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

[Tomasz Nowicki]

On 02.06.2016 14:32, Arnd Bergmann wrote:
> On Thursday, June 2, 2016 2:07:43 PM CEST Tomasz Nowicki wrote:
> > On 02.06.2016 13:42, Arnd Bergmann wrote:
> > > 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 wanted to get associated bus_shift and use it to setup configuration
> > region properly before calling pci_ecam_create. Please see next patch.
>
> I see. It feels really odd to do it this way though, since having a
> nonstandard bus_shift essentially means not using anything resembling
> ECAM to start with.
>
> I realize that a lot of the host bridges are not ECAM, but because
> of this, it would be more logical to have their own pci_ops instead
> of pci_ecam_ops.

Well, we have bus_shift there to express bus shift differentiation. So I 
would say we should change just structure name to prevent misunderstanding.

Thanks,
Tomasz