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.

src/drivers/gps/gps.cpp

@@ -174,7 +174,7 @@ private:
 #ifdef __PX4_LINUX
 	int				_spi_fd {-1};					///< SPI interface to GPS
 #endif
-	Serial 			*_uart = nullptr;				///< UART interface to GPS
+	Serial 			_uart {};				///< UART interface to GPS
 	unsigned			_baudrate{0};					///< current baudrate
 	const unsigned			_configured_baudrate{0};			///< configured baudrate (0=auto-detect)
 	char				_port[20] {};					///< device / serial port path
@@ -416,8 +416,8 @@ int GPS::callback(GPSCallbackType type, void *data1, int data2, void *user)
 
 			int ret = 0;
 
-			if (gps->_uart) {
-				ret = gps->_uart->write((void *) data1, (size_t) data2);
+			if (gps->_interface == GPSHelper::Interface::UART) {
+				ret = gps->_uart.write((void *) data1, (size_t) data2);
 
 #ifdef __PX4_LINUX
 
@@ -477,8 +477,8 @@ int GPS::pollOrRead(uint8_t *buf, size_t buf_length, int timeout)
 
 	handleInjectDataTopic();
 
-	if ((_interface == GPSHelper::Interface::UART) && (_uart)) {
-		ret = _uart->readAtLeast(buf, buf_length, character_count, timeout_adjusted);
+	if (_interface == GPSHelper::Interface::UART) {
+		ret = _uart.readAtLeast(buf, buf_length, character_count, timeout_adjusted);
 
 // SPI is only supported on LInux
 #if defined(__PX4_LINUX)
@@ -598,8 +598,8 @@ bool GPS::injectData(uint8_t *data, size_t len)
 
 	size_t written = 0;
 
-	if ((_interface == GPSHelper::Interface::UART) && (_uart)) {
-		written = _uart->write((const void *) data, len);
+	if (_interface == GPSHelper::Interface::UART) {
+		written = _uart.write((const void *) data, len);
 
 #ifdef __PX4_LINUX
 
@@ -615,7 +615,7 @@ bool GPS::injectData(uint8_t *data, size_t len)
 int GPS::setBaudrate(unsigned baud)
 {
 	if (_interface == GPSHelper::Interface::UART) {
-		if ((_uart) && (_uart->setBaudrate(baud))) {
+		if (_uart.setBaudrate(baud)) {
 			return 0;
 		}
 
@@ -786,23 +786,19 @@ GPS::run()
 			_helper = nullptr;
 		}
 
-		if ((_interface == GPSHelper::Interface::UART) && (_uart == nullptr)) {
+		if ((_interface == GPSHelper::Interface::UART) && (! _uart.isOpen())) {
 
-			// Create the UART port instance
-			_uart = new Serial(_port);
-
-			if (_uart == nullptr) {
-				PX4_ERR("Error creating serial device %s", _port);
+			// Configure UART port
+			if (!_uart.setPort(_port)) {
+				PX4_ERR("Error configuring serial device on port %s", _port);
 				px4_sleep(1);
 				continue;
 			}
-		}
 
-		if ((_interface == GPSHelper::Interface::UART) && (! _uart->isOpen())) {
 			// Configure the desired baudrate if one was specified by the user.
 			// Otherwise the default baudrate will be used.
 			if (_configured_baudrate) {
-				if (! _uart->setBaudrate(_configured_baudrate)) {
+				if (! _uart.setBaudrate(_configured_baudrate)) {
 					PX4_ERR("Error setting baudrate to %u on %s", _configured_baudrate, _port);
 					px4_sleep(1);
 					continue;
@@ -810,7 +806,7 @@ GPS::run()
 			}
 
 			// Open the UART. If this is successful then the UART is ready to use.
-			if (! _uart->open()) {
+			if (! _uart.open()) {
 				PX4_ERR("Error opening serial device  %s", _port);
 				px4_sleep(1);
 				continue;
@@ -1029,10 +1025,8 @@ GPS::run()
 			}
 		}
 
-		if ((_interface == GPSHelper::Interface::UART) && (_uart)) {
-			(void) _uart->close();
-			delete _uart;
-			_uart = nullptr;
+		if (_interface == GPSHelper::Interface::UART) {
+			(void) _uart.close();
 
 #ifdef __PX4_LINUX
 
@@ -1528,7 +1522,7 @@ GPS *GPS::instantiate(int argc, char *argv[], Instance instance)
 
 	GPS *gps = nullptr;
 	if (instance == Instance::Main) {
-		if (device_name && (access(device_name, R_OK|W_OK) == 0)) {
+		if (Serial::validatePort(device_name)) {
 			gps = new GPS(device_name, mode, interface, instance, baudrate_main);
 
 		} else {
@@ -1551,7 +1545,7 @@ GPS *GPS::instantiate(int argc, char *argv[], Instance instance)
 			}
 		}
 	} else { // secondary instance
-		if (device_name_secondary && (access(device_name_secondary, R_OK|W_OK) == 0)) {
+		if (Serial::validatePort(device_name_secondary)) {
 			gps = new GPS(device_name_secondary, mode, interface_secondary, instance, baudrate_secondary);
 
 		} else {

src/lib/drivers/device/qurt/uart.c

@@ -25,19 +25,32 @@ void configure_uart_callbacks(open_uart_func_t open_func,
 	}
 }
 
-int qurt_uart_open(const char *dev, speed_t speed)
+int qurt_uart_get_port(const char *dev)
 {
-	if (_callbacks_configured) {
+	if (dev != NULL) {
 		// Convert device string into a uart port number
 		char *endptr = NULL;
-		uint8_t port_number = (uint8_t) strtol(dev, &endptr, 10);
+		int port_number = strtol(dev, &endptr, 10);
 
 		if ((port_number == 0) && (endptr == dev)) {
 			PX4_ERR("Could not convert %s into a valid uart port number", dev);
 			return -1;
-		}
 
-		return _open_uart(port_number, speed);
+		} else {
+			return port_number;
+		}
+	}
+
+	return -1;
+}
+
+int qurt_uart_open(const char *dev, speed_t speed)
+{
+	int port_number = qurt_uart_get_port(dev);
+
+	if (_callbacks_configured && (port_number >= 0)) {
+
+		return _open_uart((uint8_t) port_number, speed);
 
 	} else {
 		PX4_ERR("Cannot open uart until callbacks have been configured");

src/lib/drivers/device/qurt/uart.h

@@ -7,6 +7,7 @@ extern "C" {
 #include <stdbool.h>
 #include <termios.h>
 
+int qurt_uart_get_port(const char *dev);
 int qurt_uart_open(const char *dev, speed_t speed);
 int qurt_uart_write(int fd, const char *buf, size_t len);
 int qurt_uart_read(int fd, char *buf, size_t len, uint32_t timeout_us);