linux-kernel - Re: [PATCH v10] media: uvcvideo: Fix bandwidth issue for Alcor camera.

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Message-ID: <20250515081202.GA8748@pendragon.ideasonboard.com>
Date: Thu, 15 May 2025 10:12:02 +0200
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Ricardo Ribalda <ribalda@...omium.org>
Cc: chenchangcheng <ccc194101@....com>, hdegoede@...hat.com,
	mchehab@...nel.org, linux-kernel@...r.kernel.org,
	linux-media@...r.kernel.org,
	chenchangcheng <chenchangcheng@...inos.cn>
Subject: Re: [PATCH v10] media: uvcvideo: Fix bandwidth issue for Alcor
 camera.

On Wed, May 14, 2025 at 11:17:06AM +0200, Ricardo Ribalda wrote:
> Hi chenchangcheng
> 
> Thanks for your patience fixing the warnings from media-ci :)
> 
> Regards
> 
> On Sat, 10 May 2025 at 08:18, chenchangcheng <ccc194101@....com> wrote:
> >
> > From: chenchangcheng <chenchangcheng@...inos.cn>
> >
> > Some broken device return wrong dwMaxPayloadTransferSize fields
> > as follows:
> >     [  218.632537] [pid:20427,cpu6,guvcview,8]uvcvideo: Device requested 2752512 B/frame bandwidth.
> >     [  218.632598] [pid:20427,cpu6,guvcview,9]uvcvideo: No fast enough alt setting for requested bandwidth.
> >
> > When dwMaxPayloadTransferSize is greater than maxpsize,
> > it will prevent the camera from starting.
> > So use the bandwidth of maxpsize.
> >
> > Signed-off-by: chenchangcheng <chenchangcheng@...inos.cn>

> Reviewed-by: Ricardo Ribalda <ribalda@...omium.org>
>
> > ---
> >  drivers/media/usb/uvc/uvc_video.c | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> >
> > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> > index e3567aeb0007..a74cf89852d1 100644
> > --- a/drivers/media/usb/uvc/uvc_video.c
> > +++ b/drivers/media/usb/uvc/uvc_video.c
> > @@ -262,6 +262,15 @@ static void uvc_fixup_video_ctrl(struct uvc_streaming *stream,
> >
> >                 ctrl->dwMaxPayloadTransferSize = bandwidth;
> >         }
> > +
> > +       if (stream->intf->num_altsetting > 1 &&
> > +           ctrl->dwMaxPayloadTransferSize > stream->maxpsize) {
> > +               dev_warn_ratelimited(&stream->intf->dev,
> > +                                    "the max payload transmission size (%d) exceededs the size of the ep max packet (%d). Using the max size.\n",
> > +                                    ctrl->dwMaxPayloadTransferSize,
> 
> Minor nitpick. I am trying to standarize "UVC non compliance" header
> in the logs for this kind of things.
> 
> "UVC non compliance: the max payload transmission size (%d) exceededs
> the size of the ep max packet (%d). Using the max size.\n"

s/exceededs/exceeds/

I will also replauce %d with %u as both variables are unsigned.

Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

> > +                                    stream->maxpsize);
> > +               ctrl->dwMaxPayloadTransferSize = stream->maxpsize;
> > +       }
> >  }
> >
> >  static size_t uvc_video_ctrl_size(struct uvc_streaming *stream)
> >
> > base-commit: d76bb1ebb5587f66b0f8b8099bfbb44722bc08b3

-- 
Regards,

Laurent Pinchart