linux-kernel - Re: [patch 2/2] PNP: don't check disabled PCI BARs for conflicts in quirk_system_pci

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Message-Id: <200809301316.55780.bjorn.helgaas@hp.com>
Date:	Tue, 30 Sep 2008 13:16:54 -0600
From:	Bjorn Helgaas <bjorn.helgaas@...com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Rene Herman <rene.herman@...access.nl>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Len Brown <lenb@...nel.org>, Frans Pop <elendil@...net.nl>,
	"Rafael J. Wysocki" <rjw@...k.pl>, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-acpi@...r.kernel.org,
	Adam Belay <abelay@....edu>, Avuton Olrich <avuton@...il.com>,
	Karl Bellve <karl.bellve@...ssmed.edu>,
	Willem Riede <wriede@...de.org>,
	Matthew Hall <mhall@...omputing.net>
Subject: Re: [patch 2/2] PNP: don't check disabled PCI BARs for conflicts in quirk_system_pci_resources()

On Tuesday 30 September 2008 12:01:38 pm Linus Torvalds wrote:
> 
> On Tue, 30 Sep 2008, Linus Torvalds wrote:
> > 
> > In contrast, the PnP fixup thing is called from pnp_fixup_device, called 
> > from __pnp_add_device(), called from pnp_add_device() (and 
> > pnp_add_card(), but that should be later), and those in turn from
> > pnpacpi_add_device and pnpacpi_init(). 
> > 
> > And pnpacpi_init is _also_ a subsys_initcall [...]
> 
> Btw, why is that? We very much have a separate
> 
> 	/**
> 	 * Reserve motherboard resources after PCI claim BARs,
> 	 * but before PCI assign resources for uninitialized PCI devices
> 	 */
> 	fs_initcall(pnp_system_init);
> 
> which is called much later. That seems to be the _right_ point for any 
> quirks. It seems that the _real_ problem here is that the PnP device fixup 
> is simply called from the wrong point. Ie, why do we do device discovery - 
> and thus PnP quirks - in pnp_init (before the PCI bus is actually fully 
> initialized!), rather than in pnp_system_init?

Right.  The point of this quirk (quirk_system_pci_resources()) is to
prevent the PNP system driver from claiming resources that are actually
used by PCI.  So I don't think there's any reason to run it before we
bind the driver to the device.  PNP doesn't currently have any early/
late concept for quirks, but we probably should add one.

Feels like a post-2.6.27 project though.

Bjorn


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