Hi,
On 01/27/2013 03:06 PM, Mauro Carvalho Chehab wrote:
Em Fri, 25 Jan 2013 11:40:13 +0100
Hans Verkuil <hverkuil@xxxxxxxxx> escreveu:
On Fri January 25 2013 10:51:57 Hans de Goede wrote:
<modified the CC list to be more appropriate>
Hi,
On 12/25/2012 05:56 AM, Mauro Carvalho Chehab wrote:
The pwc driver can currently return -ENOENT at VIDIOC_S_FMT ioctl. This
doesn't seem right. Instead, it should be getting the closest format to
the requested one and return 0, passing the selected format back to
userspace, just like the other drivers do. I'm c/c Hans de Goede for him
to take a look on it.
I've been looking into this today, and the ENOENT gets returned by
pwc_set_video_mode and through that by:
1) Device init
2) VIDIOC_STREAMON
3) VIDIOC_S_PARM
4) VIDIOC_S_FMT
But only when the requested width + height + pixelformat is an
unsupported combination, and it being a supported combination
already gets enforced by a call to pwc_get_size in
pwc_vidioc_try_fmt, which also gets called from pwc_s_fmt_vid_cap
before it does anything else.
So the ENOENT can only happen on some internal driver error,
I'm open for suggestions for a better error code to return in
this case.
Perhaps returning EINVAL but adding a WARN_ON would be a good compromise.
What I did notice is that pwc_vidioc_try_fmt returns EINVAL when
an unsupported pixelformat is requested. IIRC we agreed that the
correct behavior in this case is to instead just change the
pixelformat to a default format, so I'll write a patch fixing
this.
There are issues with that idea in the case of TV capture cards, since
some important apps (tvtime and mythtv to a lesser extent) assume -EINVAL
in the case of unsupported pixelformats.
Webcam apps can't assume that since gspca never returned -EINVAL, so I
think it should be OK to fix this in pwc, but Mauro may disagree.
It is known that both MythTV and tvtime have issues.
Well, I don't think that MythTV has webcam support. So, it will likely
fail with pwc anyway, as it doesn't have a tuner. So, webcam drivers don't
need to care with breaking anything on it.
Tvtime can work with webcams, if they provide a resolution that it is
compatible with it and if it supports UVYV or YUYV. This is not the case
of pwc, that seems to support only pwc proprietary formats and yuv420.
So, neither tvtime or MythTV currently works with pwc cameras.
However, the issue is a little more complex, as we don't really know if
there aren't any other applications that use a code similar to tvtime
or MythYV.
I understand. A patch to change pwc to the behavior discussed in Barcelona
(so changing the format to a supported one rather then returning -EINVAL),
is part of my last pull-req, I'll leave it up to you whether you will take
it or not :)
If you don't take it I'll drop it from my tree, so that it does not
show up again in my next pull-req.
Regards,
Hans
Regards,
Mauro
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