linux-kernel - Re: [PATCH v7 3/8] media: uvcvideo: Support minimum for V4L2_CTRL_TYPE

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Date:   Fri, 17 Jun 2022 16:15:49 +0200
From:   Ricardo Ribalda <ribalda@...omium.org>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        tfiga@...omium.org, senozhatsky@...omium.org, yunkec@...gle.com
Subject: Re: [PATCH v7 3/8] media: uvcvideo: Support minimum for V4L2_CTRL_TYPE_MENU

Hi Laurent

On Fri, 17 Jun 2022 at 16:11, Laurent Pinchart
<laurent.pinchart@...asonboard.com> wrote:
>
> Hi Ricardo,
>
> On Fri, Jun 17, 2022 at 03:55:52PM +0200, Ricardo Ribalda wrote:
> > On Fri, 17 Jun 2022 at 15:50, Laurent Pinchart wrote:
> > > On Fri, Jun 17, 2022 at 12:36:40PM +0200, Ricardo Ribalda wrote:
> > > > Currently all mappings of type V4L2_CTRL_TYPE_MENU, have a minimum of 0,
> > > > but there are some controls (limited powerline), that start with a value
> > > > different than 0.
> > > >
> > > > Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
> > > > ---
> > > >  drivers/media/usb/uvc/uvc_ctrl.c | 5 +++--
> > > >  drivers/media/usb/uvc/uvcvideo.h | 1 +
> > > >  2 files changed, 4 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> > > > index 092decfdaa62..3b20b23abd1e 100644
> > > > --- a/drivers/media/usb/uvc/uvc_ctrl.c
> > > > +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> > > > @@ -1144,7 +1144,7 @@ static int __uvc_query_v4l2_ctrl(struct uvc_video_chain *chain,
> > > >
> > > >       switch (mapping->v4l2_type) {
> > > >       case V4L2_CTRL_TYPE_MENU:
> > > > -             v4l2_ctrl->minimum = 0;
> > > > +             v4l2_ctrl->minimum = mapping->menu_min;
> > > >               v4l2_ctrl->maximum = mapping->menu_count - 1;
> > > >               v4l2_ctrl->step = 1;
> > > >
> > > > @@ -1264,7 +1264,8 @@ int uvc_query_v4l2_menu(struct uvc_video_chain *chain,
> > > >               goto done;
> > > >       }
> > > >
> > > > -     if (query_menu->index >= mapping->menu_count) {
> > > > +     if (query_menu->index < mapping->menu_min ||
> > > > +         query_menu->index >= mapping->menu_count) {
> > > >               ret = -EINVAL;
> > > >               goto done;
> > > >       }
> > > > diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
> > > > index fff5c5c99a3d..6ceb7f7b964d 100644
> > > > --- a/drivers/media/usb/uvc/uvcvideo.h
> > > > +++ b/drivers/media/usb/uvc/uvcvideo.h
> > > > @@ -254,6 +254,7 @@ struct uvc_control_mapping {
> > > >       u32 data_type;
> > > >
> > > >       const struct uvc_menu_info *menu_info;
> > > > +     u32 menu_min;
> > > >       u32 menu_count;
> > >
> > > That's a bit of a stop-gap measure, could we turn it into a bitmask
> > > instead ?
> >
> > Unfortunately that is uAPI :(
> >
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/v4l2-controls.h#n101
> >
> > We have to keep the control type and its values.
>
> Sure, I didn't mean changing that, but replacing menu_min and menu_count
> in uvc_control_mapping with a menu_mask that stores a bitmask of all
> supported values. This will allow skipping the first value in the power
> line frequency control case, but will also support skipping other menu
> entries for other controls in the future.

Ahh gotcha. Will implement that in the next version.

Thanks!

>
> > > >
> > > >       u32 master_id;
>
> --
> Regards,
>
> Laurent Pinchart



-- 
Ricardo Ribalda