ATH_TXDESC
"tx", ath_txbuf, ATH_TXDESC);
bf->bf_nseg = ATH_TXDESC+1;
m = ath_defrag(m0, M_DONTWAIT, ATH_TXDESC);
KASSERTMSG(bf->bf_nseg <= ATH_TXDESC,
#define ATH_MAX_SCATTER ATH_TXDESC /* max(tx,rx,beacon) desc's */