linux-kernel - Re: [PATCH v2 10/12] media: uvcvideo: Add get_* functions to uvc

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Message-ID: <CANiDSCsu0RT4dcGyBJRutP=9HTe+niUoohxTZE=qJ8O_9ez=+A@mail.gmail.com>
Date: Tue, 1 Jul 2025 13:13:10 +0200
From: Ricardo Ribalda <ribalda@...omium.org>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: Hans de Goede <hdegoede@...hat.com>, Mauro Carvalho Chehab <mchehab@...nel.org>, 
	Hans Verkuil <hverkuil@...all.nl>, Sakari Ailus <sakari.ailus@...ux.intel.com>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Linus Walleij <linus.walleij@...aro.org>, Bartosz Golaszewski <brgl@...ev.pl>, 
	"Rafael J. Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org>, linux-media@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-gpio@...r.kernel.org, 
	linux-acpi@...r.kernel.org
Subject: Re: [PATCH v2 10/12] media: uvcvideo: Add get_* functions to uvc_entity

Hi Laurent

On Sun, 29 Jun 2025 at 20:13, Laurent Pinchart
<laurent.pinchart@...asonboard.com> wrote:
>
> Hi Ricardo,
>
> Thank you for the patch.
>
> 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.
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@...omium.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