OS doing something fishy after DriverEntry and before FindAdapter for a video miniport driver

NTDEV
1

Hi,
We are using a PCI based Graphics adapter.
Till the time Video Miniport’s Driver Entry is called MMIO BAR has value *
xxxxxxxxxxxx*
By the time Video miniport’s FindAdapter is called, the value is different *
yyyyyyyyyyyy

*The problem here is we have another driver (used only for validation
support) which is loaded before Graphics driver, This driver reads Base
adress register of the PCI config space that is becoming invalid after the
Graphics driver is loaded.

What does the OS do here? and Can my driver be notified of this change
reconfiguration of BASE ADDRESS REGISTER?

Thanks,
Maddy

2

Madhusudan Narayan wrote:

We are using a PCI based Graphics adapter.
Till the time Video Miniport’s Driver Entry is called MMIO BAR has
value *xxxxxxxxxxxx*
By the time Video miniport’s FindAdapter is called, the value is
different *yyyyyyyyyyyy
*

What were the actual numbers?

**The problem here is we have another driver (used only for validation
support) which is loaded before Graphics driver, This driver reads
Base adress register of the PCI config space that is becoming invalid
after the Graphics driver is loaded.

What does the OS do here? and Can my driver be notified of this change
reconfiguration of BASE ADDRESS REGISTER?

Not unless your other driver is part of the video miniport’s stack. How
early does your “other driver” load? What kind of driver is it? The
right way to do this is to have that driver communicate with the
miniport after it has been assigned the resource.

–
Tim Roberts, xxxxx@probo.com
Providenza & Boekelheide, Inc.

3

Intially
ff000004
Later:fd400004

On Tue, Nov 11, 2008 at 12:30 AM, Tim Roberts wrote:

> Madhusudan Narayan wrote:
> >
> > We are using a PCI based Graphics adapter.
> > Till the time Video Miniport’s Driver Entry is called MMIO BAR has
> > value xxxxxxxxxxxx
> > By the time Video miniport’s FindAdapter is called, the value is
> > different *yyyyyyyyyyyy
> > *
>
> What were the actual numbers?
>
>
> > **The problem here is we have another driver (used only for validation
> > support) which is loaded before Graphics driver, This driver reads
> > Base adress register of the PCI config space that is becoming invalid
> > after the Graphics driver is loaded.
> >
> > What does the OS do here? and Can my driver be notified of this change
> > reconfiguration of BASE ADDRESS REGISTER?
>
> Not unless your other driver is part of the video miniport’s stack. How
> early does your “other driver” load? What kind of driver is it? The
> right way to do this is to have that driver communicate with the
> miniport after it has been assigned the resource.
>
> –
> Tim Roberts, xxxxx@probo.com
> Providenza & Boekelheide, Inc.
>
>
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