linux-kernel - Re: [PATCH v2 RESEND] media: uvcvideo: uvc_ctrl_get_rel

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Date: Tue, 19 Mar 2024 10:43:52 +0100
From: Ricardo Ribalda <ribalda@...omium.org>
To: Gergo Koteles <soyer@....hu>
Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>, 
	Mauro Carvalho Chehab <mchehab@...nel.org>, linux-media@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 RESEND] media: uvcvideo: uvc_ctrl_get_rel_speed: use 0
 as default

Hi Gergo

I missed sending the reviewed-by sorry :)

Btw, do you still have access to the device? Could you tell me what
you get from  and UVC_GET_MAX, UVC_GET_MIN for
UVC_CT_PANTILT_RELATIVE_CONTROL and UVC_CT_ZOOM_RELATIVE_CONTROL ?

Thanks!

On Mon, 20 Nov 2023 at 19:53, Gergo Koteles <soyer@....hu> wrote:
>
> Devices with pan/tilt controls but without pan/tilt speed controls
> return 1 for the default value of V4L2_CID_PAN_SPEED or
> V4L2_CID_TILT_SPEED. For these controls, the value of 1 means a
> move and that's not a good default.
>
> Currently, for these controls the UVC_GET_DEF query returns
> bPanSpeed or bTiltSpeed of CT_PANTILT_RELATIVE_CONTROL.
>
> According to the UVC 1.5 specification, the default value of bPanSpeed
> or bTiltSpeed should be 1 if the pan/tilt control doesn't support
> speed control.
>
> "If the control does not support speed control for the Tilt control,
> it will return the value 1 in this field for all these requests."
>
> This patch modifies the uvc_ctrl_get_rel_speed to return hardcoded 0
> for UVC_GET_DEF query, because that's the stop or don't move value
> for these V4L2 controls.
>
> Previous discussion
> Link: https://lore.kernel.org/all/CAP_ceTy6XVmvTTAmvCp1YU2wxHwXqnarm69Yaz8K4FmpJqYxAg@mail.gmail.com/
>
> Signed-off-by: Gergo Koteles <soyer@....hu>
Reviewed-by: Ricardo Ribalda <ribalda@...omium.org>
> ---
>  drivers/media/usb/uvc/uvc_ctrl.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> index 5e9d3da862dd..e131958c0930 100644
> --- a/drivers/media/usb/uvc/uvc_ctrl.c
> +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> @@ -444,9 +444,10 @@ static s32 uvc_ctrl_get_rel_speed(struct uvc_control_mapping *mapping,
>                 return -data[first+1];
>         case UVC_GET_MAX:
>         case UVC_GET_RES:
> +               return data[first+1];
>         case UVC_GET_DEF:
>         default:
> -               return data[first+1];
> +               return 0;
>         }
>  }
>
>
> base-commit: be9aac187433af6abba5fcc2e73d91d0794ba360
> --
> 2.42.0
>
>


-- 
Ricardo Ribalda