Re: [PATCH v9 31/36] media: subdev: add stream based configuration

[Hans Verkuil <hverkuil-cisco@xs4all.nl>]

On 05/10/2021 10:57, Tomi Valkeinen wrote:
> Add support to manage configurations (format, crop, compose) per stream,

Isn't that 'pad+stream'? This sentence suggests that 'stream' replaces 'pad',
but it is 'in addition to', right?

> instead of per pad. This is accomplished with data structures that hold
> an array of all subdev's stream configurations.
> 
> The number of streams can vary at runtime based on routing. Every time
> the routing is changed, the stream configurations need to be
> re-initialized.

Is this documented? I can't remember reading this, but I may have missed this.
And what if the new routing leaves one stream unchanged, and changes a second,
does that still mean that both stream configurations need to be re-initialized,
or just that of the changed stream?

If changing the routing, even if the route of an existing stream stays unchanged,
will require this re-initialization, then that has to be documented clearly, including
in the affected ioctls.

Regards,

	Hans

> 
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
> ---
>  .../v4l/vidioc-subdev-enum-frame-interval.rst |   5 +-
>  .../v4l/vidioc-subdev-enum-frame-size.rst     |   5 +-
>  .../v4l/vidioc-subdev-enum-mbus-code.rst      |   5 +-
>  .../media/v4l/vidioc-subdev-g-crop.rst        |   5 +-
>  .../media/v4l/vidioc-subdev-g-fmt.rst         |   5 +-
>  .../v4l/vidioc-subdev-g-frame-interval.rst    |   5 +-
>  .../media/v4l/vidioc-subdev-g-selection.rst   |   5 +-
>  drivers/media/v4l2-core/v4l2-subdev.c         | 140 +++++++++++++++++-
>  include/media/v4l2-subdev.h                   |  48 ++++++
>  include/uapi/linux/v4l2-subdev.h              |  28 +++-
>  10 files changed, 229 insertions(+), 22 deletions(-)
> 
> diff --git a/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-frame-interval.rst b/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-frame-interval.rst
> index 3703943b412f..8def4c05d3da 100644
> --- a/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-frame-interval.rst
> +++ b/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-frame-interval.rst
> @@ -92,7 +92,10 @@ multiple pads of the same sub-device is not defined.
>        - Frame intervals to be enumerated, from enum
>  	:ref:`v4l2_subdev_format_whence <v4l2-subdev-format-whence>`.
>      * - __u32
> -      - ``reserved``\ [8]
> +      - ``stream``
> +      - Stream identifier.
> +    * - __u32
> +      - ``reserved``\ [7]
>        - Reserved for future extensions. Applications and drivers must set
>  	the array to zero.
>  
> diff --git a/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-frame-size.rst b/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-frame-size.rst
> index c25a9896df0e..3ef361c0dca7 100644
> --- a/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-frame-size.rst
> +++ b/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-frame-size.rst
> @@ -97,7 +97,10 @@ information about try formats.
>        - Frame sizes to be enumerated, from enum
>  	:ref:`v4l2_subdev_format_whence <v4l2-subdev-format-whence>`.
>      * - __u32
> -      - ``reserved``\ [8]
> +      - ``stream``
> +      - Stream identifier.
> +    * - __u32
> +      - ``reserved``\ [7]
>        - Reserved for future extensions. Applications and drivers must set
>  	the array to zero.
>  
> diff --git a/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-mbus-code.rst b/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-mbus-code.rst
> index 417f1a19bcc4..248f6f9ee7c5 100644
> --- a/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-mbus-code.rst
> +++ b/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-mbus-code.rst
> @@ -73,7 +73,10 @@ information about the try formats.
>        - ``flags``
>        - See :ref:`v4l2-subdev-mbus-code-flags`
>      * - __u32
> -      - ``reserved``\ [7]
> +      - ``stream``
> +      - Stream identifier.
> +    * - __u32
> +      - ``reserved``\ [6]
>        - Reserved for future extensions. Applications and drivers must set
>  	the array to zero.
