kfifo_dma_out_prepare — setup a scatterlist for DMA output
address of the fifo to be used
pointer to the scatterlist array
number of entries in the scatterlist array
number of elements to transfer
This macro fills a scatterlist for DMA output which at most
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.