USB: cdc-acm: only raise DTR on transitions from B0

commit 4473d054ceb572557954f9536731d39b20937b0c upstream.

Make sure to only raise DTR on transitions from B0 in set_termios.

Also allow set_termios to be called from open with a termios_old of
NULL. Note that DTR will not be raised prematurely in this case.

Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 537e1d32f92b9f76cdc9d3bbd830cf1b72384242..1e71f918eb9fbbfbdf979826a4d01f022d0f8101 100644 (file)
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -883,11 +883,12 @@ static void acm_tty_set_termios(struct tty_struct *tty,
        /* FIXME: Needs to clear unsupported bits in the termios */
        acm->clocal = ((termios->c_cflag & CLOCAL) != 0);
 
-       if (!newline.dwDTERate) {
+       if (C_BAUD(tty) == B0) {
                newline.dwDTERate = acm->line.dwDTERate;
                newctrl &= ~ACM_CTRL_DTR;
-       } else
+       } else if (termios_old && (termios_old->c_cflag & CBAUD) == B0) {
                newctrl |=  ACM_CTRL_DTR;
+       }
 
        if (newctrl != acm->ctrlout)
                acm_set_control(acm, acm->ctrlout = newctrl);