>  
> diff --git a/Documentation/userspace-api/media/v4l/vidioc-subdev-g-crop.rst b/Documentation/userspace-api/media/v4l/vidioc-subdev-g-crop.rst
> index bd15c0a5a66b..1d267f7e7991 100644
> --- a/Documentation/userspace-api/media/v4l/vidioc-subdev-g-crop.rst
> +++ b/Documentation/userspace-api/media/v4l/vidioc-subdev-g-crop.rst
> @@ -96,7 +96,10 @@ modified format should be as close as possible to the original request.
>        - ``rect``
>        - Crop rectangle boundaries, in pixels.
>      * - __u32
> -      - ``reserved``\ [8]
> +      - ``stream``
> +      - Stream identifier.
> +    * - __u32
> +      - ``reserved``\ [7]
>        - Reserved for future extensions. Applications and drivers must set
>  	the array to zero.
>  
> diff --git a/Documentation/userspace-api/media/v4l/vidioc-subdev-g-fmt.rst b/Documentation/userspace-api/media/v4l/vidioc-subdev-g-fmt.rst
> index 7acdbb939d89..ed253a1e44b7 100644
> --- a/Documentation/userspace-api/media/v4l/vidioc-subdev-g-fmt.rst
> +++ b/Documentation/userspace-api/media/v4l/vidioc-subdev-g-fmt.rst
> @@ -102,7 +102,10 @@ should be as close as possible to the original request.
>        - Definition of an image format, see :c:type:`v4l2_mbus_framefmt` for
>  	details.
>      * - __u32
> -      - ``reserved``\ [8]
> +      - ``stream``
> +      - Stream identifier.
> +    * - __u32
> +      - ``reserved``\ [7]
>        - Reserved for future extensions. Applications and drivers must set
>  	the array to zero.
>  
> diff --git a/Documentation/userspace-api/media/v4l/vidioc-subdev-g-frame-interval.rst b/Documentation/userspace-api/media/v4l/vidioc-subdev-g-frame-interval.rst
> index d7fe7543c506..842f962d2aea 100644
> --- a/Documentation/userspace-api/media/v4l/vidioc-subdev-g-frame-interval.rst
> +++ b/Documentation/userspace-api/media/v4l/vidioc-subdev-g-frame-interval.rst
> @@ -90,7 +90,10 @@ the same sub-device is not defined.
>        - ``interval``
>        - Period, in seconds, between consecutive video frames.
>      * - __u32
> -      - ``reserved``\ [9]
> +      - ``stream``
> +      - Stream identifier.
> +    * - __u32
> +      - ``reserved``\ [8]
>        - Reserved for future extensions. Applications and drivers must set
>  	the array to zero.
>  
> diff --git a/Documentation/userspace-api/media/v4l/vidioc-subdev-g-selection.rst b/Documentation/userspace-api/media/v4l/vidioc-subdev-g-selection.rst
> index f9172a42f036..6b629c19168c 100644
> --- a/Documentation/userspace-api/media/v4l/vidioc-subdev-g-selection.rst
> +++ b/Documentation/userspace-api/media/v4l/vidioc-subdev-g-selection.rst
> @@ -94,7 +94,10 @@ Selection targets and flags are documented in
>        - ``r``
>        - Selection rectangle, in pixels.
>      * - __u32
> -      - ``reserved``\ [8]
> +      - ``stream``
> +      - Stream identifier.
> +    * - __u32
> +      - ``reserved``\ [7]
>        - Reserved for future extensions. Applications and drivers must set
>  	the array to zero.
>  
> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> index af53f827ec27..f63826755057 100644
> --- a/drivers/media/v4l2-core/v4l2-subdev.c
> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> @@ -149,14 +149,45 @@ static inline int check_pad(struct v4l2_subdev *sd, u32 pad)
>  	return 0;
>  }
>  
> -static int check_state_pads(u32 which, struct v4l2_subdev_state *state)
> +static int check_state_pads(struct v4l2_subdev *sd, u32 which,
> +			    struct v4l2_subdev_state *state)
>  {
> +	if (sd->flags & V4L2_SUBDEV_FL_MULTIPLEXED)
> +		return 0;
> +
>  	if (which == V4L2_SUBDEV_FORMAT_TRY && (!state || !state->pads))
>  		return -EINVAL;
>  
>  	return 0;
>  }
>  
> +static int check_state_pad_stream(struct v4l2_subdev *sd,
> +				  struct v4l2_subdev_state *state, u32 pad,
> +				  u32 stream)
> +{
> +	struct v4l2_mbus_framefmt *fmt;
> +
> +	if (!(sd->flags & V4L2_SUBDEV_FL_MULTIPLEXED))
> +		return 0;
> +
> +	/*
> +	 * We need to take the state lock to access the format, but as we then
> +	 * have to unlock, nothing prevents someone changing the state before
> +	 * this call thread enters the driver's op and the driver has the
> +	 * change to lock the state.
