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

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Message-ID: <alpine.DEB.2.21.2205041516110.9548@angie.orcam.me.uk>
Date:   Wed, 4 May 2022 15:24:39 +0100 (BST)
From:   "Maciej W. Rozycki" <macro@...am.me.uk>
To:     Arnd Bergmann <arnd@...nel.org>
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, 4 May 2022, Arnd Bergmann wrote:

> >  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.

 Well, yes, except I would expect POWER9_CPU (and any higher versions we 
eventually get) to clear HAS_IOPORT.  Generic configurations (GENERIC_CPU) 
would set HAS_IOPORT of course, as would any lower architecture variants 
that do or may support port I/O (it's not clear to me if there are any 
that do not).  Ideally a generic configuration would not issue accesses to 
random MMIO locations for port I/O accesses via `inb'/`outb', etc. for 
systems that do not support port I/O (which it now does, or at least used 
to until recently).

  Maciej