Commit 5e8754fd authored by Masahiro Yamada's avatar Masahiro Yamada Committed by Michal Marek
Browse files

kconfig.h: allow to use IS_{ENABLE,REACHABLE} in macro expansion 



The typical usage of IS_ENABLED() is

    if (IS_ENABLED(CONFIG_FOO)) {
            ...
    }

or

    #if IS_ENABLED(CONFIG_FOO)
            ...
    #endif

The current implementation of IS_ENABLED() includes "||" operator,
which works well in those expressions like above.

However, there is a case where we want to evaluate a config option
beyond those use cases.

For example, the OF_TABLE() in include/asm-generic/vmlinux.lds.h
needs to evaluate a config option in macro expansion:

  #define ___OF_TABLE(cfg, name)  _OF_TABLE_##cfg(name)
  #define __OF_TABLE(cfg, name)   ___OF_TABLE(cfg, name)
  #define OF_TABLE(cfg, name)     __OF_TABLE(config_enabled(cfg), name)
  #define _OF_TABLE_0(name)
  #define _OF_TABLE_1(name)  \
          ...

Here, we can not use IS_ENABLED() because of the "||" operator in
its define.  It is true config_enabled() works well, but it is a bit
ambiguous to be used against config options.

This commit makes IS_ENABLED() available in more generic context by
calculating "or" with macro expansion only.

Do likewise for IS_REACHABLE().

Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: default avatarMichal Marek <mmarek@suse.com>
parent 05a25c8e

include/linux/kconfig.h

+18 −6
Original line number Diff line number Diff line
@@ -3,6 +3,21 @@ 


#include <generated/autoconf.h>



#define __ARG_PLACEHOLDER_1 0,

#define __take_second_arg(__ignored, val, ...) val



/*

 * The use of "&&" / "||" is limited in certain expressions.

 * The followings enable to calculate "and" / "or" with macro expansion only.

 */

#define __and(x, y)			___and(x, y)

#define ___and(x, y)			____and(__ARG_PLACEHOLDER_##x, y)

#define ____and(arg1_or_junk, y)	__take_second_arg(arg1_or_junk y, 0)



#define __or(x, y)			___or(x, y)

#define ___or(x, y)			____or(__ARG_PLACEHOLDER_##x, y)

#define ____or(arg1_or_junk, y)		__take_second_arg(arg1_or_junk 1, y)



/*

 * Helper macros to use CONFIG_ options in C/CPP expressions. Note that

 * these only work with boolean and tristate options.
@@ -16,12 +31,10 @@ 
 * When CONFIG_BOOGER is not defined, we generate a (... 1, 0) pair, and when

 * the last step cherry picks the 2nd arg, we get a zero.

 */

#define __ARG_PLACEHOLDER_1 0,

#define config_enabled(cfg)		___is_defined(cfg)

#define __is_defined(x)			___is_defined(x)

#define ___is_defined(val)		____is_defined(__ARG_PLACEHOLDER_##val)

#define ____is_defined(arg1_or_junk)	__take_second_arg(arg1_or_junk 1, 0)

#define __take_second_arg(__ignored, val, ...) val



/*

 * IS_BUILTIN(CONFIG_FOO) evaluates to 1 if CONFIG_FOO is set to 'y', 0
@@ -42,14 +55,13 @@ 
 * This is similar to IS_ENABLED(), but returns false when invoked from

 * built-in code when CONFIG_FOO is set to 'm'.

 */

#define IS_REACHABLE(option) (IS_BUILTIN(option) || \

		 (IS_MODULE(option) && __is_defined(MODULE)))

#define IS_REACHABLE(option) __or(IS_BUILTIN(option), \

				__and(IS_MODULE(option), __is_defined(MODULE)))



/*

 * IS_ENABLED(CONFIG_FOO) evaluates to 1 if CONFIG_FOO is set to 'y' or 'm',

 * 0 otherwise.

 */

#define IS_ENABLED(option) \

	(IS_BUILTIN(option) || IS_MODULE(option))

#define IS_ENABLED(option) __or(IS_BUILTIN(option), IS_MODULE(option))



#endif /* __LINUX_KCONFIG_H */

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