libcamera: Add pointer to MediaDevice to MediaObject

Add a MediaDevice member field to the MediaObject class hierarcy.
Each media object now has a reference to the media device it belongs to,
and which it has been created by.

Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>

src/libcamera/include/media_object.h

@@ -21,14 +21,17 @@ class MediaPad;
 class MediaObject
 {
 public:
+	MediaDevice *device() { return dev_; }
 	unsigned int id() const { return id_; }
 
 protected:
 	friend class MediaDevice;
 
-	MediaObject(unsigned int id) : id_(id) { }
+	MediaObject(MediaDevice *dev, unsigned int id) :
+		dev_(dev), id_(id) { }
 	virtual ~MediaObject() { }
 
+	MediaDevice *dev_;
 	unsigned int id_;
 };
 
@@ -93,7 +96,7 @@ public:
 private:
 	friend class MediaDevice;
 
-	MediaEntity(const struct media_v2_entity *entity,
+	MediaEntity(MediaDevice *dev, const struct media_v2_entity *entity,
 		    unsigned int major = 0, unsigned int minor = 0);
 	MediaEntity(const MediaEntity &) = delete;
 	~MediaEntity();