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References: <20221118022302.112121-1-aichao@kylinos.cn>
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From:   Ricardo Ribalda <ribalda@chromium.org>
Date:   Fri, 18 Nov 2022 09:15:43 +0100
Message-ID: <CANiDSCs746jMSfzPJN9SzUfU-1xhRqG7G2Z9mVF_h=zThNoPxA@mail.gmail.com>
Subject: Re: [PATCH v3] media: uvcvideo: Fix bandwidth error for Alcor camera
To:     Ai Chao <aichao@kylinos.cn>
Cc:     laurent.pinchart@ideasonboard.com, mchehab@kernel.org,
        linux-media@vger.kernel.org, linux-kernel@vger.kernel.org
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Hi Ai

Thanks for your patch!

On Fri, 18 Nov 2022 at 03:23, Ai Chao <aichao@kylinos.cn> wrote:
>
> For Alcor Corp. Slave camera(1b17:6684/2017:0011), 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. For some device, device requested 2752512
>  B/frame bandwidth. For some device, device requested 3072
>  B/frame bandwidth. so we check the dwMaxPayloadTransferSize
>  fields,if it large than 0x1000, reset dwMaxPayloadTransferSize
> to 1024, and the camera preview normally.

3072 is smaller than 0x1000.

It is ok to have values between 1024 and 0x1000 (4096) ?

Thanks

>
> Signed-off-by: Ai Chao <aichao@kylinos.cn>
>
> ---
> change for v3
> - Add VID/PID 2017:0011
>
> change for v2
> - Used usb_match_one_id to check VID and PID
> ---
> ---
>  drivers/media/usb/uvc/uvc_video.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> index d2eb9066e4dc..1260800ef8bd 100644
> --- a/drivers/media/usb/uvc/uvc_video.c
> +++ b/drivers/media/usb/uvc/uvc_video.c
> @@ -135,6 +135,10 @@ static void uvc_fixup_video_ctrl(struct uvc_streaming *stream,
>         static const struct usb_device_id elgato_cam_link_4k = {
>                 USB_DEVICE(0x0fd9, 0x0066)
>         };
> +       static const struct usb_device_id alcor_corp_slave_cam = {
> +               USB_DEVICE(0x1b17, 0x6684),
> +               USB_DEVICE(0x2017, 0x0011),
> +       };
>         struct uvc_format *format = NULL;
>         struct uvc_frame *frame = NULL;
>         unsigned int i;
> @@ -234,6 +238,13 @@ 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) &&
> +            usb_match_one_id(stream->dev->intf, &alcor_corp_slave_cam)) {
> +               ctrl->dwMaxPayloadTransferSize = 1024;
> +       }
>  }
>
>  static size_t uvc_video_ctrl_size(struct uvc_streaming *stream)
> --
> 2.25.1
>


-- 
Ricardo Ribalda