kfifo_dma_out_prepare (9)

kfifo_dma_out_prepare(fifo, sgl, nents, len);

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

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.