Date: Thu, 31 Jul 2008 19:23:15 +0100
From: Ralf Baechle <ralf@linux-mips.org>
To: Sam Ravnborg <sam@ravnborg.org>
Cc: linux arch <linux-arch@vger.kernel.org>,
       LKML <linux-kernel@vger.kernel.org>
Subject: Re: kbuild now support arch/$ARCH/include - time for ARCHs to
	convert
Message-ID: <20080731182315.GA18060@linux-mips.org>
References: <20080728200500.GA14284@uranus.ravnborg.org>
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On Mon, Jul 28, 2008 at 10:05:00PM +0200, Sam Ravnborg wrote:

> The traditional location of the arch specific Makefiles
> has been at:
> 
> 	include/asm-$ARCH
> 
> But as suggested by several people over time and lately
> by Linus in the following post:
> http://kerneltrap.org/mailarchive/linux-kernel/2008/5/21/1903924
> 
> is is suggested to move the arch specific files under arch/
> and for the header files this is arch/$ARCH/include.
> 
> So I have hacked up support for this in kbuild so
> for the simpler cases a simple move of header files as
> in:
> 	git mv include/asm-$ARCH arch/$ARCH/include/asm
> 
> is enough.
> 
> If Linus will accept it then I think -rc1 is a perfect
> time to do it as people has less stuff pending touching
> the header files that are moved.
> Validation is easy - does the usual configs build?
> 
> For the archs that plays games with symlinks this is a
> splendid opportunity to get rid af these.
> The receipe is simple:
> Use 
> 	KBUILD_CFLAGS += -Iarch/$ARCH/include/$CPU
> 
> to select the CPU and then do a copy of the header files
> like this:
> 
> 	git mv include/asm-$ARCH/$CPU arch/$ARCH/include/$CPU/cpu
> 
> Then the code can continue to use:
> 
> 	#include <cpu/foo.h>
> 
> I already converted sparc to use arch/sparc/include -
> while I merged the header files for sparc and sparc64.
> This change is already upstream.
> 
> And for SH I posted a receipe which you can read here:
> http://lkml.org/lkml/2008/7/28/83
> 
> It is SH specific but anyway pretty generic.
> 
> I am limited in time and resources at the moment but I
> would be glad to help out as time permits should there
> be any questions.

I just did the necessary changes for MIPS and the first testbuild is running
successfully so far.

One of the ugly things in the MIPS makefiles is the use of platform-
specific headers in include/asm-mips/mach-* which contain platform specific
headers.  Ideally those should be included through something like
<mach/somefile.h> or <plat/something.h> and I think a directory like
arch/$ARCH/$PLATFORM/include/plat/foobar.h could be a good place in the
new scheme?  I assume other platforms have similar issues with subplatforms,
processor sub-architectures etc.?

  Ralf
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