Date:   Fri, 26 Jun 2020 11:15:48 +0200
From:   Ramzi Ben Meftah <rbmeftah@...adit-jv.com>
To:     Hans Verkuil <hverkuil@...all.nl>
CC:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Ramzi Ben Meftah <rbmeftah@...adit-jv.com>,
        Jacopo Mondi <jacopo@...ndi.org>,
        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

On Fri, Jun 26, 2020 at 11:09:13AM +0200, Ramzi Ben Meftah wrote:
> Hi Laurent, Hans,
> 
> On Thu, Jun 25, 2020 at 12:35:02PM +0200, Hans Verkuil wrote:
> > On 25/06/2020 12:29, Laurent Pinchart wrote:
> > > Hi Ramzi,
> > > 
> > > On Thu, Jun 25, 2020 at 12:18:35PM +0200, Ramzi Ben Meftah wrote:
> > >> On Thu, Jun 25, 2020 at 12:47:24PM +0300, Laurent Pinchart wrote:
> > >>> On Thu, Jun 25, 2020 at 11:30:46AM +0200, Ramzi Ben Meftah wrote:
> > >>>> On Thu, Jun 25, 2020 at 05:01:38AM +0300, Laurent Pinchart wrote:
> > >>>>> 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.
> > >>>>
> > >>>> ENUMINPUT ioctl allow to get the input signal status. Is there an alternative
> > >>>> with Media Controller?
> > >>>
> > >>> No there isn't at the moment. I'm not opposed to adding such a feature,
> > >>> but VIDIOC_ENUMINPUT isn't the right choice. This would have to be a
> > >>> subdev pad operation (v4l2_subdev_pad_ops), not a video operation
> > >>> (v4l2_subdev_video_ops). We also likely shouldn't call it "enum" input,
> > >>> as it would retrieve properties of the input corresponding to the pad,
> > >>> not enumerate inputs.
> > >>
> > >> Looking to v4l2_subdev_pad_ops, there is g_input_status which seems to fulfill
> > >> this need. But, seems this is not expose to user space although many drivers
> > >> do implememt it.
> > >> Should I add VIDIOC_SUBDEV_G_INPUT_STATUS?
> > > 
> > > Isn't g_input_status a video operation ? I would propose adding a
> > > g_input_status pad operation, and expose that to userspace. We should
> > > take that as an opportunity to consider designing that new operation
> > > from scratch (possibly naming it differently) and make sure it could
> > > address both analog and digital systems (for instance being able to
> > > report the status of an SDI input).
> 
> Sorry, my mistake. But, does it make sens that it belongs to video ops?
> I think it should be part of pad ops, it is used now as alternative to 
> ENUMINPUT and we agreed that it should(if we are going to implement it) be 
> part of pad ops.
> 
> > 
> > Yes, I was wondering the same. The status bits are ancient and we might
> > want to improve on it.
> > 
> > Ramzi, what exactly is your use-case? Is this for an HDMI input? Analog
> > video input? Before adding a new ioctl I'd like to know why you think
> > you need it :-)
> 
> I need to know if the input signal(analog and digital) is there, before
> starting streaming. I am not aware of other way to check for it.

There is also no alternative for V4L2_IN_ST_NO_POWER and V4L2_IN_ST_NO_COLOR
I am not using these two, but these were available with ENUMINPUT ioctl
and a subdev driver that could offer these info has no way to pass them to
userspace.

> 
> > 
> > Regards,
> > 
> > 	Hans
> > 
> > > 
> > >>>>>>> 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,
> > > 
> > 
> 
> -- 
> Best Regards,
> Ramzi Ben Meftah.

-- 
Best Regards,
Ramzi Ben Meftah.

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