xenbus_read_driver_state
XenbusState xenbus_read_driver_state(const char *path);
if (xenbus_read_driver_state(xbusd->xbusd_path) !=
while (xenbus_read_driver_state(sc->sc_xbusd->xbusd_otherend)
state = xenbus_read_driver_state(xdev->xbusd_otherend);