Re: [RFC PATCH 1/3] pci, acpi: Match PCI config space accessors against platfrom specific ECAM quirks.

[David Daney]

On 06/03/2016 08:32 AM, Gabriele Paoloni wrote:
[...]
> > > +struct pci_ecam_ops *pci_mcfg_get_ops(struct acpi_pci_root *root)
> > > +{
> > > +	int bus_num = root->secondary.start;
> > > +	int domain = root->segment;
> > > +	struct pci_cfg_fixup *f;
> > > +
> > > +	if (!mcfg_table)
> > > +		return &pci_generic_ecam_ops;
> > > +
> > > +	/*
> > > +	 * Match against platform specific quirks and return
> > corresponding
> > > +	 * CAM ops.
> > > +	 *
> > > +	 * First match against PCI topology <domain:bus> then use OEM ID
> > and
> > > +	 * OEM revision from MCFG table standard header.
> > > +	 */
> > > +	for (f = __start_acpi_mcfg_fixups; f < __end_acpi_mcfg_fixups;
> > f++) {
> > > +		if ((f->domain == domain || f->domain ==
> > PCI_MCFG_DOMAIN_ANY) &&
> > > +		    (f->bus_num == bus_num || f->bus_num ==
> > PCI_MCFG_BUS_ANY) &&
> > > +		    (!strncmp(f->oem_id, mcfg_table->header.oem_id,
> > > +			      ACPI_OEM_ID_SIZE)) &&
> > > +		    (f->oem_revision == mcfg_table->header.oem_revision))
> >
> > Is this more likely to be updated between quirky and fixed platforms
> > than oem_table_id? What do folks think about using oem_table_id instead
> > of, or in addition to, oem_revision?
>
>  From my understanding we need to stick to this mechanism as (otherwise)
> there are platforms out in the field that would need a FW update.
>
> So I don't think that using oem_table_id "instead" is possible; about
> "in addition" I think it is doable, but I do not see the advantage much.
> I mean that if a platform gets fixed the oem revision should change too,
> Right?

I think you are correct.  My take away on discussions about using this 
style of quirk matching was that we would require the oem_revision to 
change as different quirks (or lack of quirks) were required.

David Daney


> Thanks
>
> Gab