From 4ae6aeed7ed7f7ee9be11439b3f80cdd42de4d51 Mon Sep 17 00:00:00 2001
From: Peter Barker <pbarker@barker.dropbear.id.au>
Date: Wed, 25 Jul 2018 09:30:23 +1000
Subject: [PATCH] AP_Mount: add singleton

---
 libraries/AP_Mount/AP_Mount.cpp | 21 +++++++++++++++++++++
 libraries/AP_Mount/AP_Mount.h   | 11 +++++++++++
 2 files changed, 32 insertions(+)

diff --git a/libraries/AP_Mount/AP_Mount.cpp b/libraries/AP_Mount/AP_Mount.cpp
index 10224c3e4a..2c2f67cce5 100644
--- a/libraries/AP_Mount/AP_Mount.cpp
+++ b/libraries/AP_Mount/AP_Mount.cpp
@@ -397,6 +397,14 @@ AP_Mount::AP_Mount(const AP_AHRS_TYPE &ahrs, const struct Location &current_loc)
     _ahrs(ahrs),
     _current_loc(current_loc)
 {
+    if (_singleton != nullptr) {
+#if CONFIG_HAL_BOARD == HAL_BOARD_SITL
+        AP_HAL::panic("Mount must be singleton");
+#endif
+        return;
+    }
+    _singleton = this;
+
 	AP_Param::setup_object_defaults(this, var_info);
 }
 
@@ -635,3 +643,16 @@ void AP_Mount::send_gimbal_report(mavlink_channel_t chan)
         }
     }    
 }
+
+
+// singleton instance
+AP_Mount *AP_Mount::_singleton;
+
+namespace AP {
+
+AP_Mount *mount()
+{
+    return AP_Mount::get_singleton();
+}
+
+};
diff --git a/libraries/AP_Mount/AP_Mount.h b/libraries/AP_Mount/AP_Mount.h
index 27697cd976..96bc2931bd 100644
--- a/libraries/AP_Mount/AP_Mount.h
+++ b/libraries/AP_Mount/AP_Mount.h
@@ -61,6 +61,10 @@ public:
     AP_Mount(const AP_Mount &other) = delete;
     AP_Mount &operator=(const AP_Mount&) = delete;
 
+    // get singleton instance
+    static AP_Mount *get_singleton() {
+        return _singleton;
+    }
 
     // Enums
     enum MountType {
@@ -139,6 +143,9 @@ public:
     static const struct AP_Param::GroupInfo        var_info[];
 
 protected:
+
+    static AP_Mount *_singleton;
+
     // private members
     const AP_AHRS_TYPE     &_ahrs;
     const struct Location   &_current_loc;  // reference to the vehicle's current location
@@ -183,3 +190,7 @@ protected:
         struct Location _roi_target;        // roi target location
     } state[AP_MOUNT_MAX_INSTANCES];
 };
+
+namespace AP {
+    AP_Mount *mount();
+};