wsevent_read
error = wsevent_read(&sc->evar, uio, flag);
int wsevent_read(struct wseventvar *, struct uio *, int);
error = wsevent_read(sc->sc_base.me_evp, uio, flags);
error = wsevent_read(sc->sc_base.me_evp, uio, flags);
error = wsevent_read(evar, uio, flags);