linux-kernel - Re: RFC: kconfig select warnings bogus?

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Message-ID: <Pine.LNX.4.58.0705201243500.1671@shell4.speakeasy.net>
Date:	Sun, 20 May 2007 12:57:58 -0700 (PDT)
From:	Trent Piepho <xyzzy@...akeasy.org>
To:	Stefan Richter <stefanr@...6.in-berlin.de>
cc:	Satyam Sharma <satyam.sharma@...il.com>,
	Adrian Bunk <bunk@...sta.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Sam Ravnborg <sam@...nborg.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Roman Zippel <zippel@...ux-m68k.org>,
	Kumar Gala <galak@...nel.crashing.org>,
	Simon Horman <horms@...ge.net.au>
Subject: Re: RFC: kconfig select warnings bogus?

On Sun, 20 May 2007, Stefan Richter wrote:
>
> >> Iterating upwards and downwards the dependency graph is the duty of
> >> "make snafuconfig", not of the maintainers.
>
> ...multi-level dependencies are no problem for it.
>
> There is nothing wrong with
>
> 	A... depends on B
>
> 	B... depends on C
>
> 	# CONFIG_C is not set
>
> -> A is unavailable.

select doesn't appear to work quite like this.  For example:

config A
	bool "A"

config B
	bool "B"
	depends on A

config C
	bool "C"
	select B

In this case, it's possible to turn C on and A off.  B will be on, even
though it depends on A and A is off.

The kconfig docs say that "B..  depends on A" sets the maximum value of B
to be that of A.  Since A=0, the max value of B is 0.

The kconfig docs also say that "C..  select B" sets the minimum value of B
to be that of C.  Since C=2, the minimum value of B is 2.

So we have B>=2 and B<=0, which is obviously impossible.  Yet *config has
no problem with this, and will set B=2 even the 'depends' means B must be
0.  It seems like "select" will override any other dependencies.
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