bwi_txbuf_hdr
struct bwi_txbuf_hdr *hdr;
hdr = mtod(m, struct bwi_txbuf_hdr *);
struct bwi_txbuf_hdr *hdr;
hdr = mtod(m, struct bwi_txbuf_hdr *);
const struct bwi_txbuf_hdr *hdr =
mtod(tb->tb_mbuf, const struct bwi_txbuf_hdr *);
ic->ic_headroom = sizeof(struct bwi_txbuf_hdr);