libcamera: pipeline: Utilise shared MediaDevice pointers

Adapt the PipelineHandler::acquireMediaDevice() support function to
return a shared pointer instead of the underlying raw pointer.

Propagate this update to all pipeline handlers that use the MediaDevice
and store a std::shared_ptr<MediaDevice> accordingly.

This is required to support media devices that are potentially shared
among multiple pipeline handlers, like a dewarper implemented as v4l2
m2m device.

Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
Reviewed-by: Isaac Scott <isaac.scott@ideasonboard.com>

include/libcamera/internal/pipeline_handler.h

@@ -38,8 +38,8 @@ public:
 	virtual ~PipelineHandler();
 
 	virtual bool match(DeviceEnumerator *enumerator) = 0;
-	MediaDevice *acquireMediaDevice(DeviceEnumerator *enumerator,
-					const DeviceMatch &dm);
+	std::shared_ptr<MediaDevice> acquireMediaDevice(DeviceEnumerator *enumerator,
+							const DeviceMatch &dm);
 
 	bool acquire(Camera *camera);
 	void release(Camera *camera);
@@ -72,7 +72,7 @@ public:
 
 protected:
 	void registerCamera(std::shared_ptr<Camera> camera);
-	void hotplugMediaDevice(MediaDevice *media);
+	void hotplugMediaDevice(std::shared_ptr<MediaDevice> media);
 	unsigned int useCount() const { return useCount_; }
 
 	virtual int queueRequestDevice(Camera *camera, Request *request) = 0;
@@ -87,7 +87,7 @@ protected:
 private:
 	void unlockMediaDevices();
 
-	void mediaDeviceDisconnected(MediaDevice *media);
+	void mediaDeviceDisconnected(std::shared_ptr<MediaDevice> media);
 	virtual void disconnect();
 
 	void doQueueRequest(Request *request);