NVL_PHYSPATH
rv = nvlist_add_string(devnvl, NVL_PHYSPATH, devfspath);
(void) nvlist_lookup_string(thisdev, NVL_PHYSPATH, &mpxpath);
(void) nvlist_lookup_string(thisdev, NVL_PHYSPATH, &mpxpath);
((readonlyroot) ? NVL_PHYSPATH :