AP_HAL_Linux: make flow_control a property of SerialDevice rather than UARTDriver's

Make it possible to change flow control settings for individual devices.

libraries/AP_HAL_Linux/SerialDevice.h

@@ -3,6 +3,8 @@
 #include <stdint.h>
 #include <stdlib.h>
 
+#include "AP_HAL_Linux.h"
+
 class SerialDevice {
 public: 
     virtual ~SerialDevice() {}
@@ -13,4 +15,9 @@ public:
     virtual ssize_t read(uint8_t *buf, uint16_t n) = 0;
     virtual void set_blocking(bool blocking) = 0;
     virtual void set_speed(uint32_t speed) = 0;
+    virtual AP_HAL::UARTDriver::flow_control get_flow_control(void) { return AP_HAL::UARTDriver::FLOW_CONTROL_ENABLE; }
+    virtual void set_flow_control(AP_HAL::UARTDriver::flow_control flow_control_setting)
+    {
+        /* most devices simply igmore this setting */
+    };
 };

libraries/AP_HAL_Linux/UARTDevice.cpp

@@ -109,3 +109,24 @@ void UARTDevice::set_speed(uint32_t baudrate)
     cfsetspeed(&t, baudrate);
     tcsetattr(_fd, TCSANOW, &t);
 }
+
+void UARTDevice::set_flow_control(AP_HAL::UARTDriver::flow_control flow_control_setting)
+{
+    struct termios t;
+
+    if (_flow_control == flow_control_setting) {
+        return;
+    }
+
+    tcgetattr(_fd, &t);
+
+    if (flow_control_setting != AP_HAL::UARTDriver::FLOW_CONTROL_DISABLE) {
+        t.c_cflag |= CRTSCTS;
+    } else {
+        t.c_cflag &= ~CRTSCTS;
+    }
+
+    tcsetattr(_fd, TCSANOW, &t);
+
+    _flow_control = flow_control_setting;
+}

libraries/AP_HAL_Linux/UARTDevice.h

@@ -14,9 +14,15 @@ public:
     virtual ssize_t read(uint8_t *buf, uint16_t n) override;
     virtual void set_blocking(bool blocking) override;
     virtual void set_speed(uint32_t speed) override;
+    virtual void set_flow_control(enum AP_HAL::UARTDriver::flow_control flow_control_setting) override;
+    virtual AP_HAL::UARTDriver::flow_control get_flow_control(void) override
+    {
+        return _flow_control;
+    }
 
 private:
     void _disable_crlf();
+    AP_HAL::UARTDriver::flow_control _flow_control = AP_HAL::UARTDriver::flow_control::FLOW_CONTROL_DISABLE;
 
     int _fd = -1;
     const char *_device_path;

libraries/AP_HAL_Linux/UARTDriver.cpp

@@ -35,8 +35,7 @@ using namespace Linux;
 
 UARTDriver::UARTDriver(bool default_console) :
     device_path(NULL),
-    _packetise(false),
-    _flow_control(FLOW_CONTROL_DISABLE)
+    _packetise(false)
 {
     if (default_console) {
         _console = true;
@@ -74,21 +73,18 @@ void UARTDriver::begin(uint32_t b, uint16_t rxS, uint16_t txS)
         case DEVICE_TCP:
         {
             _tcp_start_connection();
-            _flow_control = FLOW_CONTROL_ENABLE;
             break;
         }
 
         case DEVICE_UDP:
         {
             _udp_start_connection();
-            _flow_control = FLOW_CONTROL_ENABLE;
             break;
         }
 
         case DEVICE_UDPIN:
         {
             _udpin_start_connection();
-            _flow_control = FLOW_CONTROL_ENABLE;
             break;
         }
         
@@ -96,7 +92,6 @@ void UARTDriver::begin(uint32_t b, uint16_t rxS, uint16_t txS)
         case DEVICE_QFLIGHT:
         {
             _qflight_start_connection();
-            _flow_control = FLOW_CONTROL_DISABLE;
             break;
         }
 #endif
@@ -275,7 +270,6 @@ bool UARTDriver::_serial_start_connection()
     _device = new UARTDevice(device_path);
     _connected = _device->open();
     _device->set_blocking(false);
-    _flow_control = FLOW_CONTROL_DISABLE;
 
     return true;
 }
@@ -285,7 +279,6 @@ bool UARTDriver::_qflight_start_connection()
 {
     _device = new QFLIGHTDevice(device_path);
     _connected = _device->open();
-    _flow_control = FLOW_CONTROL_DISABLE;
 
     return true;
 }

libraries/AP_HAL_Linux/UARTDriver.h

@@ -36,7 +36,15 @@ public:
     bool _write_pending_bytes(void);
     virtual void _timer_tick(void);
 
-    enum flow_control get_flow_control(void) { return _flow_control; }
+    virtual enum flow_control get_flow_control(void) override
+    {
+        return _device->get_flow_control();
+    }
+
+    virtual void set_flow_control(enum flow_control flow_control_setting) override
+   {
+       _device->set_flow_control(flow_control_setting);
+   }
 
 private:
     AP_HAL::OwnPtr<SerialDevice> _device;
@@ -48,7 +56,6 @@ private:
     char *_flag;
     bool _connected; // true if a client has connected         
     bool _packetise; // true if writes should try to be on mavlink boundaries
-    enum flow_control _flow_control;
 
     void _allocate_buffers(uint16_t rxS, uint16_t txS);
     void _deallocate_buffers();