HAL_SITL: allowed SITL to reopen uart connections

libraries/AP_HAL_SITL/UARTDriver.cpp

@@ -86,7 +86,9 @@ void UARTDriver::begin(uint32_t baud, uint16_t rxSpace, uint16_t txSpace)
         } else if (strcmp(devtype, "uart") == 0) {
             uint32_t baudrate = args2? atoi(args2) : baud;
             ::printf("UART connection %s:%u\n", args1, baudrate);
-            _uart_start_connection(args1, baudrate);
+            _uart_path = strdup(args1);
+            _uart_baudrate = baudrate;
+            _uart_start_connection();
         } else {
             AP_HAL::panic("Invalid device path: %s", path);
         }
@@ -299,19 +301,22 @@ void UARTDriver::_tcp_start_client(const char *address, uint16_t port)
 /*
   start a UART connection for the serial port
  */
-void UARTDriver::_uart_start_connection(const char *path, uint32_t baudrate)
+void UARTDriver::_uart_start_connection(void)
 {
     struct termios t {};
     if (!_connected) {
-        ::printf("Opening %s\n", path);
-        _fd = ::open(path, O_RDWR | O_CLOEXEC);
+        _fd = ::open(_uart_path, O_RDWR | O_CLOEXEC);
+        if (_fd == -1) {
+            return;
+        }
         // use much smaller buffer sizes on real UARTs
         _writebuffer.set_size(1024);
         _readbuffer.set_size(512);
+        ::printf("Opened %s\n", _uart_path);
     }
 
     if (_fd == -1) {
-        AP_HAL::panic("Unable to open UART %s", path);
+        AP_HAL::panic("Unable to open UART %s", _uart_path);
     }
 
     // set non-blocking
@@ -332,7 +337,7 @@ void UARTDriver::_uart_start_connection(const char *path, uint32_t baudrate)
 
     // set baudrate
     tcgetattr(_fd, &t);
-    cfsetspeed(&t, baudrate);
+    cfsetspeed(&t, _uart_baudrate);
     tcsetattr(_fd, TCSANOW, &t);
 
     _connected = true;
@@ -390,9 +395,18 @@ void UARTDriver::_set_nonblocking(int fd)
     fcntl(fd, F_SETFL, v | O_NONBLOCK);
 }
 
+void UARTDriver::_check_reconnect(void)
+{
+    if (!_uart_path) {
+        return;
+    }
+    _uart_start_connection();
+}
+
 void UARTDriver::_timer_tick(void)
 {
     if (!_connected) {
+        _check_reconnect();
         return;
     }
     uint32_t navail;
@@ -402,6 +416,11 @@ void UARTDriver::_timer_tick(void)
     if (readptr && navail > 0) {
         if (!_use_send_recv) {
             nwritten = ::write(_fd, readptr, navail);
+            if (nwritten == -1 && errno != EAGAIN && _uart_path) {
+                close(_fd);
+                _fd = -1;
+                _connected = false;
+            }
         } else {
             nwritten = send(_fd, readptr, navail, MSG_DONTWAIT);
         }
@@ -420,6 +439,11 @@ void UARTDriver::_timer_tick(void)
     if (!_use_send_recv) {
         int fd = _console?0:_fd;
         nread = ::read(fd, buf, space);
+        if (nread == -1 && errno != EAGAIN && _uart_path) {
+            close(_fd);
+            _fd = -1;
+            _connected = false;
+        }
     } else {
         if (_select_check(_fd)) {
             nread = recv(_fd, buf, space, MSG_DONTWAIT);

libraries/AP_HAL_SITL/UARTDriver.h

@@ -73,11 +73,15 @@ private:
     ByteBuffer _readbuffer{16384};
     ByteBuffer _writebuffer{16384};
 
+    const char *_uart_path;
+    uint32_t _uart_baudrate;
+
     // IPv4 address of target for uartC
     const char *_tcp_client_addr;
 
     void _tcp_start_connection(uint16_t port, bool wait_for_connection);
-    void _uart_start_connection(const char *path, uint32_t baudrate);
+    void _uart_start_connection(void);
+    void _check_reconnect();
     void _tcp_start_client(const char *address, uint16_t port);
     void _check_connection(void);
     static bool _select_check(int );