include/linux/kconfig.h

   1 #ifndef __LINUX_KCONFIG_H
   2 #define __LINUX_KCONFIG_H
   3
   4 #include <generated/autoconf.h>
   5
   6 #define __ARG_PLACEHOLDER_1 0,
   7 #define __take_second_arg(__ignored, val, ...) val
   8
   9 /*
  10  * The use of "&&" / "||" is limited in certain expressions.
  11  * The following enable to calculate "and" / "or" with macro expansion only.
  12  */
  13 #define __and(x, y)                     ___and(x, y)
  14 #define ___and(x, y)                    ____and(__ARG_PLACEHOLDER_##x, y)
  15 #define ____and(arg1_or_junk, y)        __take_second_arg(arg1_or_junk y, 0)
  16
  17 #define __or(x, y)                      ___or(x, y)
  18 #define ___or(x, y)                     ____or(__ARG_PLACEHOLDER_##x, y)
  19 #define ____or(arg1_or_junk, y)         __take_second_arg(arg1_or_junk 1, y)
  20
  21 /*
  22  * Helper macros to use CONFIG_ options in C/CPP expressions. Note that
  23  * these only work with boolean and tristate options.
  24  */
  25
  26 /*
  27  * Getting something that works in C and CPP for an arg that may or may
  28  * not be defined is tricky.  Here, if we have "#define CONFIG_BOOGER 1"
  29  * we match on the placeholder define, insert the "0," for arg1 and generate
  30  * the triplet (0, 1, 0).  Then the last step cherry picks the 2nd arg (a one).
  31  * When CONFIG_BOOGER is not defined, we generate a (... 1, 0) pair, and when
  32  * the last step cherry picks the 2nd arg, we get a zero.
  33  */
  34 #define __is_defined(x)                 ___is_defined(x)
  35 #define ___is_defined(val)              ____is_defined(__ARG_PLACEHOLDER_##val)
  36 #define ____is_defined(arg1_or_junk)    __take_second_arg(arg1_or_junk 1, 0)
  37
  38 /*
  39  * IS_BUILTIN(CONFIG_FOO) evaluates to 1 if CONFIG_FOO is set to 'y', 0
  40  * otherwise. For boolean options, this is equivalent to
  41  * IS_ENABLED(CONFIG_FOO).
  42  */
  43 #define IS_BUILTIN(option) __is_defined(option)
  44
  45 /*
  46  * IS_MODULE(CONFIG_FOO) evaluates to 1 if CONFIG_FOO is set to 'm', 0
  47  * otherwise.
  48  */
  49 #define IS_MODULE(option) __is_defined(option##_MODULE)
  50
  51 /*
  52  * IS_REACHABLE(CONFIG_FOO) evaluates to 1 if the currently compiled
  53  * code can call a function defined in code compiled based on CONFIG_FOO.
  54  * This is similar to IS_ENABLED(), but returns false when invoked from
  55  * built-in code when CONFIG_FOO is set to 'm'.
  56  */
  57 #define IS_REACHABLE(option) __or(IS_BUILTIN(option), \
  58                                 __and(IS_MODULE(option), __is_defined(MODULE)))
  59
  60 /*
  61  * IS_ENABLED(CONFIG_FOO) evaluates to 1 if CONFIG_FOO is set to 'y' or 'm',
  62  * 0 otherwise.
  63  */
  64 #define IS_ENABLED(option) __or(IS_BUILTIN(option), IS_MODULE(option))
  65
  66 #endif /* __LINUX_KCONFIG_H */