[PATCH 3.17 202/319] USB: cdc-acm: only raise DTR on transitions from B0

[Greg Kroah-Hartman]

3.17-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Johan Hovold <johan@xxxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/usb/class/cdc-acm.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -980,11 +980,12 @@ static void acm_tty_set_termios(struct t
 	/* 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);


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