GCS_MAVLink: keep a bitmap of what mavlink channels are active

- this will allow for looping over active channels in libraries
- expose active channel mask

libraries/GCS_MAVLink/GCS.h

@@ -195,6 +195,10 @@ public:
     void send_sensor_offsets(const AP_InertialSensor &ins, const Compass &compass, AP_Baro &barometer);
     void send_ahrs(AP_AHRS &ahrs);
 
+    // return a bitmap of active channels. Used by libraries to loop
+    // over active channels to send to all active channels    
+    static uint8_t active_channel_mask(void) { return mavlink_active; }
+
 private:
     void        handleMessage(mavlink_message_t * msg);
 
@@ -293,7 +297,8 @@ private:
     uint8_t next_deferred_message;
     uint8_t num_deferred_messages;
 
-    static bool mavlink_active;
+    // bitmask of what mavlink channels are active
+    static uint8_t mavlink_active;
 
     // vehicle specific message send function
     bool try_send_message(enum ap_message id);

libraries/GCS_MAVLink/GCS_Common.cpp

@@ -23,7 +23,7 @@
 extern const AP_HAL::HAL& hal;
 
 uint32_t GCS_MAVLINK::last_radio_status_remrssi_ms;
-bool GCS_MAVLINK::mavlink_active = false;
+uint8_t GCS_MAVLINK::mavlink_active = 0;
 
 GCS_MAVLINK::GCS_MAVLINK() :
     waypoint_receive_timeout(5000)
@@ -871,7 +871,7 @@ GCS_MAVLINK::update(void (*run_cli)(AP_HAL::UARTDriver *))
         if (run_cli != NULL) {
             /* allow CLI to be started by hitting enter 3 times, if no
              *  heartbeat packets have been received */
-            if (!mavlink_active && (hal.scheduler->millis() - _cli_timeout) < 20000 && 
+            if ((mavlink_active==0) && (hal.scheduler->millis() - _cli_timeout) < 20000 && 
                 comm_is_idle(chan)) {
                 if (c == '\n' || c == '\r') {
                     crlf_count++;
@@ -889,7 +889,7 @@ GCS_MAVLINK::update(void (*run_cli)(AP_HAL::UARTDriver *))
             // we exclude radio packets to make it possible to use the
             // CLI over the radio
             if (msg.msgid != MAVLINK_MSG_ID_RADIO && msg.msgid != MAVLINK_MSG_ID_RADIO_STATUS) {
-                mavlink_active = true;
+                mavlink_active |= (1U<<chan);
             }
             handleMessage(&msg);
         }

libraries/GCS_MAVLink/message_definitions/common.xml

@@ -2298,9 +2298,8 @@
             <description>Request for terrain data and terrain status</description>
             <field type="uint32_t" name="lat">Latitude of SW corner of first grid (degrees *10^7)</field>
             <field type="uint32_t" name="lon">Longitude of SW corner of first grid (in degrees *10^7)</field>
-            <field type="uint16_t" name="mask">Bitmask of requested 5x5 grids (row major 4x4 array of grids)</field>
             <field type="uint16_t" name="grid_spacing">Grid spacing in meters</field>
-            <field type="uint16_t" name="flags">Terrain status flags</field>
+            <field type="uint8_t[9]" name="mask">Bitmask of requested 5x5 grids (row major 9x9 array of grids)</field>
          </message>
          <message id="134" name="TERRAIN_DATA">
             <description>Terrain data sent from GCS</description>