Hi Greg Reason: We found without this, Poll() infinitely wait because OUTPUT queue will never signaled after last CAPTURE queue is de-queued. And some buffer can't be popped as expected. commit id: 566463afdbc43c7744c5a1b89250fc808df03833 subject: "media: v4l2-mem2mem: always consider OUTPUT queue during poll" This should be applied to 4.4+ without conflict after (f1a81afc98e315f4bf600d28f8a19a5655f7cfe0 "[media] m2m: fix bad unlock balance") Thanks, Lecopzer