Merge remote-tracking branch 'px4/beta_mavlink2' into beta_mavlink2_camera

Conflicts:
	src/modules/mavlink/mavlink_messages.cpp

src/modules/mavlink/mavlink_main.cpp

@@ -254,7 +254,6 @@ Mavlink::Mavlink() :
 		break;
 	}
 
-	LL_APPEND(_mavlink_instances, this);
 }
 
 Mavlink::~Mavlink()
@@ -589,7 +588,7 @@ int Mavlink::mavlink_open_uart(int baud, const char *uart_name, struct termios *
 
 		/* setup output flow control */
 		if (enable_flow_control(true)) {
-			warnx("ERR FLOW CTRL EN");
+			warnx("hardware flow control not supported");
 		}
 	}
 
@@ -1769,6 +1768,7 @@ Mavlink::task_main(int argc, char *argv[])
 		configure_stream("GLOBAL_POSITION_INT", 3.0f * rate_mult);
 		configure_stream("LOCAL_POSITION_NED", 3.0f * rate_mult);
 		configure_stream("RC_CHANNELS_RAW", 1.0f * rate_mult);
+		configure_stream("NAMED_VALUE_FLOAT", 1.0f * rate_mult);
 		break;
 
 	case MAVLINK_MODE_CAMERA:
@@ -1791,6 +1791,9 @@ Mavlink::task_main(int argc, char *argv[])
 	/* set main loop delay depending on data rate to minimize CPU overhead */
 	_main_loop_delay = MAIN_LOOP_DELAY / rate_mult;
 
+	/* now the instance is fully initialized and we can bump the instance count */
+	LL_APPEND(_mavlink_instances, this);
+
 	while (!_task_should_exit) {
 		/* main loop */
 		usleep(_main_loop_delay);
@@ -1937,10 +1940,18 @@ int Mavlink::start_helper(int argc, char *argv[])
 int
 Mavlink::start(int argc, char *argv[])
 {
+	// Wait for the instance count to go up one
+	// before returning to the shell
+	int ic = Mavlink::instance_count();
+
 	// Instantiate thread
 	char buf[24];
-	sprintf(buf, "mavlink_if%d", Mavlink::instance_count());
+	sprintf(buf, "mavlink_if%d", ic);
 
+	// This is where the control flow splits
+	// between the starting task and the spawned
+	// task - start_helper() only returns
+	// when the started task exits.
 	task_spawn_cmd(buf,
 		       SCHED_DEFAULT,
 		       SCHED_PRIORITY_DEFAULT,
@@ -1948,6 +1959,25 @@ Mavlink::start(int argc, char *argv[])
 		       (main_t)&Mavlink::start_helper,
 		       (const char **)argv);
 
+	// Ensure that this shell command
+	// does not return before the instance
+	// is fully initialized. As this is also
+	// the only path to create a new instance,
+	// this is effectively a lock on concurrent
+	// instance starting. XXX do a real lock.
+
+	// Sleep 500 us between each attempt
+	const unsigned sleeptime = 500;
+
+	// Wait 100 ms max for the startup.
+	const unsigned limit = 100 * 1000 / sleeptime;
+
+	unsigned count = 0;
+	while (ic == Mavlink::instance_count() && count < limit) {
+		::usleep(sleeptime);
+		count++;
+	}
+
 	return OK;
 }
 
@@ -2001,7 +2031,10 @@ Mavlink::stream(int argc, char *argv[])
 			inst->configure_stream_threadsafe(stream_name, rate);
 
 		} else {
-			errx(1, "mavlink for device %s is not running", device_name);
+
+			// If the link is not running we should complain, but not fall over
+			// because this is so easy to get wrong and not fatal. Warning is sufficient.
+			errx(0, "mavlink for device %s is not running", device_name);
 		}
 
 	} else {