AP_Compass: probe for IST8308 on external buses

libraries/AP_Compass/AP_Compass.cpp

@@ -11,6 +11,7 @@
 #include "AP_Compass_BMM150.h"
 #include "AP_Compass_HIL.h"
 #include "AP_Compass_HMC5843.h"
+#include "AP_Compass_IST8308.h"
 #include "AP_Compass_IST8310.h"
 #include "AP_Compass_LSM303D.h"
 #include "AP_Compass_LSM9DS1.h"
@@ -681,6 +682,12 @@ void Compass::_probe_external_i2c_compasses(void)
                                                                   all_external, default_rotation));
         }
     }
+
+    // external i2c bus
+    FOREACH_I2C_EXTERNAL(i) {
+        ADD_BACKEND(DRIVER_IST8308, AP_Compass_IST8308::probe(GET_I2C_DEVICE(i, HAL_COMPASS_IST8308_I2C_ADDR),
+                                                              true, ROTATION_NONE));
+    }
 #endif // HAL_MINIMIZE_FEATURES
 }
 

libraries/AP_Compass/AP_Compass.h

@@ -378,6 +378,7 @@ private:
         DRIVER_QMC5883  =12,
         DRIVER_SITL     =13,
         DRIVER_MAG3110  =14,
+        DRIVER_IST8308  = 15,
     };
 
     bool _driver_enabled(enum DriverType driver_type);