Re: [PATCH] PCI: add missing DT binding for linux,pci-domain property

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On Thu, Nov 06, 2014 at 02:57:35PM +0000, Rob Herring wrote:
> On Thu, Nov 6, 2014 at 4:05 AM, Liviu Dudau <Liviu.Dudau@xxxxxxx> wrote:
> > On Wed, Nov 05, 2014 at 11:17:43PM +0000, Bjorn Helgaas wrote:
> >> On Tue, Nov 04, 2014 at 12:47:40PM +0100, Lucas Stach wrote:
> >> > This property was added by 41e5c0f81d3e
> >> > (of/pci: Add pci_get_new_domain_nr() and of_get_pci_domain_nr())
> >> > without the required binding documentation. As this property
> >> > will be supported by a number of host bridge drivers going forward,
> >> > add it to the common PCI binding doc.
> >> >
> >> > Signed-off-by: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
> >>
> >> I merged 41e5c0f81d3e through my tree, and I could merge something like
> >> this if a consensus develops with some acks.  But I'll just let you guys
> >> handle it unless you poke me again.
> >
> > While I think the "linux,pci-domain" property *must* be documented, I
> > would like to get a consensus first on the usage. If we agree that
> > the property is mandatory to all host bridge drivers that use OF then
> > we need to patch existing drivers (partially done through Lorenzo's
> > patches, but other arches are ignoring it). If we say all *new* drivers
> > need to use it then we also need to come up with a strategy on how to
> > deal with old vs new school drivers.
> >
> > My preferred approach is the 3rd way: "linux,pci-domain" becomes part of
> > the core PCI infrastructure (and we find the common ground with ACPI).
> > That way the host bridge drivers don't have to do anything, but the DT
> > creators have to specify a value.
> 
> I'm okay with it being in the core. It was the mixture of using the
> property and automatic numbering that I had issues with. Any mixture
> whether in DT or in drivers should be an error. Also, I think having a
> mixture of root bus host drivers would be rare, so I'm not too
> concerned about some drivers supporting the property and others not.
> In any case, these issues are all with the kernel and not really the
> concern for the binding. For the binding, simply all hosts set the
> domain or none of them do.

Repeating what you've said to verify my understanding: you are OK with
the "linux,pci-domain" being handled in the PCI framework and mandatory
to all OF-based host bridges and architectures. Failure to include
the property should be an error and no host bridge driver should default
to the auto-generation of domain numbers.

Is that correct?

Thanks,
Liviu

> 
> Rob
> 

-- 
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