sio_nfds
int sio_nfds(struct sio_hdl *);
nfds = sio_nfds(hdl);
if (sio_nfds(hdl) > NFDS) {
n = sio_nfds(dev_sh);
d->sio.file = file_new(&dev_sio_ops, d, "dev", sio_nfds(d->sio.hdl));