Re: [PATCH v2 10/12] media: uvcvideo: Add get_* functions to uvc_entity

[Ricardo Ribalda <ribalda@chromium.org>]

Hi Laurent

On Mon, 14 Jul 2025 at 16:30, Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> On Tue, Jul 01, 2025 at 01:13:10PM +0200, Ricardo Ribalda wrote:
> > On Sun, 29 Jun 2025 at 20:13, Laurent Pinchart wrote:
> > > On Thu, Jun 05, 2025 at 05:53:03PM +0000, Ricardo Ribalda wrote:
> > > > Virtual entities need to provide more values than get_cur and get_cur
> > >
> > > I think you meant "get_info and get_cur".
> > >
> > > > for their controls. Add support for get_def, get_min, get_max and
> > > > get_res.
> > >
> > > Do they ? The UVC specification defines controls that don't list
> > > GET_DEF, GET_MIN, GET_MAX and GET_RES as mandatory requests. Can't we do
> > > the same for the software controls ? This patch is meant to support the
> > > UVC_SWENTITY_ORIENTATION and UVC_SWENTITY_ROTATION control in the next
> > > patch, and those are read-only controls. Aren't GET_INFO and GET_CUR
> > > enough ?
> >
> > V4L2_CID_CAMERA_ROTATION has the type UVC_CTRL_DATA_TYPE_UNSIGNED,
> > that time requires get_min and get_max.
>
> Where does that requirement come from ? Is it because how the
> corresponding V4L2 type (V4L2_CTRL_TYPE_INTEGER) is handled in
> uvc_ctrl_clamp() ? uvc_ctrl_clamp() is only called when setting a
> control, from uvc_ctrl_set(), and V4L2_CID_CAMERA_ROTATION should be
> read-only.

It its for VIDIOC_QUERY_EXT_CTRL

uvc_query_v4l2_ctrl -> __uvc_query_v4l2_ctrl -> __uvc_queryctrl_boundaries

We need to list the min, max, def and step for every control. They are
fetched with uvc_ctrl_populate_cache()



>
> > We can create a new type UVC_CTRL_DATA_TYPE_UNSIGNED_READ_ONLY that
> > fakes min, max and res, but I think that it is cleaner this approach.
> >
> > > > This is a preparation patch.
> > > >
> > > > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> > > > ---
> > > >  drivers/media/usb/uvc/uvc_ctrl.c | 12 ++++++++++++
> > > >  drivers/media/usb/uvc/uvcvideo.h |  8 ++++++++
> > > >  2 files changed, 20 insertions(+)
> > > >
> > > > diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> > > > index 21ec7b978bc7aca21db7cb8fd5d135d876f3330c..59be62ae24a4219fa9d7aacf2ae7382c95362178 100644
> > > > --- a/drivers/media/usb/uvc/uvc_ctrl.c
> > > > +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> > > > @@ -596,6 +596,18 @@ static int uvc_ctrl_query_entity(struct uvc_device *dev,
> > > >       if (query == UVC_GET_CUR && ctrl->entity->get_cur)
> > > >               return ctrl->entity->get_cur(dev, ctrl->entity,
> > > >                                            ctrl->info.selector, data, len);
> > > > +     if (query == UVC_GET_DEF && ctrl->entity->get_def)
> > > > +             return ctrl->entity->get_def(dev, ctrl->entity,
> > > > +                                          ctrl->info.selector, data, len);
> > > > +     if (query == UVC_GET_MIN && ctrl->entity->get_min)
> > > > +             return ctrl->entity->get_min(dev, ctrl->entity,
> > > > +                                          ctrl->info.selector, data, len);
> > > > +     if (query == UVC_GET_MAX && ctrl->entity->get_max)
> > > > +             return ctrl->entity->get_max(dev, ctrl->entity,
> > > > +                                          ctrl->info.selector, data, len);
> > > > +     if (query == UVC_GET_RES && ctrl->entity->get_res)
> > > > +             return ctrl->entity->get_res(dev, ctrl->entity,
> > > > +                                          ctrl->info.selector, data, len);
> > > >       if (query == UVC_GET_INFO && ctrl->entity->get_info)
> > > >               return ctrl->entity->get_info(dev, ctrl->entity,
> > > >                                             ctrl->info.selector, data);
> > > > diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
> > > > index a931750bdea25b9062dcc7644bf5f2ed89c1cb4c..d6da8ed3ad4cf3377df49923e051fe04d83d2e38 100644
> > > > --- a/drivers/media/usb/uvc/uvcvideo.h
> > > > +++ b/drivers/media/usb/uvc/uvcvideo.h
> > > > @@ -261,6 +261,14 @@ struct uvc_entity {
> > > >                       u8 cs, u8 *caps);
> > > >       int (*get_cur)(struct uvc_device *dev, struct uvc_entity *entity,
> > > >                      u8 cs, void *data, u16 size);
> > > > +     int (*get_def)(struct uvc_device *dev, struct uvc_entity *entity,
> > > > +                    u8 cs, void *data, u16 size);
> > > > +     int (*get_min)(struct uvc_device *dev, struct uvc_entity *entity,
> > > > +                    u8 cs, void *data, u16 size);
> > > > +     int (*get_max)(struct uvc_device *dev, struct uvc_entity *entity,
> > > > +                    u8 cs, void *data, u16 size);
> > > > +     int (*get_res)(struct uvc_device *dev, struct uvc_entity *entity,
> > > > +                    u8 cs, void *data, u16 size);
> > > >
> > > >       unsigned int ncontrols;
> > > >       struct uvc_control *controls;
>
> --
> Regards,
>
> Laurent Pinchart



--
Ricardo Ribalda