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

From: [email-masked] (David Daney)
Date: Fri, 03 Jun 2016 09:57:40 -0700

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