linux-kernel - Re: [RFC/PATCH] of: Match PCI devices to OF nodes generically

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Date:	Tue, 05 Apr 2011 07:03:17 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	David Miller <davem@...emloft.net>
Cc:	linux-arch@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [RFC/PATCH] of: Match PCI devices to OF nodes generically

On Mon, 2011-04-04 at 00:48 -0700, David Miller wrote:
> From: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Date: Mon, 04 Apr 2011 13:27:10 +1000
> 
> > +struct device_node * __weak pcibios_get_phb_of_node(struct pci_bus *bus)
> > +{
> > +	/* This should only be called for PHBs */
> > +	if (WARN_ON(bus->self || bus->parent))
> > +		return NULL;
> 
> This WARN_ON() will always trigger on sparc, because we use the OF
> device tree object at the "parent" of the PCI bus devices we create
> for the PCI controller domains.
> 
> I'm really surprised you don't link the PCI bus roots into the rest of
> the global device hierarchy on powerpc.

But in the above test bus->parent is the "struct pci_bus *" parent, not
the "struct device *" nor "struct device_node *" parent... That
shouldn't be linked to anything on a PHB.

To answer your other point, we do link PHBs on some platforms, not
others. Historical stuff here. Most of our platforms discover PCI
bridges very early from setup_arch() before we have any struct device
around. Mostly because that's how we always did and there's some
subtle/nasty corner cases to deal with if we change that.

Cheers,
Ben.

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