xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

pps: Add pps_lookup_dev() function

Browse Source 
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
Download Patch File Download Diff File Expand all files Collapse all files

33
drivers/pps/pps.c
View File

@@ -352,10 +352,43 @@ free_idr:
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
*/