Merge remote-tracking branch 'upstream/master' into ros_messagelayer_merge

Conflicts:
	src/modules/attitude_estimator_ekf/attitude_estimator_ekf_main.cpp
	src/modules/uORB/topics/vehicle_attitude.h

src/modules/sensors/sensor_params.c

@@ -98,6 +98,12 @@ PARAM_DEFINE_FLOAT(SENS_GYRO_YSCALE, 1.0f);
  */
 PARAM_DEFINE_FLOAT(SENS_GYRO_ZSCALE, 1.0f);
 
+/**
+ * ID of Magnetometer the calibration is for.
+ *
+ * @group Sensor Calibration
+ */
+PARAM_DEFINE_INT32(SENS_MAG_ID, 0);
 
 /**
  * Magnetometer X-axis offset

src/modules/sensors/sensors.cpp

@@ -1,6 +1,6 @@
 /****************************************************************************
  *
- *   Copyright (c) 2012-2014 PX4 Development Team. All rights reserved.
+ *   Copyright (c) 2012-2015 PX4 Development Team. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -1465,7 +1465,7 @@ Sensors::parameter_update_poll(bool forced)
 
 		/* this sensor is optional, abort without error */
 
-		if (fd > 0) {
+		if (fd >= 0) {
 			struct airspeed_scale airscale = {
 				_parameters.diff_pres_offset_pa,
 				1.0f,