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linux-stable/Documentation/ABI/stable/sysfs-bus-nvmem

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nvmem: core: Implement force_ro sysfs attribute Implement "force_ro" sysfs attribute to allow users to set read-write devices as read-only and back to read-write from userspace. The choice of the name is based on MMC core 'force_ro' attribute. This solves a situation where an AT24 I2C EEPROM with GPIO based nWP signal may have to be occasionally updated. Such I2C EEPROM device is usually set as read-only during most of the regular system operation, but in case it has to be updated in a controlled manner, it could be unlocked using this new "force_ro" sysfs attribute and then re-locked again. The "read-only" DT property and config->read_only configuration is respected and is used to set default state of the device, read-only or read-write, for devices which do implement .reg_write function. For devices which do not implement .reg_write function, the device is unconditionally read-only and the "force_ro" attribute is not visible. Signed-off-by: Marek Vasut <marex@denx.de> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org> Link: https://lore.kernel.org/r/20240705074852.423202-16-srinivas.kandagatla@linaro.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-07-05 08:48:52 +01:00
What: /sys/bus/nvmem/devices/.../force_ro
Date: June 2024
KernelVersion: 6.11
Contact: Marek Vasut <marex@denx.de>
Description:
This read/write attribute allows users to set read-write
devices as read-only and back to read-write from userspace.
This can be used to unlock and relock write-protection of
devices which are generally locked, except during sporadic
programming operation.
Read returns '0' or '1' for read-write or read-only modes
respectively.
Write parses one of 'YyTt1NnFf0', or [oO][NnFf] for "on"
and "off", i.e. what kstrbool() supports.
Note: This file is only present if CONFIG_NVMEM_SYSFS
is enabled.
Documentation/ABI: document the nvmem sysfs files NVMEM has been in kernel since v4.2 but the ABI document was missing since then. userspace interface did not change since then and seems stable, so this patch documents the nvmem ABI. Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-07-26 12:09:02 +02:00
What: /sys/bus/nvmem/devices/.../nvmem
Date: July 2015
nvmem: Replace spaces with tab in documentation Replace two spaces with tab in the sysfs attribute documentation. No functional change. Signed-off-by: Marek Vasut <marex@denx.de> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org> Link: https://lore.kernel.org/r/20240705074852.423202-13-srinivas.kandagatla@linaro.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-07-05 08:48:49 +01:00
KernelVersion: 4.2
Documentation/ABI: document the nvmem sysfs files NVMEM has been in kernel since v4.2 but the ABI document was missing since then. userspace interface did not change since then and seems stable, so this patch documents the nvmem ABI. Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-07-26 12:09:02 +02:00
Contact: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Description:
This file allows user to read/write the raw NVMEM contents.
Permissions for write to this file depends on the nvmem
provider configuration.
nvmem: core: add NVMEM_SYSFS Kconfig Many nvmem providers are not very keen on having default sysfs nvmem entry, as most of the usecases for them are inside kernel itself. And in some cases read/writes to some areas in nvmem are restricted and trapped at secure monitor level, so accessing them from userspace would result in board reboots. This patch adds new NVMEM_SYSFS Kconfig to make binary sysfs entry an optional one. This provision will give more flexibility to users. This patch also moves existing sysfs code to a new file so that its not compiled in when its not really required. Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org> Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com> Reviewed-by: Gaurav Kohli <gkohli@codeaurora.org> Tested-by: Gaurav Kohli <gkohli@codeaurora.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-04-16 10:59:24 +01:00
Note: This file is only present if CONFIG_NVMEM_SYSFS
is enabled
Documentation/ABI: document the nvmem sysfs files NVMEM has been in kernel since v4.2 but the ABI document was missing since then. userspace interface did not change since then and seems stable, so this patch documents the nvmem ABI. Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-07-26 12:09:02 +02:00
docs: ABI: stable: make files ReST compatible Several entries at the stable ABI files won't parse if we pass them directly to the ReST output. Adjust them, in order to allow adding their contents as-is at the stable ABI book. Acked-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org> Acked-by: Jonathan Corbet <corbet@lwn.net> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Link: https://lore.kernel.org/r/467a0dfbcdf00db710a629d3fe4a2563750339d8.1604042072.git.mchehab+huawei@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-10-30 08:40:38 +01:00
ex::
Documentation/ABI: document the nvmem sysfs files NVMEM has been in kernel since v4.2 but the ABI document was missing since then. userspace interface did not change since then and seems stable, so this patch documents the nvmem ABI. Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-07-26 12:09:02 +02:00
docs: ABI: stable: make files ReST compatible Several entries at the stable ABI files won't parse if we pass them directly to the ReST output. Adjust them, in order to allow adding their contents as-is at the stable ABI book. Acked-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org> Acked-by: Jonathan Corbet <corbet@lwn.net> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Link: https://lore.kernel.org/r/467a0dfbcdf00db710a629d3fe4a2563750339d8.1604042072.git.mchehab+huawei@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-10-30 08:40:38 +01:00
hexdump /sys/bus/nvmem/devices/qfprom0/nvmem
0000000 0000 0000 0000 0000 0000 0000 0000 0000
*
00000a0 db10 2240 0000 e000 0c00 0c00 0000 0c00
0000000 0000 0000 0000 0000 0000 0000 0000 0000
...
*
0001000
nvmem: Document type attribute Document a type attribute used by userspace to discern different types of NVMEM devices. The implementation is already present, the ABI document is missing, add it. Reviewed-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Signed-off-by: Marek Vasut <marex@denx.de> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org> Link: https://lore.kernel.org/r/20240705074852.423202-14-srinivas.kandagatla@linaro.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-07-05 08:48:50 +01:00
What: /sys/bus/nvmem/devices/.../type
Date: November 2018
KernelVersion: 5.0
Contact: Alexandre Belloni <alexandre.belloni@bootlin.com>
Description:
This read-only attribute allows user to read the NVMEM
device type. Supported types are "Unknown", "EEPROM",
"OTP", "Battery backed", "FRAM".
Note: This file is only present if CONFIG_NVMEM_SYSFS
is enabled.
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