Re: [PATCH v3 1/5] v4l2-dev/ioctl: Add V4L2_CAP_IO_MC

[Hans Verkuil <hverkuil@xs4all.nl>]

On 1/13/20 1:09 PM, Sakari Ailus wrote:
> Hejssan!
> 
> Tack för lappan!
> 
> On Mon, Jan 13, 2020 at 12:24:54AM +0100, Niklas Söderlund wrote:
>> Add a video device capability flag to indicate that its inputs and/or
>> outputs are controlled by the Media Controller instead of the V4L2 API.
>> When this flag is set, ioctl for enum inputs and outputs are
>> automatically enabled and programmed to call a helper function.
>>
>> As a bonus fallback default handlers for VIDIOC_{G,S}_{INPUT,OUTPUT} are
>> provided which can be used by drivers who only provide one input/output.
>> Such drivers need just not declare vidioc_{g,s}_{input,output} in its
>> struct v4l2_ioctl_ops and v4l2 will fallback to the single input/output
>> defaults.
>>
>> Suggested-by: Hans Verkuil <hverkuil@xs4all.nl>
>> Signed-off-by: Helen Koike <helen.koike@collabora.com>
>> Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
>> ---
>> * Changes since v2
>> - Merged the two patches touching V4L2 core stuff to a single patch.
>> - Updated documentation for V4L2_CAP_IO_MC
>> - Added is_io_mc bool in determine_valid_ioctls()
>> - Folded or moved code closer to where it's used
>> - Remove unneeded memset()
>> - Use strscpy() instead of strlcpy()
>> ---
>>  .../media/uapi/v4l/vidioc-querycap.rst        |  5 ++
>>  .../media/videodev2.h.rst.exceptions          |  1 +
>>  drivers/media/v4l2-core/v4l2-dev.c            | 19 +++--
>>  drivers/media/v4l2-core/v4l2-ioctl.c          | 69 +++++++++++++++++--
>>  include/uapi/linux/videodev2.h                |  2 +
>>  5 files changed, 86 insertions(+), 10 deletions(-)
>>
>> diff --git a/Documentation/media/uapi/v4l/vidioc-querycap.rst b/Documentation/media/uapi/v4l/vidioc-querycap.rst
>> index 5f9930195d624c73..da17e0e3c6f9a571 100644
>> --- a/Documentation/media/uapi/v4l/vidioc-querycap.rst
>> +++ b/Documentation/media/uapi/v4l/vidioc-querycap.rst
>> @@ -264,6 +264,11 @@ specification the ioctl returns an ``EINVAL`` error code.
>>      * - ``V4L2_CAP_TOUCH``
>>        - 0x10000000
>>        - This is a touch device.
>> +    * - ``V4L2_CAP_IO_MC``
>> +      - 0x20000000
>> +      - There is only one input and/or output seen from userspace. Which I/O
>> +        entity is routed to the input/output is controlled by the Media
>> +        Controller. See :ref:`media_controller`.
> 
> I feel we should think of the MC flag in a bit wider context of device
> profiles. They've been suggested but I don't think anyone has implemented
> any code to support them.

There is implicit code: i.e. v4l2-dev.c does ever more checking of which ioctls
should be disabled based on the device capabilities, and v4l2-compliance is also
checking that. But nothing of that is really written down.

> Valid formats, for instance, also are determined by the format
> configuration on the MC pipeline in this case.

How about this:

      - There is only one input and/or output seen from userspace. The whole
        video topology configuration, including which I/O entity is routed to
        the input/output, is configured by userspace via the Media Controller.
        See :ref:`media_controller`.

That makes it more explicit that 1) it is userspace that configures this, and
2) that there is a lot more that is configured besides the routing.

