Callback Functions

Installable drivers can notify the application, window, or task that opened the given instance about events by using the DriverCallback32NQPJ function. This function gives the driver the means to return information to an application or DLL while continuing to process a request.

If a driver supports callback functions, the application or DLL that opens the instance must supply a value this is either the address of a callback function, a window handle, or a task handle. This value and a flag identifying the type of the value are typically passed in a structure pointed to by the second parameter of the DRV_OPEN1MPXASX message.