include/linux/kconfig.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef __LINUX_KCONFIG_H
   3 #define __LINUX_KCONFIG_H
   4
   5 /* CONFIG_CC_VERSION_TEXT (Do not delete this comment. See help in Kconfig) */
   6
   7 #include <generated/autoconf.h>
   8
   9 #ifdef CONFIG_CPU_BIG_ENDIAN
  10 #define __BIG_ENDIAN 4321
  11 #else
  12 #define __LITTLE_ENDIAN 1234
  13 #endif
  14
  15 #define __ARG_PLACEHOLDER_1 0,
  16 #define __take_second_arg(__ignored, val, ...) val
  17
  18 /*
  19  * The use of "&&" / "||" is limited in certain expressions.
  20  * The following enable to calculate "and" / "or" with macro expansion only.
  21  */
  22 #define __and(x, y)                     ___and(x, y)
  23 #define ___and(x, y)                    ____and(__ARG_PLACEHOLDER_##x, y)
  24 #define ____and(arg1_or_junk, y)        __take_second_arg(arg1_or_junk y, 0)
  25
  26 #define __or(x, y)                      ___or(x, y)
  27 #define ___or(x, y)                     ____or(__ARG_PLACEHOLDER_##x, y)
  28 #define ____or(arg1_or_junk, y)         __take_second_arg(arg1_or_junk 1, y)
  29
  30 /*
  31  * Helper macros to use CONFIG_ options in C/CPP expressions. Note that
  32  * these only work with boolean and tristate options.
  33  */
  34
  35 /*
  36  * Getting something that works in C and CPP for an arg that may or may
  37  * not be defined is tricky.  Here, if we have "#define CONFIG_BOOGER 1"
  38  * we match on the placeholder define, insert the "0," for arg1 and generate
  39  * the triplet (0, 1, 0).  Then the last step cherry picks the 2nd arg (a one).
  40  * When CONFIG_BOOGER is not defined, we generate a (... 1, 0) pair, and when
  41  * the last step cherry picks the 2nd arg, we get a zero.
  42  */
  43 #define __is_defined(x)                 ___is_defined(x)
  44 #define ___is_defined(val)              ____is_defined(__ARG_PLACEHOLDER_##val)
  45 #define ____is_defined(arg1_or_junk)    __take_second_arg(arg1_or_junk 1, 0)
  46
  47 /*
  48  * IS_BUILTIN(CONFIG_FOO) evaluates to 1 if CONFIG_FOO is set to 'y', 0
  49  * otherwise. For boolean options, this is equivalent to
  50  * IS_ENABLED(CONFIG_FOO).
  51  */
  52 #define IS_BUILTIN(option) __is_defined(option)
  53
  54 /*
  55  * IS_MODULE(CONFIG_FOO) evaluates to 1 if CONFIG_FOO is set to 'm', 0
  56  * otherwise.
  57  */
  58 #define IS_MODULE(option) __is_defined(option##_MODULE)
  59
  60 /*
  61  * IS_REACHABLE(CONFIG_FOO) evaluates to 1 if the currently compiled
  62  * code can call a function defined in code compiled based on CONFIG_FOO.
  63  * This is similar to IS_ENABLED(), but returns false when invoked from
  64  * built-in code when CONFIG_FOO is set to 'm'.
  65  */
  66 #define IS_REACHABLE(option) __or(IS_BUILTIN(option), \
  67                                 __and(IS_MODULE(option), __is_defined(MODULE)))
  68
  69 /*
  70  * IS_ENABLED(CONFIG_FOO) evaluates to 1 if CONFIG_FOO is set to 'y' or 'm',
  71  * 0 otherwise.
  72  */
  73 #define IS_ENABLED(option) __or(IS_BUILTIN(option), IS_MODULE(option))
  74
  75 #endif /* __LINUX_KCONFIG_H */