Al Harper
That call is a normal part of a WDM driver's AddDevice function. Is that
how you're trying to use it? If so, you just pass it the address of a
DEVICE_OBJECT you've created and the address of the PDO you got as an
argument. It returns a DEVICE_OBJECT* (not necessarily the same as the
PDO because there may be intervening filter drivers), which you save
somewhere -- most likely in your device extension. When you want to pass
requests down, you use this pointer in your call to IoCallDriver or
PoCallDriver.
Al Harper