diff --git a/libraries/AP_InertialSensor/AP_InertialSensor.cpp b/libraries/AP_InertialSensor/AP_InertialSensor.cpp
index fccb056792..199b7fa0c8 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor.cpp
+++ b/libraries/AP_InertialSensor/AP_InertialSensor.cpp
@@ -2,13 +2,24 @@
 
 #include <assert.h>
 
-#include "AP_InertialSensor.h"
-
 #include <AP_Common/AP_Common.h>
 #include <AP_HAL/AP_HAL.h>
+#include <AP_Math/AP_Math.h>
 #include <AP_Notify/AP_Notify.h>
 #include <AP_Vehicle/AP_Vehicle.h>
-#include <AP_Math/AP_Math.h>
+
+#include "AP_InertialSensor.h"
+#include "AP_InertialSensor_Backend.h"
+#include "AP_InertialSensor_Flymaple.h"
+#include "AP_InertialSensor_HIL.h"
+#include "AP_InertialSensor_L3G4200D.h"
+#include "AP_InertialSensor_LSM9DS0.h"
+#include "AP_InertialSensor_MPU6000.h"
+#include "AP_InertialSensor_MPU9250.h"
+#include "AP_InertialSensor_PX4.h"
+#include "AP_InertialSensor_QURT.h"
+#include "AP_InertialSensor_SITL.h"
+#include "AP_InertialSensor_qflight.h"
 
 /*
   enable TIMING_DEBUG to track down scheduling issues with the main
@@ -45,7 +56,7 @@ extern const AP_HAL::HAL& hal;
 const AP_Param::GroupInfo AP_InertialSensor::var_info[] = {
     // @Param: PRODUCT_ID
     // @DisplayName: IMU Product ID
-    // @Description: Which type of IMU is installed (read-only). 
+    // @Description: Which type of IMU is installed (read-only).
     // @User: Advanced
     // @Values: 0:Unknown,1:APM1-1280,2:APM1-2560,88:APM2,3:SITL,4:PX4v1,5:PX4v2,256:Flymaple,257:Linux
     AP_GROUPINFO("PRODUCT_ID",  0, AP_InertialSensor, _product_id,   0),
@@ -339,7 +350,7 @@ AP_InertialSensor::AP_InertialSensor() :
         AP_HAL::panic("Too many inertial sensors");
     }
     _s_instance = this;
-    AP_Param::setup_object_defaults(this, var_info);        
+    AP_Param::setup_object_defaults(this, var_info);
     for (uint8_t i=0; i<INS_MAX_BACKENDS; i++) {
         _backends[i] = NULL;
     }
@@ -551,13 +562,13 @@ AP_InertialSensor::detect_backends(void)
 /*
   _calculate_trim - calculates the x and y trim angles. The
   accel_sample must be correctly scaled, offset and oriented for the
-  board 
+  board
 */
 bool AP_InertialSensor::_calculate_trim(const Vector3f &accel_sample, float& trim_roll, float& trim_pitch)
 {
     trim_pitch = atan2f(accel_sample.x, pythagorous2(accel_sample.y, accel_sample.z));
     trim_roll = atan2f(-accel_sample.y, -accel_sample.z);
-    if (fabsf(trim_roll) > radians(10) || 
+    if (fabsf(trim_roll) > radians(10) ||
         fabsf(trim_pitch) > radians(10)) {
         hal.console->println("trim over maximum of 10 degrees");
         return false;
@@ -682,7 +693,7 @@ bool AP_InertialSensor::calibrate_trim(float &trim_roll, float &trim_pitch)
 
 failed:
     _calibrating = false;
-    return false;    
+    return false;
 }
 
 /*
@@ -918,7 +929,7 @@ void AP_InertialSensor::update(void)
         }
 
         // adjust health status if a sensor has a non-zero error count
-        // but another sensor doesn't. 
+        // but another sensor doesn't.
         bool have_zero_accel_error_count = false;
         bool have_zero_gyro_error_count = false;
         for (uint8_t i=0; i<INS_MAX_INSTANCES; i++) {
@@ -961,10 +972,10 @@ void AP_InertialSensor::update(void)
 
 /*
   wait for a sample to be available. This is the function that
-  determines the timing of the main loop in ardupilot. 
+  determines the timing of the main loop in ardupilot.
 
   Ideally this function would return at exactly the rate given by the
-  sample_rate argument given to AP_InertialSensor::init(). 
+  sample_rate argument given to AP_InertialSensor::init().
 
