@jani BTW, were you asking about loopback driver or was it someone else? Yesterday, after year not touching the code I migrated the driver to use VB2, remove all other features except capture, and implemented file descriptor based life-cycle model for the /dev/videoX devices.
Someone pinged me about i t around Dec and that got me so stressed that I actually had to open the text editor ;-)
Those three issues were basically lowest common denominator to send RFC patches. I need to polish what I came up for some time but it is now in my internal queue :-)