aq_txc_desc
.isc_nrxd_default = {PAGE_SIZE / sizeof(volatile union aq_txc_desc) * 4},
.isc_ntxd_default = {PAGE_SIZE / sizeof(volatile union aq_txc_desc) * 4},
volatile union aq_txc_desc *txc)
volatile union aq_txc_desc *txc;
txc = (volatile union aq_txc_desc *)&ring->tx_descs[pidx];