Re: [PATCHv3] media: venus: provide video device lock

[Vikash Garodia <quic_vgarodia@quicinc.com>]

Hi Hans,

On 5/24/2023 8:14 PM, Hans Verkuil wrote:
> On 24/05/2023 16:29, Bryan O'Donoghue wrote:
>> On 24/05/2023 15:12, Sergey Senozhatsky wrote:
>>> Video device has to provide ->lock so that __video_do_ioctl()
>>> can serialize IOCTL calls. Provided dedicated enc/dec mutex-s
>>> for that purpose.
>>>
>>> Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> 
> Since these are m2m devices, I think this should set vfh->m2m_ctx->q_lock
> instead.
> 
> The vb2_queue is per filehandle for such devices, so by just setting
> vdev->lock you will have all vb2_queues use the same mutex.
> 
> Instead the struct v4l2_m2m_ctx q_lock pointer, if set, will use that
> mutex for all vb2 operations.

Recently we came across a race between queryctrl and s_fmt. Above lock would
synchronize the operations for IOCTL with flag INFO_FL_QUEUE. Any suggestion on
how other IOCTLs can be serialized as well, for ex s_fmt and queryctrl which are
of type INFO_FL_PRIO and INFO_FL_CTRL.

Thanks,
Vikash
> I think you can set it to the 'lock' mutex in struct venus_inst.
> 
> Regards,
> 
> 	Hans