igc_adv_tx_desc
union igc_adv_tx_desc *txdesc;
(sizeof(union igc_adv_tx_desc)) * sc->num_tx_desc);
sc->num_tx_desc * sizeof(union igc_adv_tx_desc));
tsize = roundup2(sc->num_tx_desc * sizeof(union igc_adv_tx_desc),
txr->tx_base = (union igc_adv_tx_desc *)txr->txdma.dma_vaddr;
union igc_adv_tx_desc *txdesc;
union igc_adv_tx_desc *tx_base;