linux-kernel - Re: [PATCH] kconfig.h: explain IS_MODULE(), IS

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Date:   Sat, 5 Jun 2021 23:47:37 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Randy Dunlap <rdunlap@...radead.org>,
        Bjorn Helgaas <helgaas@...nel.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Arnd Bergmann <arnd@...db.de>,
        Paul Cercueil <paul@...pouillou.net>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH] kconfig.h: explain IS_MODULE(), IS_ENABLED()

On Wed, Jun 2, 2021 at 6:53 AM Randy Dunlap <rdunlap@...radead.org> wrote:
>
> On 6/1/21 2:31 PM, Bjorn Helgaas wrote:
> > From: Bjorn Helgaas <bhelgaas@...gle.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@...gle.com>
>
> Acked-by: Randy Dunlap <rdunlap@...radead.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