Merge branch 'master' of github.com:PX4/Firmware into fmuv2_bringup

src/drivers/hmc5883/hmc5883.cpp

@@ -1221,7 +1221,8 @@ start()
 	int fd;
 
 	if (g_dev != nullptr)
-		errx(1, "already started");
+		/* if already started, the still command succeeded */
+		errx(0, "already started");
 
 	/* create the driver, attempt expansion bus first */
 	g_dev = new HMC5883(PX4_I2C_BUS_EXPANSION);

src/drivers/mpu6000/mpu6000.cpp

@@ -1063,7 +1063,8 @@ start()
 	int fd;
 
 	if (g_dev != nullptr)
-		errx(1, "already started");
+		/* if already started, the still command succeeded */
+		errx(0, "already started");
 
 	/* create the driver */
 	g_dev = new MPU6000(1 /* XXX magic number */, (spi_dev_e)PX4_SPIDEV_MPU);

src/drivers/ms5611/ms5611.cpp

@@ -791,7 +791,8 @@ start()
 	prom_u prom_buf;
 
 	if (g_dev != nullptr)
-		errx(1, "already started");
+		/* if already started, the still command succeeded */
+		errx(0, "already started");
 
 	device::Device *interface = nullptr;
 
@@ -1050,4 +1051,4 @@ ms5611_main(int argc, char *argv[])
 	}
 
 	errx(1, "unrecognised command, try 'start', 'test', 'reset' or 'info'");
-}
+}