[ofw] RE: Ibbus as a filter driver for mthca.

[Fab Tillier]

Hi Leo,

> One important question was missed: How IBBUS coexist with WinVerbs
> filter driver ? Today WinVerbs is a simple filter driver AFAIK and will
> sit under IBBUS. How will it use IBAL interface (for CM, for example) ?
> I'd say, that it should be a class filter driver, dependent on IBBUS -
> if it is possible to require - and sit above IBBUS. Sean ?

You shouldn't depend on load ordering of filter drivers and instead query for the device interface by sending the query interface IRP to the top of the driver stack for the current devnode.  You can use IoGetAttachedDeviceReference to get the device object at the top of the devnode's driver stack.

-Fab