This section is specific to ISA devices utilizing the Direct Memory Access controller.
If the OS wishes to support devices that utilize DMA, then basic routines must be provided to allow access to the DMA controller.
The Linux drivers directly access the DMA controller themselves, with macros and with embedded assembly. All devices that utilize the DMA controller must be in the same driver set, as there is not way to arbitrate between different driver sets. Because this shortcoming is in the encapsulated drivers, and would take significant effort to correct, we have not provided an interface to access the DMA controller, although we may in the future.