When a baud rate of 0 is requested, both the 8250 driver and the FTDI
driver reset the baud rate to the default of 9600 (see the comment above
the uart_get_baud_rate function). Some old versions of the NXP blhost
utility depend on this behavior. However, the CP210x driver resets the
baud rate to the minimum supported rate of 300. Special-case B0 so that
it returns the baud rate to the more sensible default of 9600.
Signed-off-by: Alex Henrie <alexh@xxxxxxxxxxx>
---
drivers/usb/serial/cp210x.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
index 3bcec419f463..2c910550dca8 100644
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -1051,9 +1051,14 @@ static void cp210x_change_speed(struct tty_struct *tty,
* This maps the requested rate to the actual rate, a valid rate on
* cp2102 or cp2103, or to an arbitrary rate in [1M, max_speed].
*
- * NOTE: B0 is not implemented.
+ * NOTE: B0 is not implemented, apart from returning the baud rate to
+ * the default of B9600.
*/
- baud = clamp(tty->termios.c_ospeed, priv->min_speed, priv->max_speed);
+ if (tty->termios.c_ospeed) {
+ baud = clamp(tty->termios.c_ospeed, priv->min_speed, priv->max_speed);
+ } else {
+ baud = 9600;
+ }
if (priv->use_actual_rate)
baud = cp210x_get_actual_rate(baud);
@@ -1069,7 +1074,8 @@ static void cp210x_change_speed(struct tty_struct *tty,
baud = 9600;
}
- tty_encode_baud_rate(tty, baud, baud);
+ if (tty->termios.c_ospeed)
+ tty_encode_baud_rate(tty, baud, baud);
}
static void cp210x_enable_event_mode(struct usb_serial_port *port)
--
2.38.1
