DMA_C_INDEX_MASK
& DMA_C_INDEX_MASK;
txbds_ready = (c_index - ring->c_index) & DMA_C_INDEX_MASK;
drop = (ring->prod_index - ring->c_index) & DMA_C_INDEX_MASK;
ring->prod_index = ring->c_index & DMA_C_INDEX_MASK;
rxpkttoprocess = (p_index - ring->c_index) & DMA_C_INDEX_MASK;
ring->c_index = (ring->c_index + 1) & DMA_C_INDEX_MASK;
ring->c_index, c_index & DMA_C_INDEX_MASK,