Add termios2 support (allows custom baud rates)

Author: philj56

configure.ac

@@ -150,6 +150,8 @@ fi
 AC_CHECK_DECLS([TIOCSRS485], [], [], [[#include <sys/ioctl.h>]])
 # Check for RTS flags
 AC_CHECK_DECLS([TIOCM_RTS], [], [], [[#include <sys/ioctl.h>]])
+# Check for termios2 support
+AC_CHECK_TYPES([struct termios2], [], [], [[#include <asm/termbits.h>]])
 
 WARNING_CFLAGS="-Wall \
 -Wmissing-declarations -Wmissing-prototypes \

src/modbus-rtu-private.h

@@ -16,6 +16,13 @@
 #if defined(_WIN32)
 #include <windows.h>
 #else
+#if defined(HAVE_STRUCT_TERMIOS2)
+/* Prevent duplicate definitions of "struct termios"
+ * when including <asm/termbits.h> and <termios.h>. */
+#define termios
+#include <asm/termbits.h>
+#undef termios
+#endif
 #include <termios.h>
 #endif
 
@@ -57,6 +64,9 @@ typedef struct _modbus_rtu {
 #if defined(_WIN32)
     struct win32_ser w_ser;
     DCB old_dcb;
+#elif defined(HAVE_STRUCT_TERMIOS2)
+    /* Save old termios settings */
+    struct termios2 old_tios;
 #else
     /* Save old termios settings */
     struct termios old_tios;

src/modbus-rtu.c

@@ -12,6 +12,9 @@
 #ifndef _MSC_VER
 #include <unistd.h>
 #endif
+#if defined(HAVE_STRUCT_TERMIOS2)
+#include <sys/ioctl.h>
+#endif
 #include "modbus-private.h"
 #include <assert.h>
 
@@ -503,6 +506,7 @@ static int _modbus_rtu_connect(modbus_t *ctx)
 }
 #else
 
+#ifndef HAVE_STRUCT_TERMIOS2
 static speed_t _get_termios_speed(int baud, int debug)
 {
     speed_t speed;
@@ -614,13 +618,18 @@ static speed_t _get_termios_speed(int baud, int debug)
 
     return speed;
 }
+#endif
 
 /* POSIX */
 static int _modbus_rtu_connect(modbus_t *ctx)
 {
+#ifdef HAVE_STRUCT_TERMIOS2
+    struct termios2 tios;
+#else
+    speed_t speed;
     struct termios tios;
+#endif
     int flags;
-    speed_t speed;
     modbus_rtu_t *ctx_rtu = ctx->backend_data;
 
     if (ctx->debug) {
@@ -656,21 +665,30 @@ static int _modbus_rtu_connect(modbus_t *ctx)
     }
 
     /* Save */
+#ifdef HAVE_STRUCT_TERMIOS2
+    ioctl(ctx->s, TCGETS2, &ctx_rtu->old_tios);
+#else
     tcgetattr(ctx->s, &ctx_rtu->old_tios);
+#endif
 
-    memset(&tios, 0, sizeof(struct termios));
+    memset(&tios, 0, sizeof(tios));
 
     /* C_ISPEED     Input baud (new interface)
        C_OSPEED     Output baud (new interface)
     */
 
     /* Set the baud rate */
 
+#ifdef HAVE_STRUCT_TERMIOS2
+	tios.c_cflag |= BOTHER;  /* Allow custom baud rate. */
+	tios.c_ispeed = ctx_rtu->baud;  /* Set input baud rate. */
+	tios.c_ospeed = ctx_rtu->baud;  /* Set output baud rate. */
+#else
     /*
     On MacOS, constants of baud rates are equal to the integer in argument but
     that's not the case under Linux so we have to find the corresponding
-    constant. Until the code is upgraded to termios2, the list of possible
-    values is limited (no 14400 for example).
+    constant. Without termios2, the list of possible values is limited
+    (no 14400 for example).
     */
     if (9600 == B9600) {
         speed = ctx_rtu->baud;
@@ -683,6 +701,7 @@ static int _modbus_rtu_connect(modbus_t *ctx)
         ctx->s = -1;
         return -1;
     }
+#endif
 
     /* C_CFLAG      Control options
        CLOCAL       Local line - do not change "owner" of port
@@ -852,11 +871,28 @@ static int _modbus_rtu_connect(modbus_t *ctx)
     tios.c_cc[VMIN] = 0;
     tios.c_cc[VTIME] = 0;
 
+#ifdef HAVE_STRUCT_TERMIOS2
+    if (ioctl(ctx->s, TCSETS2, &tios) < 0) {
+        close(ctx->s);
+        ctx->s = -1;
+        return -1;
+    }
+    if (ctx->debug) {
+        ioctl(ctx->s, TCGETS2, &tios);
+        if (tios.c_ispeed != (unsigned int)ctx_rtu->baud) {
+            fprintf(stderr,
+                    "WARNING Failed to set baud rate %d (%d used)\n",
+                    ctx_rtu->baud,
+                    tios.c_ispeed);
+        }
+    }
+#else
     if (tcsetattr(ctx->s, TCSANOW, &tios) < 0) {
         close(ctx->s);
         ctx->s = -1;
         return -1;
     }
+#endif
 
     return 0;
 }
@@ -1107,6 +1143,12 @@ static void _modbus_rtu_close(modbus_t *ctx)
                 "ERROR Error while closing handle (LastError %d)\n",
                 (int) GetLastError());
     }
+#elif defined(HAVE_STRUCT_TERMIOS2)
+    if (ctx->s >= 0) {
+        ioctl(ctx->s, TCSETS2, &ctx_rtu->old_tios);
+        close(ctx->s);
+        ctx->s = -1;
+    }
 #else
     if (ctx->s >= 0) {
         tcsetattr(ctx->s, TCSANOW, &ctx_rtu->old_tios);