> 
> I wonder if the MC input type (as below) would address this bit, without
> going to the device profiles yet?
> 
>>      * - ``V4L2_CAP_DEVICE_CAPS``
>>        - 0x80000000
>>        - The driver fills the ``device_caps`` field. This capability can
>> diff --git a/Documentation/media/videodev2.h.rst.exceptions b/Documentation/media/videodev2.h.rst.exceptions
>> index cb6ccf91776e6b56..a625fb90e3a989a7 100644
>> --- a/Documentation/media/videodev2.h.rst.exceptions
>> +++ b/Documentation/media/videodev2.h.rst.exceptions
>> @@ -176,6 +176,7 @@ replace define V4L2_CAP_STREAMING device-capabilities
>>  replace define V4L2_CAP_META_OUTPUT device-capabilities
>>  replace define V4L2_CAP_DEVICE_CAPS device-capabilities
>>  replace define V4L2_CAP_TOUCH device-capabilities
>> +replace define V4L2_CAP_IO_MC device-capabilities
>>  
>>  # V4L2 pix flags
>>  replace define V4L2_PIX_FMT_PRIV_MAGIC :c:type:`v4l2_pix_format`
>> diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c
>> index da42d172714adcb5..3c1a1200aa1fa9f3 100644
>> --- a/drivers/media/v4l2-core/v4l2-dev.c
>> +++ b/drivers/media/v4l2-core/v4l2-dev.c
>> @@ -552,6 +552,7 @@ static void determine_valid_ioctls(struct video_device *vdev)
>>  		       (vdev->device_caps & meta_caps);
>>  	bool is_rx = vdev->vfl_dir != VFL_DIR_TX;
>>  	bool is_tx = vdev->vfl_dir != VFL_DIR_RX;
>> +	bool is_io_mc = vdev->device_caps & V4L2_CAP_IO_MC;
>>  
>>  	bitmap_zero(valid_ioctls, BASE_VIDIOC_PRIVATE);
>>  
>> @@ -725,22 +726,28 @@ static void determine_valid_ioctls(struct video_device *vdev)
>>  		SET_VALID_IOCTL(ops, VIDIOC_G_STD, vidioc_g_std);
>>  		if (is_rx) {
>>  			SET_VALID_IOCTL(ops, VIDIOC_QUERYSTD, vidioc_querystd);
>> -			SET_VALID_IOCTL(ops, VIDIOC_ENUMINPUT, vidioc_enum_input);
>> -			SET_VALID_IOCTL(ops, VIDIOC_G_INPUT, vidioc_g_input);
>> -			SET_VALID_IOCTL(ops, VIDIOC_S_INPUT, vidioc_s_input);
>> +			set_bit(_IOC_NR(VIDIOC_G_INPUT), valid_ioctls);
>> +			set_bit(_IOC_NR(VIDIOC_S_INPUT), valid_ioctls);
>>  			SET_VALID_IOCTL(ops, VIDIOC_ENUMAUDIO, vidioc_enumaudio);
>>  			SET_VALID_IOCTL(ops, VIDIOC_G_AUDIO, vidioc_g_audio);
>>  			SET_VALID_IOCTL(ops, VIDIOC_S_AUDIO, vidioc_s_audio);
>>  			SET_VALID_IOCTL(ops, VIDIOC_QUERY_DV_TIMINGS, vidioc_query_dv_timings);
>>  			SET_VALID_IOCTL(ops, VIDIOC_S_EDID, vidioc_s_edid);
>> +			if (is_io_mc)
>> +				set_bit(_IOC_NR(VIDIOC_ENUMINPUT), valid_ioctls);
>> +			else
>> +				SET_VALID_IOCTL(ops, VIDIOC_ENUMINPUT, vidioc_enum_input);
>>  		}
>>  		if (is_tx) {
>> -			SET_VALID_IOCTL(ops, VIDIOC_ENUMOUTPUT, vidioc_enum_output);
>> -			SET_VALID_IOCTL(ops, VIDIOC_G_OUTPUT, vidioc_g_output);
>> -			SET_VALID_IOCTL(ops, VIDIOC_S_OUTPUT, vidioc_s_output);