   The key output of this function is _delta_time, which is the time
   over which the gyro and accel integration will happen for this
@@ -999,7 +1010,7 @@ void AP_InertialSensor::wait_for_sample(void)
             timing_printf("shortsleep %u\n", (unsigned)(_next_sample_usec-now2));
         }
         if (now2 > _next_sample_usec+400) {
-            timing_printf("longsleep %u wait_usec=%u\n", 
+            timing_printf("longsleep %u wait_usec=%u\n",
                           (unsigned)(now2-_next_sample_usec),
                           (unsigned)wait_usec);
         }
@@ -1056,7 +1067,7 @@ check_sample:
         if (counter++ == 400) {
             counter = 0;
             hal.console->printf("now=%lu _delta_time_sum=%lu diff=%ld\n",
-                                (unsigned long)now, 
+                                (unsigned long)now,
                                 (unsigned long)delta_time_sum,
                                 (long)(now - delta_time_sum));
         }
@@ -1070,7 +1081,7 @@ check_sample:
 /*
   get delta angles
  */
-bool AP_InertialSensor::get_delta_angle(uint8_t i, Vector3f &delta_angle) const 
+bool AP_InertialSensor::get_delta_angle(uint8_t i, Vector3f &delta_angle) const
 {
     if (_delta_angle_valid[i]) {
         delta_angle = _delta_angle[i];
@@ -1284,7 +1295,7 @@ void AP_InertialSensor::acal_init()
 }
 
 // update accel calibrator
-void AP_InertialSensor::acal_update() 
+void AP_InertialSensor::acal_update()
 {
     if(_acal == NULL) {
         return;
@@ -1346,10 +1357,10 @@ void AP_InertialSensor::_acal_save_calibrations()
             /* no break */
     }
 
-    if (fabsf(_trim_roll) > radians(10) || 
+    if (fabsf(_trim_roll) > radians(10) ||
         fabsf(_trim_pitch) > radians(10)) {
         hal.console->print("ERR: Trim over maximum of 10 degrees!!");
-        _new_trim = false;  //we have either got faulty level during acal or highly misaligned accelerometers 
+        _new_trim = false;  //we have either got faulty level during acal or highly misaligned accelerometers
     }
 
     _accel_cal_requires_reboot = true;
@@ -1364,7 +1375,7 @@ void AP_InertialSensor::_acal_event_failure()
 }
 
 /*
-    Returns true if new valid trim values are available and passes them to reference vars    
+    Returns true if new valid trim values are available and passes them to reference vars
 */
 bool AP_InertialSensor::get_new_trim(float& trim_roll, float &trim_pitch)
 {
@@ -1377,7 +1388,7 @@ bool AP_InertialSensor::get_new_trim(float& trim_roll, float &trim_pitch)
     return false;
 }
 
-/*    
+/*
     Returns body fixed accelerometer level data averaged during accel calibration's first step
 */
 bool AP_InertialSensor::get_fixed_mount_accel_cal_sample(uint8_t sample_num, Vector3f& ret) const
@@ -1390,7 +1401,7 @@ bool AP_InertialSensor::get_fixed_mount_accel_cal_sample(uint8_t sample_num, Vec
     return true;
 }
 
-/*    
+/*
     Returns Primary accelerometer level data averaged during accel calibration's first step
 */
 bool AP_InertialSensor::get_primary_accel_cal_sample_avg(uint8_t sample_num, Vector3f& ret) const
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor.h b/libraries/AP_InertialSensor/AP_InertialSensor.h
index 11ff2cc0df..114f656c01 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor.h
@@ -1,7 +1,5 @@
 /// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
-
-#ifndef __AP_INERTIAL_SENSOR_H__
-#define __AP_INERTIAL_SENSOR_H__
+#pragma once
 
 // Gyro and Accelerometer calibration criteria
 #define AP_INERTIAL_SENSOR_ACCEL_TOT_MAX_OFFSET_CHANGE  4.0f
@@ -20,12 +18,12 @@
 #define INS_VIBRATION_CHECK_INSTANCES 2
 