> +	 */
> +	v4l2_subdev_lock_state(state);
> +
> +	fmt = v4l2_state_get_stream_format(state, pad, stream);
> +
> +	v4l2_subdev_unlock_state(state);
> +
> +	if (!fmt)
> +		return -EINVAL;
> +
> +	return 0;
> +}
> +
>  static inline int check_format(struct v4l2_subdev *sd,
>  			       struct v4l2_subdev_state *state,
>  			       struct v4l2_subdev_format *format)
> @@ -165,7 +196,8 @@ static inline int check_format(struct v4l2_subdev *sd,
>  		return -EINVAL;
>  
>  	return check_which(format->which) ? : check_pad(sd, format->pad) ? :
> -	       check_state_pads(format->which, state);
> +	       check_state_pads(sd, format->which, state) ? :
> +	       check_state_pad_stream(sd, state, format->pad, format->stream);
>  }
>  
>  static int call_get_fmt(struct v4l2_subdev *sd,
> @@ -192,7 +224,8 @@ static int call_enum_mbus_code(struct v4l2_subdev *sd,
>  		return -EINVAL;
>  
>  	return check_which(code->which) ? : check_pad(sd, code->pad) ? :
> -	       check_state_pads(code->which, state) ? :
> +	       check_state_pads(sd, code->which, state) ? :
> +	       check_state_pad_stream(sd, state, code->pad, code->stream) ? :
>  	       sd->ops->pad->enum_mbus_code(sd, state, code);
>  }
>  
> @@ -204,7 +237,8 @@ static int call_enum_frame_size(struct v4l2_subdev *sd,
>  		return -EINVAL;
>  
>  	return check_which(fse->which) ? : check_pad(sd, fse->pad) ? :
> -	       check_state_pads(fse->which, state) ? :
> +	       check_state_pads(sd, fse->which, state) ? :
> +	       check_state_pad_stream(sd, state, fse->pad, fse->stream) ? :
>  	       sd->ops->pad->enum_frame_size(sd, state, fse);
>  }
>  
> @@ -239,7 +273,8 @@ static int call_enum_frame_interval(struct v4l2_subdev *sd,
>  		return -EINVAL;
>  
>  	return check_which(fie->which) ? : check_pad(sd, fie->pad) ? :
> -	       check_state_pads(fie->which, state) ? :
> +	       check_state_pads(sd, fie->which, state) ? :
> +	       check_state_pad_stream(sd, state, fie->pad, fie->stream) ? :
>  	       sd->ops->pad->enum_frame_interval(sd, state, fie);
>  }
>  
> @@ -251,7 +286,8 @@ static inline int check_selection(struct v4l2_subdev *sd,
>  		return -EINVAL;
>  
>  	return check_which(sel->which) ? : check_pad(sd, sel->pad) ? :
> -	       check_state_pads(sel->which, state);
> +	       check_state_pads(sd, sel->which, state) ? :
> +	       check_state_pad_stream(sd, state, sel->pad, sel->stream);
>  }
>  
>  static int call_get_selection(struct v4l2_subdev *sd,
> @@ -867,6 +903,71 @@ const struct v4l2_file_operations v4l2_subdev_fops = {
>  	.poll = subdev_poll,
>  };
>  
> +static int
> +v4l2_init_stream_configs(struct v4l2_subdev_stream_configs *stream_configs,
> +			 const struct v4l2_subdev_krouting *routing)
> +{
> +	u32 num_configs = 0;
> +	unsigned int i;
> +	u32 format_idx = 0;
> +
> +	kvfree(stream_configs->configs);
> +	stream_configs->configs = NULL;
> +	stream_configs->num_configs = 0;
> +
> +	/* Count number of formats needed */
> +	for (i = 0; i < routing->num_routes; ++i) {
> +		struct v4l2_subdev_route *route = &routing->routes[i];
> +
> +		if (!(route->flags & V4L2_SUBDEV_ROUTE_FL_ACTIVE))
> +			continue;
> +
> +		/*
> +		 * Each route needs a format on both ends of the route, except
> +		 * for source streams which only need one format.
