linux-kernel - Re: [PATCH v7 4/6] pci: Introduce a domain number for pci_host

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Date:	Tue, 8 Apr 2014 10:28:39 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	linux-pci <linux-pci@...r.kernel.org>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	linaro-kernel <linaro-kernel@...ts.linaro.org>,
	Arnd Bergmann <arnd@...db.de>,
	LKML <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	LAKML <linux-arm-kernel@...ts.infradead.org>,
	Tanmay Inamdar <tinamdar@....com>,
	Grant Likely <grant.likely@...retlab.ca>
Subject: Re: [PATCH v7 4/6] pci: Introduce a domain number for pci_host_bridge.

On Tue, Apr 8, 2014 at 4:20 AM, Liviu Dudau <Liviu.Dudau@....com> wrote:
> On Mon, Apr 07, 2014 at 11:44:51PM +0100, Bjorn Helgaas wrote:

>> Let me try to explain my concern about the
>> pci_create_root_bus_in_domain() interface.  We currently have these
>> interfaces:
>>
>>   pci_scan_root_bus()
>>   pci_scan_bus()
>>   pci_scan_bus_parented()
>>   pci_create_root_bus()
>> ...

>> One alternative is to add an _in_domain() variant of each of these
>> interfaces, but that doesn't seem very convenient either.  My idea of
>> passing in a structure would also require adding variants, so there's
>> not really an advantage there, but I am thinking of the next
>> unification effort, e.g., for NUMA node info.  I don't really want to
>> have to change all the _in_domain() interfaces to also take yet
>> another parameter for the node number.
>
> OK, what about this: all the functions that you have mentioned take a
> void *sysdata parameter. Should we convert this opaque pointer into a
> specific structure that holds the domain_nr and (in future) the NUMA
> node info?

I doubt if we can make sysdata itself generic because I suspect we
need a way to have *some* arch-specific data.  But maybe the arch
could supply a structure containing a struct device *, domain, struct
pci_ops *, list of resources, aperture info, etc.  I wonder if struct
pci_host_bridge would be a reasonable place to put this stuff, e.g.,
something like this:

  struct pci_host_bridge {
    int domain;
    int node;
    struct device *dev;
    struct pci_ops *ops;
    struct list_head resources;
    void *sysdata;
    struct pci_bus *bus;  /* filled in by core, not by arch */
    ... /* other existing contents managed by core */
  };

  struct pci_bus *pci_scan_host_bridge(struct pci_host_bridge *bridge);
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