Before we all go on a well deserved weekend, let me recap what we know. If I did not get something correctly, let me know. 1) Well behaved devices do not allow to set or get an incomplete async control. They will stall instead (ref: Figure 2-21 in UVC 1.5 ) 2) Both Laurent and Ricardo consider that there is a big chance that some camera modules do not implement this properly. (ref: years of crying over broken module firmware :) ) 3) ctrl->handle is designed to point to the fh that originated the control. So the logic can decide if the originator needs to be notified or not. (ref: uvc_ctrl_send_event() ) 4) Right now we replace the originator in ctrl->handle for unfinished async controls. (ref: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/media/usb/uvc/uvc_ctrl.c#n2050) My interpretation is that: A) We need to change 4). We shall not change the originator of unfinished ctrl->handle. B) Well behaved cameras do not need the patch "Do not set an async control owned by another fh" C) For badly behaved cameras, it is fine if we slightly break the v4l2-compliance in corner cases, if we do not break any internal data structure. I will send a new version with my interpretation. Thanks for a great discussion
