linux-kernel - Re: def

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Message-ID: <20080804211640.GC29902@uranus.ravnborg.org>
Date:	Mon, 4 Aug 2008 23:16:41 +0200
From:	Sam Ravnborg <sam@...nborg.org>
To:	Jan Beulich <jbeulich@...ell.com>
Cc:	mingo@...e.hu, Harvey Harrison <harvey.harrison@...il.com>,
	tglx@...utronix.de, Roman Zippel <zippel@...ux-m68k.org>,
	Nick Piggin <npiggin@...e.de>, linux-kernel@...r.kernel.org
Subject: Re: def_bool n

On Mon, Aug 04, 2008 at 01:29:06PM +0100, Jan Beulich wrote:
> Could either of you clarify what the significance of such a construct
> (encountered several times in arch/x86/Kconfig alone) is?
> 
> At first, I noticed it only with GENERIC_LOCKBREAK (it is my
> understanding that this block can go away entirely), but then realized
> that with the bool->def_bool conversion this was introduced in various
> other places (where "default n" was used before, which seems as
> pointless a statement). Am I missing something?

No.

arch/x86/Kconfig:
config GENERIC_LOCKBREAK
        def_bool n

I assume this is solely to document that x86 does
NOT use GENERIC_LOCKBREAK as it serves no other purpose.

Notice that we may see:

init/Kconfig:
config FOO
	def_bool y

arch/$ARCH/Kconfig:
config FOO
	def_bool n

And this will result in setting FOO to the last seen value.
All the HAVE_* stuff is btw to avoid such double definition
of a config symbol.

GENERIC_LOCKBREAK is another candidate.

	Sam
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