libcamera: request: Add Request::Private::prepare()

Add a prepare() function to the Private Request representation.

The prepare() function is used by the PipelineHandler class to
prepare a Request to be queued to the hardware.

The current implementation of prepare() handles the fences associated
with the Framebuffers part of a Request. The function starts an event
notifier for each of those and emits the Request::prepared signal when
all fences have been signalled or an optional timeout has expired.

The optional timeout allows to interrupt blocked waits and notify the
Request as failed so that it can be cancelled.

Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

include/libcamera/internal/request.h

@@ -7,10 +7,17 @@
 #ifndef __LIBCAMERA_INTERNAL_REQUEST_H__
 #define __LIBCAMERA_INTERNAL_REQUEST_H__
 
+#include <chrono>
+#include <map>
 #include <memory>
 
+#include <libcamera/base/event_notifier.h>
+#include <libcamera/base/timer.h>
+
 #include <libcamera/request.h>
 
+using namespace std::chrono_literals;
+
 namespace libcamera {
 
 class Camera;
@@ -32,16 +39,25 @@ public:
 	void cancel();
 	void reuse();
 
+	void prepare(std::chrono::milliseconds timeout = 0ms);
+	Signal<> prepared;
+
 private:
 	friend class PipelineHandler;
 
 	void doCancelRequest();
+	void emitPrepareCompleted();
+	void notifierActivated(FrameBuffer *buffer);
+	void timeout();
 
 	Camera *camera_;
 	bool cancelled_;
 	uint32_t sequence_ = 0;
+	bool prepared_ = false;
 
 	std::unordered_set<FrameBuffer *> pending_;
+	std::map<FrameBuffer *, std::unique_ptr<EventNotifier>> notifiers_;
+	std::unique_ptr<Timer> timer_;
 };
 
 } /* namespace libcamera */