linux-kernel - Re: [PATCH 1/6] media: uvcvideo: Add UVC_CTRL_FLAG_ENTITY_GET

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Date:   Wed, 4 Nov 2020 14:08:30 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Ricardo Ribalda <ribalda@...omium.org>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        tfiga@...omium.org
Subject: Re: [PATCH 1/6] media: uvcvideo: Add UVC_CTRL_FLAG_ENTITY_GET_INFO

Hi Ricardo,

On Wed, Nov 04, 2020 at 12:48:25PM +0100, Ricardo Ribalda wrote:
> On Wed, Nov 4, 2020 at 12:10 PM Laurent Pinchart wrote:
> > On Thu, Oct 22, 2020 at 03:37:48PM +0200, Ricardo Ribalda wrote:
> > > This flag allows controls to get their properties from an entity defined
> >
> > s/entity defined/entity-defined/
> >
> > > function instead of via a query to the USB device.
> > >
> > > Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
> > > ---
> > >  drivers/media/usb/uvc/uvc_ctrl.c | 9 +++++++--
> > >  drivers/media/usb/uvc/uvcvideo.h | 3 +++
> > >  include/uapi/linux/uvcvideo.h    | 2 ++
> > >  3 files changed, 12 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> > > index f479d8971dfb..7acdc055613b 100644
> > > --- a/drivers/media/usb/uvc/uvc_ctrl.c
> > > +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> > > @@ -1708,8 +1708,13 @@ static int uvc_ctrl_get_flags(struct uvc_device *dev,
> > >       if (data == NULL)
> > >               return -ENOMEM;
> > >
> > > -     ret = uvc_query_ctrl(dev, UVC_GET_INFO, ctrl->entity->id, dev->intfnum,
> > > -                          info->selector, data, 1);
> > > +     if (ctrl->info.flags & UVC_CTRL_FLAG_ENTITY_GET_INFO)
> >
> > Do we need the flag, couldn't we use entity->get_info if it is non-null,
> > and call uvc_query_ctrl() otherwise ?
> 
> The idea behind the flag is to support in the same entity controls
> that are uvc_query_ctrl() based
> and "entity private functions".
> 
> As this moment, there is only the " GPIO entity"  that has has private
> functions, and does not require it.
> 
> So I can simply remove the flag and add it later (if needed).

I hope we won't need more hacks of this kind ;-)

(It's a pretty clever hack I have to say)

> > > +             ret = ctrl->entity->get_info ?
> > > +                     ctrl->entity->get_info(ctrl->entity, ctrl->info.selector, data) :
> > > +                     -EINVAL;
> > > +     else
> > > +             ret = uvc_query_ctrl(dev, UVC_GET_INFO, ctrl->entity->id, dev->intfnum,
> > > +                                  info->selector, data, 1);
> > >       if (!ret)
> > >               info->flags |= (data[0] & UVC_CONTROL_CAP_GET ?
> > >                               UVC_CTRL_FLAG_GET_CUR : 0)
> > > diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
> > > index a3dfacf069c4..08922d889bb6 100644
> > > --- a/drivers/media/usb/uvc/uvcvideo.h
> > > +++ b/drivers/media/usb/uvc/uvcvideo.h
> > > @@ -353,6 +353,9 @@ struct uvc_entity {
> > >       u8 bNrInPins;
> > >       u8 *baSourceID;
> > >
> > > +     int (*get_info)(struct uvc_entity *entity, u8 cs, u8 *caps);
> > > +     int (*get_cur)(struct uvc_entity *entity, u8 cs, void *data, u16 size);
> >
> > Looks like the second function should be part of patch 2/6 instead. I
> > would however squash 1/6 and 2/6.
> >
> > > +
> > >       unsigned int ncontrols;
> > >       struct uvc_control *controls;
> > >  };
> > > diff --git a/include/uapi/linux/uvcvideo.h b/include/uapi/linux/uvcvideo.h
> > > index f80f05b3c423..69b636290c31 100644
> > > --- a/include/uapi/linux/uvcvideo.h
> > > +++ b/include/uapi/linux/uvcvideo.h
> > > @@ -30,6 +30,8 @@
> > >  #define UVC_CTRL_FLAG_AUTO_UPDATE    (1 << 7)
> > >  /* Control supports asynchronous reporting */
> > >  #define UVC_CTRL_FLAG_ASYNCHRONOUS   (1 << 8)
> > > +/* Entity queries */
> > > +#define UVC_CTRL_FLAG_ENTITY_GET_INFO        (1 << 9)
> > >
> > >  #define UVC_CTRL_FLAG_GET_RANGE \
> > >       (UVC_CTRL_FLAG_GET_CUR | UVC_CTRL_FLAG_GET_MIN | \

-- 
Regards,

Laurent Pinchart