ngbe_tx_desc
tsize = roundup2(sc->num_tx_desc * sizeof(union ngbe_tx_desc),
txr->tx_base = (union ngbe_tx_desc *)txr->txdma.dma_vaddr;
(sizeof(union ngbe_tx_desc)) * sc->num_tx_desc);
union ngbe_tx_desc *txd = NULL;
union ngbe_tx_desc *tx_desc;
tx_desc = (union ngbe_tx_desc *)&txr->tx_base[last];
union ngbe_tx_desc *tx_base;