USB: serial: kobil_sct: fix TIOCMBIS and TIOCMBIC

Asserting or deasserting a modem control line using TIOCMBIS or TIOCMBIC
should not deassert any lines that are not in the mask.

Fix this long-standing issue dating back to 2003 when the support for
these ioctls was added with the introduction of the tiocmset() callback.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>

Author: jhovold

drivers/usb/serial/kobil_sct.c

@@ -418,7 +418,7 @@ static int kobil_tiocmset(struct tty_struct *tty,
 	struct usb_serial_port *port = tty->driver_data;
 	struct device *dev = &port->dev;
 	struct kobil_private *priv;
-	int result;
+	int result = 0;
 	int dtr = 0;
 	int rts = 0;
 
@@ -435,34 +435,34 @@ static int kobil_tiocmset(struct tty_struct *tty,
 	if (set & TIOCM_DTR)
 		dtr = 1;
 	if (clear & TIOCM_RTS)
-		rts = 0;
+		rts = 1;
 	if (clear & TIOCM_DTR)
-		dtr = 0;
+		dtr = 1;
 
-	if (priv->device_type == KOBIL_ADAPTER_B_PRODUCT_ID) {
-		if (dtr != 0)
+	if (dtr && priv->device_type == KOBIL_ADAPTER_B_PRODUCT_ID) {
+		if (set & TIOCM_DTR)
 			dev_dbg(dev, "%s - Setting DTR\n", __func__);
 		else
 			dev_dbg(dev, "%s - Clearing DTR\n", __func__);
 		result = usb_control_msg(port->serial->dev,
 			  usb_sndctrlpipe(port->serial->dev, 0),
 			  SUSBCRequest_SetStatusLinesOrQueues,
 			  USB_TYPE_VENDOR | USB_RECIP_ENDPOINT | USB_DIR_OUT,
-			  ((dtr != 0) ? SUSBCR_SSL_SETDTR : SUSBCR_SSL_CLRDTR),
+			  ((set & TIOCM_DTR) ? SUSBCR_SSL_SETDTR : SUSBCR_SSL_CLRDTR),
 			  0,
 			  NULL,
 			  0,
 			  KOBIL_TIMEOUT);
-	} else {
-		if (rts != 0)
+	} else if (rts) {
+		if (set & TIOCM_RTS)
 			dev_dbg(dev, "%s - Setting RTS\n", __func__);
 		else
 			dev_dbg(dev, "%s - Clearing RTS\n", __func__);
 		result = usb_control_msg(port->serial->dev,
 			usb_sndctrlpipe(port->serial->dev, 0),
 			SUSBCRequest_SetStatusLinesOrQueues,
 			USB_TYPE_VENDOR | USB_RECIP_ENDPOINT | USB_DIR_OUT,
-			((rts != 0) ? SUSBCR_SSL_SETRTS : SUSBCR_SSL_CLRRTS),
+			((set & TIOCM_RTS) ? SUSBCR_SSL_SETRTS : SUSBCR_SSL_CLRRTS),
 			0,
 			NULL,
 			0,