 #include <stdint.h>
+
+#include <AP_AccelCal/AP_AccelCal.h>
 #include <AP_HAL/AP_HAL.h>
 #include <AP_Math/AP_Math.h>
-#include <AP_AccelCal/AP_AccelCal.h>
-#include "AP_InertialSensor_UserInteract.h"
-#include <Filter/LowPassFilter.h>
 #include <Filter/LowPassFilter2p.h>
+#include <Filter/LowPassFilter.h>
 
 class AP_InertialSensor_Backend;
 class AuxiliaryBus;
@@ -101,7 +99,7 @@ public:
 
     float get_delta_angle_dt(uint8_t i) const;
     float get_delta_angle_dt() const { return get_delta_angle_dt(_primary_accel); }
-    
+
     //get delta velocity if available
     bool get_delta_velocity(uint8_t i, Vector3f &delta_velocity) const;
     bool get_delta_velocity(Vector3f &delta_velocity) const { return get_delta_velocity(_primary_accel, delta_velocity); }
@@ -176,7 +174,7 @@ public:
 
     // return the main loop delta_t in seconds
     float get_loop_delta_t(void) const { return _loop_delta_t; }
-    
+
     uint16_t error_count(void) const { return 0; }
     bool healthy(void) const { return get_gyro_health() && get_accel_health(); }
 
@@ -283,7 +281,7 @@ private:
     // the selected sample rate
     uint16_t _sample_rate;
     float _loop_delta_t;
-    
+
     // Most recent accelerometer reading
     Vector3f _accel[INS_MAX_INSTANCES];
     Vector3f _delta_velocity[INS_MAX_INSTANCES];
@@ -301,7 +299,7 @@ private:
     Vector3f _gyro_filtered[INS_MAX_INSTANCES];
     bool _new_accel_data[INS_MAX_INSTANCES];
     bool _new_gyro_data[INS_MAX_INSTANCES];
-    
+
     // Most recent gyro reading
     Vector3f _gyro[INS_MAX_INSTANCES];
     Vector3f _delta_angle[INS_MAX_INSTANCES];
@@ -371,7 +369,7 @@ private:
 
     // target time for next wait_for_sample() return
     uint32_t _next_sample_usec;
-    
+
     // time between samples in microseconds
     uint32_t _sample_period_usec;
 
@@ -427,19 +425,3 @@ private:
 
     bool _accel_cal_requires_reboot;
 };
-
-#include "AP_InertialSensor_Backend.h"
-#include "AP_InertialSensor_MPU6000.h"
-#include "AP_InertialSensor_PX4.h"
-#include "AP_InertialSensor_MPU9250.h"
-#include "AP_InertialSensor_L3G4200D.h"
-#include "AP_InertialSensor_Flymaple.h"
-#include "AP_InertialSensor_LSM9DS0.h"
-#include "AP_InertialSensor_HIL.h"
-#include "AP_InertialSensor_SITL.h"
-#include "AP_InertialSensor_qflight.h"
-#include "AP_InertialSensor_QURT.h"
-#include "AP_InertialSensor_UserInteract_Stream.h"
-#include "AP_InertialSensor_UserInteract_MAVLink.h"
-
-#endif // __AP_INERTIAL_SENSOR_H__
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_Backend.h b/libraries/AP_InertialSensor/AP_InertialSensor_Backend.h
index 083a51f7de..d902b545f7 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_Backend.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_Backend.h
@@ -21,10 +21,16 @@
   Note that drivers can implement just gyros or just accels, and can
   also provide multiple gyro/accel instances.
  */
-#ifndef __AP_INERTIALSENSOR_BACKEND_H__
-#define __AP_INERTIALSENSOR_BACKEND_H__
+#pragma once
+
+#include <inttypes.h>
+
+#include <AP_Math/AP_Math.h>
+
+#include "AP_InertialSensor.h"
 
 class AuxiliaryBus;
+class DataFlash_Class;
 
 class AP_InertialSensor_Backend
 {
@@ -36,7 +42,7 @@ public:
     // override with a custom destructor if need be.
     virtual ~AP_InertialSensor_Backend(void) {}
 
-    /* 
+    /*
      * Update the sensor data. Called by the frontend to transfer
      * accumulated sensor readings to the frontend structure via the
      * _publish_gyro() and _publish_accel() functions
@@ -129,8 +135,8 @@ protected:
     uint16_t get_sample_rate_hz(void) const;
 
     // access to frontend dataflash
-    DataFlash_Class *get_dataflash(void) const { 
-        return _imu._log_raw_data? _imu._dataflash : NULL; 
+    DataFlash_Class *get_dataflash(void) const {
+        return _imu._log_raw_data? _imu._dataflash : NULL;
     }
 
