AP_ICEngine: don't allow engine run with safety on

Cherry-pick source:
 - AP_ICEngine: don't allow engine run with safety on : e070848
 - AP_EFI: fixed ignition while disarmed : 2956810

Cherry-pick was not sufficient, since the code has changed since 4.3.25. This code is tested after changes.

libraries/AP_EFI/AP_EFI_Serial_Hirth.cpp

@@ -165,7 +165,21 @@ void AP_EFI_Serial_Hirth::send_request()
 
     // check for change or timeout for throttle value
     if ((new_throttle != last_throttle) || (now - last_req_send_throttle_ms > 500)) {
-        request_was_sent = send_target_values(new_throttle);
+        bool allow_throttle = hal.util->get_soft_armed();
+        if (!allow_throttle) {
+            const auto *ice = AP::ice();
+            if (ice != nullptr) {
+                allow_throttle = ice->allow_throttle_disarmed();
+            }
+        }
+
+        if (allow_throttle) {
+            request_was_sent = send_target_values(new_throttle);
+        }
+        else {
+            request_was_sent = send_target_values(0);
+        }
+
         last_throttle = new_throttle;
         last_req_send_throttle_ms = now;
     } else {

libraries/AP_ICEngine/AP_ICEngine.cpp

@@ -355,7 +355,12 @@ void AP_ICEngine::update(void)
 
     case ICE_STARTING:
         set_ignition(true);
-        set_starter(true);
+
+        if (allow_throttle_disarmed()) {
+            set_starter(true);
+        } else {
+            set_starter(false);
+        }
 
         if (starter_start_time_ms == 0) {
             starter_start_time_ms = now;
@@ -546,6 +551,15 @@ void AP_ICEngine::update_idle_governor(int8_t &min_throttle)
     min_throttle = roundf(idle_governor_integrator);
 }
 
+/*
+  Allows throttle when disarmed and Safety Switch is not ON
+ */
+bool AP_ICEngine::allow_throttle_disarmed() const
+{
+    return option_set(Options::THROTTLE_WHILE_DISARMED) &&
+        hal.util->safety_switch_state() != AP_HAL::Util::SAFETY_DISARMED;
+}
+
 /*
   set ignition state
  */

libraries/AP_ICEngine/AP_ICEngine.h

@@ -69,6 +69,8 @@ class AP_ICEngine {
 
     static AP_ICEngine *get_singleton() { return _singleton; }
 
+    bool allow_throttle_disarmed() const;
+
 private:
     static AP_ICEngine *_singleton;