linux-kernel - Re: [PATCH 1/3] v4l2-subdev: Add subdev ioctl support for ENUM/GET/SET INPUT

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Message-ID: <20200625020138.GW5980@pendragon.ideasonboard.com>
Date:   Thu, 25 Jun 2020 05:01:38 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Jacopo Mondi <jacopo@...ndi.org>
Cc:     Ramzi BEN MEFTAH <rbmeftah@...adit-jv.com>,
        niklas soderlund <niklas.soderlund@...natech.se>,
        Kieran Bingham <kieran.bingham@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Janusz Krzysztofik <jmkrzyszt@...il.com>,
        Steve Longerbeam <steve_longerbeam@...tor.com>,
        Ezequiel Garcia <ezequiel@...labora.com>,
        Arnd Bergmann <arnd@...db.de>, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Michael Rodin <mrodin@...adit-jv.com>,
        efriedrich@...adit-jv.com, erosca@...adit-jv.com
Subject: Re: [PATCH 1/3] v4l2-subdev: Add subdev ioctl support for
 ENUM/GET/SET INPUT

Hi Jacopo,

On Wed, Jun 24, 2020 at 09:53:07AM +0200, Jacopo Mondi wrote:
> On Tue, Jun 16, 2020 at 12:00:15PM +0200, Ramzi BEN MEFTAH wrote:
> > From: Steve Longerbeam <steve_longerbeam@...tor.com>
> 
>  +Niklas, +Laurent
> 
> Niklas, Laurent, how does this play with CAP_IO_MC ?

I don't think it's related to CAP_IO_MC, but I don't think it's a good
idea either :-) Routing doesn't go through the subdev [gs]_input
operations in MC-based drivers. It should be configured through link
setup instead. This patch goes in the wrong direction, sorry Steve.

> > This commit enables VIDIOC_ENUMINPUT, VIDIOC_G_INPUT, and VIDIOC_S_INPUT
> > ioctls for use via v4l2 subdevice node.
> >
> > This commit should probably not be pushed upstream, because the (old)
> > idea of video inputs conflicts with the newer concept of establishing
> > media links between src->sink pads.
> >
> > However it might make sense for some subdevices to support enum/get/set
> > inputs. One example would be the analog front end subdevice for the
> > ADV748x. By providing these ioctls, selecting the ADV748x analog inputs
> > can be done without requiring the implementation of media entities that
> > would define the analog source for which to establish a media link.
> >
> > Signed-off-by: Steve Longerbeam <steve_longerbeam@...tor.com>
> > ---
> >  drivers/media/v4l2-core/v4l2-subdev.c |  9 +++++++++
> >  include/media/v4l2-subdev.h           | 11 +++++++++++
> >  2 files changed, 20 insertions(+)
> >
> > diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> > index 6b989fe..73fbfe9 100644
> > --- a/drivers/media/v4l2-core/v4l2-subdev.c
> > +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> > @@ -378,6 +378,15 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
> >  			return -ENOTTY;
> >  		return v4l2_querymenu(vfh->ctrl_handler, arg);
> >
> > +	case VIDIOC_ENUMINPUT:
> > +		return v4l2_subdev_call(sd, video, enuminput, arg);
> > +
> > +	case VIDIOC_G_INPUT:
> > +		return v4l2_subdev_call(sd, video, g_input, arg);
> > +
> > +	case VIDIOC_S_INPUT:
> > +		return v4l2_subdev_call(sd, video, s_input, *(u32 *)arg);
> > +
> >  	case VIDIOC_G_CTRL:
> >  		if (!vfh->ctrl_handler)
> >  			return -ENOTTY;
> > diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
> > index f7fe78a..6e1a9cd 100644
> > --- a/include/media/v4l2-subdev.h
> > +++ b/include/media/v4l2-subdev.h
> > @@ -383,6 +383,14 @@ struct v4l2_mbus_frame_desc {
> >   * @g_input_status: get input status. Same as the status field in the
> >   *	&struct &v4l2_input
> >   *
> > + * @enuminput: enumerate inputs. Should return the same input status as
> > + *      @g_input_status if the passed input index is the currently active
> > + *      input.
> > + *
> > + * @g_input: returns the currently active input index.
> > + *
> > + * @s_input: set the active input.
> > + *
> >   * @s_stream: used to notify the driver that a video stream will start or has
> >   *	stopped.
> >   *
> > @@ -423,6 +431,9 @@ struct v4l2_subdev_video_ops {
> >  	int (*g_tvnorms)(struct v4l2_subdev *sd, v4l2_std_id *std);
> >  	int (*g_tvnorms_output)(struct v4l2_subdev *sd, v4l2_std_id *std);
> >  	int (*g_input_status)(struct v4l2_subdev *sd, u32 *status);
> > +	int (*enuminput)(struct v4l2_subdev *sd, struct v4l2_input *input);
> > +	int (*g_input)(struct v4l2_subdev *sd, u32 *index);
> > +	int (*s_input)(struct v4l2_subdev *sd, u32 index);
> >  	int (*s_stream)(struct v4l2_subdev *sd, int enable);
> >  	int (*g_pixelaspect)(struct v4l2_subdev *sd, struct v4l2_fract *aspect);
> >  	int (*g_frame_interval)(struct v4l2_subdev *sd,

-- 
Regards,

Laurent Pinchart