MAVLink app: Allocate buffers only as they are needed

src/modules/mavlink/CMakeLists.txt

@@ -36,7 +36,6 @@ px4_add_module(
 	STACK_MAIN 1200
 	STACK_MAX 1500
 	COMPILE_FLAGS
-		-DMAVLINK_COMM_NUM_BUFFERS=4
 		-Os
 	SRCS
 		mavlink.c

src/modules/mavlink/mavlink_main.cpp

@@ -136,7 +136,12 @@ void mavlink_end_uart_send(mavlink_channel_t chan, int length)
  */
 mavlink_status_t *mavlink_get_channel_status(uint8_t channel)
 {
-	return Mavlink::get_status_for_instance(channel);
+	Mavlink* m = Mavlink::get_instance((unsigned)channel);
+	if (m != nullptr) {
+		return m->get_status();
+	} else {
+		return nullptr;
+	}
 }
 
 /*
@@ -144,15 +149,18 @@ mavlink_status_t *mavlink_get_channel_status(uint8_t channel)
  */
 mavlink_message_t *mavlink_get_channel_buffer(uint8_t channel)
 {
-	return Mavlink::get_buffer_for_instance(channel);
+	Mavlink* m = Mavlink::get_instance((unsigned)channel);
+	if (m != nullptr) {
+		return m->get_buffer();
+	} else {
+		return nullptr;
+	}
 }
 
 static void usage(void);
 
 bool Mavlink::_boot_complete = false;
 bool Mavlink::_config_link_on = false;
-mavlink_message_t Mavlink::_mavlink_buffer[MAVLINK_COMM_NUM_BUFFERS] = {};
-mavlink_status_t Mavlink::_mavlink_status[MAVLINK_COMM_NUM_BUFFERS] = {};
 
 Mavlink::Mavlink() :
 	_device_name("/dev/ttyS1"),
@@ -161,6 +169,8 @@ Mavlink::Mavlink() :
 	_instance_id(0),
 	_mavlink_log_pub(nullptr),
 	_task_running(false),
+	_mavlink_buffer{},
+	_mavlink_status{},
 	_hil_enabled(false),
 	_generate_rc(false),
 	_use_hil_gps(false),
@@ -2268,9 +2278,9 @@ Mavlink::start(int argc, char *argv[])
 	// before returning to the shell
 	int ic = Mavlink::instance_count();
 
-	if (ic == MAVLINK_COMM_NUM_BUFFERS) {
+	if (ic == Mavlink::MAVLINK_MAX_INSTANCES) {
 		warnx("Maximum MAVLink instance count of %d reached.",
-			(int)MAVLINK_COMM_NUM_BUFFERS);
+			(int)Mavlink::MAVLINK_MAX_INSTANCES);
 		return 1;
 	}
 

src/modules/mavlink/mavlink_main.h

@@ -114,13 +114,9 @@ public:
 
 	static Mavlink 		*get_instance_for_network_port(unsigned long port);
 
-	static mavlink_message_t *get_buffer_for_instance(unsigned instance) { return &_mavlink_buffer[instance]; }
+	mavlink_message_t 	*get_buffer() { return &_mavlink_buffer; }
 
-	mavlink_message_t 	*get_buffer() { return Mavlink::get_buffer_for_instance(_instance_id); }
-
-	static mavlink_status_t *get_status_for_instance(unsigned instance) { return &_mavlink_status[instance]; }
-
-	mavlink_status_t 	*get_status() { return Mavlink::get_status_for_instance(_instance_id); }
+	mavlink_status_t 	*get_status() { return &_mavlink_status; }
 
 	/**
 	 * Set the MAVLink version
@@ -404,8 +400,9 @@ private:
 	orb_advert_t		_mavlink_log_pub;
 	bool			_task_running;
 	static bool		_boot_complete;
-	static mavlink_message_t _mavlink_buffer[MAVLINK_COMM_NUM_BUFFERS];
-	static mavlink_status_t _mavlink_status[MAVLINK_COMM_NUM_BUFFERS];
+	static const unsigned MAVLINK_MAX_INSTANCES = 4;
+	mavlink_message_t _mavlink_buffer;
+	mavlink_status_t _mavlink_status;
 
 	/* states */
 	bool			_hil_enabled;		/**< Hardware In the Loop mode */