Re: [PATCH] media: uvcvideo: preserve status URB interval on resubmit

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

On Fri, Oct 02, 2026 at 02:18:56AM +0300, Laurent Pinchart wrote:
> On Thu, Aug 13, 2026 at 03:46:32PM +0800, raoxu wrote:
> > From: Xu Rao <raoxu@uniontech.com>
> > 
> > usb_fill_int_urb() takes an endpoint interval value and stores the
> > period expected by usb_submit_urb() in urb->interval. For high-speed
> > and SuperSpeed interrupt endpoints, it converts the logarithmic
> > descriptor encoding to the corresponding microframe period.
> > 
> > The UVC status URB is initialized once in uvc_status_init(), including
> > the UVC_QUIRK_STATUS_INTERVAL adjustment required by high-speed devices
> > that report bInterval using the old full-speed convention. The first
> > submission therefore carries the intended interval.
> > 
> > Both status resubmit paths, however, overwrite urb->interval with the
> > raw endpoint bInterval before submitting the same URB again. On
> > high-speed and SuperSpeed devices this mixes the descriptor encoding
> > with the already converted URB interval representation. For devices
> > using UVC_QUIRK_STATUS_INTERVAL it also deterministically discards the
> > quirk adjustment after the first status completion, making the
> > workaround effective only for the initial submission.
> > 
> > This has been easy to miss because the initial status submission is
> > correct, full-speed interrupt endpoints do not have the same
> > logarithmic encoding mismatch, and the status endpoint carries
> > relatively infrequent control and streaming notifications rather than
> > the video payload itself. The problem only appears after the status URB
> > has completed and is resubmitted, and the externally visible effect
> > also depends on how the host controller handles the resulting period.
> > 
> > Do not restore bInterval when resubmitting the status URB. Reuse the
> > interval established by usb_fill_int_urb() and usb_submit_urb(), which
> > also preserves the quirk-adjusted value. No additional state or
> > interval conversion is needed because the same URB is being reused.
> > 
> 
> This commit message is also very long and has a large amount of
> irrelevant, when not borderline incorrect, information. Is this missing
> an Assisted-by tag ?
> 
> > Fixes: c0efd232929c ("V4L/DVB (8145a): USB Video Class driver")
> > Fixes: e5225c820c05 ("media: uvcvideo: Send a control event when a Control Change interrupt arrives")

Also, how is stable supposed to make sense of this ?

> > Cc: stable@vger.kernel.org
> > Signed-off-by: Xu Rao <raoxu@uniontech.com>
> > ---
> >  drivers/media/usb/uvc/uvc_ctrl.c   | 1 -
> >  drivers/media/usb/uvc/uvc_status.c | 1 -
> >  2 files changed, 2 deletions(-)
> > 
> > diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> > index 3ca108b83f1d..6552f541aa0d 100644
> > --- a/drivers/media/usb/uvc/uvc_ctrl.c
> > +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> > @@ -2196,7 +2196,6 @@ static void uvc_ctrl_status_event_work(struct work_struct *work)
> >  		return;
> > 
> >  	/* Resubmit the URB. */
> > -	w->urb->interval = dev->int_ep->desc.bInterval;
> >  	ret = usb_submit_urb(w->urb, GFP_KERNEL);
> >  	if (ret < 0)
> >  		dev_err(&dev->intf->dev,
> > diff --git a/drivers/media/usb/uvc/uvc_status.c b/drivers/media/usb/uvc/uvc_status.c
> > index b632cf5e3fe9..680c6c7f4ad7 100644
> > --- a/drivers/media/usb/uvc/uvc_status.c
> > +++ b/drivers/media/usb/uvc/uvc_status.c
> > @@ -245,7 +245,6 @@ static void uvc_status_complete(struct urb *urb)
> >  	}
> > 
> >  	/* Resubmit the URB. */
> > -	urb->interval = dev->int_ep->desc.bInterval;
> >  	ret = usb_submit_urb(urb, GFP_ATOMIC);
> >  	if (ret < 0)
> >  		dev_err(&dev->intf->dev,

-- 
Regards,

Laurent Pinchart