RE_DESC_ALIGN
i = roundup2(sizeof(union RxDesc)*RE_RX_BUF_NUM, RE_DESC_ALIGN);
RE_DESC_ALIGN, 0, /* alignment, boundary */
i = roundup2(sizeof(union TxDesc)*RE_TX_BUF_NUM, RE_DESC_ALIGN);
RE_DESC_ALIGN, 0, /* alignment, boundary */