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>
1 file changed