     // common gyro update function for all backends
@@ -138,14 +144,12 @@ protected:
 
     // common accel update function for all backends
     void update_accel(uint8_t instance);
-    
+
     // support for updating filter at runtime
     int8_t _last_accel_filter_hz[INS_MAX_INSTANCES];
     int8_t _last_gyro_filter_hz[INS_MAX_INSTANCES];
-    
+
     // note that each backend is also expected to have a static detect()
     // function which instantiates an instance of the backend sensor
     // driver if the sensor is available
 };
-
-#endif // __AP_INERTIALSENSOR_BACKEND_H__
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_Flymaple.h b/libraries/AP_InertialSensor/AP_InertialSensor_Flymaple.h
index 43e590b77a..c166701e41 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_Flymaple.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_Flymaple.h
@@ -1,15 +1,15 @@
 /// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
-
-#ifndef __AP_INERTIAL_SENSOR_FLYMAPLE_H__
-#define __AP_INERTIAL_SENSOR_FLYMAPLE_H__
+#pragma once
 
 #include <AP_HAL/AP_HAL.h>
 #if CONFIG_HAL_BOARD == HAL_BOARD_FLYMAPLE
 
-#include "AP_InertialSensor.h"
 #include <Filter/Filter.h>
 #include <Filter/LowPassFilter2p.h>
 
+#include "AP_InertialSensor.h"
+#include "AP_InertialSensor_Backend.h"
+
 class AP_InertialSensor_Flymaple : public AP_InertialSensor_Backend
 {
 public:
@@ -34,4 +34,3 @@ private:
     uint32_t _last_accel_timestamp;
 };
 #endif
-#endif // __AP_INERTIAL_SENSOR_FLYMAPLE_H__
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_HIL.h b/libraries/AP_InertialSensor/AP_InertialSensor_HIL.h
index 6ab5e15331..f3f326d23d 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_HIL.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_HIL.h
@@ -1,9 +1,8 @@
 /// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
-
-#ifndef __AP_INERTIALSENSOR_HIL_H__
-#define __AP_INERTIALSENSOR_HIL_H__
+#pragma once
 
 #include "AP_InertialSensor.h"
+#include "AP_InertialSensor_Backend.h"
 
 class AP_InertialSensor_HIL : public AP_InertialSensor_Backend
 {
@@ -19,5 +18,3 @@ public:
 private:
     bool _init_sensor(void);
 };
-
-#endif // __AP_INERTIALSENSOR_HIL_H__
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_L3G4200D.h b/libraries/AP_InertialSensor/AP_InertialSensor_L3G4200D.h
index 66043842c7..2fe991e16a 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_L3G4200D.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_L3G4200D.h
@@ -4,12 +4,11 @@
 #include <AP_HAL/AP_HAL.h>
 #if CONFIG_HAL_BOARD == HAL_BOARD_LINUX
 
-#include <pthread.h>
-
 #include <Filter/Filter.h>
 #include <Filter/LowPassFilter2p.h>
 
 #include "AP_InertialSensor.h"
+#include "AP_InertialSensor_Backend.h"
 
 class AP_InertialSensor_L3G4200D : public AP_InertialSensor_Backend
 {
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_LSM9DS0.h b/libraries/AP_InertialSensor/AP_InertialSensor_LSM9DS0.h
index bc5938b34a..59dbc18925 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_LSM9DS0.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_LSM9DS0.h
@@ -1,11 +1,11 @@
-
-#ifndef __AP_INERTIAL_SENSOR_LSM9DS0_H__
-#define __AP_INERTIAL_SENSOR_LSM9DS0_H__
+#pragma once
 
 #define LSM9DS0_DEBUG 0
 
 #include <AP_HAL/AP_HAL.h>
+
 #include "AP_InertialSensor.h"
+#include "AP_InertialSensor_Backend.h"
 
 class AP_InertialSensor_LSM9DS0 : public AP_InertialSensor_Backend
 {
@@ -90,5 +90,3 @@ private:
     void        _dump_registers();
 #endif
 };
-
-#endif /* __AP_INERTIAL_SENSOR_LSM9DS0_H__ */
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_MPU6000.h b/libraries/AP_InertialSensor/AP_InertialSensor_MPU6000.h
index d75d2f62d6..618483987f 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_MPU6000.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_MPU6000.h
@@ -12,6 +12,7 @@
 #include <Filter/LowPassFilter.h>
 
