linux-kernel - [PATCH Resend] USB: cdc-acm: only raise DTR on transitions from B0

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Message-Id: <1415209319-14076-1-git-send-email-johan@kernel.org>
Date:	Wed,  5 Nov 2014 18:41:59 +0100
From:	Johan Hovold <johan@...nel.org>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	linux-usb@...r.kernel.org, Jim Paris <jim@...n.com>,
	Oliver Neukum <oneukum@...e.de>,
	Peter Hurley <peter@...leysoftware.com>,
	linux-kernel@...r.kernel.org, Johan Hovold <johan@...nel.org>,
	stable <stable@...r.kernel.org>
Subject: [PATCH Resend] USB: cdc-acm: only raise DTR on transitions from B0

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.

Cc: stable <stable@...r.kernel.org>
Signed-off-by: Johan Hovold <johan@...nel.org>
---

Greg,

I just noticed that this one did not make into usb-linus yet, although
24cb4502c97b ("cdc-acm: ensure that termios get set when the port is
activated"), which depend on this patch did.

Johan


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

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 6771f884cb82..9d6495424b06 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -985,11 +985,12 @@ 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);
-- 
2.0.4

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