RFC: V4L2: Proposal to remove fallback for missing CMD_STOP
One thing that make the old video4linux very difficult to work with is that it have a lot of "legacy" fallback for extremely ancient kernel or vendor stuff. While I don't believe it good to remove them all, there is few ones that I think would help cleaning up the code if we could drop them. The one I would like to immediately remove is the fallback for missing V4L2_DEC_CMD_STOP. This is used to drain decoder, the fallback is to push an empty buffer. The challenge is that the stateful decoder/encoder are threaded, and having code in both thread pushing buffer is racy. Removing this fallback would allow doing things like triggering a drain from the output thread safely, and fixing an issue with the SRC_CH event handling.