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WdfDeviceSetAlignmentRequirement 方法

The WdfDeviceSetAlignmentRequirement method sets a device's address alignment requirement for the data buffers that the device uses during memory transfer operations.

语法

VOID WdfDeviceSetAlignmentRequirement(
  [in]  WDFDEVICE Device,
  [in]  ULONG AlignmentRequirement
);

参数

Device [in]

A handle to a framework device object.

AlignmentRequirement [in]

The alignment requirement for a data buffer. This value must be one less than the alignment boundary. For example, you can specify 15 for a 16-byte alignment boundary and 31 for a 32-byte alignment boundary. You can also use one of the FILE_Xxxx_ALIGNMENT constants that are defined in Wdm.h.

返回值

None.

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

评论

The driver can call WdfDeviceGetAlignmentRequirement to obtain the current value for the device's alignment requirement.

The I/O manager sets an alignment requirement value for the device when the driver calls WdfDeviceCreate. For more information about a device's alignment requirement value and when a driver must change the value, see Initializing a Device Object in the WDM documentation.

If your driver specifies an alignment requirement that is greater that the computer's page size (PAGE_SIZE), the logical addresses that the WdfCommonBufferGetAlignedLogicalAddress method returns are always aligned to the specified alignment requirement, but the virtual addresses that the WdfCommonBufferGetAlignedVirtualAddress method returns might not be aligned to the alignment requirement.

If your driver specifies an alignment requirement that is less than the computer's page size, all logical and virtual addresses are aligned to the specified alignment requirement.

For more information about calling WdfDeviceSetAlignmentRequirement, see Enabling DMA Transactions and Using Common Buffers.

示例

The following code example is from the AMCC5933 sample driver. This example checks a device's current alignment requirement and sets the alignment requirement to a new value, if necessary.

ULONG alignReq;

alignReq = WdfDeviceGetAlignmentRequirement(device);
if (alignReq < AMCC5933_ALIGNMENT__32BITS) {
//
// Set the S5933 alignment requirement to a new value.
//
WdfDeviceSetAlignmentRequirement(
                                 device,
                                 AMCC5933_ALIGNMENT__32BITS
                                 );
}

要求

版本

Available in version 1.0 and later versions of KMDF.

标头

Wdfdevice.h (包括Wdf.h)

Wdf<MajorVersionNumber>000.sys (see Framework Library Versions.)

IRQL

<= DISPATCH_LEVEL

另请参见

WdfCommonBufferGetAlignedLogicalAddress
WdfCommonBufferGetAlignedVirtualAddress
WdfDeviceGetAlignmentRequirement

 

 

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