item to transaction
If not already attached,
Allocate log item
Attach log item to owner item
Attach log item to transaction
5. Modify item
Record modifications in log item
6. Transaction commit
Pin item in memory if not pinned in CIL
Format item into log vector + buffer
Attach log vector and buffer to log item
Insert log item into CIL
Write CIL context sequence into transaction
Unlock item
<next log force>
7. CIL push
lock CIL flush
Chain log vectors and buffers together
Remove items from CIL
unlock CIL flush
write log vectors into log
sequence commit records
attach checkpoint context to log buffer
<log buffer IO dispatched>
<log buffer IO completes>
8. Checkpoint completion
Mark log item committed
Insert item into AIL
Write commit LSN into log item
Unpin log item
9. AIL traversal
Lock item
Mark log item clean
Flush item to disk
<item IO completion>
10. Log item removed from AIL
Moves log tail
Item unlocked
From this, it can be seen that the only life cycle differences between the two
logging methods are in the middle of the life cycle - they still have the same
beginning and end and execution constraints. The only differences are in the
commiting of the log items to the log itself and the completion processing.
Hence delayed logging should not introduce any constraints on log item
behaviour, allocation or freeing that don't already exist.
As a result of this zero-impact "insertion" of delayed logging infrastructure
and the design of the internal structures to avoid on disk format changes, we
can basically switch between delayed logging and the existing mechanism with a
mount option. Fundamentally, there is no reason why the log manager would not
be able to swap methods automatically and transparently depending on load
characteristics, but this should not be necessary if delayed logging works as
designed.
Roadmap:
2.6.35 Inclusion in mainline as an experimental mount option
=> approximately 2-3 months to merge window
=> needs to be in xfs-dev tree in 4-6 weeks
=> code is nearing readiness for review
2.6.37 Remove experimental tag from mount option
=> should be roughly 6 months after initial merge
=> enough time to:
=> gain confidence and fix problems reported by early
adopters (a.k.a. guinea pigs)
=> address worst performance regressions and undesired
behaviours
=> start tuning/optimising code for parallelism
=> start tuning/optimising algorithms consuming
excessive CPU time
2.6.39 Switch default mount option to use delayed logging
=> should be roughly 12 months after initial merge
=> enough time to shake out remaining problems before next round of
enterprise distro kernel rebases

51
Documentation/hwmon/dme1737
View File

@ -9,11 +9,15 @@ Supported chips:
* SMSC SCH3112, SCH3114, SCH3116
Prefix: 'sch311x'
Addresses scanned: none, address read from Super-I/O config space
Datasheet: http://www.nuhorizons.com/FeaturedProducts/Volume1/SMSC/311x.pdf
Datasheet: Available on the Internet
* SMSC SCH5027
Prefix: 'sch5027'
Addresses scanned: I2C 0x2c, 0x2d, 0x2e
Datasheet: Provided by SMSC upon request and under NDA
* SMSC SCH5127
Prefix: 'sch5127'
Addresses scanned: none, address read from Super-I/O config space
Datasheet: Provided by SMSC upon request and under NDA
Authors:
Juerg Haefliger <juergh@gmail.com>
@ -36,8 +40,8 @@ Description
-----------
This driver implements support for the hardware monitoring capabilities of the
SMSC DME1737 and Asus A8000 (which are the same), SMSC SCH5027, and SMSC
SCH311x Super-I/O chips. These chips feature monitoring of 3 temp sensors
SMSC DME1737 and Asus A8000 (which are the same), SMSC SCH5027, SCH311x,
and SCH5127 Super-I/O chips. These chips feature monitoring of 3 temp sensors
temp[1-3] (2 remote diodes and 1 internal), 7 voltages in[0-6] (6 external and
1 internal) and up to 6 fan speeds fan[1-6]. Additionally, the chips implement
up to 5 PWM outputs pwm[1-3,5-6] for controlling fan speeds both manually and
@ -48,14 +52,14 @@ Fan[3-6] and pwm[3,5-6] are optional features and their availability depends on
the configuration of the chip. The driver will detect which features are
present during initialization and create the sysfs attributes accordingly.
For the SCH311x, fan[1-3] and pwm[1-3] are always present and fan[4-6] and
pwm[5-6] don't exist.
For the SCH311x and SCH5127, fan[1-3] and pwm[1-3] are always present and
fan[4-6] and pwm[5-6] don't exist.
The hardware monitoring features of the DME1737, A8000, and SCH5027 are only
accessible via SMBus, while the SCH311x only provides access via the ISA bus.
The driver will therefore register itself as an I2C client driver if it detects
a DME1737, A8000, or SCH5027 and as a platform driver if it detects a SCH311x
chip.
accessible via SMBus, while the SCH311x and SCH5127 only provide access via
the ISA bus. The driver will therefore register itself as an I2C client driver
if it detects a DME1737, A8000, or SCH5027 and as a platform driver if it
detects a SCH311x or SCH5127 chip.
Voltage Monitoring
@ -76,7 +80,7 @@ DME1737, A8000:
in6: Vbat (+3.0V) 0V - 4.38V
SCH311x:
in0: +2.5V 0V - 6.64V
in0: +2.5V 0V - 3.32V
in1: Vccp (processor core) 0V - 2V
in2: VCC (internal +3.3V) 0V - 4.38V
in3: +5V 0V - 6.64V
@ -93,6 +97,15 @@ SCH5027:
in5: VTR (+3.3V standby) 0V - 4.38V
in6: Vbat (+3.0V) 0V - 4.38V
SCH5127:
in0: +2.5 0V - 3.32V
in1: Vccp (processor core) 0V - 3V
in2: VCC (internal +3.3V) 0V - 4.38V
in3: V2_IN 0V - 1.5V
in4: V1_IN 0V - 1.5V
in5: VTR (+3.3V standby) 0V - 4.38V
in6: Vbat (+3.0V) 0V - 4.38V
Each voltage input has associated min and max limits which trigger an alarm
when crossed.
@ -293,3 +306,21 @@ pwm[1-3]_auto_point1_pwm RW Auto PWM pwm point. Auto_point1 is the
pwm[1-3]_auto_point2_pwm RO Auto PWM pwm point. Auto_point2 is the
full-speed duty-cycle which is hard-
wired to 255 (100% duty-cycle).
Chip Differences
----------------
Feature dme1737 sch311x sch5027 sch5127
-------------------------------------------------------
temp[1-3]_offset yes yes
vid yes
zone3 yes yes yes
zone[1-3]_hyst yes yes
pwm min/off yes yes
fan3 opt yes opt yes
pwm3 opt yes opt yes
fan4 opt opt
fan5 opt opt
pwm5 opt opt
fan6 opt opt
pwm6 opt opt

