Em Thu, 25 Sep 2014 15:59:12 +0200
Frank Schäfer <fschaefer....@googlemail.com> escreveu:
>
> Am 24.09.2014 um 01:18 schrieb Mauro Carvalho Chehab:
> > Em Tue, 23 Sep 2014 21:32:02 +0200
> > Frank Schäfer <fschaefer....@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 <mche...@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.
Did you read the video_ioctl_ops struct?
See:
.vidioc_g_fmt_vid_cap = vidioc_g_fmt_vid_cap,
.vidioc_try_fmt_vid_cap = vidioc_try_fmt_vid_cap,
.vidioc_s_fmt_vid_cap = vidioc_s_fmt_vid_cap,
.vidioc_g_fmt_vbi_cap = vidioc_g_fmt_vbi_cap,
.vidioc_try_fmt_vbi_cap = vidioc_g_fmt_vbi_cap,
.vidioc_s_fmt_vbi_cap = vidioc_g_fmt_vbi_cap,
.vidioc_enum_framesizes = vidioc_enum_framesizes,
.vidioc_g_audio = vidioc_g_audio,
.vidioc_s_audio = vidioc_s_audio,
Only the video node calls s_fmt_vid_cap. There's nothing to be
set for VBI. In other words, a call to VIDIOC_S_FMT will
actually call vidioc_g_fmt_vbi_cap() if called from VBI.
So, I was unable to see any potencial issues.
> > 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.
On my tests with the 3 existing VBI apps, they all worked fine
after the patch, no matter if the VBI or the video application
is started first.
That's why I asked.
Regards,
Mauro
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