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* [PATCH] kconfig.h: explain IS_MODULE(), IS_ENABLED()
@ 2021-06-01 21:31 Bjorn Helgaas
  2021-06-01 21:53 ` Randy Dunlap
  0 siblings, 1 reply; 3+ messages in thread
From: Bjorn Helgaas @ 2021-06-01 21:31 UTC (permalink / raw)
  To: linux-kernel
  Cc: Masahiro Yamada, Kees Cook, Linus Walleij, Arnd Bergmann,
	Paul Cercueil, Krzysztof Wilczyński, Bjorn Helgaas

From: Bjorn Helgaas <bhelgaas@google.com>

Extend IS_MODULE() and IS_ENABLED comments to explain why one might use
"#if IS_ENABLED(CONFIG_FOO)" instead of "#ifdef CONFIG_FOO".

To wit, "#ifdef CONFIG_FOO" is true only for CONFIG_FOO=y, while
"#if IS_ENABLED(CONFIG_FOO)" is true for both CONFIG_FOO=y and
CONFIG_FOO=m.

This is because "CONFIG_FOO=m" in .config does not result in "CONFIG_FOO"
being defined.  The actual definitions are in autoconf.h, where:

  CONFIG_FOO=y   results in   #define CONFIG_FOO 1
  CONFIG_FOO=m   results in   #define CONFIG_FOO_MODULE 1

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
---
 include/linux/kconfig.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/linux/kconfig.h b/include/linux/kconfig.h
index cc8fa109cfa3..20d1079e92b4 100644
--- a/include/linux/kconfig.h
+++ b/include/linux/kconfig.h
@@ -51,7 +51,8 @@
 
 /*
  * IS_MODULE(CONFIG_FOO) evaluates to 1 if CONFIG_FOO is set to 'm', 0
- * otherwise.
+ * otherwise.  CONFIG_FOO=m results in "#define CONFIG_FOO_MODULE 1" in
+ * autoconf.h.
  */
 #define IS_MODULE(option) __is_defined(option##_MODULE)
 
@@ -66,7 +67,8 @@
 
 /*
  * IS_ENABLED(CONFIG_FOO) evaluates to 1 if CONFIG_FOO is set to 'y' or 'm',
- * 0 otherwise.
+ * 0 otherwise.  Note that CONFIG_FOO=y results in "#define CONFIG_FOO 1" in
+ * autoconf.h, while CONFIG_FOO=m results in "#define CONFIG_FOO_MODULE 1".
  */
 #define IS_ENABLED(option) __or(IS_BUILTIN(option), IS_MODULE(option))
 
-- 
2.25.1


^ permalink raw reply related	[flat|nested] 3+ messages in thread
* Re: [PATCH] kconfig.h: explain IS_MODULE(), IS_ENABLED()
  2021-06-01 21:31 [PATCH] kconfig.h: explain IS_MODULE(), IS_ENABLED() Bjorn Helgaas
@ 2021-06-01 21:53 ` Randy Dunlap
  2021-06-05 14:47   ` Masahiro Yamada
  0 siblings, 1 reply; 3+ messages in thread
From: Randy Dunlap @ 2021-06-01 21:53 UTC (permalink / raw)
  To: Bjorn Helgaas, linux-kernel
  Cc: Masahiro Yamada, Kees Cook, Linus Walleij, Arnd Bergmann,
	Paul Cercueil, Krzysztof Wilczyński, Bjorn Helgaas

On 6/1/21 2:31 PM, Bjorn Helgaas wrote:
> From: Bjorn Helgaas <bhelgaas@google.com>
> 
> Extend IS_MODULE() and IS_ENABLED comments to explain why one might use
> "#if IS_ENABLED(CONFIG_FOO)" instead of "#ifdef CONFIG_FOO".
> 
> To wit, "#ifdef CONFIG_FOO" is true only for CONFIG_FOO=y, while
> "#if IS_ENABLED(CONFIG_FOO)" is true for both CONFIG_FOO=y and
> CONFIG_FOO=m.
> 
> This is because "CONFIG_FOO=m" in .config does not result in "CONFIG_FOO"
> being defined.  The actual definitions are in autoconf.h, where:
> 
>   CONFIG_FOO=y   results in   #define CONFIG_FOO 1
>   CONFIG_FOO=m   results in   #define CONFIG_FOO_MODULE 1
> 
> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

Acked-by: Randy Dunlap <rdunlap@infradead.org>


Thanks.

