On Wed, 16 Jan 2019, Paul Elder wrote: > On Mon, Jan 14, 2019 at 10:24:44AM -0500, Alan Stern wrote: > > On Mon, 14 Jan 2019, Paul Elder wrote: > > > > > > > > Can you check your uvc > > > > > > changes using dummy_hcd with the patch below? > > > > > > > > > > I'm not sure what to make of the test results. I get the same results > > > > > with or without the patch. Which I guess makes sense... in dummy_queue, > > > > > this is getting hit when the uvc function driver tries to complete the > > > > > delayed status: > > > > > > > > > > req = usb_request_to_dummy_request(_req); > > > > > if (!_req || !list_empty(&req->queue) || !_req->complete) > > > > > return -EINVAL; > > > > > > > > > > So the delayed/explicit status stage is never completed, afaict. > > > > > > > > I presume you are hitting the !list_empty(&req->queue) test, yes? The > > > > other two tests are trivial. > > > > > > Yes, that is what's happening. > > > > > > > Triggering the !list_empty() test means the request has already been > > > > submitted and not yet completed. This probably indicates there is a > > > > bug in the uvc function driver code. > > > > > > The uvc function driver works with musb, though :/ > > > > > > I compared the sequence of calls to the uvc setup, completion handler, > > > and status stage sending, and for some reason dummy_hcd, after an OUT > > > setup-completion-status sequence, calls a completion-status-completion > > > sequence, and then goes on the the next request. musb simply goes on to > > > the next request after the setup-completion-status sequence. > > > > I don't quite understand. There's a control-OUT transfer, the setup, > > data, and status transactions all complete normally, and then what > > happens? What do you mean by "a completion-status-completion > > sequence"? A more detailed description would help. > > > > I meant the functions (procedures) in the function driver, so the setup > handler (uvc_function_setup), the completion handler > (uvc_function_ep0_complete), and the status sender (uvc_send_response), > although the last one actually sends the data stage for control IN. > So after the status is sent on the uvc gadget driver's end, its > completion handler is called again without the setup handler being > called beforehand and I cant figure out why. Isn't this what you should expect? Every usb_request, if it is queued successfully, eventually gets a completion callback. That promise is made by every UDC driver; it's part of the gadget API. So for a control transfer with a data stage, you expect to have: Setup handler called Data-stage request submitted Data-stage request completion callback Status-stage request submitted Status-stage request completion callback Thus, two completion callbacks but only one setup callback. > > > I commented out the paranoia block in dummy_timer, and dummy_hcd still > > > does the extra completion, but it doesn't error out anymore. I doubt > > > that's the/a solution though, especially since I get: > > > > > > [ 22.616577] uvcvideo: Failed to query (129) UVC probe control : -75 (exp. 26). > > > [ 22.624481] uvcvideo: Failed to initialize the device (-5). > > > > > > Not sure if that's a result of dummy_hcd not supporting isochronous > > > transfers or not. > > > > > > I'm not sure where to continue investigating :/ > > > > Perhaps removing the "#if 0" protecting the dev_dbg line in > > dummy_queue() would provide some helpful output. > > It did, but didn't get me much farther :/ > > > Another thing to check would be if the "implement an emulated > > single-request FIFO" in dummy_queue() is causing trouble. There's no > > harm in replacing the long "if" condition with "if (0)". > > That didn't change anything. > > Although I did notice that the dummy_queue that calls the completion > handler without the preceeding setup handler says that it's in the > status stage (ep->status_stage == 1). That is consistent with the events outlined above. Alan Stern
