[Fwd: Re: [PATCH 2/5]PCI: x86 MMCONFIG: add legacy pci conf functions]

[Tony Camuso <tcamuso@redhat.com>]

-------- Original Message --------
Subject: Re: [PATCH 2/5]PCI: x86 MMCONFIG: add legacy pci conf functions
Date: Wed, 19 Dec 2007 19:07:27 -0500
From: Tony Camuso <tcamuso@redhat.com>
Reply-To: tcamuso@redhat.com
To: Greg KH <gregkh@suse.de>
References: 
<20071219221746.20362.39243.sendpatchset@dhcp83-188.boston.redhat.com> 
<20071219221756.20362.84805.sendpatchset@dhcp83-188.boston.redhat.com> 
<20071219230615.GB24219@suse.de>

Greg KH wrote:

> > +struct pci_ops pci_legacy_ops = {
> > +	.read =		pci_ops_legacy_read,
> > +	.write =	pci_ops_legacy_write,
> > +};
>
> This whole structure is never used in this patch, why add it now?

It gets used by the routine pcibios_fix_bus_scan_quirk in
arch/x86/pci/common.c

> >  /*
> >   * Before we decide to use direct hardware access mechanisms, we try to do some
> > @@ -258,18 +284,28 @@ void __init pci_direct_init(int type)
> >  {
> >  	if (type == 0)
> >  		return;
> > -	printk(KERN_INFO "PCI: Using configuration type %d\n", type);
> > -	if (type == 1)
> > +	if (type == 1) {
> >  		raw_pci_ops = &pci_direct_conf1;
> > -	else
> > +		pci_legacy_conf = &pci_direct_conf1;
> > +	} else {
> >  		raw_pci_ops = &pci_direct_conf2;
> > +		pci_legacy_conf = &pci_direct_conf2;
>
> Why have two pointers to the same thing?  What is pci_legacy_conf going
> to be used for?  Why not just use raw_pci_ops?
>
> thanks,
>
> greg k-h

The way the code works today, when raw_pci_ops is set to use mmconf,
it is platform-wide. Legacy pci config reads are not available.

I would have simply used the pci_direct_conf1, but because there can
also be a pci_direct_conf2, I thought it best to abstract it as
pci_legacy_conf.

A pointer to struct pci_ops pci_legacy_ops data is written into the
pci_bus.ops field for buses that must use legacy pci config access.

The other busses can continue to use the pointer to the mmconf pci_ops.



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