On Sat, 16 Oct 2010 10:44:56 -0300
Mauro Carvalho Chehab <mche...@infradead.org> wrote:
> drivers/media/video/via-camera.c: In function ‘viacam_open’:
> drivers/media/video/via-camera.c:651: error: too few arguments to function
> ‘videobuf_queue_sg_init’
> The fix for this one is trivial:
> drivers/media/video/via-camera.c:651: error: too few arguments to function
> ‘videobuf_queue_sg_init’
>
> Just add an extra NULL parameter to the function.
So I'm looking into this stuff. The extra NULL parameter is a struct
mutex, which seems to be used in one place in videobuf_waiton():
is_ext_locked = q->ext_lock && mutex_is_locked(q->ext_lock);
/* Release vdev lock to prevent this wait from blocking outside access
to
the device. */
if (is_ext_locked)
mutex_unlock(q->ext_lock);
I'd be most curious to know what the reasoning behind this code is; to my
uneducated eye, it looks like a real hack. How does this function know who
locked ext_lock? Can it really just unlock it safely? It seems to me that
this is a sign of locking issues which should really be dealt with
elsewhere, but, as I said, I'm uneducated, and the changelogs don't help me
much. Can somebody educate me?
Thanks,
jon
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