 #include "AP_InertialSensor.h"
+#include "AP_InertialSensor_Backend.h"
 #include "AuxiliaryBus.h"
 
 // enable debug to see a register dump on startup
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_MPU9250.h b/libraries/AP_InertialSensor/AP_InertialSensor_MPU9250.h
index 2122b49ed2..3e6a3868bf 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_MPU9250.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_MPU9250.h
@@ -1,13 +1,14 @@
 /// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
-
-#ifndef __AP_INERTIAL_SENSOR_MPU9250_H__
-#define __AP_INERTIAL_SENSOR_MPU9250_H__
+#pragma once
 
 #include <stdint.h>
+
 #include <AP_HAL/AP_HAL.h>
 #include <AP_Math/AP_Math.h>
 #include <Filter/Filter.h>
 #include <Filter/LowPassFilter2p.h>
+
+#include "AP_InertialSensor_Backend.h"
 #include "AP_InertialSensor.h"
 #include "AuxiliaryBus.h"
 
@@ -164,5 +165,3 @@ private:
 
     uint8_t _ext_sens_data = 0;
 };
-
-#endif // __AP_INERTIAL_SENSOR_MPU9250_H__
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_PX4.h b/libraries/AP_InertialSensor/AP_InertialSensor_PX4.h
index 845c968e97..150a5fe1f6 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_PX4.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_PX4.h
@@ -1,12 +1,11 @@
 /// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
-
-#ifndef __AP_INERTIAL_SENSOR_PX4_H__
-#define __AP_INERTIAL_SENSOR_PX4_H__
+#pragma once
 
 #include <AP_HAL/AP_HAL.h>
 #if CONFIG_HAL_BOARD == HAL_BOARD_PX4 || CONFIG_HAL_BOARD == HAL_BOARD_VRBRAIN
 
 #include "AP_InertialSensor.h"
+#include "AP_InertialSensor_Backend.h"
 #include <drivers/drv_accel.h>
 #include <drivers/drv_gyro.h>
 #include <uORB/uORB.h>
@@ -70,5 +69,4 @@ private:
     float _accel_dt_max[INS_MAX_INSTANCES];
 #endif // AP_INERTIALSENSOR_PX4_DEBUG
 };
-#endif // CONFIG_HAL_BOARD
-#endif // __AP_INERTIAL_SENSOR_PX4_H__
+#endif
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_QURT.h b/libraries/AP_InertialSensor/AP_InertialSensor_QURT.h
index 8cc7874ef6..bec9b2896f 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_QURT.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_QURT.h
@@ -1,12 +1,15 @@
 /// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
-
 #pragma once
 
-#include "AP_InertialSensor.h"
+#include <AP_HAL/AP_HAL.h>
 #if CONFIG_HAL_BOARD == HAL_BOARD_QURT
+
+#include "AP_InertialSensor.h"
+#include "AP_InertialSensor_Backend.h"
+
 extern "C" {
 #undef DEG_TO_RAD
-#include "mpu9x50.h"
+#include <mpu9x50.h>
 }
 #include <AP_HAL/utility/RingBuffer.h>
 
@@ -20,23 +23,23 @@ public:
     /* update accel and gyro state */
     bool update() override;
     void accumulate(void) override;
-    
+
     // detect the sensor
     static AP_InertialSensor_Backend *detect(AP_InertialSensor &imu);
 
     void data_ready(void);
-    
+
 private:
     bool init_sensor();
     void init_mpu9250();
 
     uint64_t last_timestamp;
     uint32_t start_time_ms;
-    
+
     uint8_t gyro_instance;
     uint8_t accel_instance;
 
     ObjectBuffer<mpu9x50_data> buf{100};
 };
 
-#endif // CONFIG_HAL_BOARD
+#endif
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_SITL.h b/libraries/AP_InertialSensor/AP_InertialSensor_SITL.h
index 45304c3c6e..75fefc61f9 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_SITL.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_SITL.h
@@ -1,10 +1,10 @@
 /// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
+#pragma once
 
-#ifndef __AP_INERTIALSENSOR_SITL_H__
-#define __AP_INERTIALSENSOR_SITL_H__
+#include <SITL/SITL.h>
 
 #include "AP_InertialSensor.h"
-#include <SITL/SITL.h>
+#include "AP_InertialSensor_Backend.h"
 
