+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;
+}
+