GCS_MAVLink: implement BRD_OPTIONS bit for setting of internal parameters

libraries/GCS_MAVLink/GCS_Param.cpp

@@ -18,6 +18,7 @@
 
 #include "GCS.h"
 #include <AP_Logger/AP_Logger.h>
+#include <AP_BoardConfig/AP_BoardConfig.h>
 
 extern const AP_HAL::HAL& hal;
 
@@ -276,6 +277,14 @@ void GCS_MAVLINK::handle_param_set(const mavlink_message_t &msg)
 
     float old_value = vp->cast_to_float(var_type);
 
+    if (parameter_flags & AP_PARAM_FLAG_INTERNAL_USE_ONLY) {
+        // the user can set BRD_OPTIONS to enable set of internal
+        // parameters, for developer testing or unusual use cases
+        if (AP_BoardConfig::allow_set_internal_parameters()) {
+            parameter_flags &= ~AP_PARAM_FLAG_INTERNAL_USE_ONLY;
+        }
+    }
+
     if ((parameter_flags & AP_PARAM_FLAG_INTERNAL_USE_ONLY) || vp->is_read_only()) {
         gcs().send_text(MAV_SEVERITY_WARNING, "Param write denied (%s)", key);
         // send the readonly value