 #define INS_SITL_INSTANCES 2
 
@@ -24,11 +24,9 @@ private:
     void timer_update();
     float rand_float(void);
     float gyro_drift(void);
-    
+
     SITL::SITL *sitl;
 
     uint8_t gyro_instance[INS_SITL_INSTANCES];
     uint8_t accel_instance[INS_SITL_INSTANCES];
 };
-
-#endif // __AP_INERTIALSENSOR_SITL_H__
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_UserInteract.h b/libraries/AP_InertialSensor/AP_InertialSensor_UserInteract.h
index 5e54541b15..b2465fc3b9 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_UserInteract.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_UserInteract.h
@@ -1,6 +1,4 @@
-
-#ifndef __AP_INERTIAL_SENSOR_USER_INTERACT_H__
-#define __AP_INERTIAL_SENSOR_USER_INTERACT_H__
+#pragma once
 
 #include <AP_Common/AP_Common.h>
 
@@ -10,6 +8,3 @@ public:
     virtual bool blocking_read() = 0;
     virtual void printf(const char *, ...) FMT_PRINTF(2, 3) = 0;
 };
-
-#endif // __AP_INERTIAL_SENSOR_USER_INTERACT_H__
-
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_UserInteract_MAVLink.h b/libraries/AP_InertialSensor/AP_InertialSensor_UserInteract_MAVLink.h
index 6adbc63ec4..468a0c889d 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_UserInteract_MAVLink.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_UserInteract_MAVLink.h
@@ -1,13 +1,12 @@
-
-#ifndef __AP_INERTIAL_SENSOR_USER_INTERACT_MAVLINK_H__
-#define __AP_INERTIAL_SENSOR_USER_INTERACT_MAVLINK_H__
-
-#include "AP_InertialSensor_UserInteract.h"
+#pragma once
 
 #include <AP_Common/AP_Common.h>
 #include <AP_HAL/AP_HAL.h>
 #include <GCS_MAVLink/GCS_MAVLink.h>
 
+
+#include "AP_InertialSensor_UserInteract.h"
+
 class GCS_MAVLINK;
 
 /**
@@ -23,6 +22,3 @@ public:
 private:
     GCS_MAVLINK *_gcs;
 };
-
-#endif // __AP_INERTIAL_SENSOR_USER_INTERACT_MAVLINK_H__
-
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_UserInteract_Stream.h b/libraries/AP_InertialSensor/AP_InertialSensor_UserInteract_Stream.h
index 1face45944..01569eba56 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_UserInteract_Stream.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_UserInteract_Stream.h
@@ -1,16 +1,14 @@
-
-#ifndef __AP_INERTIAL_SENSOR_USER_INTERACT_STREAM_H__
-#define __AP_INERTIAL_SENSOR_USER_INTERACT_STREAM_H__
+#pragma once
 
 #include <AP_Common/AP_Common.h>
 #include <AP_HAL/AP_HAL.h>
+
 #include "AP_InertialSensor_UserInteract.h"
 
 /**
  * AP_InertialSensor_UserInteract, implemented in terms of a BetterStream.
  */
-class AP_InertialSensor_UserInteractStream :
-    public AP_InertialSensor_UserInteract {
+class AP_InertialSensor_UserInteractStream : public AP_InertialSensor_UserInteract {
 public:
     AP_InertialSensor_UserInteractStream(AP_HAL::BetterStream *s) :
         _s(s) {}
@@ -20,6 +18,3 @@ public:
 private:
     AP_HAL::BetterStream *_s;
 };
-
-#endif // __AP_INERTIAL_SENSOR_USER_INTERACT_STREAM_H__
-
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_qflight.h b/libraries/AP_InertialSensor/AP_InertialSensor_qflight.h
index 610f983f14..317c51bb23 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_qflight.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_qflight.h
@@ -1,12 +1,14 @@
 /// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
-
 #pragma once
 
-#include "AP_InertialSensor.h"
+#include <AP_HAL/AP_HAL.h>
 #if CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_QFLIGHT
 
 #include <AP_HAL_Linux/qflight/qflight_buffer.h>
 
+#include "AP_InertialSensor.h"
+#include "AP_InertialSensor_Backend.h"
+
 class AP_InertialSensor_QFLIGHT : public AP_InertialSensor_Backend
 {
 public:
@@ -27,4 +29,4 @@ private:
     DSPBuffer::IMU *imubuf;
 };
 
-#endif // CONFIG_HAL_BOARD_SUBTYPE
+#endif