TTY: add tty_port_tty_hangup helper

It allows for cleaning up on a considerable amount of places. They did
port_get, hangup, kref_put. Now the only thing needed is to call
tty_port_tty_hangup which does exactly that. And they can also decide
whether to consider CLOCAL or completely ignore that.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
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 755766e..27a1874 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -292,7 +292,6 @@
 {
 	struct acm *acm = urb->context;
 	struct usb_cdc_notification *dr = urb->transfer_buffer;
-	struct tty_struct *tty;
 	unsigned char *data;
 	int newctrl;
 	int retval;
@@ -327,17 +326,12 @@
 		break;
 
 	case USB_CDC_NOTIFY_SERIAL_STATE:
-		tty = tty_port_tty_get(&acm->port);
 		newctrl = get_unaligned_le16(data);
 
-		if (tty) {
-			if (!acm->clocal &&
-				(acm->ctrlin & ~newctrl & ACM_CTRL_DCD)) {
-				dev_dbg(&acm->control->dev,
-					"%s - calling hangup\n", __func__);
-				tty_hangup(tty);
-			}
-			tty_kref_put(tty);
+		if (!acm->clocal && (acm->ctrlin & ~newctrl & ACM_CTRL_DCD)) {
+			dev_dbg(&acm->control->dev, "%s - calling hangup\n",
+					__func__);
+			tty_port_tty_hangup(&acm->port, false);
 		}
 
 		acm->ctrlin = newctrl;
@@ -1498,15 +1492,9 @@
 static int acm_reset_resume(struct usb_interface *intf)
 {
 	struct acm *acm = usb_get_intfdata(intf);
-	struct tty_struct *tty;
 
-	if (test_bit(ASYNCB_INITIALIZED, &acm->port.flags)) {
-		tty = tty_port_tty_get(&acm->port);
-		if (tty) {
-			tty_hangup(tty);
-			tty_kref_put(tty);
-		}
-	}
+	if (test_bit(ASYNCB_INITIALIZED, &acm->port.flags))
+		tty_port_tty_hangup(&acm->port, false);
 
 	return acm_resume(intf);
 }