From 9486bf2b9cc873392803398204e5780b7751662c Mon Sep 17 00:00:00 2001
From: Michael du Breuil <wicked.shell.scripts@gmail.com>
Date: Mon, 19 Jul 2021 16:53:50 -0700
Subject: [PATCH] AP_ICEngine: Add a flag to allow starting the engine while
 disarmed

---
 libraries/AP_ICEngine/AP_ICEngine.cpp | 26 ++++++++++++++++++++------
 libraries/AP_ICEngine/AP_ICEngine.h   |  4 +++-
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/libraries/AP_ICEngine/AP_ICEngine.cpp b/libraries/AP_ICEngine/AP_ICEngine.cpp
index b5b85d38dd..ade41a1578 100644
--- a/libraries/AP_ICEngine/AP_ICEngine.cpp
+++ b/libraries/AP_ICEngine/AP_ICEngine.cpp
@@ -238,6 +238,11 @@ void AP_ICEngine::update(void)
         should_run = true;
     } else if (start_chan_last_value <= RC_Channel::AUX_PWM_TRIGGER_LOW) {
         should_run = false;
+
+        // clear the single start flag now that we will be stopping the engine
+        if (state != ICE_OFF) {
+            allow_single_start_while_disarmed = false;
+        }
     } else if (state != ICE_OFF) {
         should_run = true;
     }
@@ -247,9 +252,16 @@ void AP_ICEngine::update(void)
         should_run = false;
     }
 
-    if (option_set(Options::NO_RUNNING_WHILE_DISARMED) && !hal.util->get_soft_armed()) {
-        // disable the engine if disarmed
-        should_run = false;
+    if (option_set(Options::NO_RUNNING_WHILE_DISARMED)) {
+        if (hal.util->get_soft_armed()) {
+            // clear the disarmed start flag, as we are now armed, if we disarm again we expect the engine to stop
+            allow_single_start_while_disarmed = false;
+        } else {
+            // check if we are blocking disarmed starts
+            if (!allow_single_start_while_disarmed) {
+                should_run = false;
+            }
+        }
     }
 
 #if HAL_PARACHUTE_ENABLED
@@ -464,15 +476,18 @@ bool AP_ICEngine::throttle_override(float &percentage, const float base_throttle
     return false;
 }
 
-
 /*
   handle DO_ENGINE_CONTROL messages via MAVLink or mission
 */
-bool AP_ICEngine::engine_control(float start_control, float cold_start, float height_delay)
+bool AP_ICEngine::engine_control(float start_control, float cold_start, float height_delay, uint32_t flags)
 {
     if (!enable) {
         return false;
     }
+
+    // always update the start while disarmed flag
+    allow_single_start_while_disarmed = (flags & ENGINE_CONTROL_OPTIONS_ALLOW_START_WHILE_DISARMED) != 0;
+
     if (start_control <= 0) {
         state = ICE_OFF;
         return true;
@@ -576,7 +591,6 @@ void AP_ICEngine::update_idle_governor(int8_t &min_throttle)
 #endif // AP_RPM_ENABLED
 }
 
-
 // singleton instance. Should only ever be set in the constructor.
 AP_ICEngine *AP_ICEngine::_singleton;
 namespace AP {
diff --git a/libraries/AP_ICEngine/AP_ICEngine.h b/libraries/AP_ICEngine/AP_ICEngine.h
index 1c243dd88f..743f8ccb99 100644
--- a/libraries/AP_ICEngine/AP_ICEngine.h
+++ b/libraries/AP_ICEngine/AP_ICEngine.h
@@ -52,7 +52,7 @@ public:
     ICE_State get_state(void) const { return !enable?ICE_DISABLED:state; }
 
     // handle DO_ENGINE_CONTROL messages via MAVLink or mission
-    bool engine_control(float start_control, float cold_start, float height_delay);
+    bool engine_control(float start_control, float cold_start, float height_delay, uint32_t flags);
 
     // update min throttle for idle governor
     void update_idle_governor(int8_t &min_throttle);
@@ -138,6 +138,8 @@ private:
     // we are waiting for valid height data
     bool height_pending:1;
 
+    bool allow_single_start_while_disarmed;
+
     // idle governor
     float idle_governor_integrator;