Re: [RFC] Get rid of SUBARCH

[Rob Landley <rob@landley.net>]

On 08/21/2013 07:07:33 AM, Geert Uytterhoeven wrote:
> On Wed, Aug 21, 2013 at 10:19 AM, Richard Weinberger <richard@nod.at>  
> wrote:
> > This series is an attempt to remove the SUBARCH make parameter.
> > It as introduced at the times of Linux 2.5 for UML to tell the UML
> > build system what the real architecture is.
> >
> > But we actually don't need SUBARCH, we can store this information
> > in the .config file.
> 
> Haha, now you have OS_ARCH (shouldn't that be called HOST_ARCH?)  
> instead,
> which is available only for UM?
> 
> > The series touches also m68k, sh, mips and unicore32.
> > These architectures magically select a cross compiler if ARCH !=  
> SUBARCH.
> > Do really need that behavior?
> 
> This does remove functionality.
> It allows to build a kernel using e.g. "make ARCH=m68k".

   make ARCH=m68k CROSS_COMPILE=m68k-
   make ARCH=arm CROSS_COMPILE=armv5l-
   make ARCH=sparc CROSS_COMPILE=sparc-
   make ARCH=ppc CROSS_COMPILE=powerpc-
   make ARCH=sh CROSS_COMPILE=sh4-
   make ARCH=mips CROSS_COMPILE=mipsel-
   make ARCH=x86 CROSS_COMPILE=i686-
   make ARCH=alpha CROSS_COMPILE=alpha-

Works the same way on all the targets I've tried so far. You specify  
the architecture, you specify the cross compiler prefix, you feed it a  
config file, you build.

(If a target supplies its own default cross compiler prefix I just have  
to override it with what mine's called anyway...)

> Perhaps this can be moved to generic code? Most (not all!)  
> cross-toolchains
> are called $ARCH-{unknown-,}linux{,-gnu}.
> Exceptions are e.g. am33_2.0-linux and bfin-uclinux.

The linaro toolchain is arm-linux-gnueabihf- and the one on kernel.org  
is arm-unknown-linux-gnueabi- and the one I build is armv5l- (because  
the FSF's  
$ARCH-unknown-gnu-format-tuple-all-hail-stallman-gnu-gnu-gnu-dammit-gcc  
is just nuts: why would I say -linux- in a linux-to-linux toolchain? Do  
windows toolchains say -windows-?)

Other toolchain sources use other prefixes (-unknown- is often  
-$VENDORNAME-), and then of course there's llvm... which is why you  
specify CROSS_COMPILE= on the make command line.

Rob
From swarren@wwwdotorg.org Wed Aug 21 20:24:41 2013
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Date:   Wed, 21 Aug 2013 12:24:34 -0600
From:   Stephen Warren <swarren@wwwdotorg.org>
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To:     James Hogan <james.hogan@imgtec.com>
CC:     Ralf Baechle <ralf@linux-mips.org>,
        Stephen Warren <swarren@nvidia.com>,
        Michal Marek <mmarek@suse.cz>,
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        Mark Rutland <mark.rutland@arm.com>,
        Pawel Moll <pawel.moll@arm.com>,
        Rob Herring <rob.herring@calxeda.com>,
        linux-mips@linux-mips.org, devicetree@vger.kernel.org,
        linux-kbuild@vger.kernel.org
Subject: Re: [PATCH] MIPS: add <dt-bindings/> symlink
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On 08/21/2013 08:36 AM, James Hogan wrote:
> Add symlink to include/dt-bindings from arch/mips/boot/dts/include/ to
> match the ones in ARM and Meta architectures so that preprocessed device
> tree files can include various useful constant definitions.
> 
> See commit c58299a (kbuild: create an "include chroot" for DT bindings)
> merged in v3.10-rc1 for details.
> 
> MIPS structures it's dts files a little differently to other
> architectures, having a separate dts directory for each SoC/platform,
> but most of the definitions in the dt-bindings/ directory are common so
> for now lets just have a single "include chroot" for all MIPS platforms.

Acked-by: Stephen Warren <swarren@nvidia.com>