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

[Hans Verkuil]

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@xxxxxxxxxx>
>>>>>>>>
>>>>>>>>  +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.

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@xxxxxxxxxx>
>>>>>>>>> ---
>>>>>>>>>  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,
>>>
>>
>