LXR linux/include/linux/kconfig.h

   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 */
  74