libcamera: mediadevice: Fix graph parsing error handling

Most errors recorded during graph parsing are logged but not propagated
to the caller. Fix this and delete objects that are created but not
successfully added to the graph to avoid memory leaks. As the error code
returned from the addObject() and populate*() functions doesn't matter
much, turn them into bool functions.

Additionally, add a way to query whether the media graph was valid, and
clear objects before populating the graph to avoid leaking them.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/libcamera/include/media_device.h

@@ -28,6 +28,7 @@ public:
 	void close();
 
 	int populate();
+	bool valid() const { return valid_; }
 
 	const std::string driver() const { return driver_; }
 	const std::string devnode() const { return devnode_; }
@@ -37,18 +38,19 @@ private:
 	std::string driver_;
 	std::string devnode_;
 	int fd_;
+	bool valid_;
 
 	std::map<unsigned int, MediaObject *> objects_;
 	MediaObject *object(unsigned int id);
-	int addObject(MediaObject *obj);
+	bool addObject(MediaObject *obj);
 	void clear();
 
 	std::vector<MediaEntity *> entities_;
 	MediaEntity *getEntityByName(const std::string &name);
 
-	void populateEntities(const struct media_v2_topology &topology);
-	int populatePads(const struct media_v2_topology &topology);
-	int populateLinks(const struct media_v2_topology &topology);
+	bool populateEntities(const struct media_v2_topology &topology);
+	bool populatePads(const struct media_v2_topology &topology);
+	bool populateLinks(const struct media_v2_topology &topology);
 };
 
 } /* namespace libcamera */