WdfDevicePostEvent function (wdfdevice.h)

[Applies to UMDF only]

The WdfDevicePostEvent method asynchronously notifies applications that are waiting for the specified event from a driver.

Syntax

NTSTATUS WdfDevicePostEvent(
  [in] WDFDEVICE      Device,
  [in] REFGUID        EventGuid,
  [in] WDF_EVENT_TYPE WdfEventType,
  [in] BYTE           *Data,
  [in] ULONG          DataSizeCb
);

Parameters

[in] Device

A handle to a framework device object.

[in] EventGuid

The GUID for the event. The GUID is determined by the application and the driver and is opaque to the framework.

[in] WdfEventType

A WDF_EVENT_TYPE-typed value that identifies the type of event. In the current version of UMDF, the driver must set EventType to WdfEventBroadcast (1). WdfEventBroadcast indicates that the event is broadcast. Applications can subscribe to WdfEventBroadcast-type events. To receive broadcast events, the application must register for notification through the Microsoft Win32 RegisterDeviceNotification function. WdfEventBroadcast-type events are exposed as DBT_CUSTOMEVENT-type events to applications.

[in] Data

A pointer to a buffer that contains data that is associated with the event. NULL is a valid value.

[in] DataSizeCb

The size, in bytes, of data that Data points to. Zero is a valid size value if Data is set to NULL.

Return value

If the operation succeeds, WdfDevicePostEvent returns STATUS_SUCCESS. Additional return values include:

The method might return other NTSTATUS values.

Remarks

When the driver calls WdfDevicePostEvent to notify the requesting application about an event, UMDF sends the event to the operating system. The operating system sends the event on to the requesting application in an asynchronous operation. If the operating system initially returns no error, WdfDevicePostEvent returns STATUS_SUCCESS.

However, later, if the operating system receives an error while it attempts to deliver the event (possibly because of a low memory condition), the operating system is unable to inform the driver about the error. Because of the asynchronous nature of this event notification, delivery of the event to the requesting application is not guaranteed.

If event information is lost on its way up to the requesting application, the application should be able to recover from the lost event.

Requirements

See also

IWDFDevice::PostEvent

WDF_EVENT_TYPE