WdfIoTargetPurge function

[Applies to KMDF and UMDF]

The WdfIoTargetPurge method cancels all I/O requests queued to a local, remote, or specialized I/O target and prevents any new I/O requests from being queued. The method also attempts to cancel I/O requests that have left the I/O target's queue and entered lower drivers.


void WdfIoTargetPurge(
  WDFIOTARGET                                       IoTarget,
  _Strict_type_match_ WDF_IO_TARGET_PURGE_IO_ACTION Action



A handle to a local or remote I/O target object that was obtained from a previous call to WdfDeviceGetIoTarget or WdfIoTargetCreate, or from a method supplied by a specialized I/O target, such as WdfUsbTargetPipeGetIoTarget.


A WDF_IO_TARGET_PURGE_IO_ACTION-typed value that indicates whether the framework should wait to return from WdfIoTargetPurge until all delivered requests are completed or canceled.

Return Value


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


If the driver has previously called WdfUsbTargetPipeConfigContinuousReader, WdfIoTargetPurge must be called at IRQL = PASSIVE_LEVEL. If the driver has not called WdfUsbTargetPipeConfigContinuousReader and if the Action parameter of WdfIoTargetPurge is WdfIoTargetPurgeIo, WdfIoTargetPurge can be called at IRQL <= DISPATCH_LEVEL. Otherwise, WdfIoTargetPurge must be called at IRQL = PASSIVE_LEVEL.

To make WdfIoTargetPurge a synchronous call, the driver can set the WdfIoTargetPurgeIoAndWait value of the Action parameter. In this case, WdfIoTargetPurge waits to return until all delivered requests are completed or canceled.

After a driver has called WdfIoTargetPurge, it can still send a request to the target by setting the WDF_REQUEST_SEND_OPTION_IGNORE_TARGET_STATE flag in the request's WDF_REQUEST_SEND_OPTIONS structure. For example, a driver might send a request, such as a request to reset a USB pipe (see WdfUsbTargetPipeResetSynchronously), to a device after the driver has called WdfIoTargetPurge.

When a driver calls WdfIoTargetPurge, the framework does not attempt to cancel or wait for I/O requests that were previously sent to the target using either the WDF_REQUEST_SEND_OPTION_IGNORE_TARGET_STATE flag or the WDF_REQUEST_SEND_OPTION_SEND_AND_FORGET flag in the request's WDF_REQUEST_SEND_OPTIONS structure.

After a driver has purged an I/O queue, it can restart the queue by calling WdfIoTargetStart.

Your driver must call WdfIoTargetStart, WdfIoTargetStop and WdfIoTargetPurge synchronously. After the driver calls one of these functions, it must not call any of the others until the previous call returns.

Your driver can call WdfIoTargetPurge multiple times without calling WdfIoTargetStart. For example, your driver might do the following:

  1. Call WdfIoTargetPurge and specify an Action value of WdfIoTargetPurgeIo.
  2. Determine whether the target should resume processing I/O requests.
  3. If the target should resume, call WdfIoTargetStart. Otherwise, call WdfIoTargetPurge again with an Action value of WdfIoTargetPurgeIoAndWait.

For more information about I/O target states, see Controlling a General I/O Target's State.

For more information about I/O targets, see Using I/O Targets.


The following code example shows how an EvtDeviceD0Exit callback function can call WdfIoTargetPurge, if the driver uses a continuous reader for a USB pipe.

    IN  WDFDEVICE Device,
    PDEVICE_CONTEXT  pDeviceContext;
    pDeviceContext = GetMyDeviceContext(Device);


    return STATUS_SUCCESS;


Target Platform Universal
Minimum KMDF version 1.11
Minimum UMDF version 2.0
Header wdfiotarget.h (include Wdf.h)
Library Wdf01000.sys (KMDF); WUDFx02000.dll (UMDF)
IRQL See Remarks section.
DDI compliance rules DriverCreate

See Also