7
Documentation/hwmon/lm63
View File

@ -7,6 +7,11 @@ Supported chips:
Addresses scanned: I2C 0x4c
Datasheet: Publicly available at the National Semiconductor website
http://www.national.com/pf/LM/LM63.html
* National Semiconductor LM64
Prefix: 'lm64'
Addresses scanned: I2C 0x18 and 0x4e
Datasheet: Publicly available at the National Semiconductor website
http://www.national.com/pf/LM/LM64.html
Author: Jean Delvare <khali@linux-fr.org>
@ -55,3 +60,5 @@ The lm63 driver will not update its values more frequently than every
second; reading them more often will do no harm, but will return 'old'
values.
The LM64 is effectively an LM63 with GPIO lines. The driver does not
support these GPIO lines at present.

2
Documentation/hwmon/lm85
View File

@ -157,7 +157,7 @@ temperature configuration points:
There are three PWM outputs. The LM85 datasheet suggests that the
pwm3 output control both fan3 and fan4. Each PWM can be individually
configured and assigned to a zone for it's control value. Each PWM can be
configured and assigned to a zone for its control value. Each PWM can be
configured individually according to the following options.
* pwm#_auto_pwm_min - this specifies the PWM value for temp#_auto_temp_off

4
Documentation/hwmon/ltc4245
View File

@ -72,9 +72,7 @@ in6_min_alarm 5v output undervoltage alarm
in7_min_alarm 3v output undervoltage alarm
in8_min_alarm Vee (-12v) output undervoltage alarm
in9_input GPIO #1 voltage data
in10_input GPIO #2 voltage data
in11_input GPIO #3 voltage data
in9_input GPIO voltage data
power1_input 12v power usage (mW)
power2_input 5v power usage (mW)

13
Documentation/hwmon/sysfs-interface
View File

@ -80,9 +80,9 @@ All entries (except name) are optional, and should only be created in a
given driver if the chip has the feature.
********
* Name *
********
*********************
* Global attributes *
*********************
name The chip name.
This should be a short, lowercase string, not containing
@ -91,6 +91,13 @@ name The chip name.
I2C devices get this attribute created automatically.
RO
update_rate The rate at which the chip will update readings.
Unit: millisecond
RW
Some devices have a variable update rate. This attribute
can be used to change the update rate to the desired
frequency.
************
* Voltages *

26
Documentation/hwmon/tmp102 Normal file
View File

@ -0,0 +1,26 @@
Kernel driver tmp102
====================
Supported chips:
* Texas Instruments TMP102
Prefix: 'tmp102'
Addresses scanned: none
Datasheet: http://focus.ti.com/docs/prod/folders/print/tmp102.html
Author:
Steven King <sfking@fdwdc.com>
Description
-----------
The Texas Instruments TMP102 implements one temperature sensor. Limits can be
set through the Overtemperature Shutdown register and Hysteresis register. The
sensor is accurate to 0.5 degree over the range of -25 to +85 C, and to 1.0
degree from -40 to +125 C. Resolution of the sensor is 0.0625 degree. The
operating temperature has a minimum of -55 C and a maximum of +150 C.
The TMP102 has a programmable update rate that can select between 8, 4, 1, and
0.5 Hz. (Currently the driver only supports the default of 4 Hz).
The driver provides the common sysfs-interface for temperatures (see
Documentation/hwmon/sysfs-interface under Temperatures).

8
Documentation/i2c/busses/i2c-i801
View File

@ -27,7 +27,13 @@ Authors:
Module Parameters
-----------------
None.
* disable_features (bit vector)
Disable selected features normally supported by the device. This makes it
possible to work around possible driver or hardware bugs if the feature in
question doesn't work as intended for whatever reason. Bit values:
1 disable SMBus PEC
2 disable the block buffer
8 disable the I2C block read functionality
Description

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