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

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Message-ID: <CANiDSCsXPgQZVtq9RL_TkXCAW9Bt3kMO3-cR4X8GZaQvmYCQyA@mail.gmail.com>
Date: Wed, 14 May 2025 11:17:06 +0200
From: Ricardo Ribalda <ribalda@...omium.org>
To: chenchangcheng <ccc194101@....com>
Cc: laurent.pinchart@...asonboard.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.

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"
> +                                    stream->maxpsize);
> +               ctrl->dwMaxPayloadTransferSize = stream->maxpsize;
> +       }
>  }
>
>  static size_t uvc_video_ctrl_size(struct uvc_streaming *stream)
>
> base-commit: d76bb1ebb5587f66b0f8b8099bfbb44722bc08b3
> --
> 2.25.1
>


-- 
Ricardo Ribalda