linux-kernel - Re: [RFC PATCH] Kconfig: Enable Kconfig fragments to be used for defconfig

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Message-ID: <1279310976.18579.8.camel@e102109-lin.cambridge.arm.com>
Date:	Fri, 16 Jul 2010 21:09:36 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Nicolas Pitre <nico@...xnic.net>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Daniel Walker <dwalker@...eaurora.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	linux-kbuild@...r.kernel.org, Tony Lindgren <tony@...mide.com>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>,
	lkml <linux-kernel@...r.kernel.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	linuxppc-dev@...ts.ozlabs.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC PATCH] Kconfig: Enable Kconfig fragments to be used for
 defconfig

On Fri, 2010-07-16 at 19:46 +0100, Linus Torvalds wrote:
> On Fri, Jul 16, 2010 at 11:40 AM, Nicolas Pitre <nico@...xnic.net> wrote:
> >
> > DOH.
> 
> Well, it's possible that the correct approach is a mixture.
> 
> Automatically do the trivial cases (recursive selects, dependencies
> that are simple or of the form "x && y" etc), and warn about the cases
> that aren't trivial (where "not trivial" may not necessarily be about
> fundamentally ambiguous ones, but just "complex enough that I won't
> even try").

There is still a risk with this approach when the Kconfig isn't entirely
correct. For example, on ARM we have (I pushed a patch already):

config CPU_32v6K
	depends on CPU_V6

config CPU_V7
	select CPU_32v6K

In this simple approach, we end up selecting CPU_V6 when we only need
CPU_V7. There other places like this in the kernel.

Of course, kbuild could still warn but if people rely on this feature to
select options automatically I suspect they would ignore the warnings.

-- 
Catalin

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