Hi All I'm testing with 4.19 and finding that testEvents in v4l2-compliance is failing with ""failed to find event for control '%s' type %u", ie it hasn't got the event for the inital values. This is with the various BCM2835 drivers that I'm involved with. Having looked at the v4l2-core history I tried reverting "ad608fb media: v4l: event: Prevent freeing event subscriptions while accessed". The test passes again. Enabling all logging, and adding a couple of logging messages at the beginning and end of v4l2_ctrl_add_event and __v4l2_event_queue_fh error path, I get the following logs: [ 90.629999] v4l2_ctrl_add_event: ctrl a2b86fa8 "User Controls" type 6, flags 0001 [ 90.630002] video0: VIDIOC_SUBSCRIBE_EVENT: type=0x3, id=0x980001, flags=0x1 [ 91.630166] videodev: v4l2_poll: video0: poll: 00000000 [ 91.630311] videodev: v4l2_poll: video0: poll: 00000000 [ 91.630325] video0: VIDIOC_UNSUBSCRIBE_EVENT: type=0x3, id=0x980001, flags=0x1 [ 91.630396] v4l2_ctrl_add_event: ctrl 8f6fcc61 "Brightness" type 1, flags 0001 [ 91.630403] __v4l2_event_queue_fh: Not subscribed to event type 3 id 0x980001 [ 91.630407] v4l2_ctrl_add_event: ctrl 8f6fcc61 "Brightness" type 1 - initial values queued [ 91.630409] video0: VIDIOC_SUBSCRIBE_EVENT: type=0x3, id=0x980900, flags=0x1 [ 92.630513] videodev: v4l2_poll: video0: poll: 00000000 [ 92.630660] videodev: v4l2_poll: video0: poll: 00000000 [ 92.630729] videodev: v4l2_release: video0: release So __v4l2_event_queue_fh is dropping the event as we aren't subscribed at the point that the initial values are queued. Sorry, I don't have any other devices that support subscribing for events to hand (uvcvideo passes the test as it reports unsupported). I don't have a media tree build immediately available either, but I can't see anything related to this in the recent history. I can go down that route if needed. v4l-utils repo was synced today - head at "f9881444e8 cec-compliance: wake-up on Active Source is warn for <2.0" Could someone test on other hardware to confirm that it's not the drivers I'm using? I'm fairly certain it isn't as that patch does call sev->ops->add(sev, elems); before list_add(&sev->list, &fh->subscribed), and that is guaranteed to fail if sev->ops->add immediately queues an event. Thanks Dave
