zyd_tx_desc
struct zyd_tx_desc *desc;
desc = (struct zyd_tx_desc *)data->buf;
xferlen = sizeof (struct zyd_tx_desc) + m->m_pkthdr.len;
pktlen = sizeof (struct zyd_tx_desc) + 10;
data->buf + sizeof (struct zyd_tx_desc));
bzero(data->buf, sizeof (struct zyd_tx_desc));
(sizeof (struct zyd_tx_desc) + IEEE80211_MAX_LEN)