uavcan_v1: Clean up handling of invalid port IDs

Always convert 'invalid' port ID values (e.g., the default PX4 port-ID
parameter value of -1) to CANARD_PORT_ID_UNSET in all comparisons.

src/drivers/uavcan_v1/Publishers/Publisher.hpp

@@ -60,6 +60,7 @@ class UavcanPublisher
 {
 public:
 	static constexpr uint16_t CANARD_PORT_ID_UNSET = 65535U;
+	static constexpr uint16_t CANARD_PORT_ID_MAX   = 32767U;
 
 	UavcanPublisher(CanardInstance &ins, UavcanParamManager &pmgr, const char *subject_name, uint8_t instance = 0) :
 		_canard_instance(ins), _param_manager(pmgr), _subject_name(subject_name), _instance(instance) { };
@@ -67,6 +68,8 @@ public:
 	// Update the uORB Subscription and broadcast a UAVCAN message
 	virtual void update() = 0;
 
+	bool isValidPortId(int32_t id) const { return id >= 0 && id <= CANARD_PORT_ID_MAX; }
+
 	CanardPortID id() { return _port_id; };
 
 	void updateParam()
@@ -79,9 +82,16 @@ public:
 		_param_manager.GetParamByName(uavcan_param, value);
 		int32_t new_id = value.integer32.value.elements[0];
 
+		// Allow, for example, a default PX4 param value of '-1' to disable publication
+		if (!isValidPortId(new_id)) {
+			// but always use the standard 'unset' value for comparison
+			new_id = CANARD_PORT_ID_UNSET;
+		}
+
 		if (_port_id != new_id) {
 			if (new_id == CANARD_PORT_ID_UNSET) {
 				PX4_INFO("Disabling publication of subject %s.%d", _subject_name, _instance);
+				_port_id = CANARD_PORT_ID_UNSET;
 
 			} else {
 				_port_id = (CanardPortID)new_id;

src/drivers/uavcan_v1/Subscribers/BaseSubscriber.hpp

@@ -51,6 +51,7 @@ class UavcanBaseSubscriber
 {
 public:
 	static constexpr uint16_t CANARD_PORT_ID_UNSET = 65535U;
+	static constexpr uint16_t CANARD_PORT_ID_MAX   = 32767U;
 
 	UavcanBaseSubscriber(CanardInstance &ins, const char *subject_name, uint8_t instance = 0) :
 		_canard_instance(ins), _instance(instance)
@@ -64,6 +65,8 @@ public:
 		unsubscribe();
 	}
 
+	bool isValidPortId(int32_t id) const { return id >= 0 && id <= CANARD_PORT_ID_MAX; }
+
 	virtual void subscribe() = 0;
 	virtual void unsubscribe()
 	{
@@ -96,6 +99,10 @@ public:
 
 	bool hasPortID(CanardPortID port_id)
 	{
+		if (!isValidPortId((int32_t)port_id)) {
+			return false;
+		}
+
 		SubjectSubscription *curSubj = &_subj_sub;
 
 		while (curSubj != NULL) {

src/drivers/uavcan_v1/Subscribers/DynamicPortSubscriber.hpp

@@ -72,6 +72,12 @@ public:
 			if (_param_manager.GetParamByName(uavcan_param, value)) {
 				int32_t new_id = value.integer32.value.elements[0];
 
+				// Allow, for example, a default PX4 param value of '-1' to disable subscription
+				if (!isValidPortId(new_id)) {
+					// but always use the standard 'unset' value for comparison
+					new_id = CANARD_PORT_ID_UNSET;
+				}
+
 				/* FIXME how about partial subscribing */
 				if (curSubj->_canard_sub.port_id != new_id) {
 					if (new_id == CANARD_PORT_ID_UNSET) {