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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Thu, 15 Jul 2021 21:11:42 +0200
Message-ID: <CAK8P3a3H38aeO6hUNeLAxV4ypfX+qTaCoRAJWYdP9wbvc9HuVQ@mail.gmail.com>
Subject: Re: [RFC v4 1/7] PCI: Introduce domain_nr in pci_host_bridge
To:     Boqun Feng <boqun.feng@gmail.com>
Cc:     Bjorn Helgaas <helgaas@kernel.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Arnd Bergmann <arnd@arndb.de>, Marc Zyngier <maz@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        "K. Y. Srinivasan" <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Wei Liu <wei.liu@kernel.org>, Dexuan Cui <decui@microsoft.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        Rob Herring <robh@kernel.org>,
        =?UTF-8?Q?Krzysztof_Wilczy=C5=84ski?= <kw@linux.com>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux on Hyper-V List <linux-hyperv@vger.kernel.org>,
        linux-pci <linux-pci@vger.kernel.org>,
        Sunil Muthuswamy <sunilmut@microsoft.com>,
        Mike Rapoport <rppt@kernel.org>
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On Thu, Jul 15, 2021 at 7:30 PM Boqun Feng <boqun.feng@gmail.com> wrote:
> On Wed, Jul 14, 2021 at 02:33:19PM -0500, Bjorn Helgaas wrote:
> > On Wed, Jul 14, 2021 at 06:27:31PM +0800, Boqun Feng wrote:
> > >  #ifdef CONFIG_PCI_DOMAINS_GENERIC
> > > -   bus->domain_nr = pci_bus_find_domain_nr(bus, parent);
> > > +   if (bridge->domain_nr == PCI_DOMAIN_NR_NOT_SET)
> > > +           bus->domain_nr = pci_bus_find_domain_nr(bus, parent);
> > > +   else
> > > +           bus->domain_nr = bridge->domain_nr;
> >
> > The domain_nr in struct pci_bus is really only used by
> > pci_domain_nr().  It seems like it really belongs in the struct
> > pci_host_bridge and probably doesn't need to be duplicated in the
> > struct pci_bus.  But that's probably a project for the future.
> >

+1

> Agreed. Maybe we can define pci_bus_domain_nr() as:
>
>         static inline int pci_domain_nr(struct pci_bus *bus)
>         {
>                 struct device *bridge = bus->bridge;
>                 struct pci_host_bridge *b = container_of(bridge, struct pci_host_bridge, dev);
>
>                 return b->domain_nr;
>         }
>
> but apart from corretness (e.g. should we use get_device() for
> bus->bridge?), it makes more sense if ->domain_nr of pci_host_bridge
> is used (as a way to set domain number at probing time) for most of
> drivers and archs. ;-)

It needs to be "pci_find_host_bridge(bus)" instead of bus->bridge
and container_of().

Then again, if we get pci_domain_nr() to be completely generic, I'd
prefer to change most callers to just open-code the bridge->domain_nr
access, as most of them will already have a pointer to the pci_host_bridge
when calling this.

       Arnd