EKF2: Allocate distance sensor subscriptions as member variables

Just create the subscriptions and keep them, instead of
re-creating them continuously

Signed-off-by: Jukka Laitinen <jukkax@ssrc.tii.ae>

src/modules/ekf2/EKF2.cpp

@@ -1708,18 +1708,15 @@ void EKF2::UpdateMagSample(ekf2_timestamps_s &ekf2_timestamps)
 void EKF2::UpdateRangeSample(ekf2_timestamps_s &ekf2_timestamps)
 {
 	if (!_distance_sensor_selected) {
-		// get subscription index of first downward-facing range sensor
-		uORB::SubscriptionMultiArray<distance_sensor_s> distance_sensor_subs{ORB_ID::distance_sensor};
 
-		if (distance_sensor_subs.advertised()) {
-			for (unsigned i = 0; i < distance_sensor_subs.size(); i++) {
+		if (_distance_sensor_subs.advertised()) {
+			for (unsigned i = 0; i < _distance_sensor_subs.size(); i++) {
 				distance_sensor_s distance_sensor;
 
-				if (distance_sensor_subs[i].copy(&distance_sensor)) {
+				if (_distance_sensor_subs[i].update(&distance_sensor)) {
 					// only use the first instace which has the correct orientation
 					if ((hrt_elapsed_time(&distance_sensor.timestamp) < 100_ms)
 					    && (distance_sensor.orientation == distance_sensor_s::ROTATION_DOWNWARD_FACING)) {
-
 						if (_distance_sensor_sub.ChangeInstance(i)) {
 							int ndist = orb_group_count(ORB_ID(distance_sensor));
 

src/modules/ekf2/EKF2.hpp

@@ -264,6 +264,8 @@ private:
 	uORB::SubscriptionCallbackWorkItem _sensor_combined_sub{this, ORB_ID(sensor_combined)};
 	uORB::SubscriptionCallbackWorkItem _vehicle_imu_sub{this, ORB_ID(vehicle_imu)};
 
+	uORB::SubscriptionMultiArray<distance_sensor_s> _distance_sensor_subs{ORB_ID::distance_sensor};
+
 	bool _callback_registered{false};
 
 	bool _distance_sensor_selected{false}; // because we can have several distance sensor instances with different orientations