Re: [PATCH 2/2] em28xx: fix VBI handling logic

["Frank Schäfer" <fschaefer.oss@googlemail.com>]

Am 24.09.2014 um 01:18 schrieb Mauro Carvalho Chehab:
> Em Tue, 23 Sep 2014 21:32:02 +0200
> Frank Schäfer <fschaefer.oss@googlemail.com> escreveu:
>
>> Am 19.09.2014 um 18:02 schrieb Mauro Carvalho Chehab:
>>> When both VBI and video are streaming, and video stream is stopped,
>>> a subsequent trial to restart it will fail, because S_FMT will
>>> return -EBUSY.
>>>
>>> That prevents applications like zvbi to work properly.
>>>
>>> Please notice that, while this fix it fully for zvbi, the
>>> best is to get rid of streaming_users and res_get logic as a hole.
>>>
>>> However, this single-line patch is better to be merged at -stable.
>>>
>>> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
>>>
>>> diff --git a/drivers/media/usb/em28xx/em28xx-video.c b/drivers/media/usb/em28xx/em28xx-video.c
>>> index 08569cbccd95..d75e7f82dfb9 100644
>>> --- a/drivers/media/usb/em28xx/em28xx-video.c
>>> +++ b/drivers/media/usb/em28xx/em28xx-video.c
>>> @@ -1351,7 +1351,7 @@ static int vidioc_s_fmt_vid_cap(struct file *file, void *priv,
>>>  	struct em28xx *dev = video_drvdata(file);
>>>  	struct em28xx_v4l2 *v4l2 = dev->v4l2;
>>>  
>>> -	if (v4l2->streaming_users > 0)
>>> +	if (vb2_is_busy(&v4l2->vb_vidq))
>> Looks dangerous.
> Why Dangerous? 
You are an experienced kernel developer. If you still fail to see that
after so many years, sorry, I can't help you.

> Did you identify any problem?
Yes I've identified a potential problem.
Read it again, it's in the line you skipped in this reply.

> With what application?
I would be willing to spend more time on this and test this critical
patch (like I already did in the past).
But I don't have access to analog TV here at the moment, sorry. It would
have to wait ~2 weeks.

My fault. I shouldn't have wasted any time on reviewing your patch.

Regards,
Frank