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

[Catalin Marinas]

On Fri, Jul 11, 2014 at 07:02:06PM +0100, Catalin Marinas wrote:
> On Fri, Jul 11, 2014 at 06:02:56PM +0100, Bjorn Helgaas wrote:
> > On Fri, Jul 11, 2014 at 8:11 AM, Catalin Marinas
> > <catalin.marinas@xxxxxxx> wrote:
> > > On Thu, Jul 10, 2014 at 11:36:10PM +0100, Bjorn Helgaas wrote:
> > >> 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 think that's what we were trying to avoid, adding an arm64-specific
> > > pci_sys_data structure (and arm64-specific API). IIUC, avoiding this
> > > would allow the host controller drivers to use the sysdata pointer for
> > > their own private data structures.
> > >
> > > Also since you can specify the domain number via DT (and in Liviu's
> > > v8 patches read by of_create_pci_host_bridge), I think it would make
> > > sense to have it stored in some generic data structures (e.g.
> > > pci_host_bridge) rather than in an arm64 private sysdata.
> > 
> > It would definitely be nice to keep the domain in a generic data
> > structure rather than an arm64-specific one.  But every other arch
> > keeps it in an arch-specific structure today, and I think following
> > that existing pattern is the quickest way forward.
> 
> In this case we end up with an arm64-specific struct pci_sys_data and I
> assume some API that takes care of this data structure to populate the
> domain nr.
> 
> In Liviu's implementation, of_create_pci_host_bridge() is called by the
> host controller driver directly and reads the domain_nr from the DT. It
> also gets a void *host_data which it stores as sysdata in the pci_bus
> structure (but that's specific to the host controller driver rather than
> arm64). Since sysdata is opaque to of_create_pci_host_bridge(), it
> cannot set the domain_nr.

Some more thinking, so I guess we could get away without changing the
API. On top of Liviu's tree here:

http://linux-arm.org/git?p=linux-ld.git;a=shortlog;h=refs/heads/for-upstream/pci_v8

I reverted "pci: Introduce a domain number for pci_host_bridge.":

http://linux-arm.org/git?p=linux-ld.git;a=commitdiff;h=b44e1c7d6b01c436f6f55662a1414e925161c9ca

and added this patch on top (if you agree with the idea, we can split it
nicely in arm64, OF and PCI specific parts). What we get is the
domain_nr in a generic structure and free the sysdata pointer for the
host controller driver.

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