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HankB
Asked: 2019-03-28 05:43:59 +0800 CST

What is "Unknown pixelformat 0x00000000" in dmesg output

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I ran sudo dmesg --follow shortly after rebooting and found these messages at the end of the output. It seems to come out several times. A few lines around that are 

[  139.356270] ------------[ cut here ]------------
[  139.356272] Unknown pixelformat 0x00000000
[  139.356309] WARNING: CPU: 1 PID: 3056 at /build/linux-7kdHqT/linux-4.15.0/drivers/media/v4l2-core/v4l2-ioctl.c:1291 v4l_fill_fmtdesc+0xf41/0x1250 [videodev]

More dmesg output can be seen at https://pastebin.com/4YxinP3Z

System is a Dell XPS-13 9370 with Intel video adapter.

hbarta@karakum:~$ cat /etc/issue
Ubuntu 18.04.2 LTS \n \l

hbarta@karakum:~$ uname -a
Linux karakum 4.15.0-46-generic #49-Ubuntu SMP Wed Feb 6 09:33:07 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
hbarta@karakum:~$ lspci|grep VGA
00:02.0 VGA compatible controller: Intel Corporation UHD Graphics 620 (rev 07)
hbarta@karakum:~$

What problem is being reported? Should I be concerned? How can I fix and should I file a bug report?

I was not looking for an issue when I say this so on the surface, it seems innocuous.

Thanks!

webcam dmesg

1 Answers

  1. Best Answer

    This warning message is issues by the Video4Linux driver when a VIDIOC_ENUM_FMT ioctl() command is actioned on some video device (for example, a webcamera). An application is using the ioctl command to enumerate image formats and passing a v4l2_fmtdesc structure with the pixelformat field set to zero, which is not correct. The driver detects this and emits the warning message.

    If you are interested, the warning comes from function v4l_fill_fmtdesc in https://github.com/torvalds/linux/blob/master/drivers/media/v4l2-core/v4l2-ioctl.c

    So, this is not a kernel issue, it's some application that is misusing the ioctl command VIDIOC_ENUM_FMT

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