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

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Message-ID: <cc072f11-c562-af95-58a9-ebfcf3dfdfcd@xs4all.nl>
Date:   Wed, 24 Jun 2020 12:16:33 +0200
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Ramzi BEN MEFTAH <rbmeftah@...adit-jv.com>,
        Kieran Bingham <kieran.bingham@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Janusz Krzysztofik <jmkrzyszt@...il.com>,
        Jacopo Mondi <jacopo@...ndi.org>,
        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
Cc:     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 24/06/2020 12:08, Hans Verkuil wrote:
> On 16/06/2020 12:00, Ramzi BEN MEFTAH wrote:
>> From: Steve Longerbeam <steve_longerbeam@...tor.com>
>>
>> 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>
> 
> Nacked-by: Hans Verkuil <hverkuil-cisco@...all.nl>
> 
> This doesn't work: these ioctls refer to physical inputs on a backplane
> of a device. But subdevices have no idea about that. This is high-level
> information that is typically only known to a bridge driver based on
> board information.
> 
> For PCI/USB drivers this comes from card definitions in the driver itself.
> 
> For platform drivers this should come from the device tree, but this hasn't
> been fully implemented yet.
> 
> So if this is something that you want to implement, then look at:
> 
> Documentation/devicetree/bindings/display/connector/hdmi-connector.txt
> 
> and add this to the DT for your board, and implement code to query this
> in the platform driver.

Follow-up: in system with a media device and v4l-subdev devices (so MC-centric)
this might make sense, provided the connector data is obtained from the DT.

An alternative is to expose the connectors in the media topology and use
SETUP_LINK to choose which connector to pick.

I don't have a strong preference, but in both cases this information should
come from the device tree.

Regards,

	Hans

> 
> Regards,
> 
> 	Hans
> 
>> ---
>>  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,
>>
>