Re: [PATCH v4 1/3] v4l2-dev/ioctl: Add V4L2_CAP_IO_MC

[Sakari Ailus <sakari.ailus@linux.intel.com>]

Hi Hans,

On Mon, Mar 09, 2020 at 02:53:15PM +0100, Hans Verkuil wrote:
> On 3/9/20 2:47 PM, Sakari Ailus wrote:
> > Hi Niklas,
> > 
> > Thanks for the update!
> > 
> > On Fri, Mar 06, 2020 at 05:39:33PM +0100, Niklas Söderlund wrote:
> >> From: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
> >>
> >> 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.
> >>
> >> 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 v3
> >> - Update documentation for V4L2_CAP_IO_MC
> >> - Only enable VIDIOC_{G,S}_{INPUT,OUTPUT} if V4L2_CAP_IO_MC is set
> >>   (instead of unconditionally)
> >> - Merge v4l2_ioctl_enum_input_mc() into v4l_enuminput()
> >> - Merge v4l2_ioctl_enum_output_mc() into v4l_enumoutput()
> >>
> >> * 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        |  6 ++
> >>  .../media/videodev2.h.rst.exceptions          |  1 +
> >>  drivers/media/v4l2-core/v4l2-dev.c            | 25 ++++++--
> >>  drivers/media/v4l2-core/v4l2-ioctl.c          | 57 +++++++++++++++++--
> >>  include/uapi/linux/videodev2.h                |  2 +
> >>  5 files changed, 81 insertions(+), 10 deletions(-)
> >>
> >> diff --git a/Documentation/media/uapi/v4l/vidioc-querycap.rst b/Documentation/media/uapi/v4l/vidioc-querycap.rst
> >> index 5f9930195d624c73..497a6aa2cbebad71 100644
> >> --- a/Documentation/media/uapi/v4l/vidioc-querycap.rst
> >> +++ b/Documentation/media/uapi/v4l/vidioc-querycap.rst
> >> @@ -264,6 +264,12 @@ 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. 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`.
> >>      * - ``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 97b6a3af13614639..a593ea0598b551b4 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);
> >>  
> >> @@ -725,9 +726,15 @@ 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);
> >> +			if (is_io_mc) {
> >> +				set_bit(_IOC_NR(VIDIOC_ENUMINPUT), valid_ioctls);
> >> +				set_bit(_IOC_NR(VIDIOC_G_INPUT), valid_ioctls);
> >> +				set_bit(_IOC_NR(VIDIOC_S_INPUT), valid_ioctls);
> >> +			} else {
> >> +				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_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);
> >> @@ -735,9 +742,15 @@ static void determine_valid_ioctls(struct video_device *vdev)
> >>  			SET_VALID_IOCTL(ops, VIDIOC_S_EDID, vidioc_s_edid);
> >>  		}
> >>  		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);
> >> +			if (is_io_mc) {
> >> +				set_bit(_IOC_NR(VIDIOC_ENUMOUTPUT), valid_ioctls);
> >> +				set_bit(_IOC_NR(VIDIOC_G_OUTPUT), valid_ioctls);
> >> +				set_bit(_IOC_NR(VIDIOC_S_OUTPUT), valid_ioctls);
> >> +			} else {
> >> +				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_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);
> >> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> >> index fbcc7a20eedf553a..58e9e728f0a7aa4b 100644
> >> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> >> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> >> @@ -1085,6 +1085,32 @@ 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)
> >> +{
> >> +	struct video_device *vfd = video_devdata(file);
> >> +
> >> +	if (vfd->device_caps & V4L2_CAP_IO_MC) {
> >> +		*(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)
> >> +{
> >> +	struct video_device *vfd = video_devdata(file);
> >> +
> >> +	if (vfd->device_caps & V4L2_CAP_IO_MC) {
> >> +		*(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 +1120,21 @@ static int v4l_s_input(const struct v4l2_ioctl_ops *ops,
> >>  	ret = v4l_enable_media_source(vfd);
> >>  	if (ret)
> >>  		return ret;
> >> +
> >> +	if (vfd->device_caps & V4L2_CAP_IO_MC)
> >> +		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)
> >>  {
> >> +	struct video_device *vfd = video_devdata(file);
> >> +
> >> +	if (vfd->device_caps & V4L2_CAP_IO_MC)
> >> +		return  *(unsigned int *)arg ? -EINVAL : 0;
> > 
> > The type is int, not unsigned int. The same on the rest above.
> > 
> >> +
> >>  	return ops->vidioc_s_output(file, fh, *(unsigned int *)arg);
> >>  }
> >>  
> >> @@ -1143,6 +1178,14 @@ 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) {
> >> +		if (p->index)
> >> +			return -EINVAL;
> >> +		strscpy(p->name, vfd->name, sizeof(p->name));
> >> +		p->type = V4L2_INPUT_TYPE_CAMERA;
> >> +		return 0;
> >> +	}
> >> +
> >>  	return ops->vidioc_enum_input(file, fh, p);
> >>  }
> >>  
> >> @@ -1161,6 +1204,14 @@ 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) {
> >> +		if (p->index)
> >> +			return -EINVAL;
> >> +		strscpy(p->name, vfd->name, sizeof(p->name));
> >> +		p->type = V4L2_OUTPUT_TYPE_ANALOG;
> > 
> > How about adding a new INPUT and OUTPUT types just for IO_MC device cap?
> 
> V4L2_OUTPUT_TYPE_ANALOG is an old term that is in practice used for anything video,
> except for TV modulators. I'm all in favor of changing this to:
> 
> #define V4L2_OUTPUT_TYPE_VIDEO 2
> #ifndef __KERNEL__
> #define V4L2_OUTPUT_TYPE_ANALOG V4L2_OUTPUT_TYPE_VIDEO
> #endif
> 
> in videodev2.h, if others agree with that. But that can be done in a separate
> follow-up patch since this needs to be adapted throughout the kernel & documentation.
> 
> The same is true for V4L2_INPUT_TYPE_CAMERA: in practice it's used for any video,
> except TV tuners.

My point was rather that here, we don't know what kind of device really is
the source (or the sink) of the data path. Having a designated input and
output type for that would be entirely appropriate.

Although if the user gets a misleading value using an interface that
(s)he's not supposed to use to begin with, I guess I'd fine with that as
well.

-- 
Regards,

Sakari Ailus