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EvtRequestCancel function

[Applies to KMDF and UMDF]

A driver's EvtRequestCancel event callback function handles operations that must be performed when an I/O request is canceled.

Syntax


EVT_WDF_REQUEST_CANCEL EvtRequestCancel;

VOID EvtRequestCancel(
  _In_  WDFREQUEST Request
)
{ ... }

Parameters

Request [in]

A handle to a framework request object that represents the I/O request that is being canceled.

Return value

None

Remarks

To register an EvtRequestCancel callback function, the driver must call WdfRequestMarkCancelable or WdfRequestMarkCancelableEx.

When the framework calls your driver's EvtRequestCancel callback function, if the driver can cancel the request, it must:

  1. Finish or stop processing the request, along with subrequests that it might have created.

  2. Call WdfRequestComplete, specifying a status value of STATUS_CANCELLED.

For more information about this callback function, see Canceling I/O Requests.

Examples

To define an EvtRequestCancel callback function, you must first provide a function declaration that identifies the type of callback function you’re defining. Windows provides a set of callback function types for drivers. Declaring a function using the callback function types helps Code Analysis for Drivers, Static Driver Verifier (SDV), and other verification tools find errors, and it’s a requirement for writing drivers for the Windows operating system.

For example, to define an EvtRequestCancel callback function that is named MyRequestCancel, use the EVT_WDF_REQUEST_CANCEL type as shown in this code example:


EVT_WDF_REQUEST_CANCEL  MyRequestCancel;

Then, implement your callback function as follows:


_Use_decl_annotations_
VOID
 MyRequestCancel (
    WDFREQUEST  Request
    )
  {...}

The EVT_WDF_REQUEST_CANCEL function type is defined in the Wdfrequest.h header file. To more accurately identify errors when you run the code analysis tools, be sure to add the _Use_decl_annotations_ annotation to your function definition. The _Use_decl_annotations_ annotation ensures that the annotations that are applied to the EVT_WDF_REQUEST_CANCEL function type in the header file are used. For more information about the requirements for function declarations, see Declaring Functions by Using Function Role Types for KMDF Drivers. For information about _Use_decl_annotations_, see Annotating Function Behavior.

Requirements

Minimum KMDF version

1.0

Minimum UMDF version

2.0

Header

Wdfrequest.h (include Wdf.h)

IRQL

<=DISPATCH_LEVEL

See also

WdfRequestComplete
WdfRequestMarkCancelable
WdfRequestMarkCancelableEx

 

 

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