Maybe you want to handle this with a quirk? I suspect that some devices might work differently with this patches? On Sun, Jun 6, 2021 at 3:36 PM Hans Petter Selasky <hps@xxxxxxxxxxx> wrote: > > Hi, > > Some USB video class compliant devices, like Genesys Logic camera chips, > used in cheap microscopes, doesn't provide any image if there are UVC > SET current value commands for the processing unit, before the camera > stream is activated. Fix this by not issuing any UVC SET current value > commands, if the value was not changed. This should also work fine with > existing UVC compliant webcams and optimized the number of needed > processing unit control endpoint requests. > > Signed-off-by: Hans Petter Selasky <hps@xxxxxxxxxxx> > > diff --git a/drivers/media/usb/uvc/uvc_ctrl.c > b/drivers/media/usb/uvc/uvc_ctrl.c > index b3dde98499f4..0d7137eca331 100644 > --- a/drivers/media/usb/uvc/uvc_ctrl.c > +++ b/drivers/media/usb/uvc/uvc_ctrl.c > @@ -1697,7 +1697,13 @@ int uvc_ctrl_set(struct uvc_fh *handle, > if (ctrl->info.flags & UVC_CTRL_FLAG_ASYNCHRONOUS) > ctrl->handle = handle; > > - ctrl->dirty = 1; > + /* Avoid setting the current value. */ > + if (!ctrl->dirty && > + memcmp(uvc_ctrl_data(ctrl, UVC_CTRL_DATA_BACKUP), > + uvc_ctrl_data(ctrl, UVC_CTRL_DATA_CURRENT), > + ctrl->info.size) != 0) > + ctrl->dirty = 1; > + > ctrl->modified = 1; > return 0; > } -- Ricardo Ribalda
