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Message-Id: <20070628160152.3f36af82.akpm@linux-foundation.org>
Date: Thu, 28 Jun 2007 16:01:52 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Jeff Dike <jdike@...toit.com>
Cc: Alan Cox <alan@...rguk.ukuu.org.uk>,
Geert Uytterhoeven <geert@...ux-m68k.org>,
Heiko Carstens <heiko.carstens@...ibm.com>,
linux-kernel@...r.kernel.org,
Martin Schwidefsky <schwidefsky@...ibm.com>,
Roman Zippel <zippel@...ux-m68k.org>
Subject: Re: [patch -mm] Make check_signature() depend on CONFIG_HAS_IOMEM
On Thu, 28 Jun 2007 18:45:11 -0400
Jeff Dike <jdike@...toit.com> wrote:
> On Thu, Jun 28, 2007 at 11:25:37PM +0100, Alan Cox wrote:
> > This completely bogus. readb() should be present on M68K, fix the
> > platform to implement readb() for MMIO, even if your MMIO readb is a
> > moveb instruction.
> >
> > check_signature is relevant for anything with MMIO space (for example you
> > can legitimately want to check_signature a MAC68K Nubus ROM).
> >
> > S/390 is a bit of a special case as no S/390 usage of check_signature
> > appears sane but equally it isn't used so you can stub it out.
>
> This is a problem for UML too.
>
> I have a patch in my tree, which basically stubs readb, waiting to see
> how this is fixed for the other arches.
>
What a mess.
I guess we could add an empty readb() implementation to lib/lib.a so the
arch will pick that up if all else fails. But it's pretty stinky. And
it won't work either because we don't know at compile-time to declare
the prototype for that thing appropriately.
So... what's the proper fix here? "The arch must implement readb"? That's
bad: if the arch really cannot implement readb(), we want builds to fail
if someone tries to use it.
I think I'll go shopping instead.
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