kfifo_dma_out_prepare(9) centos man page | unix.com

KFIFO_DMA_OUT_PREPAR(9) 					    FIFO Buffer 					   KFIFO_DMA_OUT_PREPAR(9)

NAME
       kfifo_dma_out_prepare - setup a scatterlist for DMA output

SYNOPSIS
       kfifo_dma_out_prepare(fifo, sgl, nents, len);

ARGUMENTS
       fifo
	   address of the fifo to be used

       sgl
	   pointer to the scatterlist array

       nents
	   number of entries in the scatterlist array

       len
	   number of elements to transfer

DESCRIPTION
       This macro fills a scatterlist for DMA output which at most len bytes to transfer. It returns the number entries in the scatterlist array.
       A zero means there is no space available and the scatterlist is not filled.

       Note that with only one concurrent reader and one concurrent writer, you don't need extra locking to use these macros.

COPYRIGHT
Kernel Hackers Manual 3.10					     June 2014						   KFIFO_DMA_OUT_PREPAR(9)