Additions to the Serial UART API (#22953)

- Added an empty constructor, setPort, and validatePort functions for Serial API
- Changed GPS to not allocate Serial object dynamically
- Moved access check on serial port name into the Serial API
- Improved the Qurt platform validatePort Serial function to implement a more rigorous check. Added safety check
to the setPort Serial function to make sure it isn't called after the port has been already opened.

platforms/common/Serial.cpp

@@ -36,6 +36,10 @@
 namespace device
 {
 
+Serial::Serial() :
+	_impl(nullptr, 57600, ByteSize::EightBits, Parity::None, StopBits::One, FlowControl::Disabled) {}
+
+
 Serial::Serial(const char *port, uint32_t baudrate, ByteSize bytesize, Parity parity, StopBits stopbits,
 	       FlowControl flowcontrol) :
 	_impl(port, baudrate, bytesize, parity, stopbits, flowcontrol)
@@ -135,4 +139,14 @@ const char *Serial::getPort() const
 	return _impl.getPort();
 }
 
+bool Serial::validatePort(const char *port)
+{
+	return SerialImpl::validatePort(port);
+}
+
+bool Serial::setPort(const char *port)
+{
+	return _impl.setPort(port);
+}
+
 } // namespace device

platforms/common/include/px4_platform_common/Serial.hpp

@@ -48,6 +48,7 @@ namespace device __EXPORT
 class Serial
 {
 public:
+	Serial();
 	Serial(const char *port, uint32_t baudrate = 57600,
 	       ByteSize bytesize = ByteSize::EightBits, Parity parity = Parity::None,
 	       StopBits stopbits = StopBits::One, FlowControl flowcontrol = FlowControl::Disabled);
@@ -83,6 +84,8 @@ public:
 	FlowControl getFlowcontrol() const;
 	bool setFlowcontrol(FlowControl flowcontrol);
 
+	static bool validatePort(const char *port);
+	bool setPort(const char *port);
 	const char *getPort() const;
 
 private:

platforms/nuttx/src/px4/common/SerialImpl.cpp

@@ -53,9 +53,8 @@ SerialImpl::SerialImpl(const char *port, uint32_t baudrate, ByteSize bytesize, P
 	_stopbits(stopbits),
 	_flowcontrol(flowcontrol)
 {
-	if (port) {
-		strncpy(_port, port, sizeof(_port) - 1);
-		_port[sizeof(_port) - 1] = '\0';
+	if (validatePort(port)) {
+		setPort(port);
 
 	} else {
 		_port[0] = 0;
@@ -192,6 +191,11 @@ bool SerialImpl::open()
 		return true;
 	}
 
+	if (!validatePort(_port)) {
+		PX4_ERR("Invalid port %s", _port);
+		return false;
+	}
+
 	// Open the serial port
 	int serial_fd = ::open(_port, O_RDWR | O_NOCTTY);
 
@@ -324,6 +328,27 @@ const char *SerialImpl::getPort() const
 	return _port;
 }
 
+bool SerialImpl::validatePort(const char *port)
+{
+	return (port && (access(port, R_OK | W_OK) == 0));
+}
+
+bool SerialImpl::setPort(const char *port)
+{
+	if (_open) {
+		PX4_ERR("Cannot set port after port has already been opened");
+		return false;
+	}
+
+	if (validatePort(port)) {
+		strncpy(_port, port, sizeof(_port) - 1);
+		_port[sizeof(_port) - 1] = '\0';
+		return true;
+	}
+
+	return false;
+}
+
 uint32_t SerialImpl::getBaudrate() const
 {
 	return _baudrate;

platforms/nuttx/src/px4/common/include/SerialImpl.hpp

@@ -65,6 +65,8 @@ public:
 	ssize_t write(const void *buffer, size_t buffer_size);
 
 	const char *getPort() const;
+	static bool validatePort(const char *port);
+	bool setPort(const char *port);
 
 	uint32_t getBaudrate() const;
 	bool setBaudrate(uint32_t baudrate);

