linux-kernel - Re: Re: [PATCH v3] media: uvcvideo: Fix bandwidth error for Alcor camera

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Message-ID: <CANiDSCs2y6zOu09sxU60NX7se-N=wq3Z6USQz+XckQt7rC=3xg@mail.gmail.com>
Date:   Fri, 18 Nov 2022 10:12:05 +0100
From:   Ricardo Ribalda <ribalda@...omium.org>
To:     艾超 <aichao@...inos.cn>
Cc:     laurent.pinchart@...asonboard.com, mchehab@...nel.org,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Re: [PATCH v3] media: uvcvideo: Fix bandwidth error for Alcor camera

Hi Ai

On Fri, 18 Nov 2022 at 10:09, 艾超 <aichao@...inos.cn> wrote:
>
> Hi Ricardo
>
>
> > 3072 is smaller than 0x1000.
> > It is ok to have values between 1024 and 0x1000 (4096) ?

Wouldn't it make more sense ?
  ctrl->dwMaxPayloadTransferSize = 0x1000;


The value 1000 seems a bit random, specially when your compare your
range with 4096
>
>
> Yes,  for some new device which requested 3072 B/frame bandwidth,  that the camera preview normally.
>
>
>
>
> ----
>
>
>
>
>
>
> 主　题：Re: [PATCH v3] media: uvcvideo: Fix bandwidth error for Alcor camera
> 日　期：2022-11-18 16:15
> 发件人：ribalda@...omium.org
> 收件人：艾超
>
>
> Hi Ai
>
> Thanks for your patch!
>
> On Fri, 18 Nov 2022 at 03:23, Ai Chao <aichao@...inos.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@...inos.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



-- 
Ricardo Ribalda