DMA_CTL_LEN_DESC_BUFLENGTH_SHIFT
tmp = ENET_RX_BUF_DMA_SIZE << DMA_CTL_LEN_DESC_BUFLENGTH_SHIFT;
tmp = skb->len << DMA_CTL_LEN_DESC_BUFLENGTH_SHIFT;
len = (ctl & DMA_CTL_LEN_DESC_BUFLENGTH) >> DMA_CTL_LEN_DESC_BUFLENGTH_SHIFT;