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SubjectRe: [PATCH] kconfig.h: explain IS_MODULE(), IS_ENABLED()
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

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