tools: kwboot: Check whether baudrate was set to requested value

The tcsetattr() function can return 0 even if baudrate was not changed.
Check whether baudrate was changed to requested value, and in case of
arbitrary baudrate, check whether the set value is within 3% tolerance.

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Stefan Roese <sr@denx.de>

diff --git a/tools/kwboot.c b/tools/kwboot.c
index 7ccab29..d8b9507 100644 (file)
--- a/tools/kwboot.c
+++ b/tools/kwboot.c
@@ -568,6 +568,13 @@ kwboot_tty_baudrate_to_speed(int baudrate)
 }
 
 static int
+_is_within_tolerance(int value, int reference, int tolerance)
+{
+       return 100 * value >= reference * (100 - tolerance) &&
+              100 * value <= reference * (100 + tolerance);
+}
+
+static int
 kwboot_tty_change_baudrate(int fd, int baudrate)
 {
        struct termios tio;
@@ -601,7 +608,32 @@ kwboot_tty_change_baudrate(int fd, int baudrate)
        if (rc)
                return rc;
 
+       rc = tcgetattr(fd, &tio);
+       if (rc)
+               return rc;
+
+       if (cfgetospeed(&tio) != speed || cfgetispeed(&tio) != speed)
+               goto baud_fail;
+
+#ifdef BOTHER
+       /*
+        * Check whether set baudrate is within 3% tolerance.
+        * If BOTHER is defined, Linux always fills out c_ospeed / c_ispeed
+        * with real values.
+        */
+       if (!_is_within_tolerance(tio.c_ospeed, baudrate, 3))
+               goto baud_fail;
+
+       if (!_is_within_tolerance(tio.c_ispeed, baudrate, 3))
+               goto baud_fail;
+#endif
+
        return 0;
+
+baud_fail:
+       fprintf(stderr, "Could not set baudrate to requested value\n");
+       errno = EINVAL;
+       return -1;
 }
 
 static int