When the mouse is being disconnected, do the followings:

- Call ums_disable() to abort the pipe.
- Do not wake up processes which has been waiting or polling for mouse
  data.  It won't be available anymore.

Submitted by: Kazutaka YOKOTA <yokota@zodiac.mech.utsunomiya-u.ac.jp>

sys/dev/usb/ums.c

@@ -368,10 +368,8 @@ ums_detach(device_t self)
 {
 	struct ums_softc *sc = device_get_softc(self);
 
-	if (sc->sc_enabled) {
-		usbd_abort_pipe(sc->sc_intrpipe);
-		usbd_close_pipe(sc->sc_intrpipe);
-	}
+	if (sc->sc_enabled)
+		ums_disable(sc);
 	sc->sc_disconnected = 1;
 
 	DPRINTF(("%s: disconnected\n", USBDEVNAME(self)));
@@ -379,6 +377,14 @@ ums_detach(device_t self)
 	free(sc->sc_loc_btn, M_USB);
 	free(sc->sc_ibuf, M_USB);
 
+	/*
+	 * XXX If we wakeup the process here, the device will be gone by
+	 * the time the process gets a chance to notice. *_close and friends
+	 * should be fixed to handle this case.
+	 * Or we should do a delayed detach for this.
+	 */
+
+#if 0
 	/* someone waiting for data */
 	if (sc->state & UMS_ASLEEP) {
 		sc->state &= ~UMS_ASLEEP;
@@ -388,6 +394,7 @@ ums_detach(device_t self)
 		sc->state &= ~UMS_SELECT;
 		selwakeup(&sc->rsel);
 	}
+#endif
 
 	return 0;
 }
@@ -605,6 +612,9 @@ ums_close(dev_t dev, int flag, int fmt, struct proc *p)
 {
 	USB_GET_SC(ums, UMSUNIT(dev), sc);
 
+	if (sc == NULL)
+		return 0;
+
 	if (sc->sc_enabled)
 		ums_disable(sc);