android: hal: Add Camera3 HAL

Add libcamera Android Camera HALv3 implementation.

The initial camera HAL implementation supports the LIMITED hardware
level and uses statically defined metadata and camera characteristics.

Add a build option named 'android' and adjust the build system to
selectively compile the Android camera HAL and link it against the
required Android libraries.

Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>

src/android/camera_hal_manager.h

@@ -0,0 +1,47 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * camera_hal_manager.h - libcamera Android Camera Manager
+ */
+#ifndef __ANDROID_CAMERA_MANAGER_H__
+#define __ANDROID_CAMERA_MANAGER_H__
+
+#include <condition_variable>
+#include <mutex>
+#include <vector>
+
+#include <hardware/hardware.h>
+#include <system/camera_metadata.h>
+
+#include <libcamera/camera_manager.h>
+
+#include "thread.h"
+
+class CameraDevice;
+class CameraProxy;
+
+class CameraHalManager : public libcamera::Thread
+{
+public:
+	int init();
+
+	CameraProxy *open(unsigned int id, const hw_module_t *module);
+	int close(CameraProxy *proxy);
+
+	unsigned int numCameras() const;
+	int getCameraInfo(int id, struct camera_info *info);
+
+private:
+	void run() override;
+	camera_metadata_t *getStaticMetadata(unsigned int id);
+
+	libcamera::CameraManager *cameraManager_;
+
+	std::mutex mutex_;
+	std::condition_variable cv_;
+
+	std::vector<std::unique_ptr<CameraProxy>> proxies_;
+};
+
+#endif /* __ANDROID_CAMERA_MANAGER_H__ */