Re: [PATCH v8 6/9] pci: Introduce a domain number for pci_host_bridge.

From: Bjorn Helgaas
Date: Thu Jul 10 2014 - 18:36:36 EST

On Thu, Jul 10, 2014 at 3:47 AM, Liviu Dudau <Liviu.Dudau@xxxxxxx> wrote:

> I don't see a way out of adding new PCI interfaces if we want to have support in
> the PCI framework for unifying existing architectures. Of course, there is the painful
> alternative of changing the existing APIs and fixing arches in one go, but like you've
> said is going to be messy. I don't think I (or the people and companies wanting PCIe
> on arm64) should cop out and pick a quick fix that adds sysdata structure into arm64
> just to avoid new APIs, as this is not going to help anyone in long term. What I can
> do is to create a set of parallel APIs for pci_{scan,create}_root_bus() that take
> a pci_host_bridge pointer and start converting architectures one by one to that API
> while deprecating the existing one. That way we can add arm64 easily as it would be
> the first architecture to use new code without breaking things *and* we provide a
> migration path.

A lot of the v7 discussion was about pci_register_io_range(). I
apologize, because I think I really derailed things there and it was
unwarranted. Arnd was right that migrating other arches should be a
separate effort. I *think* I was probably thinking about the proposal
of adding pci_create_root_bus_in_domain(), and my reservations about
that got transferred to the pci_register_io_range() discussion. In
any case, I'm completely fine with pci_register_io_range() now.

Most of the rest of the v7 discussion was about "Introduce a domain
number for pci_host_bridge." I think we should add arm64 using the
existing pci_scan_root_bus() and keep the domain number in the arm64
sysdata structure like every other arch does. Isn't that feasible?
We can worry about domain unification later.

I haven't followed closely enough to know what other objections people had.

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