kconfig.h

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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __LINUX_KCONFIG_H
#define __LINUX_KCONFIG_H
 
/*
 * DCL delta: mainline includes <generated/autoconf.h>, the kbuild output.
 * This tree has no kbuild, and the CONFIG_ table it would have produced is
 * written by hand in <linux/autoconf.h>, so the include is retargeted and
 * nothing else changes.  autoconf.h has no includes of its own, so this
 * cannot cycle back through <linux/kernel.h>.
 */
#include <linux/autoconf.h>
 
#ifdef CONFIG_CPU_BIG_ENDIAN
#define __BIG_ENDIAN 4321
#else
#define __LITTLE_ENDIAN 1234
#endif
 
#define __ARG_PLACEHOLDER_1 0,
#define __take_second_arg(__ignored, val, ...) val
 
/*
 * The use of "&&" / "||" is limited in certain expressions.
 * The following 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.
 */
 
/*
 * Getting something that works in C and CPP for an arg that may or may
 * not be defined is tricky.  Here, if we have "#define CONFIG_BOOGER 1"
 * we match on the placeholder define, insert the "0," for arg1 and generate
 * the triplet (0, 1, 0).  Then the last step cherry picks the 2nd arg (a one).
 * 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 __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)
 
/*
 * IS_BUILTIN(CONFIG_FOO) evaluates to 1 if CONFIG_FOO is set to 'y', 0
 * otherwise. For boolean options, this is equivalent to
 * IS_ENABLED(CONFIG_FOO).
 */
#define IS_BUILTIN(option) __is_defined(option)
 
/*
 * IS_MODULE(CONFIG_FOO) evaluates to 1 if CONFIG_FOO is set to 'm', 0
 * otherwise.  CONFIG_FOO=m results in "#define CONFIG_FOO_MODULE 1" in
 * autoconf.h.
 */
#define IS_MODULE(option) __is_defined(option##_MODULE)
 
/*
 * IS_REACHABLE(CONFIG_FOO) evaluates to 1 if the currently compiled
 * code can call a function defined in code compiled based on CONFIG_FOO.
 * 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) __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.  Note that CONFIG_FOO=y results in "#define CONFIG_FOO 1" in
 * autoconf.h, while CONFIG_FOO=m results in "#define CONFIG_FOO_MODULE 1".
 */
#define IS_ENABLED(option) __or(IS_BUILTIN(option), IS_MODULE(option))
 
#endif /* __LINUX_KCONFIG_H */