linux-kernel - Re: [PATCH v3] x86, kconfig: Default to ARCH=x86 to avoid overriding CONFIG

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Date:	Sat, 30 Jul 2011 09:37:40 +0100
From:	David Woodhouse <dwmw2@...radead.org>
To:	Arnaud Lacombe <lacombar@...il.com>
Cc:	Michal Marek <mmarek@...e.cz>, Ted Ts'o <tytso@....edu>,
	Ingo Molnar <mingo@...e.hu>, x86@...nel.org,
	linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
	hpa@...or.com
Subject: Re: [PATCH v3] x86, kconfig: Default to ARCH=x86 to avoid
 overriding CONFIG_64BIT

On Fri, 2011-07-29 at 21:26 -0400, Arnaud Lacombe wrote:
> 
> Should we not try to fix this rather than introduce a new interface ?

This patch *does* fix it, without needing the new interface that I
presented in a separate patch. The two patches I sent are not strictly
dependent on one another.

> From my point of view, we (ie. Kbuild) should be intelligent enough to
> take the default from the .config, if one is present in the object
> directory, rather than trying to impose it's own view on what the ARCH
> should be.
> 
> Is there case where we would have a .config, but would not use its
> content ?

Heh, I think you've missed some of the history here.

I originally, a year or two ago, posted a patch which took precisely the
approach I think you're advocating. It basically made the ARCH=x86
behaviour apply in all cases. It was reverted because it made 'make
randconfig' actually *random* — *even* for the setting of CONFIG_64BIT,
*even* when ARCH=i386 or ARCH=x86_64.

The fact that KCONFIG_ALLCONFIG allows you to override *all* config
options and not just CONFIG_64BIT, and that using the legacy ARCH=
settings wasn't really necessary, was evidently not sufficient. It
apparently *had* to be possible to switch using the command line.

So I did two things — I fixed this patch so that it doesn't break that
legacy use case of 'make ARCH=i386' or 'make ARCH=x86_64' to force the
value of CONFIG_64BIT on or off, and I also posted a separate patch
which gives a more *sensible* way to force *any* config options on or
off from the 'make' command line, since the world is apparently going to
end if we can't do that.

The two patches can be considered to be entirely independent.

-- 
dwmw2

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