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

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Date:	Thu, 02 Jun 2016 13:42:43 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Tomasz Nowicki <tn@...ihalf.com>
Cc:	helgaas@...nel.org, will.deacon@....com, catalin.marinas@....com,
	rafael@...nel.org, hanjun.guo@...aro.org,
	Lorenzo.Pieralisi@....com, okaya@...eaurora.org,
	jchandra@...adcom.com, robert.richter@...iumnetworks.com,
	mw@...ihalf.com, Liviu.Dudau@....com, ddaney@...iumnetworks.com,
	wangyijing@...wei.com, Suravee.Suthikulpanit@....com,
	msalter@...hat.com, linux-pci@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org, linaro-acpi@...ts.linaro.org,
	jcm@...hat.com, andrea.gallo@...aro.org, dhdang@....com,
	jeremy.linton@....com, liudongdong3@...wei.com, cov@...eaurora.org
Subject: Re: [RFC PATCH 1/3] pci, acpi: Match PCI config space accessors against platfrom specific ECAM quirks.

On Thursday, June 2, 2016 10:41:01 AM CEST Tomasz Nowicki 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))
> +                       return f->ops;
> +       }
> +       /* No quirks, use ECAM */
> +       return &pci_generic_ecam_ops;
> +}
> +
>  int pci_mcfg_lookup(struct acpi_pci_root *root)

Can you explain the use of pci_ecam_ops instead of pci_ops here?

I was hoping we'd be able to fold all of pci-ecam code into the
generic PCI layer at some point and get rid of pci_ecam_ops in the
process.

	Arnd