kfifo_dma_out_prepare
sport->dma_tx_nents = kfifo_dma_out_prepare(&tport->xmit_fifo, sgl,
sport->dma_tx_nents = kfifo_dma_out_prepare(&tport->xmit_fifo, sgl,
kfifo_dma_out_prepare(&tport->xmit_fifo, &dma->tx_sg, 1, count);
nents = kfifo_dma_out_prepare(&fifo, sg, ARRAY_SIZE(sg), 8);