libcamera: Add MediaObject class hierarchy

Add a class hierarcy to represent all media objects a media graph represents.
Add a base MediaObject class, which retains the global unique object id,
and define the derived MediaEntity, MediaLink and MediaPad classes.

This hierarchy will be used by the MediaDevice objects which represents and
handles the media graph.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>

src/libcamera/include/media_object.h

@@ -0,0 +1,106 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2018, Google Inc.
+ *
+ * media_object.h - Media Device objects: entities, pads and links.
+ */
+#ifndef __LIBCAMERA_MEDIA_OBJECT_H__
+#define __LIBCAMERA_MEDIA_OBJECT_H__
+
+#include <string>
+#include <vector>
+
+#include <linux/media.h>
+
+namespace libcamera {
+
+class MediaDevice;
+class MediaEntity;
+class MediaPad;
+
+class MediaObject
+{
+public:
+	unsigned int id() const { return id_; }
+
+protected:
+	friend class MediaDevice;
+
+	MediaObject(unsigned int id) : id_(id) { }
+	virtual ~MediaObject() { }
+
+	unsigned int id_;
+};
+
+class MediaLink : public MediaObject
+{
+public:
+	MediaPad *source() const { return source_; }
+	MediaPad *sink() const { return sink_; }
+	unsigned int flags() const { return flags_; }
+
+private:
+	friend class MediaDevice;
+
+	MediaLink(const struct media_v2_link *link,
+		  MediaPad *source, MediaPad *sink);
+	MediaLink(const MediaLink &) = delete;
+	~MediaLink() { }
+
+	MediaPad *source_;
+	MediaPad *sink_;
+	unsigned int flags_;
+};
+
+class MediaPad : public MediaObject
+{
+public:
+	unsigned int index() const { return index_; }
+	MediaEntity *entity() const { return entity_; }
+	unsigned int flags() const { return flags_; }
+	const std::vector<MediaLink *> &links() const { return links_; }
+
+	void addLink(MediaLink *link);
+
+private:
+	friend class MediaDevice;
+
+	MediaPad(const struct media_v2_pad *pad, MediaEntity *entity);
+	MediaPad(const MediaPad &) = delete;
+	~MediaPad();
+
+	unsigned int index_;
+	MediaEntity *entity_;
+	unsigned int flags_;
+
+	std::vector<MediaLink *> links_;
+};
+
+class MediaEntity : public MediaObject
+{
+public:
+	const std::string &name() const { return name_; }
+
+	const std::vector<MediaPad *> &pads() const { return pads_; }
+
+	const MediaPad *getPadByIndex(unsigned int index) const;
+	const MediaPad *getPadById(unsigned int id) const;
+
+private:
+	friend class MediaDevice;
+
+	MediaEntity(const struct media_v2_entity *entity);
+	MediaEntity(const MediaEntity &) = delete;
+	~MediaEntity();
+
+	std::string name_;
+	std::string devnode_;
+
+	std::vector<MediaPad *> pads_;
+
+	void addPad(MediaPad *pad);
+};
+
+} /* namespace libcamera */
+
+#endif /* __LIBCAMERA_MEDIA_OBJECT_H__ */