ManualControl: avoid scheduling based on unchosen input

src/modules/manual_control/ManualControl.cpp

@@ -226,8 +226,18 @@ void ManualControl::Run()
 		// If it's valid, this should really be valid but better safe than sorry.
 		const int instance = _selector.instance();
 
-		if (instance >= 0 && instance < MAX_MANUAL_INPUT_COUNT) {
-			_manual_control_input_subs[instance].registerCallback();
+		// Attach scheduling to new samples of the chosen input
+		if (instance != _previous_manual_control_input_instance) {
+			if ((0 <= _previous_manual_control_input_instance)
+			    && (_previous_manual_control_input_instance < MAX_MANUAL_INPUT_COUNT)) {
+				_manual_control_input_subs[_previous_manual_control_input_instance].unregisterCallback();
+			}
+
+			if ((0 <= instance) && (instance < MAX_MANUAL_INPUT_COUNT)) {
+				_manual_control_input_subs[instance].registerCallback();
+			}
+
+			_previous_manual_control_input_instance = instance;
 		}
 
 		_manual_control_switches_sub.registerCallback();

src/modules/manual_control/ManualControl.hpp

@@ -131,6 +131,7 @@ private:
 	uORB::Publication<manual_control_setpoint_s> _manual_control_setpoint_pub{ORB_ID(manual_control_setpoint)};
 
 	uORB::SubscriptionInterval _parameter_update_sub{ORB_ID(parameter_update), 1_s};
+	int _previous_manual_control_input_instance{-1};
 	uORB::SubscriptionCallbackWorkItem _manual_control_input_subs[MAX_MANUAL_INPUT_COUNT] {
 		{this, ORB_ID(manual_control_input), 0},
 		{this, ORB_ID(manual_control_input), 1},