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Date:   Fri, 26 Jun 2020 12:28:45 +0200
From:   Ramzi Ben Meftah <rbmeftah@de.adit-jv.com>
To:     Hans Verkuil <hverkuil@xs4all.nl>
CC:     Ramzi Ben Meftah <rbmeftah@de.adit-jv.com>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Jacopo Mondi <jacopo@jmondi.org>,
        niklas soderlund <niklas.soderlund@ragnatech.se>,
        Kieran Bingham <kieran.bingham@ideasonboard.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Hans Verkuil <hans.verkuil@cisco.com>,
        Sakari Ailus <sakari.ailus@linux.intel.com>,
        Janusz Krzysztofik <jmkrzyszt@gmail.com>,
        Steve Longerbeam <steve_longerbeam@mentor.com>,
        Ezequiel Garcia <ezequiel@collabora.com>,
        Arnd Bergmann <arnd@arndb.de>, <linux-media@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>,
        Michael Rodin <mrodin@de.adit-jv.com>,
        <efriedrich@de.adit-jv.com>, <erosca@de.adit-jv.com>
Subject: Re: [PATCH 1/3] v4l2-subdev: Add subdev ioctl support for
 ENUM/GET/SET INPUT
Message-ID: <20200626102832.GA89964@vmlxhi-110.adit-jv.com>
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On Fri, Jun 26, 2020 at 11:25:31AM +0200, Hans Verkuil wrote:
> On 26/06/2020 11:09, 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@mentor.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.
> 
> You can check for digital timings using QUERY_DV_TIMINGS: it will return an
> error if there is no lock. Subscribe to the SOURCE_CHANGE event to know when
> the signal is found/lost.
> 
> For analog timings you have QUERYSTD and the same event. The main limitation
> with analog (SDTV) video receivers is that not all analog receivers have implemented
> this event. But the adv7180 and tvp5150 do support this.
> 
> This is the recommended way of implementing this and it has the advantage of
> being interrupt-driven, so no need to poll for a status in the application.

Thank you Hans, things are clear now.

> 
> Regards,
> 
> 	Hans
> 
> > 
> >>
> >> 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@mentor.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.