ipw_hdr
sizeof (struct ipw_hdr), ipw_dma_map_addr, &physaddr, 0);
sbd->bd->len = htole32(sizeof (struct ipw_hdr));
BUS_SPACE_MAXADDR, NULL, NULL, sizeof (struct ipw_hdr), 1,
sizeof (struct ipw_hdr), 0, NULL, NULL, &sc->hdr_dmat);
struct ipw_hdr hdr;