cdev_poll
error = cdev_poll(dev, events, l);
return cdev_poll(vp->v_rdev, ap->a_events, curlwp);
revents = cdev_poll(devctty, ap->a_events, curlwp);
revents = cdev_poll(dev, ap->a_events, curlwp);
dev_type_poll(cdev_poll);