AP_Compass: explicitely add compasses for erlebrain2, pxf and pxfmini

libraries/AP_Compass/AP_Compass.cpp

@@ -501,6 +501,13 @@ void Compass::_detect_backends(void)
                  AP_Compass_AK8963::name, false);
     _add_backend(AP_Compass_HMC5843::probe(*this, hal.i2c_mgr->get_device(HAL_COMPASS_HMC5843_I2C_BUS, HAL_COMPASS_HMC5843_I2C_ADDR), true),
                  AP_Compass_HMC5843::name, true);
+#elif CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_PXF || \
+      CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_ERLEBRAIN2 || \
+      CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_PXFMINI
+    _add_backend(AP_Compass_AK8963::probe_mpu9250(*this, 0),
+                 AP_Compass_AK8963::name, false);
+    _add_backend(AP_Compass_HMC5843::probe(*this, hal.i2c_mgr->get_device(HAL_COMPASS_HMC5843_I2C_BUS, HAL_COMPASS_HMC5843_I2C_ADDR), true),
+                 AP_Compass_HMC5843::name, true);
 #elif HAL_COMPASS_DEFAULT == HAL_COMPASS_AK8963_MPU9250
     _add_backend(AP_Compass_AK8963::probe_mpu9250(*this, 0),
                  AP_Compass_AK8963::name, false);