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.cpp

@@ -0,0 +1,138 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * camera_hal_manager.cpp - libcamera Android Camera Manager
+ */
+
+#include "camera_hal_manager.h"
+
+#include <libcamera/camera.h>
+
+#include "log.h"
+
+#include "camera_device.h"
+#include "camera_proxy.h"
+
+using namespace libcamera;
+
+LOG_DECLARE_CATEGORY(HAL);
+
+/*
+ * \class CameraHalManager
+ *
+ * The HAL camera manager is initializated at camera_module_t 'hal_init()' time
+ * and spawns its own thread where libcamera related events are dispatched to.
+ * It wraps the libcamera CameraManager operations and provides helpers for the
+ * camera_module_t operations, to retrieve the number of cameras in the system,
+ * their static information and to open and close camera devices.
+ */
+
+int CameraHalManager::init()
+{
+	/*
+	 * Start the camera HAL manager thread and wait until its
+	 * initialisation completes to be fully operational before
+	 * receiving calls from the camera stack.
+	 */
+	start();
+
+	MutexLocker locker(mutex_);
+	cv_.wait(locker);
+
+	return 0;
+}
+
+void CameraHalManager::run()
+{
+	/*
+	 * All the libcamera components must be initialised here, in
+	 * order to bind them to the camera HAL manager thread that
+	 * executes the event dispatcher.
+	 */
+	cameraManager_ = libcamera::CameraManager::instance();
+
+	int ret = cameraManager_->start();
+	if (ret) {
+		LOG(HAL, Error) << "Failed to start camera manager: "
+				<< strerror(-ret);
+		return;
+	}
+
+	/*
+	 * For each Camera registered in the system, a CameraProxy
+	 * gets created here to wraps a camera device.
+	 *
+	 * \todo Support camera hotplug.
+	 */
+	unsigned int index = 0;
+	for (auto &camera : cameraManager_->cameras()) {
+		CameraProxy *proxy = new CameraProxy(index, camera);
+		proxies_.emplace_back(proxy);
+
+		++index;
+	}
+
+	/*
+	 * libcamera has been initialized. Unlock the init() caller
+	 * as we're now ready to handle calls from the framework.
+	 */
+	cv_.notify_one();
+
+	/* Now start processing events and messages. */
+	exec();
+}
+
+CameraProxy *CameraHalManager::open(unsigned int id,
+				    const hw_module_t *hardwareModule)
+{
+	if (id < 0 || id >= numCameras()) {
+		LOG(HAL, Error) << "Invalid camera id '" << id << "'";
+		return nullptr;
+	}
+
+	CameraProxy *proxy = proxies_[id].get();
+	if (proxy->open(hardwareModule))
+		return nullptr;
+
+	LOG(HAL, Info) << "Open camera '" << id << "'";
+
+	return proxy;
+}
+
+int CameraHalManager::close(CameraProxy *proxy)
+{
+	proxy->close();
+	LOG(HAL, Info) << "Close camera '" << proxy->id() << "'";
+
+	return 0;
+}
+
+unsigned int CameraHalManager::numCameras() const
+{
+	return cameraManager_->cameras().size();
+}
+
+int CameraHalManager::getCameraInfo(int id, struct camera_info *info)
+{
+	if (!info)
+		return -EINVAL;
+
+	if (id >= numCameras() || id < 0) {
+		LOG(HAL, Error) << "Invalid camera id '" << id << "'";
+		return -EINVAL;
+	}
+
+	CameraProxy *proxy = proxies_[id].get();
+
+	/* \todo Get these info dynamically inspecting the camera module. */
+	info->facing = id ? CAMERA_FACING_FRONT : CAMERA_FACING_BACK;
+	info->orientation = 0;
+	info->device_version = 0;
+	info->resource_cost = 0;
+	info->static_camera_characteristics = proxy->getStaticMetadata();
+	info->conflicting_devices = nullptr;
+	info->conflicting_devices_length = 0;
+
+	return 0;
+}