[wdmaudiodev] Re: About Unload in MSVAD
- From: Tim Roberts <timr@xxxxxxxxx>
- To: wdmaudiodev@xxxxxxxxxxxxx
- Date: Fri, 13 Mar 2009 10:32:00 -0700
karthiksharmasg@xxxxxxx wrote:
> Thanks Tim,
>
> I have sent only a snap of the code, the complete code of adapter.cpp
> is attatched to this mail, can you please look in to that
Please keep this exchange on the mailing list. I am not a free private
consulting service.
I believe I may have given you incorrect advice. I did not realize that
you were just trying to create a "control device object" as a back door
into a standard PortCls PnP device. That changes things. Your device
object is not part of a PnP stack, so it will never get an
IRP_MN_REMOVE_DEVICE request.
Instead, I believe you will need to watch for IRP_MN_REMOVE_DEVICE
requests for the PortCls device object, and delete your device in
response to THAT. Note that you will still need to pass that request on
to PcDispatchIrp.
There's still a potential issue here, however. IF an application still
has an open file handle to your control device when you go to delete it,
the system can't really delete the device. The device can't be deleted
until the application actually closes its handle. But if the last
remaining device object in your driver is not a PnP device, then the
operating system doesn't automatically trigger an unload when it is
closed. That only happens with PnP devices. There is no solution to
this -- it's just an ugly side effect of mixing PnP and non-PnP devices
within a single driver. It's not really a problem, except that you
can't update your driver binary in that case without rebooting.
--
Tim Roberts, timr@xxxxxxxxx
Providenza & Boekelheide, Inc.
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