From c3ac1497c0d9596d76c289bf45b0324bfeeb3f9f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Beat=20K=C3=BCng?= <beat-kueng@gmx.net>
Date: Fri, 26 Apr 2019 17:26:54 +0200
Subject: [PATCH] mpu9250: fix mag publishing garbage on IMU failure (SPI only)

The Pixhawk cube as an internal mag on SPI. If there was a bad register
read (e.g. on an IMU failure), _register_wait was non-zero and there was
no transfer but _mag still published mpu_report.mag.
---
 src/drivers/imu/mpu9250/mpu9250.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/drivers/imu/mpu9250/mpu9250.cpp b/src/drivers/imu/mpu9250/mpu9250.cpp
index 14cfc35b27..2d29eb6bb9 100644
--- a/src/drivers/imu/mpu9250/mpu9250.cpp
+++ b/src/drivers/imu/mpu9250/mpu9250.cpp
@@ -1058,7 +1058,9 @@ MPU9250::measure()
 	if (_mag->is_passthrough()) {
 #   endif
 
-		_mag->_measure(mpu_report.mag);
+		if (_register_wait == 0) {
+			_mag->_measure(mpu_report.mag);
+		}
 
 #   ifdef USE_I2C