AP_UAVCAN: add Callback API to link UAVCAN backend callbacks

libraries/AP_UAVCAN/AP_UAVCAN.h

@@ -45,6 +45,18 @@
 
 #define AP_UAVCAN_MAX_LED_DEVICES 4
 
+/*
+    Frontend Backend-Registry Binder: Whenever a message of said DataType_ from new node is received,
+    the Callback will invoke registery to register the node as separate backend.
+*/
+#define UC_REGISTRY_BINDER(ClassName_, DataType_) \
+	class ClassName_ : public AP_UAVCAN::RegistryBinder<DataType_> { \
+	    public: \
+	        ClassName_() : RegistryBinder() {} \
+	        ClassName_(AP_UAVCAN* uc,  void (*ffunc)(AP_UAVCAN*, uint8_t, const ClassName_&)) : \
+				RegistryBinder(uc, (Registry)ffunc) {} \
+	}
+
 class AP_UAVCAN : public AP_HAL::CANProtocol {
 public:
     AP_UAVCAN();
@@ -57,6 +69,9 @@ public:
 
     void init(uint8_t driver_index) override;
 
+    uavcan::Node<0>* get_node() { return _node; }
+    uint8_t get_driver_index() { return _driver_index; }
+
 
     ///// SRV output /////
     void SRV_push_servos(void);
@@ -133,6 +148,33 @@ public:
     BatteryInfo_Info *find_bi_id(uint8_t id);
     void update_bi_state(uint8_t id);
 
+
+    template <typename DataType_>
+    class RegistryBinder {
+    protected:
+        typedef void* (*Registry)(AP_UAVCAN* _ap_uavcan, uint8_t _node_id, const RegistryBinder& _cb);
+        AP_UAVCAN* _uc;
+        Registry _ffunc;
+
+    public:
+        RegistryBinder() :
+        	_uc(),
+            _ffunc(),
+            msg() {}
+
+        RegistryBinder(AP_UAVCAN* uc, Registry ffunc) :
+            _uc(uc),
+            _ffunc(ffunc),
+            msg(nullptr) {}
+
+        void operator()(const uavcan::ReceivedDataStructure<DataType_>& _msg) {
+            msg = &_msg;
+            _ffunc(_uc, _msg.getSrcNodeID().get(), *this);
+        }
+
+        const uavcan::ReceivedDataStructure<DataType_> *msg;
+    };
+
 private:
     class SystemClock: public uavcan::ISystemClock, uavcan::Noncopyable {
     public: