libcamera: internal: Add MediaPipeline helper

Provide a MediaPipeline class to help identifing and managing pipelines across
a MediaDevice graph.

Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Umang Jain <umang.jain@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Stefan Klug <stefan.klug@ideasonboard.com>

include/libcamera/internal/media_pipeline.h

@@ -0,0 +1,59 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024, Ideas on Board Oy
+ *
+ * Media pipeline support
+ */
+
+#pragma once
+
+#include <list>
+#include <string>
+
+#include <libcamera/base/log.h>
+
+namespace libcamera {
+
+class CameraSensor;
+class MediaEntity;
+class MediaLink;
+class MediaPad;
+struct V4L2SubdeviceFormat;
+
+class MediaPipeline
+{
+public:
+	int init(MediaEntity *source, std::string_view sink);
+	int initLinks();
+	int configure(CameraSensor *sensor, V4L2SubdeviceFormat *);
+
+private:
+	struct Entity {
+		/* The media entity, always valid. */
+		MediaEntity *entity;
+		/*
+		 * Whether or not the entity is a subdev that supports the
+		 * routing API.
+		 */
+		bool supportsRouting;
+		/*
+		 * The local sink pad connected to the upstream entity, null for
+		 * the camera sensor at the beginning of the pipeline.
+		 */
+		const MediaPad *sink;
+		/*
+		 * The local source pad connected to the downstream entity, null
+		 * for the video node at the end of the pipeline.
+		 */
+		const MediaPad *source;
+		/*
+		 * The link on the source pad, to the downstream entity, null
+		 * for the video node at the end of the pipeline.
+		 */
+		MediaLink *sourceLink;
+	};
+
+	std::list<Entity> entities_;
+};
+
+} /* namespace libcamera */

include/libcamera/internal/meson.build

@@ -32,6 +32,7 @@ libcamera_internal_headers = files([
     'matrix.h',
     'media_device.h',
     'media_object.h',
+    'media_pipeline.h',
     'pipeline_handler.h',
     'process.h',
     'pub_key.h',