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pps: Add pps_lookup_dev() function

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The PPS serial line discipline wants to attach a PPS device to a tty
without changing the tty code to add a struct pps_device * pointer.

Since the number of PPS devices in a typical system is generally very low
(n=1 is by far the most common), it's practical to search the entire list
of allocated pps devices.  (We capture the timestamp before the lookup,
so the timing isn't affected.)

It is a bit ugly that this function, which is part of the in-kernel
PPS API, has to be in pps.c as opposed to kapi,c, but that's not
something that affects users.

Signed-off-by: George Spelvin <linux@horizon.com>
Acked-by: Rodolfo Giometti <giometti@enneenne.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
George Spelvin 2013-02-10 04:08:32 -05:00 committed by Greg Kroah-Hartman
parent 6d53c3b71d
commit 513b032c98
2 changed files with 47 additions and 3 deletions
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33
drivers/pps/pps.c
View File

@ -352,10 +352,43 @@ int pps_register_cdev(struct pps_device *pps)
void pps_unregister_cdev(struct pps_device *pps)
{
pps->lookup_cookie = NULL;
device_destroy(pps_class, pps->dev->devt);
cdev_del(&pps->cdev);
}
/*
* Look up a pps device by magic cookie.
* The cookie is usually a pointer to some enclosing device, but this
* code doesn't care; you should never be dereferencing it.
*
* This is a bit of a kludge that is currently used only by the PPS
* serial line discipline. It may need to be tweaked when a second user
* is found.
*
* There is no function interface for setting the lookup_cookie field.
* It's initialized to NULL when the pps device is created, and if a
* client wants to use it, just fill it in afterward.
*
* The cookie is automatically set to NULL in pps_unregister_source()
* so that it will not be used again, even if the pps device cannot
* be removed from the idr due to pending references holding the minor
* number in use.
*/
struct pps_device *pps_lookup_dev(void const *cookie)
{
struct pps_device *pps;
unsigned id;
rcu_read_lock();
idr_for_each_entry(&pps_idr, pps, id)
if (cookie == pps->lookup_cookie)
break;
rcu_read_unlock();
return pps;
}
EXPORT_SYMBOL(pps_lookup_dev);
/*
* Module stuff
*/

17
include/linux/pps_kernel.h
View File

@ -43,7 +43,7 @@ struct pps_source_info {
int event, void *data); /* PPS echo function */
struct module *owner;
struct device *dev;
struct device *dev; /* Parent device for device_create */
};
struct pps_event_time {
@ -69,6 +69,7 @@ struct pps_device {
wait_queue_head_t queue; /* PPS event queue */
unsigned int id; /* PPS source unique ID */
void const *lookup_cookie; /* pps_lookup_dev only */
struct cdev cdev;
struct device *dev;
struct fasync_struct *async_queue; /* fasync method */
@ -81,6 +82,16 @@ struct pps_device {
extern struct device_attribute pps_attrs[];
/*
* Internal functions.
*
* These are not actually part of the exported API, but this is a
* convenient header file to put them in.
*/
extern int pps_register_cdev(struct pps_device *pps);
extern void pps_unregister_cdev(struct pps_device *pps);
/*
* Exported functions
*/
@ -88,10 +99,10 @@ extern struct device_attribute pps_attrs[];
extern struct pps_device *pps_register_source(
struct pps_source_info *info, int default_params);
extern void pps_unregister_source(struct pps_device *pps);
extern int pps_register_cdev(struct pps_device *pps);
extern void pps_unregister_cdev(struct pps_device *pps);
extern void pps_event(struct pps_device *pps,
struct pps_event_time *ts, int event, void *data);
/* Look up a pps device by magic cookie */
struct pps_device *pps_lookup_dev(void const *cookie);
static inline void timespec_to_pps_ktime(struct pps_ktime *kt,
struct timespec ts)