libcamera: pipeline_handler: add PipelineHandler class

Provide a PipelineHandler which represents a handler for one or more
media devices and provides one or more cameras.

Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>

src/libcamera/include/pipeline_handler.h

@@ -0,0 +1,62 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2018, Google Inc.
+ *
+ * pipeline_handler.h - Pipeline handler infrastructure
+ */
+#ifndef __LIBCAMERA_PIPELINE_HANDLER_H__
+#define __LIBCAMERA_PIPELINE_HANDLER_H__
+
+#include <map>
+#include <string>
+#include <vector>
+
+#include <libcamera/camera.h>
+
+namespace libcamera {
+
+class DeviceEnumerator;
+class PipelineHandlerFactory;
+
+class PipelineHandler
+{
+public:
+	virtual ~PipelineHandler() { };
+
+	virtual bool match(DeviceEnumerator *enumerator) = 0;
+
+	virtual unsigned int count() = 0;
+	virtual Camera *camera(unsigned int id) = 0;
+};
+
+class PipelineHandlerFactory
+{
+public:
+	virtual ~PipelineHandlerFactory() { };
+
+	virtual PipelineHandler *create() = 0;
+
+	static void registerType(const std::string &name, PipelineHandlerFactory *factory);
+	static PipelineHandler *create(const std::string &name, DeviceEnumerator *enumerator);
+	static std::vector<std::string> handlers();
+
+private:
+	static std::map<std::string, PipelineHandlerFactory *> &registry();
+};
+
+#define REGISTER_PIPELINE_HANDLER(handler) \
+	class handler##Factory : public PipelineHandlerFactory { \
+	public: \
+		handler##Factory() \
+		{ \
+			PipelineHandlerFactory::registerType(#handler, this); \
+		} \
+		virtual PipelineHandler *create() { \
+			return new handler(); \
+		} \
+	}; \
+	static handler##Factory global_##handler##Factory;
+
+} /* namespace libcamera */
+
+#endif /* __LIBCAMERA_PIPELINE_HANDLER_H__ */