Sending an Event with WmiFireEvent

A driver can call WmiFireEvent to send events that do not use dynamic instance names, and that base static instance names on a single base name string or the device instance ID of a PDO.

The event must be a single instance of a block—that is, a driver cannot call WmiFireEvent to send an event that consists of a single item or multiple instances. To send such events, a driver must call IoWMIWriteEvent, as described in Sending an Event with IoWMIWriteEvent.

A driver should not send events until WMI has enabled the event. After the event has been enabled, when the event's trigger condition occurs, the driver:

1. Allocates a buffer from the nonpaged pool and writes the event data to the buffer. If the event has no data, the driver can skip this step.

2. Calls WmiFireEvent with the following parameters:

   • A pointer to the driver's device object

   • A pointer to the GUID that represents the event block

   • If the event block has multiple instances, the index of the instance

   • If data is to be sent with the event, the number of bytes of data, or 0 if none

   • If data is to be sent with the event, a pointer to the driver-allocated buffer that contains the data, or NULL if none

   The driver must allocate all parameters passed to WmiFireEvent, including the event data buffer, from nonpaged pool. WMI releases the driver-allocated memory without further intervention by the driver.

After WmiFireEvent returns, the driver resumes monitoring the event's trigger condition and sends the event each time its trigger condition occurs until WMI disables that event.