linux-kernel - Re: kernel coding style for if ... else which cross #ifdef

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Date:	Sat, 24 May 2008 20:51:15 +0200
From:	Sam Ravnborg <sam@...nborg.org>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Steve French <smfrench@...il.com>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: kernel coding style for if ... else which cross #ifdef

On Sat, May 24, 2008 at 04:45:52PM +0100, Jeremy Fitzhardinge wrote:
> Sam Ravnborg wrote:
> >We should actually do as you intially suggested and alwyas
> >define CONFIG_FOO no matter if FOO is built-in or module.
> >Because we do only want to distingush between the two in rare cases.
> >
> >But that is a separate patch and lets not do the same
> >mistage with CFG_*
> >  
> 
> I think pretty strongly that CFG_ and CONFIG_ should be exactly 
> parallel.  If you want to change the meaning of CONFIG_X in the presence 
> of modules, then change CFG_X at the same time.  Making them have 
> different meanings will just confuse anyone wanting to convert #ifdef 
> CONFIG_ code into if(CFG_) code.

We agree they should have the same semantics - we do just not agree on
the timing.
I would love to do a two patch set:
1) Introduce CFG_
2) Alwyas define CONFIG_FOO in case of modules

But I ned someone to audit the use of CONFIG_FOO before I do
such a change. 
I could just do it - but I'm pretty sure it will hurt.
And I do not want to introduce CFG_ with the same
IMO wrong semantic.

> >We may use CFG_* here and there and clash is not good.
And this needs to be checked too - but this is almost trivial to do.

> I have to say I'm not very keen on the CFG_* prefix.  It doesn't have 
> any inherent meaning and just looks like a redundant abbreviation of 
> CONFIG_; something which actually expresses the notion that it's always 
> a compile-time constant would be better.  Not that I have any 
> particularly good alternatives: CONST_? CCONST_? CONFIG_X_VAL? KCONFIG_? 
> KONFIG_? KCONST_?
Of the above I would prefer KCONFIG_FOO if we do not go for
the CFG_FOO version.
That it is const is already given by being UPPERCASE.

	Sam
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