libcamera: device_enumerator: Convey device ownership through unique_ptr

Replace usage of shared_ptr with unique_ptr to convey media device
ownership internally in the enumerators when creating the media device.
Once a media device has all its dependencies met, it is converted to a
shared_ptr to keep the external API unchanged.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/libcamera/include/device_enumerator.h

@@ -44,8 +44,8 @@ public:
 	std::shared_ptr<MediaDevice> search(const DeviceMatch &dm);
 
 protected:
-	std::shared_ptr<MediaDevice> createDevice(const std::string &deviceNode);
-	void addDevice(const std::shared_ptr<MediaDevice> &media);
+	std::unique_ptr<MediaDevice> createDevice(const std::string &deviceNode);
+	void addDevice(std::unique_ptr<MediaDevice> &&media);
 	void removeDevice(const std::string &deviceNode);
 
 private:

src/libcamera/include/device_enumerator_sysfs.h

@@ -23,7 +23,7 @@ public:
 	int enumerate();
 
 private:
-	int populateMediaDevice(const std::shared_ptr<MediaDevice> &media);
+	int populateMediaDevice(MediaDevice *media);
 	std::string lookupDeviceNode(int major, int minor);
 };
 

src/libcamera/include/device_enumerator_udev.h

@@ -43,9 +43,9 @@ private:
 	using DependencyMap = std::map<dev_t, std::list<MediaEntity *>>;
 
 	struct MediaDeviceDeps {
-		MediaDeviceDeps(const std::shared_ptr<MediaDevice> &media,
-				const DependencyMap &deps)
-			: media_(media), deps_(deps)
+		MediaDeviceDeps(std::unique_ptr<MediaDevice> &&media,
+				DependencyMap &&deps)
+			: media_(std::move(media)), deps_(std::move(deps))
 		{
 		}
 
@@ -54,7 +54,7 @@ private:
 			return media_ == other.media_;
 		}
 
-		std::shared_ptr<MediaDevice> media_;
+		std::unique_ptr<MediaDevice> media_;
 		DependencyMap deps_;
 	};