[LinuxBIOS] Winflashrom -- Current Status

Peter Stuge peter at stuge.se
Tue Aug 14 21:47:48 CEST 2007

On Tue, Aug 14, 2007 at 12:14:22PM -0500, Roman Kononov wrote:
> On 08/14/2007 07:56 AM, Peter Stuge wrote:
> > Roman did make a good point about IRQL but that does not eliminate
> > the problem, we will still be changing hardware state underneath the
> > OS and that is ALWAYS a bad idea.
> The CF8/CFC sequence can preserve CF8 port value. What other
> hardware state would be changed?

The bits that are changed in the device config space.

> > http://www.hollistech.com/Resources/Misc%20articles/getbusdata.htm
> > http://www.freelists.org/archives/wdmaudiodev/03-2004/msg00010.html
> BTW, here is the "official" example:
> http://support.microsoft.com/kb/253232
> Unfortunately, AFAIK, this approach does not work for cases like
> yours. It requires the "DeviceObject", which MUST be associated
> with a PARTICULAR PCI function.

Right, I assumed that it would be possible to get that through some
sequence of system calls that look at the PCI bus.

> Q: In the above links, among HtsReadWriteConfig() and
> WritePCIConfigSpace() argument lists, which arguments are bus
> number and device number?
> A: They are inside PDEVICE_OBJECT, which structure is "opaque".

Yup. Are you saying it is simply not possible to access PCI config
space of a device from a device driver unless the driver is in fact
part of the driver stack associated with that device?

I suppose Microsoft considers that a feature?

It would certainly explain why there aren't already several
applications for reprogramming flash on Windows.

But, on the other hand, there are a few applications that _do_.
So how do they do it?

> This means that the DPC method might be quite expensive.

If this is the only way to access PCI config space for unrelated
devices then I guess it's the best we can do - unless we can make
ourselves be part of the driver stack for the southbridge?

Or maybe there is in fact a userspace API for PCI config access?

I am by no means a Windows API or WDM expert, then I'd already
written the code. :p That world is a pretty strange place.


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