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

From: Jeff Garzik
Date: Sun Dec 23 2007 - 00:10:24 EST


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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