EvtWorkItem function

[Applies to KMDF and UMDF]

A driver's EvtWorkItem event callback function performs the work that is associated with a specified work item.

Syntax


EVT_WDF_WORKITEM EvtWorkItem;

VOID EvtWorkItem(
  _In_  WDFWORKITEM WorkItem
)
{ ... }

Parameters

WorkItem [in]

A handle to a framework work-item object.

Return value

None

Remarks

Typically, a driver's EvtWorkItem callback function performs tasks that are specified by information that the driver stored in the context memory of a work-item object.

To register an EvtWorkItem callback function, the driver calls WdfWorkItemCreate.

After the EvtWorkItem callback function has performed the specified tasks, it must call WdfObjectDelete, unless the driver reuses work items.

For more information about work items, see Using Framework Work Items.

The EvtWorkItem callback function runs at IRQL = PASSIVE_LEVEL in the context of a system worker thread.

Examples

To define an EvtWorkItem 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 EvtWorkItem callback function that is named MyWorkItem, use the EVT_WDF_WORKITEM type as shown in this code example:

To define an EvtWorkItem callback function that is named MyWorkItem, you must first provide a function declaration that SDV and other verification tools require, as follows:


EVT_WDF_WORKITEM  MyWorkItem;

Then, implement your callback function as follows:


_Use_decl_annotations_
VOID
 MyWorkItem (
    WDFWORKITEM  WorkItem
    )
  {...}

The EVT_WDF_WORKITEM function type is defined in the Wdfworkitem.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_WORKITEM 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

Wdfworkitem.h (include Wdf.h)

IRQL

PASSIVE_LEVEL (see Remarks section)

See also

WdfWorkItemCreate
WdfWorkItemEnqueue
WdfObjectDelete

 

 

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