WDF DMA 三要素

1 enable object

WDF_DMA_ENABLER_CONFIG   dmaConfig;

 

WdfDeviceSetAlignmentRequirement(DevExt->Device, PCI9656_DTE_ALIGNMENT_16 );

WDF_DMA_ENABLER_CONFIG_INIT(&dmaConfig,

                             WdfDmaProfileScatterGather64Duplex,

                             DevExt->MaximumTransferLength);

status = WdfDmaEnablerCreate(DevExt->Device,

                              &dmaConfig,

                             WDF_NO_OBJECT_ATTRIBUTES,

                             &DevExt->DmaEnabler );

if (!NT_SUCCESS (status)) {

   . . . //Error-handling code omitted

   }

 

2 common buffer

·        WdfCommonBufferGetAlignedVirtualAddress,which returns the system virtual address of the common buffer.内核地址；

·        WdfCommonBufferGetAlignedLogicalAddress,which returns the device-bus logical address of the common buffer.

设备总线空间物理地址；

// Allocate common buffer forbuilding writes

DevExt->WriteCommonBufferSize =

         sizeof( DMA_TRANSFER_ELEMENT) *DevExt->WriteTransferElements;

status = WdfCommonBufferCreate(DevExt->DmaEnabler,

                               DevExt->WriteCommonBufferSize,

                                WDF_NO_OBJECT_ATTRIBUTES,

                               &DevExt->WriteCommonBuffer );

if (!NT_SUCCESS(status)) {

   . . . //Error-handling code omitted

   }

DevExt->WriteCommonBufferBase =

            WdfCommonBufferGetAlignedVirtualAddress(

                     DevExt->WriteCommonBuffer);

DevExt->WriteCommonBufferBaseLA=

            WdfCommonBufferGetAlignedLogicalAddress(

                     DevExt->WriteCommonBuffer);

RtlZeroMemory(DevExt->WriteCommonBufferBase, DevExt->WriteCommonBufferSize);

WDF_OBJECT_ATTRIBUTES_INIT_CONTEXT_TYPE(&attributes,TRANSACTION_CONTEXT);

status = WdfDmaTransactionCreate(DevExt->DmaEnabler,

                                  &attributes,

                                 &DevExt->WriteDmaTransaction);

if(!NT_SUCCESS(status)) {

   . . . //Error-handling code omitted

   }

 

These addresses are required to programthe device in theEvtProgramDmacallback function.

3 transaction object

WdfDmaTransactionCreate,