linux-kernel - Re: [Bug #11550] pnp: Huge number of "io resource overlap" messages

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Date:	Sat, 27 Sep 2008 22:53:57 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Bjorn Helgaas <bjorn.helgaas@...com>
Cc:	Frans Pop <elendil@...net.nl>,
	Rene Herman <rene.herman@...access.nl>,
	linux-kernel@...r.kernel.org, Rene Herman <rene.herman@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Matthew Wilcox <matthew@....cx>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, bugme-daemon@...zilla.kernel.org
Subject: Re: [Bug #11550] pnp: Huge number of "io resource overlap" messages


* Bjorn Helgaas <bjorn.helgaas@...com> wrote:

> The problem seems to be that Frans has some PCI devices that are not 
> configured by the BIOS, and their BARs contain zero.  A PNP quirk 
> checks for overlaps of PCI devices and PNP devices, and those zero- 
> valued BARs of course conflict with the PNP motherboard devices that 
> describe legacy hardware.
> 
> Here's another approach based on section 3.5 of the PCI Firmware spec.
> It says:
> 
>   Since not all devices may be configured prior to the operating
>   system handoff, the operating system needs to know whether a
>   specific BAR register has been configured by firmware. The operating
>   system makes the determination by checking the I/O Enable, and
>   Memory Enable bits in the device's command register, and Expansion
>   ROM BAR enable bits. If the enable bit is set, then the corresponding
>   resource register has been configured.
> 
> So instead of checking whether the BAR contains zero, the patch below
> checks the I/O, Mem, and ROM BAR enable bits to determine whether a
> BAR is enabled.

cool! Looks like a pretty significant fix, for all sorts of legacy 
devices. Worth backporting?

	Ingo
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