WdfDmaEnablerCreate function (wdfdmaenabler.h)

[Applies to KMDF only]

The WdfDmaEnablerCreate method creates a DMA enabler object.

Syntax

NTSTATUS WdfDmaEnablerCreate(
  [in]           WDFDEVICE               Device,
  [in]           PWDF_DMA_ENABLER_CONFIG Config,
  [in, optional] PWDF_OBJECT_ATTRIBUTES  Attributes,
  [out]          WDFDMAENABLER           *DmaEnablerHandle
);

Parameters

[in] Device

A handle to a framework device object.

[in] Config

A pointer to a WDF_DMA_ENABLER_CONFIG structure. Drivers must initialize this structure by calling WDF_DMA_ENABLER_CONFIG_INIT.

[in, optional] Attributes

A pointer to a WDF_OBJECT_ATTRIBUTES structure that specifies object attributes for the new DMA enabler object. This parameter is optional and can be WDF_NO_OBJECT_ATTRIBUTES.

[out] DmaEnablerHandle

A handle to a new DMA enabler object.

Return value

WdfDmaEnablerCreate returns STATUS_SUCCESS if the operation succeeds. Otherwise, the method might return one of the following values.

For a list of other return values that the WdfDmaEnablerCreate method might return, see Framework Object Creation Errors.

This method also might return other NTSTATUS values.

A bug check occurs if the driver supplies an invalid object handle.

Remarks

Framework-based drivers must call WdfDmaEnablerCreate before creating DMA transactions for a device.

Before a driver calls WdfDmaEnablerCreate, it must call WdfDeviceSetAlignmentRequirement.

The framework device object that the Device parameter of WdfDmaEnablerCreate specifies always becomes the parent object for the new DMA enabler object. If the driver specifies a different parent in the ParentObject member of the WDF_OBJECT_ATTRIBUTES structure, the framework ignores this value. The framework deletes the DMA enabler object when it deletes the parent object.

When called with a Config parameter that requests a system-mode DMA profile, WdfDmaEnablerCreate creates a partially initialized DMA enabler. The driver must subsequently call WdfDmaEnablerConfigureSystemProfile to set up the DMA settings for the underlying channels.

For more information about DMA enabler objects and WdfDmaEnablerCreate, see Enabling DMA Transactions.

Examples

The following code example is from the PLX9x5x sample driver. This example sets a device's requirement for buffer alignment, initializes a WDF_DMA_ENABLER_CONFIG structure, and calls WdfDmaEnablerCreate.

//
// PLx PCI9656 DMA_TRANSFER_ELEMENTS must be 16-byte aligned.
//
WdfDeviceSetAlignmentRequirement(
                                 DevExt->WdfDevice,
                                 PCI9656_DTE_ALIGNMENT_16
                                 );

//
// Create a new DMA enabler object instance. 
// Use scatter/gather, 64-bit addresses, and duplex-type profile.
//
{
    WDF_DMA_ENABLER_CONFIG   dmaConfig;
    WDF_DMA_ENABLER_CONFIG_INIT(
                                &dmaConfig,
                                WdfDmaProfileScatterGather64Duplex,
                                DevExt->MaximumTransferLength
                                );
    status = WdfDmaEnablerCreate(
                                 DevExt->WdfDevice,
                                 &dmaConfig,
                                 WDF_NO_OBJECT_ATTRIBUTES,
                                 &DevExt->DmaEnabler
                                 );
    if (!NT_SUCCESS (status)) {
        // Cannot continue, so release device resources.
        return status;
    }
}

Requirements

See also

WDF_DMA_ENABLER_CONFIG

WDF_DMA_ENABLER_CONFIG_INIT

WDF_OBJECT_ATTRIBUTES

WdfDeviceSetAlignmentRequirement