linux-kernel - Re: [patch -mm] Make check_signature() depend on CONFIG_HAS

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Date:	Thu, 28 Jun 2007 20:47:33 +0200 (CEST)
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	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, Andrew Morton wrote:
> On Thu, 28 Jun 2007 20:27:22 +0200 (CEST) Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> > > >  endif
> > > >  
> > > >  obj-$(CONFIG_GENERIC_IOMAP) += iomap.o
> > > > -obj-$(CONFIG_HAS_IOMEM) += iomap_copy.o devres.o
> > > > +obj-$(CONFIG_HAS_IOMEM) += iomap_copy.o devres.o check_signature.o
> > > >  obj-$(CONFIG_DEBUG_LOCKING_API_SELFTESTS) += locking-selftest.o
> > > >  obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock_debug.o
> > > >  lib-$(CONFIG_RWSEM_GENERIC_SPINLOCK) += rwsem-spinlock.o
> > > 
> > > We didn't think of that.
> > > 
> > > Alas, m68k `make allmodconfig' creates CONFIG_ISA=n, CONFIG_PCI=n,
> > > CONFIG_HAS_IOMEM=y, so it will still be busted.
> > > 
> > > But this seems to be the correct fix.  Perhaps m68k config needs
> > > attention?
> > 
> > Euh, I don't think this is the correct fix.
> > 
> > CONFIG_HAS_IOMEM is apparently used in two meanings:
> >   1. The architecture has support for memory mapped I/O (s390 obviously
> >      hasn't)
> >   2. The architecture has ISA/PCI-style memory mapped I/O (readb() and
> >      friends)
> > 
> > check_signature() falls under the second category.
> > 
> > Setting NO_IOMEM on m68k will make us loose some drivers (e.g.
> > drivers/video/Kconfig depends on HAS_IOMEM).
> >  
> > Apart from many Kconfig dependencies on HAS_IOMEM, CONFIG_HAS_IOMEM is
> > further only used to control the build of lib/iomap_copy.c, which
> > doesn't use readb() and friends, but the __raw*() operations.
> > 
> 
> Well this is fun.
> 
> How to fix? Should we add a new CONFIG_HAS_IO?  (IOPORTS?)

There already exists a CONFIG_HAS_IOPORT :-) (for ISA/PCI-style I/O port
access).

Just make check_signature() depend on ISA || PCI (and maybe || X86_32).
According to its comment, it's used to `find BIOS signatures', which is
a legacy PC thing. Please don't pollute non-legacy architectures with it ;-)

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds
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