cdc-acm: add TIOCMIWAIT

This implements TIOCMIWAIT for TIOCM_DSR, TIOCM_RI and TIOCM_CD
Disconnect is handled as TIOCM_CD or an error.
Signed-off-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/class/cdc-acm.c

@@ -262,6 +262,7 @@ static void acm_ctrl_irq(struct urb *urb)
 	struct usb_cdc_notification *dr = urb->transfer_buffer;
 	unsigned char *data;
 	int newctrl;
+	int difference;
 	int retval;
 	int status = urb->status;
 
@@ -302,20 +303,31 @@ static void acm_ctrl_irq(struct urb *urb)
 			tty_port_tty_hangup(&acm->port, false);
 		}
 
+		difference = acm->ctrlin ^ newctrl;
+		spin_lock(&acm->read_lock);
 		acm->ctrlin = newctrl;
+		acm->oldcount = acm->iocount;
+
+		if (difference & ACM_CTRL_DSR)
+			acm->iocount.dsr++;
+		if (difference & ACM_CTRL_BRK)
+			acm->iocount.brk++;
+		if (difference & ACM_CTRL_RI)
+			acm->iocount.rng++;
+		if (difference & ACM_CTRL_DCD)
+			acm->iocount.dcd++;
+		if (difference & ACM_CTRL_FRAMING)
+			acm->iocount.frame++;
+		if (difference & ACM_CTRL_PARITY)
+			acm->iocount.parity++;
+		if (difference & ACM_CTRL_OVERRUN)
+			acm->iocount.overrun++;
+		spin_unlock(&acm->read_lock);
+
+		if (difference)
+			wake_up_all(&acm->wioctl);
 
-		dev_dbg(&acm->control->dev,
-			"%s - input control lines: dcd%c dsr%c break%c "
-			"ring%c framing%c parity%c overrun%c\n",
-			__func__,
-			acm->ctrlin & ACM_CTRL_DCD ? '+' : '-',
-			acm->ctrlin & ACM_CTRL_DSR ? '+' : '-',
-			acm->ctrlin & ACM_CTRL_BRK ? '+' : '-',
-			acm->ctrlin & ACM_CTRL_RI  ? '+' : '-',
-			acm->ctrlin & ACM_CTRL_FRAMING ? '+' : '-',
-			acm->ctrlin & ACM_CTRL_PARITY ? '+' : '-',
-			acm->ctrlin & ACM_CTRL_OVERRUN ? '+' : '-');
-			break;
+		break;
 
 	default:
 		dev_dbg(&acm->control->dev,
@@ -796,6 +808,51 @@ static int set_serial_info(struct acm *acm,
 	return retval;
 }
 
+static int wait_serial_change(struct acm *acm, unsigned long arg)
+{
+	int rv = 0;
+	DECLARE_WAITQUEUE(wait, current);
+	struct async_icount old, new;
+
+	if (arg & (TIOCM_DSR | TIOCM_RI | TIOCM_CD ))
+		return -EINVAL;
+	do {
+		spin_lock_irq(&acm->read_lock);
+		old = acm->oldcount;
+		new = acm->iocount;
+		acm->oldcount = new;
+		spin_unlock_irq(&acm->read_lock);
+
+		if ((arg & TIOCM_DSR) &&
+			old.dsr != new.dsr)
+			break;
+		if ((arg & TIOCM_CD)  &&
+			old.dcd != new.dcd)
+			break;
+		if ((arg & TIOCM_RI) &&
+			old.rng != new.rng)
+			break;
+
+		add_wait_queue(&acm->wioctl, &wait);
+		set_current_state(TASK_INTERRUPTIBLE);
+		schedule();
+		remove_wait_queue(&acm->wioctl, &wait);
+		if (acm->disconnected) {
+			if (arg & TIOCM_CD)
+				break;
+			else
+				rv = -ENODEV;
+		} else {
+			if (signal_pending(current))
+				rv = -ERESTARTSYS;
+		}
+	} while (!rv);
+
+	
+
+	return rv;
+}
+
 static int acm_tty_ioctl(struct tty_struct *tty,
 					unsigned int cmd, unsigned long arg)
 {
@@ -809,6 +866,9 @@ static int acm_tty_ioctl(struct tty_struct *tty,
 	case TIOCSSERIAL:
 		rv = set_serial_info(acm, (struct serial_struct __user *) arg);
 		break;
+	case TIOCMIWAIT:
+		rv = wait_serial_change(acm, arg);
+		break;
 	}
 
 	return rv;
@@ -1167,6 +1227,7 @@ static int acm_probe(struct usb_interface *intf,
 	acm->readsize = readsize;
 	acm->rx_buflimit = num_rx_buf;
 	INIT_WORK(&acm->work, acm_softint);
+	init_waitqueue_head(&acm->wioctl);
 	spin_lock_init(&acm->write_lock);
 	spin_lock_init(&acm->read_lock);
 	mutex_init(&acm->mutex);
@@ -1383,6 +1444,7 @@ static void acm_disconnect(struct usb_interface *intf)
 		device_remove_file(&acm->control->dev,
 				&dev_attr_iCountryCodeRelDate);
 	}
+	wake_up_all(&acm->wioctl);
 	device_remove_file(&acm->control->dev, &dev_attr_bmCapabilities);
 	usb_set_intfdata(acm->control, NULL);
 	usb_set_intfdata(acm->data, NULL);

drivers/usb/class/cdc-acm.h

@@ -106,6 +106,9 @@ struct acm {
 	struct work_struct work;			/* work queue entry for line discipline waking up */
 	unsigned int ctrlin;				/* input control lines (DCD, DSR, RI, break, overruns) */
 	unsigned int ctrlout;				/* output control lines (DTR, RTS) */
+	struct async_icount iocount;			/* counters for control line changes */
+	struct async_icount oldcount;			/* for comparison of counter */
+	wait_queue_head_t wioctl;			/* for ioctl */
 	unsigned int writesize;				/* max packet size for the output bulk endpoint */
 	unsigned int readsize,ctrlsize;			/* buffer sizes for freeing */
 	unsigned int minor;				/* acm minor number */