MTW_TX_RING_COUNT
ring->cur = (ring->cur + 1) % MTW_TX_RING_COUNT;
if (++ring->queued >= MTW_TX_RING_COUNT)
for (i = 0; i < MTW_TX_RING_COUNT; i++) {
for (i = 0; i < MTW_TX_RING_COUNT; i++) {
struct mtw_tx_data data[MTW_TX_RING_COUNT];