xenbus_read_driver_state
prev_state = xenbus_read_driver_state(pdev->xdev->nodename);
ivars->xd_state = xenbus_read_driver_state(ivars->xd_node);
newstate = xenbus_read_driver_state(ivars->xd_otherend_path);
state = xenbus_read_driver_state(devpath);
XenbusState xenbus_read_driver_state(const char *path);
return (xenbus_read_driver_state(xenbus_get_otherend_path(dev)));