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Re: [RFC] Get rid of SUBARCH

To: David Daney <>
Subject: Re: [RFC] Get rid of SUBARCH
From: Rob Landley <>
Date: Thu, 22 Aug 2013 16:32:55 -0500
Cc: Richard Weinberger <>, Geert Uytterhoeven <>, Sam Ravnborg <>, Linux-Arch <>, Michal Marek <>, Ralf Baechle <>, Paul Mundt <>, Jeff Dike <>, Guan Xuetao <>, Thomas Gleixner <>, Ingo Molnar <>, "H. Peter Anvin" <>, the arch/x86 maintainers <>, linux-kbuild <>, "" <>, linux-m68k <>, Linux MIPS Mailing List <>, Linux-sh list <>, uml-devel <>
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On 08/22/2013 03:55:20 PM, David Daney wrote:
On 08/22/2013 01:41 PM, Rob Landley wrote:
On 08/22/2013 07:58:26 AM, Geert Uytterhoeven wrote:
On Wed, Aug 21, 2013 at 9:51 PM, Sam Ravnborg <> wrote:
>> > The series touches also m68k, sh, mips and unicore32.
>> > These architectures magically select a cross compiler if ARCH !=
>> > Do really need that behavior?
>> This does remove functionality.
>> It allows to build a kernel using e.g. "make ARCH=m68k".
>> Perhaps this can be moved to generic code? Most (not all!)
>> are called $ARCH-{unknown-,}linux{,-gnu}.
>> Exceptions are e.g. am33_2.0-linux and bfin-uclinux.
> Today you can specify CROSS_COMPILE in Kconfig.
> With this we should be able to remove these hacks.

The correct CROSS_COMPILE value depends on the host environment, not
on the target configuration.

Actually it depends on _both_.

I think the important issue is not the exact dependencies of the value of CROSS_COMPILE, but rather that it varies enough that automatically choosing a value based on SUBARCH often gives the wrong result.

Removing SUBARCH and setting CROSS_COMPILE either from the make command line (or environment) or the config file, is a good idea because it simplifies the build system, makes things clearer, and yields more predictable results.

David Daney

Agreed. Expecting the build to guess the right $CROSS_COMPILE is like expecting it to guess the right $PATH. It should be specified, not heuristically probed.

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