>> +			set_bit(_IOC_NR(VIDIOC_G_OUTPUT), valid_ioctls);
>> +			set_bit(_IOC_NR(VIDIOC_S_OUTPUT), valid_ioctls);
>>  			SET_VALID_IOCTL(ops, VIDIOC_ENUMAUDOUT, vidioc_enumaudout);
>>  			SET_VALID_IOCTL(ops, VIDIOC_G_AUDOUT, vidioc_g_audout);
>>  			SET_VALID_IOCTL(ops, VIDIOC_S_AUDOUT, vidioc_s_audout);
>> +			if (is_io_mc)
>> +				set_bit(_IOC_NR(VIDIOC_ENUMOUTPUT), valid_ioctls);
>> +			else
>> +				SET_VALID_IOCTL(ops, VIDIOC_ENUMOUTPUT, vidioc_enum_output);
>>  		}
>>  		if (ops->vidioc_g_parm || ops->vidioc_g_std)
>>  			set_bit(_IOC_NR(VIDIOC_G_PARM), valid_ioctls);
>> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
>> index aaf83e25427288fd..e8e15deeb8f36a9d 100644
>> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
>> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
>> @@ -1085,6 +1085,28 @@ static int v4l_querycap(const struct v4l2_ioctl_ops *ops,
>>  	return ret;
>>  }
>>  
>> +static int v4l_g_input(const struct v4l2_ioctl_ops *ops,
>> +		       struct file *file, void *fh, void *arg)
>> +{
>> +	if (!ops->vidioc_g_input) {
>> +		*(unsigned int *)arg = 0;
>> +		return 0;
>> +	}
>> +
>> +	return ops->vidioc_g_input(file, fh, arg);
>> +}
>> +
>> +static int v4l_g_output(const struct v4l2_ioctl_ops *ops,
>> +		       struct file *file, void *fh, void *arg)
>> +{
>> +	if (!ops->vidioc_g_output) {
>> +		*(unsigned int *)arg = 0;
>> +		return 0;
>> +	}
>> +
>> +	return ops->vidioc_g_output(file, fh, arg);
>> +}
>> +
>>  static int v4l_s_input(const struct v4l2_ioctl_ops *ops,
>>  				struct file *file, void *fh, void *arg)
>>  {
>> @@ -1094,12 +1116,19 @@ static int v4l_s_input(const struct v4l2_ioctl_ops *ops,
>>  	ret = v4l_enable_media_source(vfd);
>>  	if (ret)
>>  		return ret;
>> +
>> +	if (!ops->vidioc_s_input)
>> +		return  *(unsigned int *)arg ? -EINVAL : 0;
>> +
>>  	return ops->vidioc_s_input(file, fh, *(unsigned int *)arg);
>>  }
>>  
>>  static int v4l_s_output(const struct v4l2_ioctl_ops *ops,
>>  				struct file *file, void *fh, void *arg)
>>  {
>> +	if (!ops->vidioc_s_output)
>> +		return  *(unsigned int *)arg ? -EINVAL : 0;
>> +
>>  	return ops->vidioc_s_output(file, fh, *(unsigned int *)arg);
>>  }
>>  
>> @@ -1128,6 +1157,20 @@ static int v4l_s_priority(const struct v4l2_ioctl_ops *ops,
>>  	return v4l2_prio_change(vfd->prio, &vfh->prio, *p);
>>  }
>>  
>> +static int v4l2_ioctl_enum_input_mc(struct file *file, void *priv,
>> +				    struct v4l2_input *i)
>> +{
>> +	struct video_device *vfd = video_devdata(file);
>> +
>> +	if (i->index)
>> +		return -EINVAL;
>> +
>> +	strscpy(i->name, vfd->name, sizeof(i->name));
>> +	i->type = V4L2_INPUT_TYPE_CAMERA;
> 
> Doesn't this deserve its own input type? Say, V4L2_INPUT_TYPE_MC, for
> instance?

