Commander: always allow to switch to LAND mode (PX4#23580)

Special handling for LAND mode: always allow to switch into it such that if used
as emergency mode it is always available. When triggering it the user generally wants
the vehicle to descend immediately, and if that means to switch to DESCEND it is fine.

Signed-off-by: Silvan Fuhrer <[email protected]>

src/modules/commander/Commander.cpp

@@ -887,7 +887,14 @@ Commander::handle_command(const vehicle_command_s &cmd)
 			}
 
 			if (desired_nav_state != vehicle_status_s::NAVIGATION_STATE_MAX) {
-				if (_user_mode_intention.change(desired_nav_state, getSourceFromCommand(cmd))) {
+
+				// Special handling for LAND mode: always allow to switch into it such that if used
+				// as emergency mode it is always available. When triggering it the user generally wants
+				// the vehicle to descend immediately, and if that means to switch to DESCEND it is fine.
+
+				const bool force = desired_nav_state == vehicle_status_s::NAVIGATION_STATE_AUTO_LAND;
+
+				if (_user_mode_intention.change(desired_nav_state, getSourceFromCommand(cmd), false, force)) {
 					main_ret = TRANSITION_CHANGED;
 
 				} else {
@@ -1062,7 +1069,13 @@ Commander::handle_command(const vehicle_command_s &cmd)
 		break;
 
 	case vehicle_command_s::VEHICLE_CMD_NAV_LAND: {
-			if (_user_mode_intention.change(vehicle_status_s::NAVIGATION_STATE_AUTO_LAND, getSourceFromCommand(cmd))) {
+			// Special handling for LAND mode: always allow to switch into it such that if used
+			// as emergency mode it is always available. When triggering it the user generally wants
+			// the vehicle to descend immediately, and if that means to switch to DESCEND it is fine.
+			const bool force = true;
+
+			if (_user_mode_intention.change(vehicle_status_s::NAVIGATION_STATE_AUTO_LAND, getSourceFromCommand(cmd), false,
+							force)) {
 				mavlink_log_info(&_mavlink_log_pub, "Landing at current position\t");
 				events::send(events::ID("commander_landing_current_pos"), events::Log::Info,
 					     "Landing at current position");