BUG: Video loopback broken with kernels 2.6.38 and above
These kernels no longer support v4l1. I found a v4l2loopback at https://github.com/umlaeute/v4l2loopback but motion fails with it with:
Jul 13 13:38:48 wile motion:  ioctl (VIDIOCGPICT): Invalid argument Jul 13 13:38:48 wile motion:  Failed to open video loopback
it appears to be attempting to talk to it with V4L1 calls.
Paste in your error messages, config settings, terminal window output etc in this text field.