AP_HAL: RCOutput_Tap: split baudrate set for Linux and Nuttx

On Linux (and in most of posix-like systems) the baudrate set in struct
termios via cfset[io]speed is actually the index of the standard
baudrates, it's not the baudrate per se (hence the use of B* macros).

On Linux it's possible to set the baudrate by passing the baudrate
itself to TCSETS2 ioctl.  Unfortunately it's not possible to include
asm/termbits.h and termios.h in the same compilation unit, so we need to
split it. Here we split into a Linux and a NuttX implementation.

libraries/AP_HAL/utility/RCOutput_Tap.cpp

@@ -322,24 +322,22 @@ bool RCOutput_Tap::_uart_open()
         return -1;
     }
 
-    // set baud rate
-    int speed = 250000;
     struct termios uart_config;
+    memset(&uart_config, 0, sizeof(uart_config));
     tcgetattr(_uart_fd, &uart_config);
 
     // clear ONLCR flag (which appends a CR for every LF)
     uart_config.c_oflag &= ~ONLCR;
 
-    // set baud rate
-    if (cfsetispeed(&uart_config, speed) < 0 || cfsetospeed(&uart_config, speed) < 0) {
-        ::fprintf(stderr, "failed to set baudrate for %s: %d\n",
-                  HAL_RCOUTPUT_TAP_DEVICE, termios_state);
+    if ((termios_state = tcsetattr(_uart_fd, TCSANOW, &uart_config)) < 0) {
+        ::fprintf(stderr, "tcsetattr failed for %s\n", HAL_RCOUTPUT_TAP_DEVICE);
         _uart_close();
         return false;
     }
 
-    if ((termios_state = tcsetattr(_uart_fd, TCSANOW, &uart_config)) < 0) {
-        fprintf(stderr, "tcsetattr failed for %s\n", HAL_RCOUTPUT_TAP_DEVICE);
+    if (!_uart_set_speed(250000)) {
+        ::fprintf(stderr, "failed to set baudrate for %s: %m\n",
+                  HAL_RCOUTPUT_TAP_DEVICE);
         _uart_close();
         return false;
     }

libraries/AP_HAL/utility/RCOutput_Tap.h

@@ -82,6 +82,7 @@ private:
 
     int _send_packet(EscPacket &p);
     bool _uart_open();
+    bool _uart_set_speed(int speed);
     void _uart_close();
 
     AP_HAL::Util::perf_counter_t _perf_rcout;

libraries/AP_HAL/utility/RCOutput_Tap_Linux.cpp

@@ -0,0 +1,63 @@
+/*
+ * Copyright (C) 2017  Intel Corporation. All rights reserved.
+ *
+ * This file is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This file is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include <AP_HAL/AP_HAL.h>
+
+#if CONFIG_HAL_BOARD == HAL_BOARD_LINUX
+
+#include "RCOutput_Tap.h"
+
+#include <asm/termbits.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+namespace ap {
+
+bool RCOutput_Tap::_uart_set_speed(int speed)
+{
+    struct termios2 tc;
+
+    if (_uart_fd < 0) {
+        return false;
+    }
+
+    memset(&tc, 0, sizeof(tc));
+    if (ioctl(_uart_fd, TCGETS2, &tc) == -1) {
+        return false;
+    }
+
+    /* speed is configured by c_[io]speed */
+    tc.c_cflag &= ~CBAUD;
+    tc.c_cflag |= BOTHER;
+    tc.c_ispeed = speed;
+    tc.c_ospeed = speed;
+
+    if (ioctl(_uart_fd, TCSETS2, &tc) == -1) {
+        return false;
+    }
+
+    if (ioctl(_uart_fd, TCFLSH, TCIOFLUSH) == -1) {
+        return false;
+    }
+
+    return true;
+}
+
+}
+
+#endif

libraries/AP_HAL/utility/RCOutput_Tap_Nuttx.cpp

@@ -0,0 +1,52 @@
+/*
+ * Copyright (C) 2017  Intel Corporation. All rights reserved.
+ *
+ * This file is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This file is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include <AP_HAL/AP_HAL.h>
+
+#if CONFIG_HAL_BOARD == HAL_BOARD_PX4 && CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_PX4_AEROFC_V1
+
+#include "RCOutput_Tap.h"
+
+#include <termios.h>
+#include <string.h>
+
+namespace ap {
+
+bool RCOutput_Tap::_uart_set_speed(int speed)
+{
+    if (_uart_fd < 0) {
+        return false;
+    }
+
+    struct termios uart_config;
+    memset(&uart_config, 0, sizeof(uart_config));
+    tcgetattr(_uart_fd, &uart_config);
+
+    // set baud rate
+    if (cfsetispeed(&uart_config, speed) < 0 || cfsetospeed(&uart_config, speed) < 0) {
+        return false;
+    }
+
+    if (tcsetattr(_uart_fd, TCSANOW, &uart_config) < 0) {
+        return false;
+    }
+
+    return true;
+}
+
+}
+
+#endif