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Subject: Re: [PATCH 2/4] media: v4l2-common: add helper functions to call
 s_stream() callbacks
To:     linux-media@vger.kernel.org
Cc:     kernel@collabora.com, linux-kernel@vger.kernel.org,
        linux-rockchip@lists.infradead.org, hans.verkuil@cisco.com,
        niklas.soderlund@ragnatech.se, mchehab@kernel.org
References: <20200316193305.428378-1-helen.koike@collabora.com>
 <20200316193305.428378-3-helen.koike@collabora.com>
From:   Helen Koike <helen.koike@collabora.com>
Message-ID: <b7041eb2-adfc-abf4-336e-93a2b1154482@collabora.com>
Date:   Mon, 16 Mar 2020 17:50:02 -0300
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On 3/16/20 4:33 PM, Helen Koike wrote:
> Add v4l2_pipeline_stream_{enable,disable} helper functions to iterate
> through the subdevices in a given stream (i.e following links from sink
> to source) and call .s_stream() callback.
> 
> Add stream_count on the subdevice object for simultaneous streaming from
> different video devices which shares subdevices.
> 
> Prevent calling .s_stream(true) if it was already called previously by
> another stream.
> 
> Prevent calling .s_stream(false) from one stream when there are still
> others active.
> 
> Signed-off-by: Helen Koike <helen.koike@collabora.com>
> ---
> 
>  drivers/media/v4l2-core/v4l2-common.c | 99 +++++++++++++++++++++++++++
>  include/media/v4l2-common.h           | 30 ++++++++
>  include/media/v4l2-subdev.h           |  2 +
>  3 files changed, 131 insertions(+)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-common.c b/drivers/media/v4l2-core/v4l2-common.c
> index d0e5ebc736f9..6a5a3d2c282e 100644
> --- a/drivers/media/v4l2-core/v4l2-common.c
> +++ b/drivers/media/v4l2-core/v4l2-common.c
> @@ -441,3 +441,102 @@ int v4l2_fill_pixfmt(struct v4l2_pix_format *pixfmt, u32 pixelformat,
>  	return 0;
>  }
>  EXPORT_SYMBOL_GPL(v4l2_fill_pixfmt);
> +
> +int v4l2_pipeline_stream_disable(struct media_entity *entity,
> +				 struct media_pipeline *pipe)
> +{
> +	struct media_device *mdev = entity->graph_obj.mdev;
> +	int ret = 0;
> +
> +	mutex_lock(&mdev->graph_mutex);
> +
> +	if (!pipe->streaming_count) {
> +		ret = media_graph_walk_init(&pipe->graph, mdev);
> +		if (ret) {
> +			mutex_unlock(&mdev->graph_mutex);
> +			return ret;
> +		}
> +	}
> +
> +	media_graph_walk_start(&pipe->graph, entity);
> +
> +	while ((entity = media_graph_walk_next_stream(&pipe->graph))) {
> +		struct v4l2_subdev *sd;
> +
> +		if (!is_media_entity_v4l2_subdev(entity))
> +			continue;
> +
> +		sd = media_entity_to_v4l2_subdev(entity);
> +		if (!sd->stream_count || --sd->stream_count)
> +			continue;
> +
> +		ret = v4l2_subdev_call(sd, video, s_stream, false);
> +		if (ret && ret != -ENOIOCTLCMD)

argh..., there is a missing open curly braces here (skipped when I added the check
for -ENOIOCTLCMD), sorry about that (/me embarrassed).

Fixed version can be found here https://gitlab.collabora.com/koike/linux/tree/v4l2/s_stream

I'll submit v2 after having your comments.

