TX39_SIBDMA_SIZE
ringbuf_allocate(&sc->sc_rb, TX39_SIBDMA_SIZE, UCBSND_BUFBLOCK);
n = (len + TX39_SIBDMA_SIZE - 1) / TX39_SIBDMA_SIZE;
rest = len % TX39_SIBDMA_SIZE;
error = ucbsndwrite_subr(sc, buf, TX39_SIBDMA_SIZE, uio);
static u_int8_t dmabuf_static[TX39_SIBDMA_SIZE * UCBSND_BUFBLOCK] __attribute__((__aligned__(16))); /* XXX */