[wdmaudiodev] Re: PcAddAdapterDevice & Device Extensions
- From: "Van Mieghem, Dirk" <dvm@xxxxxxxx>
- To: "'wdmaudiodev@xxxxxxxxxxxxx'" <wdmaudiodev@xxxxxxxxxxxxx>
- Date: Wed, 4 Dec 2002 23:16:09 +0100
Hi Art,
I needed the PDO for the very same reason and didn't find a reliable way to
do so. I circumvented the problem by moving most of the registry accesses to
the AddDevice routine. In my driver, I wrote an underlying bus driver also.
The WDM/KS subdevices query the bottom device stack for a private direct
call interface and end up in the child FDO's created by my bus driver. They
use this private interface to store/retrieve instance specific settings. Of
course, this bus driver thing is a bit complex just for registry access but
I needed it anyway for other purposes ;)
I guess the more or less documented way is to send an
IRP_MJ_PNP/IRP_MN_QUERY_DEVICE_RELATIONS down the stack wo get the
"TargetDeviceRelation". The bus driver is supposed to answer with the PDO of
your device.
Best regards,
Dirk
> -----Original Message-----
> From: Art Edwards [mailto:snowdog0@xxxxxxxxxxxx]
> Sent: Wednesday, December 04, 2002 9:47 PM
> To: wdmaudiodev@xxxxxxxxxxxxx
> Subject: [wdmaudiodev] Re: PcAddAdapterDevice & Device Extensions
>
>
> Dirk,
>
> Thanks for the advice.
>
> I'd like to save the PDO pointer passed to AddDevice. I want
> to be able to
> use it later on in a call to IoOpenDeviceRegistryKey. I know PORTCLS
> exports the IRegistryKey interface. I *should* be able to use that
> interface to access registry keys related to my device.
>
> However, there are bugs (I believe) in some of the methods of that
> interface. For example, specifying a RegistryKeyType of
> HwProfileRegistryKey in a call to PcNewRegistryKey returns an
> error. I
> posted a message on this about a year ago:
>
> http://groups.yahoo.com/group/wdmaudiodev/message/1949
>
> As I mentioned in that post, PORTCLS saves a pointer to the
> PDO in its
> portion of the device extension (the long word at byte offset
> 8). But, I
> don't think it's safe to rely on that. I'd like to keep my own copy.
>
> Yeah, I was afraid IoGetAttachedDeviceReference would do that.
>
> At 02:56 PM 12/4/2002 , you wrote:
> >Hi Art,
> >it looks like the documentation is wrong on this one.
> Normally, you would
> >create a device in your AddDevice routine given the PDO.
> After that you can
> >use the Functional Device Object to access your private extension.
> >PcAddAdapterDevice creates the necessary device for you but
> you have to wait
> >until the StartDevice routine is called to access your extension.
> >
> >Is there any specific reason why you want to use an
> extension? You can
> >allocate your own object and associate it to the port returned from
> >PcNewPort. You can store whatever you need in this object.
> >
> >IoGetAttachedDeviceReference does not necessarily return
> your deviceobject
> >because a filter driver could be loaded on top of yours.
> >
> >Best regards,
> >Dirk
> >
> > > -----Original Message-----
> > > From: Art Edwards [mailto:snowdog0@xxxxxxxxxxxx]
> > > Sent: Wednesday, December 04, 2002 8:25 PM
> > > To: wdmaudiodev@xxxxxxxxxxxxx
> > > Subject: [wdmaudiodev] PcAddAdapterDevice & Device Extensions
> > >
> > >
> > > There's a fragment of sample code in the DDK description of
> > > PcAddAdapterDevice. The fragment describes how an adapter
> > > driver can access its device extension after the call to
> > > PcAddAdapterDevice returns. The fragment is:
> > >
> > > PDEVICE_CONTEXT pDeviceContext =
> > > (PDEVICE_CONTEXT)(PhysicalDeviceObject->DeviceExtension);
> > > PVOID pMyExtensionData = (PVOID)((PCHAR)pDeviceContext +
> > > PORT_CLASS_DEVICE_EXTENSION_SIZE);
> > >
> > >
> > > My understanding of this is that referencing pMyExtensionData
> > > will access the PDO's device extension. That extension is
> > > owned by the bus driver right ? If so, the above
> fragment won't work.
> > >
> > > To access my device extension, I think it would be more
> > > appropriate to call IoGetAttachedDeviceReference and access
> > > its device extension pointer.
> > >
> > > Does anyone out there know about this ?
> > >
>
> Art Edwards
>
> Art's <http://members.localnet.com/~snowdog0/Resume>resume.
> Art's <http://www.soniqboom.net>band (a.k.a. Soniq Boom).
>
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