977cfbd526
A udev-based device enumerator is not sufficient, since libudev is an optional dependency, or udev might fail. In these cases, we should fall back to using sysfs to enumerate devices. Add a DeviceEnumeratorSysfs class which is a specialization of DeviceEnumerator that uses sysfs to enumerate media devices on the system. Signed-off-by: Paul Elder <paul.elder@ideasonboard.com> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>