Re: [patch] Make MMCONFIG space (extended PCI config space) a driver opt-in issue

[Jeff Garzik <jeff@garzik.org>]

Linus Torvalds wrote:
> On Sat, 22 Dec 2007, Jeff Garzik wrote:
> > But regardless of problems, enabling should be done globally, not per
> > device...
>
> I'm ok with trying the "globally" idea, but it has to be "globally but 
> only if absolutely required".
>
> And quite frankly, how do you tell whether it's absolutely required or 
> not?
>
> I have an idea: the drivers that really need it will do a "please enable 
> MMCONFIG, because I will need it" thing?
>
> Ok?
>
> And then, since we *need* such a "pci_enable_mmconfig()" call anyway, why 
> not let the driver give which device it controls too, so that we can print 
> out the information (in case the machine then hangs immediately 
> afterwards), and perhaps - if it is shown to help - only do the MMCONFIG 
> cycles for that particular device?
>
> Sounds like a plan?

As long as pci_enable_ext_cfg_space(pdev) enables extended accesses for 
-all- devices, the plan is mostly sound.

That largely eliminates the inconsistency issue.

The only thing I would worry about is whether "config space suddenly 
grew larger" condition will confuse userspace -- but that is NOT an 
objection, just a worry.

	Jeff



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