Re: [V4l2-library] Messed up syscall return value

On 07/29/2008 12:16 AM, Gregor Jasny wrote:

ioctl(3, VIDIOC_REQBUFS or VT_DISALLOCATE, 0x7fffbfda0060) = 2

Huh? Something evils seems to be going on in V4L2 land. I've spotted the following lines in videobuf-core.c:videobuf_reqbufs

    req->count = retval;

done: mutex_unlock(&q->vb_lock); return retval;

That would explain the retval '2'. It seems a retval = 0; statement is missing here for the success case.

Actually positive ioctl retval used to be often considered as OK in the past (and this approach is still used in few char drivers).

But according to v4l docco, it isn't permitted here. Anyway I wouldn't place it in videobuf-core.c, but in vivi code; letting this decision on Mauro (CCed) ;).