From: Marek Behún marek.behun@nic.cz
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 --- tools/kwboot.c | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+)
diff --git a/tools/kwboot.c b/tools/kwboot.c index 7ccab2993f..d8b950787b 100644 --- a/tools/kwboot.c +++ b/tools/kwboot.c @@ -567,6 +567,13 @@ 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) { @@ -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