Support topic groups in MAVLink subscription handling

src/modules/mavlink/mavlink_main.cpp

@@ -904,20 +904,20 @@ Mavlink::send_statustext(unsigned char severity, const char *string)
 	mavlink_logbuffer_write(&_logbuffer, &logmsg);
 }
 
-MavlinkOrbSubscription *Mavlink::add_orb_subscription(const orb_id_t topic)
+MavlinkOrbSubscription *Mavlink::add_orb_subscription(const orb_id_t topic, int instance)
 {
 	/* check if already subscribed to this topic */
 	MavlinkOrbSubscription *sub;
 
 	LL_FOREACH(_subscriptions, sub) {
-		if (sub->get_topic() == topic) {
+		if (sub->get_topic() == topic && sub->get_instance() == instance) {
 			/* already subscribed */
 			return sub;
 		}
 	}
 
 	/* add new subscription */
-	MavlinkOrbSubscription *sub_new = new MavlinkOrbSubscription(topic);
+	MavlinkOrbSubscription *sub_new = new MavlinkOrbSubscription(topic, instance);
 
 	LL_APPEND(_subscriptions, sub_new);
 

src/modules/mavlink/mavlink_main.h

@@ -171,7 +171,7 @@ public:
 
 	void			handle_message(const mavlink_message_t *msg);
 
-	MavlinkOrbSubscription *add_orb_subscription(const orb_id_t topic);
+	MavlinkOrbSubscription *add_orb_subscription(const orb_id_t topic, int instance=0);
 
 	int			get_instance_id();
 

src/modules/mavlink/mavlink_messages.cpp

@@ -1342,14 +1342,7 @@ protected:
 		_act_sub(nullptr),
 		_act_time(0)
 	{
-		orb_id_t act_topics[] = {
+		_act_sub = _mavlink->add_orb_subscription(ORB_ID(actuator_outputs), N);
-			ORB_ID(actuator_outputs_0),
-			ORB_ID(actuator_outputs_1),
-			ORB_ID(actuator_outputs_2),
-			ORB_ID(actuator_outputs_3)
-		};
-
-		_act_sub = _mavlink->add_orb_subscription(act_topics[N]);
 	}
 
 	void send(const hrt_abstime t)
@@ -1424,7 +1417,7 @@ protected:
 		_status_time(0),
 		_pos_sp_triplet_sub(_mavlink->add_orb_subscription(ORB_ID(position_setpoint_triplet))),
 		_pos_sp_triplet_time(0),
-		_act_sub(_mavlink->add_orb_subscription(ORB_ID(actuator_outputs_0))),
+		_act_sub(_mavlink->add_orb_subscription(ORB_ID(actuator_outputs))),
 		_act_time(0)
 	{}
 

src/modules/mavlink/mavlink_orb_subscription.cpp

@@ -46,10 +46,11 @@
 
 #include "mavlink_orb_subscription.h"
 
-MavlinkOrbSubscription::MavlinkOrbSubscription(const orb_id_t topic) :
+MavlinkOrbSubscription::MavlinkOrbSubscription(const orb_id_t topic, int instance) :
 	next(nullptr),
 	_topic(topic),
-	_fd(orb_subscribe(_topic)),
+	_instance(instance),
+	_fd(orb_subscribe_multi(_topic, instance)),
 	_published(false)
 {
 }
@@ -65,6 +66,12 @@ MavlinkOrbSubscription::get_topic() const
 	return _topic;
 }
 
+int
+MavlinkOrbSubscription::get_instance() const
+{
+	return _instance;
+}
+
 bool
 MavlinkOrbSubscription::update(uint64_t *time, void* data)
 {

src/modules/mavlink/mavlink_orb_subscription.h

@@ -50,7 +50,7 @@ class MavlinkOrbSubscription
 public:
 	MavlinkOrbSubscription *next;	///< pointer to next subscription in list
 
-	MavlinkOrbSubscription(const orb_id_t topic);
+	MavlinkOrbSubscription(const orb_id_t topic, int instance);
 	~MavlinkOrbSubscription();
 
 	/**
@@ -77,9 +77,11 @@ public:
 	 */
 	bool is_published();
 	orb_id_t get_topic() const;
+	int get_instance() const;
 
 private:
 	const orb_id_t _topic;		///< topic metadata
+	const int _instance;		///< get topic instance
 	int _fd;			///< subscription handle
 	bool _published;		///< topic was ever published