From 6991a1b9e9adb61299011b160165c318a837b249 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Mon, 7 Sep 2015 08:58:11 +1000
Subject: [PATCH] AP_Compass: ensure we have payload space to send MAG_CAL
 messages

---
 libraries/AP_Compass/AP_Compass_Calibration.cpp | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/libraries/AP_Compass/AP_Compass_Calibration.cpp b/libraries/AP_Compass/AP_Compass_Calibration.cpp
index c462a2f0b4..49cfe07324 100644
--- a/libraries/AP_Compass/AP_Compass_Calibration.cpp
+++ b/libraries/AP_Compass/AP_Compass_Calibration.cpp
@@ -2,6 +2,7 @@
 #include <AP_HAL/AP_HAL.h>
 #include "Compass.h"
 #include <AP_Notify/AP_Notify.h>
+#include <GCS_MAVLink/GCS.h>
 
 extern AP_HAL::HAL& hal;
 
@@ -186,6 +187,11 @@ Compass::send_mag_cal_progress(mavlink_channel_t chan)
 
             memset(completion_mask, 0, sizeof(completion_mask));
 
+            // ensure we don't try to send with no space available
+            if (!HAVE_PAYLOAD_SPACE(chan, MAG_CAL_PROGRESS)) {
+                return;
+            }
+            
             mavlink_msg_mag_cal_progress_send(
                 chan,
                 compass_id, cal_mask,
@@ -211,6 +217,11 @@ void Compass::send_mag_cal_report(mavlink_channel_t chan)
             _calibrator[compass_id].get_calibration(ofs, diag, offdiag);
             uint8_t autosaved = _calibrator[compass_id].get_autosave();
 
+            // ensure we don't try to send with no space available
+            if (!HAVE_PAYLOAD_SPACE(chan, MAG_CAL_REPORT)) {
+                return;
+            }
+            
             mavlink_msg_mag_cal_report_send(
                 chan,
                 compass_id, cal_mask,