libcamera: camera_manager: add CameraManager class

Provide a CameraManager class which will handle listing, instancing,
destruction and lifetime management of cameras.

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

include/libcamera/camera_manager.h

@@ -0,0 +1,38 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2018, Google Inc.
+ *
+ * camera_manager.h - Camera management
+ */
+#ifndef __LIBCAMERA_CAMERA_MANAGER_H__
+#define __LIBCAMERA_CAMERA_MANAGER_H__
+
+#include <vector>
+#include <string>
+
+namespace libcamera {
+
+class Camera;
+class DeviceEnumerator;
+class PipelineHandler;
+
+class CameraManager
+{
+public:
+	CameraManager();
+
+	int start();
+	void stop();
+
+	std::vector<std::string> list() const;
+	Camera *get(const std::string &name);
+	void put(Camera *camera);
+
+private:
+	DeviceEnumerator *enumerator_;
+	std::vector<PipelineHandler *> pipes_;
+};
+
+} /* namespace libcamera */
+
+#endif /* __LIBCAMERA_CAMERA_MANAGER_H__ */

include/libcamera/libcamera.h

@@ -8,6 +8,7 @@
 #define __LIBCAMERA_LIBCAMERA_H__
 
 #include <libcamera/camera.h>
+#include <libcamera/camera_manager.h>
 
 namespace libcamera {
 

include/libcamera/meson.build

@@ -1,5 +1,6 @@
 libcamera_api = files([
     'camera.h',
+    'camera_manager.h',
     'libcamera.h',
 ])
 

src/libcamera/camera_manager.cpp

@@ -0,0 +1,164 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2018, Google Inc.
+ *
+ * camera_manager.h - Camera management
+ */
+
+#include <libcamera/camera_manager.h>
+
+#include "device_enumerator.h"
+#include "pipeline_handler.h"
+
+/**
+ * \file camera_manager.h
+ * \brief Manage all cameras handled by libcamera
+ *
+ * The responsibility of the camera manager is to control the lifetime
+ * management of objects provided by libcamera.
+ *
+ * When a user wish to interact with libcamera it creates and starts a
+ * CameraManager object. Once confirmed the camera manager is running
+ * the application can list all cameras detected by the library, get
+ * one or more of the cameras and interact with them.
+ *
+ * When the user is done with the camera it should be returned to the
+ * camera manager. Once all cameras are returned to the camera manager
+ * the user is free to stop the manager.
+ *
+ * \todo Add ability to add and remove media devices based on
+ *       hot-(un)plug events coming from the device enumerator.
+ *
+ * \todo Add interface to register a notification callback to the user
+ *       to be able to inform it new cameras have been hot-plugged or
+ *       cameras have been removed due to hot-unplug.
+ */
+
+namespace libcamera {
+
+CameraManager::CameraManager()
+	: enumerator_(nullptr)
+{
+}
+
+/**
+ * \brief Start the camera manager
+ *
+ * Start the camera manager and enumerate all devices in the system. Once
+ * the start has been confirmed the user is free to list and otherwise
+ * interact with cameras in the system until either the camera manager
+ * is stopped or the camera is unplugged from the system.
+ *
+ * \return true on successful start false otherwise
+ */
+int CameraManager::start()
+{
+
+	if (enumerator_)
+		return -ENODEV;
+
+	enumerator_ = DeviceEnumerator::create();
+	if (enumerator_->enumerate())
+		return -ENODEV;
+
+	/*
+	 * TODO: Try to read handlers and order from configuration
+	 * file and only fallback on all handlers if there is no
+	 * configuration file.
+	 */
+	std::vector<std::string> handlers = PipelineHandlerFactory::handlers();
+
+	for (std::string const &handler : handlers) {
+		PipelineHandler *pipe;
+
+		/*
+		 * Try each pipeline handler until it exhaust
+		 * all pipelines it can provide.
+		 */
+		do {
+			pipe = PipelineHandlerFactory::create(handler, enumerator_);
+			if (pipe)
+				pipes_.push_back(pipe);
+		} while (pipe);
+	}
+
+	/* TODO: register hot-plug callback here */
+
+	return 0;
+}
+
+/**
+ * \brief Stop the camera manager
+ *
+ * Before stopping the camera manger the caller is responsible for making
+ * sure all cameras provided by the manager are returned to the manager.
+ *
+ * After the manager has been stopped no resource provided by the camera
+ * manager should be consider valid or functional even if they for one
+ * reason or another have yet to be deleted.
+ */
+void CameraManager::stop()
+{
+	/* TODO: unregister hot-plug callback here */
+
+	for (PipelineHandler *pipe : pipes_)
+		delete pipe;
+
+	pipes_.clear();
+
+	if (enumerator_)
+		delete enumerator_;
+
+	enumerator_ = nullptr;
+}
+
+/**
+ * \brief List all detected cameras
+ *
+ * Before calling this function the caller is responsible for ensuring that
+ * the camera manger is running.
+ *
+ * \return List of names for all detected cameras
+ */
+std::vector<std::string> CameraManager::list() const
+{
+	std::vector<std::string> list;
+
+	for (PipelineHandler *pipe : pipes_) {
+		for (unsigned int i = 0; i < pipe->count(); i++) {
+			Camera *cam = pipe->camera(i);
+			list.push_back(cam->name());
+		}
+	}
+
+	return list;
+}
+
+/**
+ * \brief Get a camera based on name
+ *
+ * \param[in] name Name of camera to get
+ *
+ * Before calling this function the caller is responsible for ensuring that
+ * the camera manger is running. A camera fetched this way shall be
+ * released by the user with the put() method of the Camera object once
+ * it is done using the camera.
+ *
+ * \return Pointer to Camera object or nullptr if camera not found
+ */
+Camera *CameraManager::get(const std::string &name)
+{
+	for (PipelineHandler *pipe : pipes_) {
+		for (unsigned int i = 0; i < pipe->count(); i++) {
+			Camera *cam = pipe->camera(i);
+			if (cam->name() == name) {
+				cam->get();
+				return cam;
+			}
+		}
+	}
+
+	return nullptr;
+}
+
+} /* namespace libcamera */

src/libcamera/meson.build

@@ -1,5 +1,6 @@
 libcamera_sources = files([
     'camera.cpp',
+    'camera_manager.cpp',
     'device_enumerator.cpp',
     'log.cpp',
     'main.cpp',