> ---
>  include/linux/kconfig.h | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/kconfig.h b/include/linux/kconfig.h
> index cc8fa109cfa3..20d1079e92b4 100644
> --- a/include/linux/kconfig.h
> +++ b/include/linux/kconfig.h
> @@ -51,7 +51,8 @@
>  
>  /*
>   * IS_MODULE(CONFIG_FOO) evaluates to 1 if CONFIG_FOO is set to 'm', 0
> - * otherwise.
> + * otherwise.  CONFIG_FOO=m results in "#define CONFIG_FOO_MODULE 1" in
> + * autoconf.h.
>   */
>  #define IS_MODULE(option) __is_defined(option##_MODULE)
>  
> @@ -66,7 +67,8 @@
>  
>  /*
>   * IS_ENABLED(CONFIG_FOO) evaluates to 1 if CONFIG_FOO is set to 'y' or 'm',
> - * 0 otherwise.
> + * 0 otherwise.  Note that CONFIG_FOO=y results in "#define CONFIG_FOO 1" in
> + * autoconf.h, while CONFIG_FOO=m results in "#define CONFIG_FOO_MODULE 1".
>   */
>  #define IS_ENABLED(option) __or(IS_BUILTIN(option), IS_MODULE(option))
>  
> 


-- 
~Randy


^ permalink raw reply	[flat|nested] 3+ messages in thread
* Re: [PATCH] kconfig.h: explain IS_MODULE(), IS_ENABLED()
  2021-06-01 21:53 ` Randy Dunlap
@ 2021-06-05 14:47   ` Masahiro Yamada
  0 siblings, 0 replies; 3+ messages in thread
From: Masahiro Yamada @ 2021-06-05 14:47 UTC (permalink / raw)
  To: Randy Dunlap, Bjorn Helgaas
  Cc: Linux Kernel Mailing List, Kees Cook, Linus Walleij,
	Arnd Bergmann, Paul Cercueil, Krzysztof Wilczyński,
	Bjorn Helgaas

On Wed, Jun 2, 2021 at 6:53 AM Randy Dunlap <rdunlap@infradead.org> wrote:
>
> On 6/1/21 2:31 PM, Bjorn Helgaas wrote:
> > From: Bjorn Helgaas <bhelgaas@google.com>
> >
> > Extend IS_MODULE() and IS_ENABLED comments to explain why one might use
> > "#if IS_ENABLED(CONFIG_FOO)" instead of "#ifdef CONFIG_FOO".
> >
> > To wit, "#ifdef CONFIG_FOO" is true only for CONFIG_FOO=y, while
> > "#if IS_ENABLED(CONFIG_FOO)" is true for both CONFIG_FOO=y and
> > CONFIG_FOO=m.
> >
> > This is because "CONFIG_FOO=m" in .config does not result in "CONFIG_FOO"
> > being defined.  The actual definitions are in autoconf.h, where:
> >
> >   CONFIG_FOO=y   results in   #define CONFIG_FOO 1
> >   CONFIG_FOO=m   results in   #define CONFIG_FOO_MODULE 1
> >
> > Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
>
> Acked-by: Randy Dunlap <rdunlap@infradead.org>
>



Applied to linux-kbuild. Thanks.




> Thanks.
>
> > ---
> >  include/linux/kconfig.h | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/linux/kconfig.h b/include/linux/kconfig.h
> > index cc8fa109cfa3..20d1079e92b4 100644
> > --- a/include/linux/kconfig.h
> > +++ b/include/linux/kconfig.h
> > @@ -51,7 +51,8 @@
> >
> >  /*
> >   * IS_MODULE(CONFIG_FOO) evaluates to 1 if CONFIG_FOO is set to 'm', 0
> > - * otherwise.
> > + * otherwise.  CONFIG_FOO=m results in "#define CONFIG_FOO_MODULE 1" in
> > + * autoconf.h.
> >   */
> >  #define IS_MODULE(option) __is_defined(option##_MODULE)
> >
> > @@ -66,7 +67,8 @@
> >
> >  /*
> >   * IS_ENABLED(CONFIG_FOO) evaluates to 1 if CONFIG_FOO is set to 'y' or 'm',
> > - * 0 otherwise.
> > + * 0 otherwise.  Note that CONFIG_FOO=y results in "#define CONFIG_FOO 1" in
> > + * autoconf.h, while CONFIG_FOO=m results in "#define CONFIG_FOO_MODULE 1".
> >   */
> >  #define IS_ENABLED(option) __or(IS_BUILTIN(option), IS_MODULE(option))
> >
> >
>
>
> --
> ~Randy
>


-- 
Best Regards
Masahiro Yamada

^ permalink raw reply	[flat|nested] 3+ messages in thread
end of thread, other threads:[~2021-06-05 14:48 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2021-06-01 21:31 [PATCH] kconfig.h: explain IS_MODULE(), IS_ENABLED() Bjorn Helgaas
2021-06-01 21:53 ` Randy Dunlap
2021-06-05 14:47   ` Masahiro Yamada

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