WdfDmaTransactionFreeResources function (wdfdmatransaction.h)

[Applies to KMDF only]

The WdfDmaTransactionFreeResources method releases DMA resources that the driver previously allocated by calling WdfDmaTransactionAllocateResources.

Syntax

void WdfDmaTransactionFreeResources(
  [in] WDFDMATRANSACTION DmaTransaction
);

Parameters

[in] DmaTransaction

A handle to the DMA transaction object that the driver provided in a previous call to WdfDmaTransactionAllocateResources.

Return value

None

Remarks

WdfDmaTransactionFreeResources must be used with a DMA enabler that specifies a packet or system profile.

On operating systems earlier than Windows 8, WdfDmaTransactionFreeResources must be used with an enabler that specifies a single-packet DMA enabler. Starting with Windows 8, WdfDmaTransactionFreeResources can also be used with an enabler that specifies a system-mode DMA enabler.

When called with a scatter/gather DMA enabler, WdfDmaTransactionFreeResources causes a verifier bug check.

The driver's call to WdfDmaTransactionFreeResources may cause the framework to call EvtProgramDma or EvtReserveDma immediately.

For more information about system-mode DMA, see Supporting System-Mode DMA.

Requirements

See also

WdfDmaTransactionAllocateResources