linux-kernel - Re: [PATCH] media: uvcvideo: Fix bandwidth error for Alcor camera

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Date:   Thu, 10 Nov 2022 11:41:52 +0100
From:   Ricardo Ribalda <ribalda@...omium.org>
To:     Ai Chao <aichao@...inos.cn>
Cc:     laurent.pinchart@...asonboard.com, mchehab@...nel.org,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] media: uvcvideo: Fix bandwidth error for Alcor camera

Hi Ai

Thanks for your patch

On Thu, 10 Nov 2022 at 09:15, Ai Chao <aichao@...inos.cn> wrote:
>
> For Alcor Corp. Slave camera(1b17:6684), it support to
> output compressed video data, and it return a wrong
>  dwMaxPayloadTransferSize fields. This is a fireware issue,

s/fireware/firmware/

> but the manufacturer cannot provide a const return fields
> by the fireware. so we check the dwMaxPayloadTransferSize fields,
> if it large than 0x1000, reset dwMaxPayloadTransferSize to 1024.


Can you also provide the output of lsusb -d 1b17:6684 -v

>
> Signed-off-by: Ai Chao <aichao@...inos.cn>
> ---
>  drivers/media/usb/uvc/uvc_video.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> index d2eb9066e4dc..49226c3f423c 100644
> --- a/drivers/media/usb/uvc/uvc_video.c
> +++ b/drivers/media/usb/uvc/uvc_video.c
> @@ -234,6 +234,14 @@ static void uvc_fixup_video_ctrl(struct uvc_streaming *stream,
>
>                 ctrl->dwMaxPayloadTransferSize = bandwidth;
>         }
> +
> +       /*Alcor Corp. Slave camera return wrong dwMaxPayloadTransferSize*/
> +       if ((format->flags & UVC_FMT_FLAG_COMPRESSED) &&
> +           (ctrl->dwMaxPayloadTransferSize > 0x1000) &&
> +           (le16_to_cpu(stream->dev->udev->descriptor.idVendor) == 0x1b17) &&
> +           (le16_to_cpu(stream->dev->udev->descriptor.idProduct) == 0x6684)) {
> +               ctrl->dwMaxPayloadTransferSize = 1024;
> +       }


What happens to transfersize between 1024 and 0x1000  (4096), are they ok?

Instead of le16_to_cpu(stream->dev->udev->descriptor.idVendor) ==
0x1b17) you can use usb_match_one_id

Thanks!

>  }
>
>  static size_t uvc_video_ctrl_size(struct uvc_streaming *stream)
> --
> 2.25.1
>


-- 
Ricardo Ribalda