[PATCH v4 2/5] media: v4l2-common: add helper functions to call s_stream() callbacks

[Dafna Hirschfeld <dafna.hirschfeld@collabora.com>]

From: Helen Koike <helen.koike@collabora.com>

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.

If .s_stream(true) fails, call .s_stream(false) in the reverse order.

Signed-off-by: Helen Koike <helen.koike@collabora.com>
Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
---
 drivers/media/v4l2-core/v4l2-common.c | 99 +++++++++++++++++++++++++++
 include/media/v4l2-common.h           | 39 +++++++++++
 2 files changed, 138 insertions(+)

diff --git a/drivers/media/v4l2-core/v4l2-common.c b/drivers/media/v4l2-core/v4l2-common.c
index 9e8eb45a5b03..734db2bf5ca9 100644
--- a/drivers/media/v4l2-core/v4l2-common.c
+++ b/drivers/media/v4l2-core/v4l2-common.c
@@ -442,3 +442,102 @@ int v4l2_fill_pixfmt(struct v4l2_pix_format *pixfmt, u32 pixelformat,
 	return 0;
 }
 EXPORT_SYMBOL_GPL(v4l2_fill_pixfmt);
+
+#if defined(CONFIG_MEDIA_CONTROLLER)
+
+/*
+ * v4l2_pipeline_subdevs_get - Assemble a list of subdevices in a pipeline
+ * @subdevs: the array to be filled.
+ * @max_size: max number of elements that can fit in subdevs array.
+ *
+ * Walk from a video node, following links from sink to source and fill the
+ * array with subdevices in the path.
+ * The walker performs a depth-first traversal, which means that, in a topology
+ * sd1->sd2->sd3->vdev, sd1 will be the first element placed in the array.
+ *
+ * Return the number of subdevices filled in the array.
+ */
+static int v4l2_pipeline_subdevs_get(struct video_device *vdev,
+				     struct v4l2_subdev **subdevs,
+				     unsigned int max_size)
+{
+	struct media_entity *entity = &vdev->entity;
+	struct media_device *mdev = entity->graph_obj.mdev;
+	struct media_graph graph;
+	int idx = 0;
+	int ret;
+
+	ret = media_graph_walk_init(&graph, mdev);
+	if (ret)
+		return ret;
+
+	media_graph_walk_start(&graph, entity);
+
+	while ((entity = media_graph_walk_next_stream(&graph))) {
+		if (!is_media_entity_v4l2_subdev(entity))
+			continue;
+		if (WARN_ON(idx >= max_size))
+			return -EINVAL;
+		subdevs[idx++] = media_entity_to_v4l2_subdev(entity);
+	}
+
+	media_graph_walk_cleanup(&graph);
+
+	return idx;
+}
+
+static void v4l2_subdevs_stream_disable(struct v4l2_subdev **subdevs, int size)
+{
+	int i;
+
+	for (i = 0; i < size; i++) {
+		struct v4l2_subdev *sd = subdevs[i];
+
+		dev_dbg(sd->dev,
+			"disabling stream for '%s'\n", sd->entity.name);
+		v4l2_subdev_call(sd, video, s_stream, false);
+	}
+}
+
+__must_check int v4l2_pipeline_stream_enable(struct video_device *vdev)
+{
+	struct media_device *mdev = vdev->entity.graph_obj.mdev;
+	struct v4l2_subdev *subdevs[MEDIA_ENTITY_ENUM_MAX_DEPTH];
+	struct v4l2_subdev *sd;
+	int i, size, ret;
+
+	size = v4l2_pipeline_subdevs_get(vdev, subdevs, ARRAY_SIZE(subdevs));
+	if (size <= 0)
+		return size;
+
+	/* Call s_stream() in reverse order to enable sensors last */
+	for (i = size - 1; i >= 0; i--) {
+		sd = subdevs[i];
+		dev_dbg(mdev->dev,
+			"enabling stream for '%s'\n", sd->entity.name);
+		ret = v4l2_subdev_call(sd, video, s_stream, true);
+		if (ret && ret != -ENOIOCTLCMD) {
+			v4l2_subdevs_stream_disable(subdevs + i + 1,
+						    size - i - 1);
+			return ret;
+		}
+	}
+	return 0;
+}
+EXPORT_SYMBOL_GPL(v4l2_pipeline_stream_enable);
+
+int v4l2_pipeline_stream_disable(struct video_device *vdev)
+{
+	struct v4l2_subdev *subdevs[MEDIA_ENTITY_ENUM_MAX_DEPTH];
+	int size;
+
+	size = v4l2_pipeline_subdevs_get(vdev, subdevs, ARRAY_SIZE(subdevs));
+	if (size < 0)
+		return size;
+
+	v4l2_subdevs_stream_disable(subdevs, size);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(v4l2_pipeline_stream_disable);
+
+#endif /* CONFIG_MEDIA_CONTROLLER */
diff --git a/include/media/v4l2-common.h b/include/media/v4l2-common.h
index 150ee16ebd81..a278bcf3c5bc 100644
--- a/include/media/v4l2-common.h
+++ b/include/media/v4l2-common.h
@@ -539,4 +539,43 @@ static inline void v4l2_buffer_set_timestamp(struct v4l2_buffer *buf,
 	buf->timestamp.tv_usec = ts.tv_nsec / NSEC_PER_USEC;
 }
 
+#if defined(CONFIG_MEDIA_CONTROLLER)
+
+/**
+ * v4l2_pipeline_stream_enable - Call .s_stream(true) callbacks in the stream
+ * @vdev: Starting video device.
+ *
+ * Call .s_stream(true) callback in all the subdevices participating in the
+ * stream, i.e. following links from sink to source.
+ *
+ * .s_stream(true) is also called from sink to source, i.e. in a topology
+ * sd1->sd2->sd3->vdev, .s_stream(true) of sd3 is called first.
+ *
+ * Calls to this function can be nested, in which case the same number of
+ * v4l2_pipeline_stream_disable() calls will be required to disable streaming
+ * through subdevices in the pipeline.
+ * The  pipeline pointer must be identical for all nested calls to
+ * v4l2_pipeline_stream_enable().
+ */
+__must_check int v4l2_pipeline_stream_enable(struct video_device *vdev);
+
+/**
+ * v4l2_pipeline_stream_disable - Call .s_stream(false) callbacks in the stream
+ * @vdev: Starting video device.
+ *
+ * Call .s_stream(false) callback in all the subdevices participating in the
+ * stream, i.e. following links from sink to source.
+ *
+ * s_stream(false) is called in a reverse order from
+ * v4l2_pipeline_stream_enable(), i.e. in a topology sd1->sd2->sd3->vdev,
+ * .s_stream(false) of sd1 is called first.
+ *
+ * If multiple calls to v4l2_pipeline_stream_enable() have been made, the same
+ * number of calls to this function are required to disable streaming through
+ * subdevices in the pipeline.
+ */
+int v4l2_pipeline_stream_disable(struct video_device *vdev);
+
+#endif /* CONFIG_MEDIA_CONTROLLER */
+
 #endif /* V4L2_COMMON_H_ */
-- 
2.17.1