> +		 */
> +		num_configs +=
> +			(route->flags & V4L2_SUBDEV_ROUTE_FL_SOURCE) ? 1 : 2;
> +	}
> +
> +	if (num_configs) {
> +		stream_configs->configs =
> +			kvcalloc(num_configs, sizeof(*stream_configs->configs),
> +				 GFP_KERNEL);
> +
> +		if (!stream_configs->configs)
> +			return -ENOMEM;
> +
> +		stream_configs->num_configs = num_configs;
> +	}
> +
> +	/*
> +	 * Fill in the 'pad' and stream' value for each item in the array from
> +	 * the routing table
> +	 */
> +	for (i = 0; i < routing->num_routes; ++i) {
> +		struct v4l2_subdev_route *route = &routing->routes[i];
> +		u32 idx;
> +
> +		if (!(route->flags & V4L2_SUBDEV_ROUTE_FL_ACTIVE))
> +			continue;
> +
> +		if (!(route->flags & V4L2_SUBDEV_ROUTE_FL_SOURCE)) {
> +			idx = format_idx++;
> +
> +			stream_configs->configs[idx].pad = route->sink_pad;
> +			stream_configs->configs[idx].stream = route->sink_stream;
> +		}
> +
> +		idx = format_idx++;
> +
> +		stream_configs->configs[idx].pad = route->source_pad;
> +		stream_configs->configs[idx].stream = route->source_stream;
> +	}
> +
> +	return 0;
> +}
> +
>  #ifdef CONFIG_MEDIA_CONTROLLER
>  
>  int v4l2_subdev_get_fwnode_pad_1_to_1(struct media_entity *entity,
> @@ -1042,7 +1143,8 @@ __v4l2_subdev_state_alloc(struct v4l2_subdev *sd, const char *lock_name,
>  
>  	__mutex_init(&state->lock, lock_name, lock_key);
>  
> -	if (sd->entity.num_pads) {
> +	/* Drivers that support streams do not need the legacy pad config */
> +	if (!(sd->flags & V4L2_SUBDEV_FL_MULTIPLEXED) && sd->entity.num_pads) {
>  		state->pads = kvmalloc_array(sd->entity.num_pads,
>  					     sizeof(*state->pads),
>  					     GFP_KERNEL | __GFP_ZERO);
> @@ -1076,6 +1178,7 @@ void __v4l2_subdev_state_free(struct v4l2_subdev_state *state)
>  	mutex_destroy(&state->lock);
>  
>  	kvfree(state->routing.routes);
> +	kvfree(state->stream_configs.configs);
>  	kvfree(state->pads);
>  	kfree(state);
>  }
> @@ -1176,6 +1279,27 @@ int v4l2_subdev_set_routing(struct v4l2_subdev *sd,
>  		dst->num_routes = src->num_routes;
>  	}
>  
> -	return 0;
> +	return v4l2_init_stream_configs(&state->stream_configs, dst);
>  }
>  EXPORT_SYMBOL_GPL(v4l2_subdev_set_routing);
> +
> +struct v4l2_mbus_framefmt *
> +v4l2_state_get_stream_format(struct v4l2_subdev_state *state, unsigned int pad,
> +			     u32 stream)
> +{
> +	struct v4l2_subdev_stream_configs *stream_configs;
> +	unsigned int i;
> +
> +	lockdep_assert_held(&state->lock);
> +
> +	stream_configs = &state->stream_configs;
> +
> +	for (i = 0; i < stream_configs->num_configs; ++i) {
> +		if (stream_configs->configs[i].pad == pad &&
> +		    stream_configs->configs[i].stream == stream)
> +			return &stream_configs->configs[i].fmt;
> +	}
> +
> +	return NULL;
> +}
> +EXPORT_SYMBOL_GPL(v4l2_state_get_stream_format);
> diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
> index b6c5cd00831e..1dc824416c1b 100644
> --- a/include/media/v4l2-subdev.h
> +++ b/include/media/v4l2-subdev.h
> @@ -694,6 +694,37 @@ struct v4l2_subdev_pad_config {
>  	struct v4l2_rect try_compose;
>  };
>  
> +/**
> + * struct v4l2_subdev_stream_config - Used for storing stream configuration.