> +			dev_dbg(mdev->dev,
> +				"couldn't disable stream for subdevice '%s'\n",
> +				entity->name);
> +			break;
> +		}
> +
> +		dev_dbg(mdev->dev,
> +			"stream disabled for subdevice '%s'\n", entity->name);
> +	}
> +
> +	if (!pipe->streaming_count)
> +		media_graph_walk_cleanup(&pipe->graph);
> +
> +	mutex_unlock(&mdev->graph_mutex);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(v4l2_pipeline_stream_disable);
> +
> +__must_check int v4l2_pipeline_stream_enable(struct media_entity *entity,
> +					     struct media_pipeline *pipe)
> +{
> +	struct media_device *mdev = entity->graph_obj.mdev;
> +	int ret = 0;
> +
> +	mutex_lock(&mdev->graph_mutex);
> +
> +	if (!pipe->streaming_count) {
> +		ret = media_graph_walk_init(&pipe->graph, mdev);
> +		if (ret) {
> +			mutex_unlock(&mdev->graph_mutex);
> +			return ret;
> +		}
> +	}
> +
> +	media_graph_walk_start(&pipe->graph, entity);
> +
> +	while ((entity = media_graph_walk_next_stream(&pipe->graph))) {
> +		struct v4l2_subdev *sd;
> +
> +		if (!is_media_entity_v4l2_subdev(entity))
> +			continue;
> +
> +		sd = media_entity_to_v4l2_subdev(entity);
> +		if (sd->stream_count++)
> +			continue;
> +
> +		ret = v4l2_subdev_call(sd, video, s_stream, true);
> +		if (ret && ret != -ENOIOCTLCMD)

Same here

Thanks,
Helen

> +			dev_dbg(mdev->dev,
> +				"couldn't enable stream for subdevice '%s'\n",
> +				entity->name);
> +			v4l2_pipeline_stream_disable(entity, pipe);
> +			break;
> +		}
> +
> +		dev_dbg(mdev->dev,
> +			"stream enabled for subdevice '%s'\n", entity->name);
> +	}
> +
> +	if (!pipe->streaming_count)
> +		media_graph_walk_cleanup(&pipe->graph);
> +
> +	mutex_unlock(&mdev->graph_mutex);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(v4l2_pipeline_stream_enable);
> diff --git a/include/media/v4l2-common.h b/include/media/v4l2-common.h
> index 150ee16ebd81..46c0857d07c4 100644
> --- a/include/media/v4l2-common.h
> +++ b/include/media/v4l2-common.h
> @@ -519,6 +519,36 @@ int v4l2_fill_pixfmt(struct v4l2_pix_format *pixfmt, u32 pixelformat,
>  int v4l2_fill_pixfmt_mp(struct v4l2_pix_format_mplane *pixfmt, u32 pixelformat,
>  			u32 width, u32 height);
>  
> +/**
> + * media_pipeline_stop - Mark a pipeline as not streaming
> + * @entity: Starting entity
> + * @pipe: Media pipeline to iterate through the topology
> + *
> + * Call .s_stream(false) callback in all the subdevices participating in the
> + * stream, i.e. following links from sink to source.
> + *
> + * If multiple calls to v4l2_pipeline_stream_enable() have been made, the
> + * same number of calls to this function are required.
> + */
> +int v4l2_pipeline_stream_disable(struct media_entity *entity,
> +				 struct media_pipeline *pipe);
> +
> +/**
> + * v4l2_pipeline_stream_enable - Call .s_stream(true) callbacks in the stream
> + * @entity: Starting entity
> + * @pipe: Media pipeline to iterate through the topology
> + *
> + * Call .s_stream(true) callback in all the subdevices participating in the
> + * stream, i.e. following links from sink to source.
> + *
> + * Calls to this function can be nested, in which case the same number of
> + * v4l2_pipeline_stream_disable() calls will be required to stop streaming.
> + * The  pipeline pointer must be identical for all nested calls to
> + * v4l2_pipeline_stream_enable().
> + */
> +__must_check int v4l2_pipeline_stream_enable(struct media_entity *entity,
> +					     struct media_pipeline *pipe);
> +
>  static inline u64 v4l2_buffer_get_timestamp(const struct v4l2_buffer *buf)
>  {
>  	/*
> diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
> index a4848de59852..20f913a9f70c 100644
> --- a/include/media/v4l2-subdev.h
> +++ b/include/media/v4l2-subdev.h
> @@ -838,6 +838,7 @@ struct v4l2_subdev_platform_data {
>   * @subdev_notifier: A sub-device notifier implicitly registered for the sub-
>   *		     device using v4l2_device_register_sensor_subdev().
>   * @pdata: common part of subdevice platform data
> + * @stream_count: Stream count for the subdevice.
>   *
>   * Each instance of a subdev driver should create this struct, either
>   * stand-alone or embedded in a larger struct.
> @@ -869,6 +870,7 @@ struct v4l2_subdev {
>  	struct v4l2_async_notifier *notifier;
>  	struct v4l2_async_notifier *subdev_notifier;
>  	struct v4l2_subdev_platform_data *pdata;
> +	unsigned int stream_count;
>  };
>  
>  
>