refactor orb: uORB::Manager is responsible for the DeviceMaster objects

This has the following benefits:
- Manager can ensure that there is at most one instance of DeviceMaster
  per Flavor
- The Manager needs access to (static) data of DeviceMaster already.
  This will make it easier to access this data in a non-static way, and
  does not introduce new dependencies.

src/modules/uORB/uORBCommon.hpp

@@ -52,8 +52,10 @@ static const unsigned orb_maxpath = 64;
 const int ERROR = -1;
 
 enum Flavor {
-	PUBSUB,
-	PARAM
+	PUBSUB = 0,
+	PARAM,
+
+	Flavor_count
 };
 
 struct orb_advertdata {

src/modules/uORB/uORBDevices_nuttx.hpp

@@ -45,6 +45,7 @@ namespace uORB
 {
 class DeviceNode;
 class DeviceMaster;
+class Manager;
 }
 
 /**
@@ -259,6 +260,8 @@ public:
 	DeviceMaster(Flavor f);
 	virtual ~DeviceMaster();
 
+	friend class uORB::Manager;
+
 	static uORB::DeviceNode *GetDeviceNode(const char *node_name);
 	virtual int   ioctl(struct file *filp, int cmd, unsigned long arg);
 private:

src/modules/uORB/uORBDevices_posix.hpp

@@ -43,6 +43,7 @@ namespace uORB
 {
 class DeviceNode;
 class DeviceMaster;
+class Manager;
 }
 
 class uORB::DeviceNode : public device::VDev
@@ -193,6 +194,8 @@ public:
 	DeviceMaster(Flavor f);
 	virtual ~DeviceMaster();
 
+	friend class uORB::Manager;
+
 	static uORB::DeviceNode *GetDeviceNode(const char *node_name);
 
 	virtual int   ioctl(device::file_t *filp, int cmd, unsigned long arg);

src/modules/uORB/uORBMain.cpp

@@ -72,18 +72,10 @@ uorb_main(int argc, char *argv[])
 		}
 
 		/* create the driver */
-		g_dev = new uORB::DeviceMaster(uORB::PUBSUB);
+		g_dev = uORB::Manager::get_instance()->get_device_master(uORB::PUBSUB);
 
 		if (g_dev == nullptr) {
-			PX4_ERR("driver alloc failed");
-			return -ENOMEM;
-		}
-
-		if (OK != g_dev->init()) {
-			PX4_ERR("driver init failed");
-			delete g_dev;
-			g_dev = nullptr;
-			return -EIO;
+			return -errno;
 		}
 
 		return OK;

src/modules/uORB/uORBManager.cpp

@@ -64,6 +64,9 @@ bool uORB::Manager::initialize()
 uORB::Manager::Manager()
 	: _comm_channel(nullptr)
 {
+	for (int i = 0; i < Flavor_count; ++i) {
+		_device_masters[i] = nullptr;
+	}
 
 #ifdef ORB_USE_PUBLISHER_RULES
 	const char *file_name = "./rootfs/orb_publisher.rules";
@@ -81,6 +84,39 @@ uORB::Manager::Manager()
 
 }
 
+uORB::Manager::~Manager()
+{
+	for (int i = 0; i < Flavor_count; ++i) {
+		if (_device_masters[i]) {
+			delete _device_masters[i];
+		}
+	}
+}
+
+uORB::DeviceMaster *uORB::Manager::get_device_master(Flavor flavor)
+{
+	if (!_device_masters[flavor]) {
+		_device_masters[flavor] = new DeviceMaster(flavor);
+
+		if (_device_masters[flavor]) {
+			int ret = _device_masters[flavor]->init();
+
+			if (ret != PX4_OK) {
+				PX4_ERR("Initialization of DeviceMaster failed (%i)", ret);
+				errno = -ret;
+				delete _device_masters[flavor];
+				_device_masters[flavor] = nullptr;
+			}
+
+		} else {
+			PX4_ERR("Failed to allocate DeviceMaster");
+			errno = ENOMEM;
+		}
+	}
+
+	return _device_masters[flavor];
+}
+
 int uORB::Manager::orb_exists(const struct orb_metadata *meta, int instance)
 {
 	/*

src/modules/uORB/uORBManager.hpp

@@ -78,6 +78,14 @@ public:
 		return _Instance;
 	}
 
+	/**
+	 * Get the DeviceMaster for a given Flavor. If it does not exist,
+	 * it will be created and initialized.
+	 * Note: the first call to this is not thread-safe.
+	 * @return nullptr if initialization failed (and errno will be set)
+	 */
+	uORB::DeviceMaster *get_device_master(Flavor flavor);
+
 	// ==== uORB interface methods ====
 	/**
 	 * Advertise as the publisher of a topic.
@@ -399,8 +407,11 @@ private: // data members
 	uORBCommunicator::IChannel *_comm_channel;
 	ORBSet _remote_subscriber_topics;
 
+	DeviceMaster *_device_masters[Flavor_count]; ///< Allow at most one DeviceMaster per Flavor
+
 private: //class methods
 	Manager();
+	~Manager();
 
 	/**
 	   * Interface to process a received AddSubscription from remote.