Scatter-Gather

Some DMA engines can accept more than one cookie. Such engines perform scatter-gather I/O without the help of the system. In this case, it is most efficient if the driver uses ddi_dma_nextcookie(9F) to get as many cookies as the DMA engine can handle and program them all into the engine. The device can then be programmed to transfer the total number of bytes covered by all these DMA cookies combined.