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WdfRequestRetrieveUnsafeUserOutputBuffer method

[Applies to KMDF only]

The WdfRequestRetrieveUnsafeUserOutputBuffer method retrieves an I/O request's output buffer, if the request's technique for accessing data buffers is neither buffered nor direct I/O.

Syntax


NTSTATUS WdfRequestRetrieveUnsafeUserOutputBuffer(
  [in]             WDFREQUEST Request,
  [in]             size_t MinimumRequiredLength,
  [out]            PVOID *OutputBuffer,
  [out, optional]  size_t *Length
);

Parameters

Request [in]

A handle to a framework request object.

MinimumRequiredLength [in]

The minimum buffer size, in bytes, that the driver needs to process the I/O request.

OutputBuffer [out]

A pointer to a location that receives the buffer's address.

Length [out, optional]

A pointer to a location that receives the buffer's size, in bytes. This parameter is optional and can be NULL.

Return value

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

Return codeDescription
STATUS_INVALID_PARAMETER

An input parameter is invalid.

STATUS_INVALID_DEVICE_REQUEST

This value is returned if one of the following occurs:

STATUS_BUFFER_TOO_SMALL

The MinimumRequiredLength parameter specifies a buffer size that is larger than the buffer's actual size.

 

This method might also return other NTSTATUS values.

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

Remarks

The WdfRequestRetrieveUnsafeUserOutputBuffer method must be called from an EvtIoInCallerContext callback function. After calling WdfRequestRetrieveUnsafeUserOutputBuffer, the driver must call WdfRequestProbeAndLockUserBufferForWrite.

The driver can call WdfRequestRetrieveUnsafeUserOutputBuffer if a request's I/O control code is IRP_MJ_READ or IRP_MJ_DEVICE_CONTROL.

The driver can access the retrieved buffer until it completes the I/O request that the Request parameter represents.

For more information about WdfRequestRetrieveUnsafeUserOutputBuffer, see Accessing Data Buffers in Framework-Based Drivers.

Examples

For a code example that uses WdfRequestRetrieveUnsafeUserOutputBuffer, see WdfRequestProbeAndLockUserBufferForRead.

Requirements

Minimum KMDF version

1.0

Header

Wdfrequest.h (include Wdf.h)

Library

Wdf01000.sys (see Framework Library Versioning.)

IRQL

PASSIVE_LEVEL

DDI compliance rules

BufAfterReqCompletedIntIoctl, BufAfterReqCompletedIntIoctlA, BufAfterReqCompletedIoctl, BufAfterReqCompletedIoctlA, BufAfterReqCompletedRead, BufAfterReqCompletedReadA, BufAfterReqCompletedWrite, DriverCreate, InvalidReqAccess, InvalidReqAccessLocal, KmdfIrql, KmdfIrql2, OutputBufferAPI

See also

WdfRequestProbeAndLockUserBufferForWrite
WdfRequestRetrieveUnsafeUserInputBuffer
EvtIoInCallerContext

 

 

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