TxDesc
static u8 tx_ring[NUM_TX_DESC * sizeof(struct TxDesc) + 256];
static u8 rx_ring[NUM_RX_DESC * sizeof(struct TxDesc) + 256];
struct TxDesc *TxDescArray; /* Index of 256-alignment Tx Descriptor buffer */
memset(tpc->TxDescArray, 0x0, NUM_TX_DESC * sizeof(struct TxDesc));
tpc->TxDescArray = (struct TxDesc *) (tpc->TxDescArrays + diff);