Providing Event Notification

The WIA service notifies a WIA minidriver of a supported device event by calling the IWiaMiniDrv::drvNotifyPnpEvent method. In this method, the minidriver implements the device-specific functionality needed to respond to the event. The WIA service calls the IWiaMiniDrv::drvNotifyPnpEvent method only for an event the minidriver has indicated the device can support in the IWiaMiniDrv::drvGetCapabilities method.

The minidriver initiates an event either through the STI event mechanism, or by using wiasQueueEvent to add an event notification from this device to the event queue.

Asynchronous Behavior: Power Management and I/O Cancellation

In most cases, the WIA service ensures that only one call is made down to the driver at a time. However, some methods are inherently asynchronous and reentrant in nature. A good example of this is the IWiaMiniDrv::drvNotifyPnpEvent method.

The WIA service uses this method to notify the driver of events that may require immediate action. For example, when the WIA service receives a Plug and Play event indicating that the device has been removed, it informs the driver immediately. Other examples include power management events and I/O cancellation requests from applications.

For a sample implementation of the IWiaMiniDrv::drvNotifyPnpEvent method, illustrating how it should respond to various kinds of events, see Adding Interrupt Event Support.