On Thu, Nov 09, 2023 at 02:12:50AM +0000, Jayant Chowdhary wrote: > When we use an async work queue to perform the function of pumping > usb requests to the usb controller, it is possible that amongst other > factors, thread scheduling affects at what cadence we're able to pump > requests. This could mean isoc usb requests miss their uframes - resulting > in video stream flickers on the host device. > > To avoid this, we make the async_wq thread only produce isoc usb_requests > with uvc buffers encoded into them. The process of queueing to the > endpoint is done by the uvc_video_complete() handler. In case no > usb_requests are ready with encoded information, we just queue a zero > length request to the endpoint from the complete handler. > > For bulk endpoints the async_wq thread still queues usb requests to the > endpoint. > > Change-Id: I8a33cbf83fb2f04376826185079f8b25404fe761 > Signed-off-by: Michael Grzeschik <m.grzeschik@xxxxxxxxxxxxxx> > Signed-off-by: Jayant Chowdhary <jchowdhary@xxxxxxxxxx> > Suggested-by: Avichal Rakesh <arakesh@xxxxxxxxxx> > Suggested-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> > --- > Based on top of > https://lore.kernel.org/linux-usb/20230930184821.310143-1-arakesh@xxxxxxxxxx/T/#t: > v1->v2: Added self Signed-Off-by and addressed review comments > v2->v3: Encode to usb requests in async_wq; queue to ep in complete handler > for isoc transfers. > v3->v4: Address review comments around code style. > v4->v5: Update comments. Remove 0 length request queueing from async_wq > thread since it is already done by the complete handler. You forgot to run checkpatch.pl :(
