AP_RPM: create singleton

libraries/AP_RPM/AP_RPM.cpp

@@ -92,6 +92,11 @@ const AP_Param::GroupInfo AP_RPM::var_info[] = {
 AP_RPM::AP_RPM(void)
 {
     AP_Param::setup_object_defaults(this, var_info);
+
+    if (_singleton != nullptr) {
+        AP_HAL::panic("AP_RPM must be singleton");
+    }
+    _singleton = this;
 }
 
 /*
@@ -173,3 +178,7 @@ bool AP_RPM::enabled(uint8_t instance) const
     }
     return true;
 }
+
+// singleton instance
+AP_RPM *AP_RPM::_singleton;
+

libraries/AP_RPM/AP_RPM.h

@@ -92,7 +92,11 @@ public:
 
     bool enabled(uint8_t instance) const;
 
+    static AP_RPM *get_singleton() { return _singleton; }
+
 private:
+    static AP_RPM *_singleton;
+
     RPM_State state[RPM_MAX_INSTANCES];
     AP_RPM_Backend *drivers[RPM_MAX_INSTANCES];
     uint8_t num_instances:2;