We want to move from using #ifdef to using if in our code. A lot of our code using #ifdef is structured like:
#ifdef CONFIG_FOO fun(CONFIG_FOO_OPT); #endif
In Kconfig you will find
config FOO bool "enable foo"
config FOO_OPT string "value for foo" depends on FOO
We cannot use CONFIG_FOO_OPT in our code directly if CONFIG_FOO is not defined.
if (IS_ENABLED(CONFIG_FOO) fun(CONFIG_FOO_OPT);
This would result in an error due to the undefined symbol CONFIG_FOO_OPT.
The new macro IF_ENABLED(CONFIG_FOO, opt_cfg, def_val) which evaluates to opt_cfg if CONFIG_FOO is set to 'y' and to def_val otherwise comes to the rescue:
if (IS_ENABLED(CONFIG_FOO) fun(IF_ENABLED(CONFIG_FOO, CONFIG_FOO_OPT, "");
If CONFIG_FOO is not defined, the compiler will see
if (0) fun("");
and be happy.
If CONFIG_FOO is defined, the compiler will see
if (1) fun(CONFIG_FOO_OPT)
and be equally happy.
Signed-off-by: Heinrich Schuchardt heinrich.schuchardt@canonical.com --- v3: new patch --- include/linux/kconfig.h | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/include/linux/kconfig.h b/include/linux/kconfig.h index 2bc704e110..7fea72da1a 100644 --- a/include/linux/kconfig.h +++ b/include/linux/kconfig.h @@ -28,6 +28,13 @@ */ #define IS_ENABLED(option) config_enabled(option, 0)
+/* + * IF_ENABLED(CONFIG_FOO, opt_cfg, def_val) evalutes to opt_cfg if + * CONFIG_FOO is set to 'y' and to def_val otherwise. + */ +#define IF_ENABLED(option, opt_cfg, def_val) \ + config_opt_enabled(IS_ENABLED(option), opt_cfg, def_val) + /* * U-Boot add-on: Helper macros to reference to different macros (prefixed by * CONFIG_, CONFIG_SPL_, CONFIG_TPL_ or CONFIG_TOOLS_), depending on the build