libcamera: thread: Support selective message dispatch to thread

Extend the current dispatchMessages() to support dispatching of
selective messsages according to the Message::Type passed in
the function argument. dispatchMessages() can now be called
explicitly to force deliver selected type's message to the
thread for processing (typically when event loop is not
running).

Signed-off-by: Umang Jain <email@uajain.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

include/libcamera/internal/thread.h

@@ -14,6 +14,7 @@
 
 #include <libcamera/signal.h>
 
+#include "libcamera/internal/message.h"
 #include "libcamera/internal/utils.h"
 
 namespace libcamera {
@@ -47,7 +48,7 @@ public:
 	EventDispatcher *eventDispatcher();
 	void setEventDispatcher(std::unique_ptr<EventDispatcher> dispatcher);
 
-	void dispatchMessages();
+	void dispatchMessages(Message::Type type = Message::Type::None);
 
 protected:
 	int exec();