PRESTERA_SDMA_TX_DESC_PER_Q
int bnum = PRESTERA_SDMA_TX_DESC_PER_Q;
int bnum = PRESTERA_SDMA_TX_DESC_PER_Q;
int bnum = PRESTERA_SDMA_TX_DESC_PER_Q;
tx_ring->next_tx = (tx_ring->next_tx + 1) % PRESTERA_SDMA_TX_DESC_PER_Q;