NM_BUFFSIZE
sndbuf_setup(ch->buffer, (u_int8_t *)rman_get_virtual(sc->buf) + chnbuf, NM_BUFFSIZE);
nm_wr(sc, NM_PBUFFER_END, sc->pbuf + NM_BUFFSIZE - ssz, 4);
nm_wr(sc, NM_RBUFFER_END, sc->rbuf + NM_BUFFSIZE, 4);
sc->pch.wmark %= NM_BUFFSIZE;
sc->rch.wmark %= NM_BUFFSIZE;
sc->rbuf = sc->cbuf - NM_BUFFSIZE;
sc->pbuf = sc->rbuf - NM_BUFFSIZE;