linux-kernel - Re: [PATCH v8] media: uvcvideo: Fix bandwidth issue for Alcor camera.

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Message-ID: <CANiDSCtbR=CnLmMG3cJi+-rVFaP7F1Cuk6OMe_ojVKL=jH68hg@mail.gmail.com>
Date: Thu, 8 May 2025 14:01:23 +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, chenchangcheng <chenchangcheng@...inos.cn>, 
	kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v8] media: uvcvideo: Fix bandwidth issue for Alcor camera.

Hi

Could you please resend ccing linux-media? Otherwise the patch wont be
processed.

Regards!


On Thu, 8 May 2025 at 03:56, 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>
> Reported-by: kernel test robot <lkp@...el.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202505072016.LlOxF8BG-lkp@intel.com/
There is no need to add the reported-by and closes:
The patch has not landed any tree yet.

> ---
>  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..0d5c17509ceb 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,
> +                                  stream->maxpsize);
> +               ctrl->dwMaxPayloadTransferSize = stream->maxpsize;
> +       }
>  }
>
>  static size_t uvc_video_ctrl_size(struct uvc_streaming *stream)
>
> base-commit: b4432656b36e5cc1d50a1f2dc15357543add530e
> --
> 2.25.1
>


--
Ricardo Ribalda