Messages in this thread | | | Subject | Re: [PATCH] kconfig.h: explain IS_MODULE(), IS_ENABLED() | From | Randy Dunlap <> | Date | Tue, 1 Jun 2021 14:53:45 -0700 |
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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
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