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

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Date: Wed, 20 Mar 2024 16:21:17 +0100
From: Gergo Koteles <soyer@....hu>
To: Ricardo Ribalda <ribalda@...omium.org>
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 Ricardo,

On Tue, 2024-03-19 at 10:43 +0100, Ricardo Ribalda wrote:
> 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 ?
> 

PTZ Pro and BCC950 only have UVC_CT_ZOOM_ABSOLUTE_CONTROL, not
UVC_CT_ZOOM_RELATIVE_CONTROL.

v4l2-ctl -l:

zoom_absolute(int): min=100 max=1000 step=1 default=100 value=100
pan_speed(int): min=-1 max=1 step=1 default=1 value=0
tilt_speed(int): min=-1 max=1 step=1 default=1 value=0

printing data[first], data[first+1] in uvc_ctrl_get_rel_speed:

GET_DEF: 0 1
GET_MIN: 0 1
GET_MAX: 0 1
GET_RES: 0 1
GET_CUR: 0 1


I found the output of Obsbot Tiny v4l2-ctl -l at
https://www.labohyt.net/blog/gadget/post-7643:

pan_absolute(int): min=-468000 max=468000 step=3600 default=0 value=0
tilt_absolute(int): min=-324000 max=324000 step=7200 default=0 value=0
focus_absolute(int): min=0 max=100 step=1 default=0 value=0
flags=inactive
focus_automatic_continuous(bool): default=1 value=1
zoom_absolute(int): min=0 max=100 step=1 default=0 value=0
zoom_continuous(int): min=0 max=100 step=1 default=100 value=0
pan_speed(int): min=-1 max=160 step=1 default=20 value=0
tilt_speed(int): min=-1 max=120 step=1 default=20 value=0

This is where the default value of pan_speed/tilt_speed/zoom_continuous
can be useful, even if they don't work exactly like the defaults for
other controls.

So this patch isn't that good after all.

Regards,
Gergo


> 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
> > 
> > 
> 
>