linux-kernel - Re: [RFC v2 25/39] pcmcia: add HAS

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Date:   Wed, 4 May 2022 16:07:09 +0200
From:   Arnd Bergmann <arnd@...nel.org>
To:     "Maciej W. Rozycki" <macro@...am.me.uk>
Cc:     Bjorn Helgaas <helgaas@...nel.org>,
        Niklas Schnelle <schnelle@...ux.ibm.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        linux-pci <linux-pci@...r.kernel.org>,
        Dominik Brodowski <linux@...inikbrodowski.net>
Subject: Re: [RFC v2 25/39] pcmcia: add HAS_IOPORT dependencies

On Wed, May 4, 2022 at 2:38 PM Maciej W. Rozycki <macro@...am.me.uk> wrote:
>
> On Wed, 4 May 2022, Arnd Bergmann wrote:
>
> > Almost all architectures that support CONFIG_PCI also provide
> > HAS_IOPORT today (at least at compile time, if not at runtime),
> > with s390 as a notable exception. Any machines that have legacy
> > PCI device support will also have I/O ports because a lot of
> > legacy PCI cards used it, and any machine with a pc-card slot
> > should also support legacy PCI devices.
> >
> > If we get new architectures without I/O space in the future, they
> > would certainly not care about supporting old cardbus devices.
>
>  POWER9 is another architecture with no port I/O space[1]:

POWER9 is just an implementation of the power architecture
that has a particular PCI host bridge. I would assume that
arch/powerpc/ would continue to set HAS_IOPORT because
it knows how to access I/O ports at compile-time.

If a particular host bridge does not declare an I/O port range
in its DT, then of course it won't be accessible, but that is
different from architectures that have no concept of I/O ports.

         Arnd