linux-kernel - Re: [PATCH] kconfig.h: remove config

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Date:   Sun, 16 Oct 2016 11:44:59 -0700
From:   hpa@...or.com
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Andrew Morton <akpm@...ux-foundation.org>
CC:     linux-arch@...r.kernel.org,
        Peter Oberparleiter <oberpar@...ux.vnet.ibm.com>,
        Arnd Bergmann <arnd@...db.de>,
        Kees Cook <keescook@...omium.org>,
        Michal Marek <mmarek@...e.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Garnier <thgarnie@...gle.com>
Subject: Re: [PATCH] kconfig.h: remove config_enabled() macro

On October 16, 2016 4:07:58 AM PDT, Masahiro Yamada <yamada.masahiro@...ionext.com> wrote:
>The use of config_enabled() is ambiguous.  For config options,
>IS_ENABLED(), IS_REACHABLE(), etc. will make intention clearer.
>Sometimes config_enabled() has been used for non-config options
>because it is useful to check whether the given symbol is defined
>or not.
>
>I have been tackling on deprecating config_enabled(), and now is the
>time to finish this work.
>
>Some new users have appeared for v4.9-rc1, but it is trivial to
>replace them:
>
> - arch/x86/mm/kaslr.c
>  replace config_enabled() with IS_ENABLED() because
>  CONFIG_X86_ESPFIX64 and CONFIG_EFI are boolean.
>
> - include/asm-generic/export.h
>  replace config_enabled() with __is_defined().
>
>Then, config_enabled() can be removed now.
>
>Going forward, please use IS_ENABLED(), IS_REACHABLE(), etc. for
>config options, and __is_defined() for non-config symbols.
>
>Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
>---
>
> arch/x86/mm/kaslr.c          | 6 +++---
> include/asm-generic/export.h | 2 +-
> include/linux/kconfig.h      | 5 ++---
> 3 files changed, 6 insertions(+), 7 deletions(-)
>
>diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c
>index ddd2661..887e571 100644
>--- a/arch/x86/mm/kaslr.c
>+++ b/arch/x86/mm/kaslr.c
>@@ -104,10 +104,10 @@ void __init kernel_randomize_memory(void)
> 	 * consistent with the vaddr_start/vaddr_end variables.
> 	 */
> 	BUILD_BUG_ON(vaddr_start >= vaddr_end);
>-	BUILD_BUG_ON(config_enabled(CONFIG_X86_ESPFIX64) &&
>+	BUILD_BUG_ON(IS_ENABLED(CONFIG_X86_ESPFIX64) &&
> 		     vaddr_end >= EFI_VA_START);
>-	BUILD_BUG_ON((config_enabled(CONFIG_X86_ESPFIX64) ||
>-		      config_enabled(CONFIG_EFI)) &&
>+	BUILD_BUG_ON((IS_ENABLED(CONFIG_X86_ESPFIX64) ||
>+		      IS_ENABLED(CONFIG_EFI)) &&
> 		     vaddr_end >= __START_KERNEL_map);
> 	BUILD_BUG_ON(vaddr_end > __START_KERNEL_map);
> 
>diff --git a/include/asm-generic/export.h
>b/include/asm-generic/export.h
>index 43199a0..63554e9 100644
>--- a/include/asm-generic/export.h
>+++ b/include/asm-generic/export.h
>@@ -70,7 +70,7 @@
> #include <generated/autoksyms.h>
> 
> #define __EXPORT_SYMBOL(sym, val, sec)				\
>-	__cond_export_sym(sym, val, sec, config_enabled(__KSYM_##sym))
>+	__cond_export_sym(sym, val, sec, __is_defined(__KSYM_##sym))
> #define __cond_export_sym(sym, val, sec, conf)			\
> 	___cond_export_sym(sym, val, sec, conf)
> #define ___cond_export_sym(sym, val, sec, enabled)		\
>diff --git a/include/linux/kconfig.h b/include/linux/kconfig.h
>index 15ec117..8f2e059 100644
>--- a/include/linux/kconfig.h
>+++ b/include/linux/kconfig.h
>@@ -31,7 +31,6 @@
>* When CONFIG_BOOGER is not defined, we generate a (... 1, 0) pair, and
>when
>  * the last step cherry picks the 2nd arg, we get a zero.
>  */
>-#define config_enabled(cfg)		___is_defined(cfg)
> #define __is_defined(x)			___is_defined(x)
> #define ___is_defined(val)		____is_defined(__ARG_PLACEHOLDER_##val)
>#define ____is_defined(arg1_or_junk)	__take_second_arg(arg1_or_junk 1,
>0)
>@@ -41,13 +40,13 @@
>  * otherwise. For boolean options, this is equivalent to
>  * IS_ENABLED(CONFIG_FOO).
>  */
>-#define IS_BUILTIN(option) config_enabled(option)
>+#define IS_BUILTIN(option) __is_defined(option)
> 
> /*
>  * IS_MODULE(CONFIG_FOO) evaluates to 1 if CONFIG_FOO is set to 'm', 0
>  * otherwise.
>  */
>-#define IS_MODULE(option) config_enabled(option##_MODULE)
>+#define IS_MODULE(option) __is_defined(option##_MODULE)
> 
> /*
>  * IS_REACHABLE(CONFIG_FOO) evaluates to 1 if the currently compiled

How is __is_defined() different from defined()?
-- 
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