linux-kernel - [v3.8-rc1] Multimedia regression, ioctl(17,..)-API changed ?

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Date:	Sun, 23 Dec 2012 17:46:07 +0100
From:	Jörg Otte <jrg.otte@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	linux-media@...r.kernel.org,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [v3.8-rc1] Multimedia regression, ioctl(17,..)-API changed ?

With kernel v3.8 all multimedia programs under KDE4 don't work (Kubuntu 12.04).
They alltogether ( at least Dragonplayer (Mediaplayer), Knotify4
(system-sound),
System-Settings-Multimedia,..) are looping forever producing 100% CPU-usage
and must be killed.

With kernel 3.7 there are no problems.

I compared an strace of Dragonplayer under 3.7 and 3.8 kernels. The
main difference
of both traces are the following corresponding outputs just before
looping in v3.8
begins:

v3.7:
ioctl(17, VIDIOC_ENUMSTD, 0x7fff6cce66a0) = -1 EINVAL (Invalid argument)
ioctl(17, VIDIOC_QUERYCTRL, 0x7fff6cce66f0) = -1 EINVAL (Invalid argument)

v3.8:
ioctl(17, VIDIOC_ENUMSTD, 0x7fffc3be6990) = -1 ENOTTY (Inappropriate
ioctl for device)
ioctl(17, VIDIOC_QUERYCTRL, 0x7fffc3be69e0) = -1 ENOENT (No such file
or directory)

So error number EINVAL was changed to ENOTTY/ENOENT

When Dragonplayer under v3.8 comes to ioctl(17, VIDIOC_QUERYCTRL,...)
and sees error
number ENOENT instead of EINVAL it loops forever producing 100% CPU
usage like so:

  .
  .
ioctl(17, VIDIOC_QUERYCTRL, 0x7fffc3be69e0) = -1 ENOENT (No such file
or directory)
ioctl(17, VIDIOC_QUERYCTRL, 0x7fffc3be69e0) = -1 ENOENT (No such file
or directory)
ioctl(17, VIDIOC_QUERYCTRL, 0x7fffc3be69e0) = -1 ENOENT (No such file
or directory)
ioctl(17, VIDIOC_QUERYCTRL, 0x7fffc3be69e0) = -1 ENOENT (No such file
or directory)
ioctl(17, VIDIOC_QUERYCTRL, 0x7fffc3be69e0) = -1 ENOENT (No such file
or directory)
ioctl(17, VIDIOC_QUERYCTRL, 0x7fffc3be69e0) = -1 ENOENT (No such file
or directory)
ioctl(17, VIDIOC_QUERYCTRL, 0x7fffc3be69e0) = -1 ENOENT (No such file
or directory)
ioctl(17, VIDIOC_QUERYCTRL, 0x7fffc3be69e0) = -1 ENOENT (No such file
or directory)
ioctl(17, VIDIOC_QUERYCTRL, 0x7fffc3be69e0) = -1 ENOENT (No such file
or directory)
ioctl(17, VIDIOC_QUERYCTRL, 0x7fffc3be69e0) = -1 ENOENT (No such file
or directory)
ioctl(17, VIDIOC_QUERYCTRL, 0x7fffc3be69e0) = -1 ENOENT (No such file
or directory)
  .
  and so on
  .

For me it looks like that KDE4 multimedia is not aware of the new error numbers.

Looking through the commits I found driver uvcvideo producing the changed
error numbers.

commit f0ed2ce840b3a59b587e8aa398538141a86e9588
Author: Laurent Pinchart <laurent.pinchart@...asonboard.com>
[media] uvcvideo: Set error_idx properly for extended controls API failures

To verify this I built a v3.8-kernel without uvcvideo (USB_VIDEO_CLASS=n)
and the problem disappeared!

Simply reverting the commit is not an option for me because then I am left
with merge conflicts and I don't know how to resolve.

Unfortunately without uvcvideo I lost my usb-camera support.

-- Jörg

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