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For subordinate DMA transfers, a Windows NT miniport calls a set of functions that consist of NdisMRegisterDmaChannel, NdisMDeregisterDmaChannel, NdisMSetupDmaTransfer, NdisMCompleteDmaTransfer, and NdisMReadDmaCounter. The Windows CE implementation of NDIS does not support these functions. Instead, the required functionality can be implemented directly in the miniport driver code.
To implement DMA transfers in a miniport, you must reserve a physical memory block from the memory map of a Windows CE-based device. Then, you must map the device's memory block to virtual address pointers by using the VirtualAllocand VirtualCopyfunctions. Mapping the device's memory block to virtual address pointers provides the miniport with a shared memory block to send and receive packet buffers.
To see an example of how to implement DMA operations in a miniport for Windows CE, consult the sample code for the National Semiconductor Fast IR Miniport Driver that is shipped with Windows CE 3.0.
Last updated on Tuesday, July 13, 2004