> + *
> + * @pad: pad number
> + * @stream: stream number
> + * @fmt: &struct v4l2_mbus_framefmt
> + * @crop: &struct v4l2_rect to be used for crop
> + * @compose: &struct v4l2_rect to be used for compose
> + *
> + * This structure stores configuration for a stream.
> + */
> +struct v4l2_subdev_stream_config {
> +	u32 pad;
> +	u32 stream;
> +
> +	struct v4l2_mbus_framefmt fmt;
> +	struct v4l2_rect crop;
> +	struct v4l2_rect compose;
> +};
> +
> +/**
> + * struct v4l2_subdev_stream_configs - A collection of stream configs.
> + *
> + * @num_configs: number of entries in @config.
> + * @configs: an array of &struct v4l2_subdev_stream_configs.
> + */
> +struct v4l2_subdev_stream_configs {
> +	u32 num_configs;
> +	struct v4l2_subdev_stream_config *configs;
> +};
> +
>  /**
>   * struct v4l2_subdev_krouting - subdev routing table
>   *
> @@ -713,6 +744,7 @@ struct v4l2_subdev_krouting {
>   * @lock: mutex for the state
>   * @pads: &struct v4l2_subdev_pad_config array
>   * @routing: routing table for the subdev
> + * @stream_configs: stream configurations (only for V4L2_SUBDEV_FL_MULTIPLEXED)
>   *
>   * This structure only needs to be passed to the pad op if the 'which' field
>   * of the main argument is set to %V4L2_SUBDEV_FORMAT_TRY. For
> @@ -722,6 +754,7 @@ struct v4l2_subdev_state {
>  	struct mutex lock;
>  	struct v4l2_subdev_pad_config *pads;
>  	struct v4l2_subdev_krouting routing;
> +	struct v4l2_subdev_stream_configs stream_configs;
>  };
>  
>  /**
> @@ -1453,4 +1486,19 @@ int v4l2_subdev_set_routing(struct v4l2_subdev *sd,
>  			    struct v4l2_subdev_state *state,
>  			    struct v4l2_subdev_krouting *routing);
>  
> +/**
> + * v4l2_state_get_stream_format() - Get pointer to a stream format
> + * @state: subdevice state
> + * @pad: pad id
> + * @stream: stream id
> + *
> + * This returns a pointer to &struct v4l2_mbus_framefmt for the given pad +
> + * stream in the subdev state.
> + *
> + * If the state does not contain the given pad + stream, NULL is returned.
