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

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Date:	Sat, 24 May 2008 17:36:11 +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 03:35:58PM +0100, Jeremy Fitzhardinge wrote:
> Sam Ravnborg wrote:
> >I assume you wanted to say:
> >  
> >>   #undef  CONFIG_FOO
> >>   #define CFG_FOO   1
> >>   #define CONFIG_FOO_MODULE
> >>   #define CFG_FOO_MODULE 1
> >>    
> >Because then the CONFIG_* is not changed
> >and we do not want to change that.
> >  
> 
> Yeah, I didn't intend to change the meaning of CONFIG_FOO.
> 
> >I'm not fully convinced about:
> >  
> >>   #define CFG_FOO   1
> >>    
> >But on the other hand it is only in odd
> >cases we distingush between built-in and module.
> >So it makes most sense.
> >  
> 
> I think CONFIG_ and CFG_ should be exact parallels, so if CONFIG_FOO is 
> undefined, CFG_FOO should be 0.

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 cooked up following patch - but I have not test-build a kernel yet.
We may use CFG_* here and there and clash is not good.

	Sam

diff --git a/scripts/kconfig/confdata.c b/scripts/kconfig/confdata.c
index ee5fe94..98a2c39 100644
--- a/scripts/kconfig/confdata.c
+++ b/scripts/kconfig/confdata.c
@@ -717,15 +717,21 @@ int conf_write_autoconf(void)
 		case S_BOOLEAN:
 		case S_TRISTATE:
 			switch (sym_get_tristate_value(sym)) {
-			case no:
-				break;
 			case mod:
 				fprintf(out, "CONFIG_%s=m\n", sym->name);
 				fprintf(out_h, "#define CONFIG_%s_MODULE 1\n", sym->name);
+				fprintf(out_h, "#define CFG_%s 1\n", sym->name);
+				fprintf(out_h, "#define CFG_%s_MODULE 1\n", sym->name);
 				break;
 			case yes:
 				fprintf(out, "CONFIG_%s=y\n", sym->name);
 				fprintf(out_h, "#define CONFIG_%s 1\n", sym->name);
+				fprintf(out_h, "#define CFG_%s 1\n", sym->name);
+				fprintf(out_h, "#define CFG_%s_MODULE 0\n", sym->name);
+				break;
+			case no:
+				fprintf(out_h, "#define CFG_%s 0\n", sym->name);
+				fprintf(out_h, "#define CFG_%s_MODULE 0\n", sym->name);
 				break;
 			}
 			break;
--
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