[Applies to KMDF and UMDF]

A driver's EvtDeviceUsageNotificationEx event callback function determines whether a device can support a special file type.



NTSTATUS EvtDeviceUsageNotificationEx(
  _In_ WDFDEVICE             Device,
  _In_ WDF_SPECIAL_FILE_TYPE NotificationType,
  _In_ BOOLEAN               IsInNotificationPath
{ ... }


Device [in]

A handle to a framework device object.

NotificationType [in]

A WDF_SPECIAL_FILE_TYPE-typed value that identifies the type of special file that the system is storing on the specified device.

IsInNotificationPath [in]

A Boolean value which, if TRUE, indicates that the system has starting using the special file and, if FALSE, indicates that the system has finished using the special file.

Return value

If the driver determines that the device can support the special file, the EvtDeviceUsageNotificationEx callback function must return STATUS_SUCCESS or another status value for which NT_SUCCESS(status) equals TRUE. Otherwise it must return a status value for which NT_SUCCESS(status) equals FALSE.


If your driver must provide driver-specific handling of special files, you must provide either an EvtDeviceUsageNotificationEx or an EvtDeviceUsageNotification event callback function. Do not provide both callback functions.

To register an EvtDeviceUsageNotificationEx callback function, a driver must call WdfDeviceInitSetPnpPowerEventCallbacks.

If the driver's EvtDeviceUsageNotificationEx callback function returns a failure status, the framework propagates failure to other stacks that it may have notified earlier.

For more information about special files, see Supporting Special Files.


To define an EvtDeviceUsageNotificationEx 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 EvtDeviceUsageNotificationEx callback function that is named MyDeviceUsageNotificationEx, use the EVT_WDF_DEVICE_USAGE_NOTIFICATION_EX type as shown in this code example:


Then, implement your callback function as follows.

 MyDeviceUsageNotificationEx (
    WDFDEVICE  Device,
    WDF_SPECIAL_FILE_TYPE NotificationType,
    BOOLEAN  IsInNotificationPath

The EVT_WDF_DEVICE_USAGE_NOTIFICATION_EX function type is defined in the Wdfdevice.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_DEVICE_USAGE_NOTIFICATION_EX 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.


Target platform


Minimum KMDF version


Minimum UMDF version



Wdfdevice.h (include Wdf.h)





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