diff options
| author | Bjorn Helgaas <bhelgaas@google.com> | 2021-06-01 16:31:43 -0500 |
|---|---|---|
| committer | Masahiro Yamada <masahiroy@kernel.org> | 2021-06-05 23:49:46 +0900 |
| commit | c7c90e121e992eefdf07945e5a6e9cf097b29463 (patch) | |
| tree | ecf6d93c6f42294695b874c2d78e3d058dc52380 /include/linux/kconfig.h | |
| parent | 43ac711053fc6d94a3f16141c4efe20059a9d918 (diff) | |
kconfig.h: explain IS_MODULE(), IS_ENABLED()
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>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Diffstat (limited to 'include/linux/kconfig.h')
| -rw-r--r-- | include/linux/kconfig.h | 6 |
1 files 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)) |