linux-kernel - Re: [PATCH 1/2] media: uvcvideo: UVC minimum relative pan/tilt/zoom speed fix

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Message-ID: <CANiDSCsyj-Zfzo+1Sxgzz_fQ4Df9rjc_Cj66Bokni_6oJk41Fg@mail.gmail.com>
Date: Tue, 2 Apr 2024 13:53:53 +0200
From: Ricardo Ribalda <ribalda@...omium.org>
To: johnebgood@...uritylive.com
Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>, 
	Mauro Carvalho Chehab <mchehab@...nel.org>, linux-media@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linh.tp.vu@...il.com, soyer@....hu
Subject: Re: [PATCH 1/2] media: uvcvideo: UVC minimum relative pan/tilt/zoom
 speed fix

Hi John

Maybe you could add a function like


static bool is_relative_ptz_ctr(__u32 id)
{
          switch (xctrl->id) {
           case V4L2_CID_ZOOM_CONTINUOUS:
           case V4L2_CID_PAN_SPEED:
            case V4L2_CID_TILT_SPEED:
                     return true;
          }
          return false;
}

to figure out if a control is relative or not, and avoid code duplication.



On Fri, 29 Mar 2024 at 00:18, John Bauer via B4 Relay
<devnull+johnebgood.securitylive.com@...nel.org> wrote:
>
> From: John Bauer <johnebgood@...uritylive.com>
>
> The minimum UVC control value for the relative pan/tilt/zoom speeds
> cannot be probed as the implementation condenses the pan and tilt
> direction and speed into two 16 bit values. The minimum cannot be
> set at probe time because it is probed first and the maximum is not
> yet known. With this fix if a relative speed control is queried
> or set the minimum is set and checked based on the additive inverse of
> the maximum at that time.
>
> Signed-off-by: John Bauer <johnebgood@...uritylive.com>
> ---
>  drivers/media/usb/uvc/uvc_ctrl.c | 37 ++++++++++++++++++++++++++++++++++---
>  1 file changed, 34 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> index e59a463c2761..b389ab3ee05d 100644
> --- a/drivers/media/usb/uvc/uvc_ctrl.c
> +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> @@ -1322,9 +1322,25 @@ static int __uvc_query_v4l2_ctrl(struct uvc_video_chain *chain,
>                 break;
>         }
>
> -       if (ctrl->info.flags & UVC_CTRL_FLAG_GET_MIN)
> -               v4l2_ctrl->minimum = mapping->get(mapping, UVC_GET_MIN,
> -                                    uvc_ctrl_data(ctrl, UVC_CTRL_DATA_MIN));
> +       if (ctrl->info.flags & UVC_CTRL_FLAG_GET_MIN) {
> +               switch (v4l2_ctrl->id) {
> +               case V4L2_CID_ZOOM_CONTINUOUS:
> +               case V4L2_CID_PAN_SPEED:
> +               case V4L2_CID_TILT_SPEED:
> +                       /*
> +                        * For the relative speed implementation the minimum
> +                        * value cannot be probed so it becomes the additive
> +                        * inverse of maximum.
> +                        */
> +                       v4l2_ctrl->minimum = -1 * mapping->get(mapping, UVC_GET_MAX,
> +                                               uvc_ctrl_data(ctrl, UVC_CTRL_DATA_MAX));
> +                       break;
> +               default:
> +                       v4l2_ctrl->minimum = mapping->get(mapping, UVC_GET_MIN,
> +                                               uvc_ctrl_data(ctrl, UVC_CTRL_DATA_MIN));
> +                       break;
> +               }
> +       }
>
>         if (ctrl->info.flags & UVC_CTRL_FLAG_GET_MAX)
>                 v4l2_ctrl->maximum = mapping->get(mapping, UVC_GET_MAX,
> @@ -1914,6 +1930,21 @@ int uvc_ctrl_set(struct uvc_fh *handle,
>                                    uvc_ctrl_data(ctrl, UVC_CTRL_DATA_MIN));
>                 max = mapping->get(mapping, UVC_GET_MAX,
>                                    uvc_ctrl_data(ctrl, UVC_CTRL_DATA_MAX));
> +
> +               /*
> +                * For the relative speed implementation the minimum
> +                * value cannot be probed so it becomes the additive
> +                * inverse of maximum.
> +                */
> +               switch (xctrl->id) {
> +               case V4L2_CID_ZOOM_CONTINUOUS:
> +               case V4L2_CID_PAN_SPEED:
> +               case V4L2_CID_TILT_SPEED:
> +                       min = max * -1;
> +               default:
> +                       break;
> +               }
> +
>                 step = mapping->get(mapping, UVC_GET_RES,
>                                     uvc_ctrl_data(ctrl, UVC_CTRL_DATA_RES));
>                 if (step == 0)
>
> --
> 2.34.1
>
>


-- 
Ricardo Ribalda