I think that will break the ABI. It's always been TYPE_CAMERA.

> Most MC-enabled drivers are related to cameras but you can attach e.g. a TV
> tuner to at least some of them. The API is really not about cameras as such
> either.

It's really an historical accident. I think I proposed at some time to add an
alias:

#define V4L2_INPUT_TYPE_VIDEO V4L2_INPUT_TYPE_CAMERA

Since 'Camera' really is used as a 'Video' input which may come from various
sources (sensors, video receivers, etc.).

Regards,

	Hans

> 
>> +
>> +	return 0;
>> +}
>> +
>>  static int v4l_enuminput(const struct v4l2_ioctl_ops *ops,
>>  				struct file *file, void *fh, void *arg)
>>  {
>> @@ -1143,9 +1186,26 @@ static int v4l_enuminput(const struct v4l2_ioctl_ops *ops,
>>  	if (is_valid_ioctl(vfd, VIDIOC_S_STD))
>>  		p->capabilities |= V4L2_IN_CAP_STD;
>>  
>> +	if (vfd->device_caps & V4L2_CAP_IO_MC)
>> +		return v4l2_ioctl_enum_input_mc(file, fh, p);
>> +
>>  	return ops->vidioc_enum_input(file, fh, p);
>>  }
>>  
>> +static int v4l2_ioctl_enum_output_mc(struct file *file, void *priv,
>> +				     struct v4l2_output *o)
>> +{
>> +	struct video_device *vfd = video_devdata(file);
>> +
>> +	if (o->index)
>> +		return -EINVAL;
>> +
>> +	strscpy(o->name, vfd->name, sizeof(o->name));
>> +	o->type = V4L2_OUTPUT_TYPE_ANALOG;
>> +
>> +	return 0;
>> +}
>> +
>>  static int v4l_enumoutput(const struct v4l2_ioctl_ops *ops,
>>  				struct file *file, void *fh, void *arg)
>>  {
>> @@ -1161,6 +1221,9 @@ static int v4l_enumoutput(const struct v4l2_ioctl_ops *ops,
>>  	if (is_valid_ioctl(vfd, VIDIOC_S_STD))
>>  		p->capabilities |= V4L2_OUT_CAP_STD;
>>  
>> +	if (vfd->device_caps & V4L2_CAP_IO_MC)
>> +		return v4l2_ioctl_enum_output_mc(file, fh, p);
>> +
>>  	return ops->vidioc_enum_output(file, fh, p);
>>  }
>>  
>> @@ -2678,10 +2741,8 @@ DEFINE_V4L_STUB_FUNC(expbuf)
>>  DEFINE_V4L_STUB_FUNC(g_std)
>>  DEFINE_V4L_STUB_FUNC(g_audio)
>>  DEFINE_V4L_STUB_FUNC(s_audio)
>> -DEFINE_V4L_STUB_FUNC(g_input)
>>  DEFINE_V4L_STUB_FUNC(g_edid)
>>  DEFINE_V4L_STUB_FUNC(s_edid)
>> -DEFINE_V4L_STUB_FUNC(g_output)
>>  DEFINE_V4L_STUB_FUNC(g_audout)
>>  DEFINE_V4L_STUB_FUNC(s_audout)
>>  DEFINE_V4L_STUB_FUNC(g_jpegcomp)
>> @@ -2730,11 +2791,11 @@ static const struct v4l2_ioctl_info v4l2_ioctls[] = {
>>  	IOCTL_INFO(VIDIOC_S_AUDIO, v4l_stub_s_audio, v4l_print_audio, INFO_FL_PRIO),
>>  	IOCTL_INFO(VIDIOC_QUERYCTRL, v4l_queryctrl, v4l_print_queryctrl, INFO_FL_CTRL | INFO_FL_CLEAR(v4l2_queryctrl, id)),
>>  	IOCTL_INFO(VIDIOC_QUERYMENU, v4l_querymenu, v4l_print_querymenu, INFO_FL_CTRL | INFO_FL_CLEAR(v4l2_querymenu, index)),
>> -	IOCTL_INFO(VIDIOC_G_INPUT, v4l_stub_g_input, v4l_print_u32, 0),
>> +	IOCTL_INFO(VIDIOC_G_INPUT, v4l_g_input, v4l_print_u32, 0),
>>  	IOCTL_INFO(VIDIOC_S_INPUT, v4l_s_input, v4l_print_u32, INFO_FL_PRIO),
>>  	IOCTL_INFO(VIDIOC_G_EDID, v4l_stub_g_edid, v4l_print_edid, INFO_FL_ALWAYS_COPY),
>>  	IOCTL_INFO(VIDIOC_S_EDID, v4l_stub_s_edid, v4l_print_edid, INFO_FL_PRIO | INFO_FL_ALWAYS_COPY),
>> -	IOCTL_INFO(VIDIOC_G_OUTPUT, v4l_stub_g_output, v4l_print_u32, 0),
>> +	IOCTL_INFO(VIDIOC_G_OUTPUT, v4l_g_output, v4l_print_u32, 0),
>>  	IOCTL_INFO(VIDIOC_S_OUTPUT, v4l_s_output, v4l_print_u32, INFO_FL_PRIO),
>>  	IOCTL_INFO(VIDIOC_ENUMOUTPUT, v4l_enumoutput, v4l_print_enumoutput, INFO_FL_CLEAR(v4l2_output, index)),
>>  	IOCTL_INFO(VIDIOC_G_AUDOUT, v4l_stub_g_audout, v4l_print_audioout, 0),
>> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
>> index 5f9357dcb0602126..c793263a37052856 100644
>> --- a/include/uapi/linux/videodev2.h
>> +++ b/include/uapi/linux/videodev2.h
>> @@ -487,6 +487,8 @@ struct v4l2_capability {
>>  
>>  #define V4L2_CAP_TOUCH                  0x10000000  /* Is a touch device */
>>  
>> +#define V4L2_CAP_IO_MC			0x20000000  /* Is input/output controlled by the media controller */
>> +
>>  #define V4L2_CAP_DEVICE_CAPS            0x80000000  /* sets device capabilities field */
>>  
>>  /*
>