platforms/posix/include/SerialImpl.hpp

@@ -65,6 +65,8 @@ public:
 	ssize_t write(const void *buffer, size_t buffer_size);
 
 	const char *getPort() const;
+	static bool validatePort(const char *port);
+	bool setPort(const char *port);
 
 	uint32_t getBaudrate() const;
 	bool setBaudrate(uint32_t baudrate);

platforms/posix/src/px4/common/SerialImpl.cpp

@@ -51,9 +51,8 @@ SerialImpl::SerialImpl(const char *port, uint32_t baudrate, ByteSize bytesize, P
 	_stopbits(stopbits),
 	_flowcontrol(flowcontrol)
 {
-	if (port) {
-		strncpy(_port, port, sizeof(_port) - 1);
-		_port[sizeof(_port) - 1] = '\0';
+	if (validatePort(port)) {
+		setPort(port);
 
 	} else {
 		_port[0] = 0;
@@ -190,6 +189,11 @@ bool SerialImpl::open()
 		return true;
 	}
 
+	if (!validatePort(_port)) {
+		PX4_ERR("Invalid port %s", _port);
+		return false;
+	}
+
 	// Open the serial port
 	int serial_fd = ::open(_port, O_RDWR | O_NOCTTY);
 
@@ -317,6 +321,27 @@ const char *SerialImpl::getPort() const
 	return _port;
 }
 
+bool SerialImpl::validatePort(const char *port)
+{
+	return (port && (access(port, R_OK | W_OK) == 0));
+}
+
+bool SerialImpl::setPort(const char *port)
+{
+	if (_open) {
+		PX4_ERR("Cannot set port after port has already been opened");
+		return false;
+	}
+
+	if (validatePort(port)) {
+		strncpy(_port, port, sizeof(_port) - 1);
+		_port[sizeof(_port) - 1] = '\0';
+		return true;
+	}
+
+	return false;
+}
+
 uint32_t SerialImpl::getBaudrate() const
 {
 	return _baudrate;

platforms/qurt/include/SerialImpl.hpp

@@ -65,6 +65,7 @@ public:
 
 	const char *getPort() const;
 	bool setPort(const char *port);
+	static bool validatePort(const char *port);
 
 	uint32_t getBaudrate() const;
 	bool setBaudrate(uint32_t baudrate);

platforms/qurt/src/px4/SerialImpl.cpp

@@ -48,9 +48,8 @@ SerialImpl::SerialImpl(const char *port, uint32_t baudrate, ByteSize bytesize, P
 	_stopbits(stopbits),
 	_flowcontrol(flowcontrol)
 {
-	if (port) {
-		strncpy(_port, port, sizeof(_port) - 1);
-		_port[sizeof(_port) - 1] = '\0';
+	if (validatePort(port)) {
+		setPort(port);
 
 	} else {
 		_port[0] = 0;
@@ -117,6 +116,11 @@ bool SerialImpl::open()
 		return false;
 	}
 
+	if (!validatePort(_port)) {
+		PX4_ERR("Invalid port %s", _port);
+		return false;
+	}
+
 	// qurt_uart_open will check validity of port and baudrate
 	int serial_fd = qurt_uart_open(_port, _baudrate);
 
@@ -256,6 +260,27 @@ const char *SerialImpl::getPort() const
 	return _port;
 }
 
+bool SerialImpl::validatePort(const char *port)
+{
+	return (qurt_uart_get_port(port) >= 0);
+}
+
+bool SerialImpl::setPort(const char *port)
+{
+	if (_open) {
+		PX4_ERR("Cannot set port after port has already been opened");
+		return false;
+	}
+
+	if (validatePort(port)) {
+		strncpy(_port, port, sizeof(_port) - 1);
+		_port[sizeof(_port) - 1] = '\0';
+		return true;
+	}
+
+	return false;
+}
+
 uint32_t SerialImpl::getBaudrate() const
 {
 	return _baudrate;