> + */
> +struct v4l2_mbus_framefmt *
> +v4l2_state_get_stream_format(struct v4l2_subdev_state *state, unsigned int pad,
> +			     u32 stream);
> +
>  #endif
> diff --git a/include/uapi/linux/v4l2-subdev.h b/include/uapi/linux/v4l2-subdev.h
> index 5ba409db47ff..f61ace2b5755 100644
> --- a/include/uapi/linux/v4l2-subdev.h
> +++ b/include/uapi/linux/v4l2-subdev.h
> @@ -44,13 +44,15 @@ enum v4l2_subdev_format_whence {
>   * @which: format type (from enum v4l2_subdev_format_whence)
>   * @pad: pad number, as reported by the media API
>   * @format: media bus format (format code and frame size)
> + * @stream: stream number, defined in subdev routing
>   * @reserved: drivers and applications must zero this array
>   */
>  struct v4l2_subdev_format {
>  	__u32 which;
>  	__u32 pad;
>  	struct v4l2_mbus_framefmt format;
> -	__u32 reserved[8];
> +	__u32 stream;
> +	__u32 reserved[7];
>  };
>  
>  /**
> @@ -58,13 +60,15 @@ struct v4l2_subdev_format {
>   * @which: format type (from enum v4l2_subdev_format_whence)
>   * @pad: pad number, as reported by the media API
>   * @rect: pad crop rectangle boundaries
> + * @stream: stream number, defined in subdev routing
>   * @reserved: drivers and applications must zero this array
>   */
>  struct v4l2_subdev_crop {
>  	__u32 which;
>  	__u32 pad;
>  	struct v4l2_rect rect;
> -	__u32 reserved[8];
> +	__u32 stream;
> +	__u32 reserved[7];
>  };
>  
>  #define V4L2_SUBDEV_MBUS_CODE_CSC_COLORSPACE	0x00000001
> @@ -80,6 +84,7 @@ struct v4l2_subdev_crop {
>   * @code: format code (MEDIA_BUS_FMT_ definitions)
>   * @which: format type (from enum v4l2_subdev_format_whence)
>   * @flags: flags set by the driver, (V4L2_SUBDEV_MBUS_CODE_*)
> + * @stream: stream number, defined in subdev routing
>   * @reserved: drivers and applications must zero this array
>   */
>  struct v4l2_subdev_mbus_code_enum {
> @@ -88,7 +93,8 @@ struct v4l2_subdev_mbus_code_enum {
>  	__u32 code;
>  	__u32 which;
>  	__u32 flags;
> -	__u32 reserved[7];
> +	__u32 stream;
> +	__u32 reserved[6];
>  };
>  
>  /**
> @@ -101,6 +107,7 @@ struct v4l2_subdev_mbus_code_enum {
>   * @min_height: minimum frame height, in pixels
>   * @max_height: maximum frame height, in pixels
>   * @which: format type (from enum v4l2_subdev_format_whence)
> + * @stream: stream number, defined in subdev routing
>   * @reserved: drivers and applications must zero this array
>   */
>  struct v4l2_subdev_frame_size_enum {
> @@ -112,19 +119,22 @@ struct v4l2_subdev_frame_size_enum {
>  	__u32 min_height;
>  	__u32 max_height;
>  	__u32 which;
> -	__u32 reserved[8];
> +	__u32 stream;
> +	__u32 reserved[7];
>  };
>  
>  /**
>   * struct v4l2_subdev_frame_interval - Pad-level frame rate
>   * @pad: pad number, as reported by the media API
>   * @interval: frame interval in seconds
> + * @stream: stream number, defined in subdev routing
>   * @reserved: drivers and applications must zero this array
>   */
>  struct v4l2_subdev_frame_interval {
>  	__u32 pad;
>  	struct v4l2_fract interval;
> -	__u32 reserved[9];
> +	__u32 stream;
> +	__u32 reserved[8];
>  };
>  
>  /**
> @@ -136,6 +146,7 @@ struct v4l2_subdev_frame_interval {
>   * @height: frame height in pixels
>   * @interval: frame interval in seconds
>   * @which: format type (from enum v4l2_subdev_format_whence)
> + * @stream: stream number, defined in subdev routing
>   * @reserved: drivers and applications must zero this array
>   */
>  struct v4l2_subdev_frame_interval_enum {
> @@ -146,7 +157,8 @@ struct v4l2_subdev_frame_interval_enum {
>  	__u32 height;
>  	struct v4l2_fract interval;
>  	__u32 which;
> -	__u32 reserved[8];
> +	__u32 stream;
> +	__u32 reserved[7];
>  };
>  
>  /**
> @@ -158,6 +170,7 @@ struct v4l2_subdev_frame_interval_enum {
>   *	    defined in v4l2-common.h; V4L2_SEL_TGT_* .
>   * @flags: constraint flags, defined in v4l2-common.h; V4L2_SEL_FLAG_*.
>   * @r: coordinates of the selection window
> + * @stream: stream number, defined in subdev routing
>   * @reserved: for future use, set to zero for now
>   *
>   * Hardware may use multiple helper windows to process a video stream.
> @@ -170,7 +183,8 @@ struct v4l2_subdev_selection {
>  	__u32 target;
>  	__u32 flags;
>  	struct v4l2_rect r;
> -	__u32 reserved[8];
> +	__u32 stream;
> +	__u32 reserved[7];
>  };
>  
>  /**
>