[linux-uvc-devel] question regarding unsupported ioctl error and -71 uvcvideo status

[Arvind Thiagarajan]

Hi,

I am trying to get a UVC camera working with Linux. It seems to work
reasonably well but occasionally stops sending data/has to be reset by
unplugging and plugging it back into the USB port. I tried doing a kernel
trace on the uvcvideo kernel module like suggested and found the following
lines in my kernel dmesg log whenever I reproduce the problem:

....
[ 4995.823002] uvcvideo: uvc_v4l2_ioctl(VIDIOC_QBUF)
[ 4995.823004] uvcvideo: uvc_v4l2_ioctl(VIDIOC_QBUF)
[ 4995.823005] uvcvideo: uvc_v4l2_ioctl(VIDIOC_STREAMON)
[ 4995.823196] uvcvideo: Allocated 5 URB buffers of 32x1024 bytes each.
[ 4995.823225] uvcvideo: uvc_v4l2_ioctl(VIDIOC_G_STD)
[ 4995.823226] uvcvideo: Unsupported ioctl 0x80085617
[ 4995.823296] uvcvideo: uvc_v4l2_poll
[ 4995.841286] uvcvideo: Non-zero status (-71) in video completion handler.
[ 4995.841342] uvcvideo: uvc_v4l2_poll
[ 4995.841362] uvcvideo: uvc_v4l2_ioctl(VIDIOC_DQBUF)
....

Just to make sure I am interpreting the log correctly, does this mean that
the camera firmware does not support the VIDIOC_G_STD ioctl call?

To get it working more smoothly, is there any workaround or solution to
reset without plugging/unplugging into the USB port?

Or is the only way to fix the problem to request the camera manufacturer to
add support in the firmware for that ioctl call?

Thanks a lot! Any advice would be appreciated on this.

Arvind