Mount_MAVLink: use SerialManager for init

use serial_manager's get_mavlink_channel

libraries/AP_Mount/AP_Mount_MAVLink.cpp

@@ -1,16 +1,24 @@
 // -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
 
 #include <AP_Mount_MAVLink.h>
+#include <GCS_MAVLink.h>
 
 // init - performs any required initialisation for this instance
-void AP_Mount_MAVLink::init()
+void AP_Mount_MAVLink::init(const AP_SerialManager& serial_manager)
 {
-    // do nothing
+    // use mavlink channel associated with MAVLink2 protocol
+    if (serial_manager.get_mavlink_channel(AP_SerialManager::SerialProtocol_MAVLink2, _chan)) {
+        _initialised = true;
+    }
 }
 
 // update mount position - should be called periodically
 void AP_Mount_MAVLink::update()
 {
+    // exit immediately if not initialised
+    if (!_initialised) {
+        return;
+    }
 
     // update based on mount mode
     switch(_frontend.get_mode(_instance)) {
@@ -60,6 +68,11 @@ bool AP_Mount_MAVLink::has_pan_control() const
 // set_mode - sets mount's mode
 void AP_Mount_MAVLink::set_mode(enum MAV_MOUNT_MODE mode)
 {
+    // exit immediately if not initialised
+    if (!_initialised) {
+        return;
+    }
+
     // map requested mode to mode that mount can actually support
     enum MAV_MOUNT_MODE mode_to_send = mode;
     switch (mode) {
@@ -98,6 +111,11 @@ void AP_Mount_MAVLink::status_msg(mavlink_channel_t chan)
 // send_angle_target - send earth-frame angle targets to mount
 void AP_Mount_MAVLink::send_angle_target(const Vector3f& target, bool target_in_degrees)
 {
+    // exit immediately if not initialised
+    if (!_initialised) {
+        return;
+    }
+
     // convert to degrees if necessary
     Vector3f target_deg = target;
     if (!target_in_degrees) {

libraries/AP_Mount/AP_Mount_MAVLink.h

@@ -24,12 +24,13 @@ public:
     // Constructor
     AP_Mount_MAVLink(AP_Mount &frontend, AP_Mount::mount_state state, uint8_t instance) :
         AP_Mount_Backend(frontend, state, instance),
+        _initialised(false),
         _chan(MAVLINK_COMM_0),
         _last_mode(MAV_MOUNT_MODE_RETRACT)
     {}
 
     // init - performs any required initialisation for this instance
-    virtual void init();
+    virtual void init(const AP_SerialManager& serial_manager);
 
     // update mount position - should be called periodically
     virtual void update();
@@ -49,6 +50,7 @@ private:
     void send_angle_target(const Vector3f& target, bool target_in_degrees);
 
     // internal variables
+    bool _initialised;              // true once the driver has been initialised
     mavlink_channel_t _chan;        // telemetry channel used to communicate with mount
     enum MAV_MOUNT_MODE _last_mode; // last mode sent to mount
     Vector3f _last_angle_target;    // last angle target sent to mount