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

From: Ingo Molnar <mingo@elte.hu>
To: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: Frans Pop <elendil@planet.nl>,
	Rene Herman <rene.herman@keyaccess.nl>,
	linux-kernel@vger.kernel.org, Rene Herman <rene.herman@gmail.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Jesse Barnes <jbarnes@virtuousgeek.org>,
	Matthew Wilcox <matthew@wil.cx>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	"Rafael J. Wysocki" <rjw@sisk.pl>,
	bugme-daemon@bugzilla.kernel.org
Subject: Re: [Bug #11550] pnp: Huge number of "io resource overlap" messages
Date: Sat, 27 Sep 2008 22:53:57 +0200	[thread overview]
Message-ID: <20080927205357.GC31650@elte.hu> (raw)
In-Reply-To: <200809261540.31443.bjorn.helgaas@hp.com>

* Bjorn Helgaas <bjorn.helgaas@hp.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