TX_DESC_RINGN_SIZE
if (!(entry & ((TX_DESC_RINGN_SIZE(ring) >> 1) - 1)))
size = TX_DESC_RINGN_SIZE(ring);
#define TX_DESC_NEXT(r, x) (((x) + 1) & (TX_DESC_RINGN_SIZE(r) - 1))
(TX_DESC_RINGN_SIZE(r) - (x) + (y)))
(cp)->tx_old[(i)] + (TX_DESC_RINGN_SIZE(i) - 1) - (cp)->tx_new[(i)] : \