Messages in this thread | | | From | Masahiro Yamada <> | Date | Sat, 5 Jun 2021 23:47:37 +0900 | Subject | Re: [PATCH] kconfig.h: explain IS_MODULE(), IS_ENABLED() |
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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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