root/include/linux/kconfig.h

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INCLUDED FROM

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