buf_pos_n
current_byte = runtime->dma_area[buf_pos_n(v_iter, channels, ch_num)];
runtime->dma_area[buf_pos_n(v_iter, channels, ch_num)] =
get_random_bytes(runtime->dma_area + buf_pos_n(v_iter, channels, i),
get_random_bytes(runtime->dma_area + buf_pos_n(v_iter, channels, i),