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

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Date:	Sun, 20 May 2007 05:49:07 +0530
From:	"Satyam Sharma" <satyam.sharma@...il.com>
To:	"Adrian Bunk" <bunk@...sta.de>
Cc:	"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 5/20/07, Adrian Bunk <bunk@...sta.de> wrote:
> On Sun, May 20, 2007 at 05:25:24AM +0530, Satyam Sharma wrote:
> > On 5/20/07, Adrian Bunk <bunk@...sta.de> wrote:
> >> On Sun, May 20, 2007 at 05:06:33AM +0530, Satyam Sharma wrote:
> >> > On 5/20/07, Adrian Bunk <bunk@...sta.de> wrote:
> >> >>...
> >> >> Consider ATARI_KBD_CORE was used by 20 drivers.
> >> >>
> >> >> Using select for such not user visible helper variables is a really
> >> nice
> >> >> thing, and much more readable (and therefore much less likely to
> >> contain
> >> >> bugs) than dependencies with tons of "||"'s.
> >> >
> >> > Well, the "default .. if .." kind of idiom is fairly common (I could say
> >> > almost standard), in arch/.../config's. It's been used for some time,
> >> > and for several symbols over there. But you're right that if 20 drivers
> >> > used ATARI_KBD_CORE, we'd get tons of ugly "||"'s there, so
> >> > perhaps we do need some kind of fix for this.
> >>
> >> And the fix is to use select.
> >>
> >> Compare the handling of options like IRQ_CPU in arch/mips/Kconfig in
> >> current kernels with the handling in kernel 2.6.0 .
> >>
> >> Or as an exercise, change drivers/net/Kconfig to no longer use
> >> "select MII". When you are finished, ensure that you are handling it
> >> properly although the option is user visible...
> >
> > "config MII" and "select MII" are _not_ equivalent to the case at hand.
> > MII is defined in drivers/net/Kconfig itself so does not print any "symbol
> > unknown kind of warnings" ... so clearly no probs in "select" for it ...
>
> Then move the "config MII" to arch/i386/Kconfig and assume all drivers
> select'ing it would depend on X86_32.

Why should we do that?

> >> There are cases where "default .. if .." is the right idiom, but there
> >> are also cases where "select" is the right idiom. And for helper code
> >> like ATARI_KBD_CORE, "select" is the right idiom.
> >
> > ATARI_KBD_CORE, unlike MII, is defined only by some archs. And the
> > correct (most widely used or standard, in any case) idiom for that is
> > "default .. if ..". Or perhaps you can convert those helper code options in
> > arch/.../config's over to select too, as an exercise? :-)
>
> Perhaps not as an exercise, but actually for real.
>
> We had "fixed" such warnings in the past similar to your patch, but that
> was actually a mistake.
>
> And "correct" can easily be the opposite of "most widely used or standard"
> if you discover that you did it wrong in the past.

In that case the correct approach here too would be to _shift_
ATARI_KBD_CORE from arch/m68k/Kconfig to drivers/input/Kconfig
and *then* use "select" from the config options that require it in
drivers/input/keyboard/Kconfig and drivers/input/mouse/Kconfig

(and repeat for other such cases in arch/...)
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