1/*-
2 * SPDX-License-Identifier: BSD-2-Clause
3 *
4 * Copyright (c) 2020 The FreeBSD Foundation
5 *
6 * This software was developed by Bj��rn Zeeb under sponsorship from
7 * the FreeBSD Foundation.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 *    notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 *    notice, this list of conditions and the following disclaimer in the
16 *    documentation and/or other materials provided with the distribution.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 * SUCH DAMAGE.
29 */
30
31#ifndef	_LINUXKPI_LINUX_KCONFIG_H_
32#define	_LINUXKPI_LINUX_KCONFIG_H_
33
34/*
35 * Checking if an option is defined would be easy if we could do CPP inside CPP.
36 * The defined case whether -Dxxx or -Dxxx=1 are easy to deal with.  In either
37 * case the defined value is "1". A more general -Dxxx=<c> case will require
38 * more effort to deal with all possible "true" values. Hope we do not have
39 * to do this as well.
40 * The real problem is the undefined case.  To avoid this problem we do the
41 * concat/varargs trick: "yyy" ## xxx can make two arguments if xxx is "1"
42 * by having a #define for yyy_1 which is "ignore,".
43 * Otherwise we will just get "yyy".
44 * Need to be careful about variable substitutions in macros though.
45 * This way we make a (true, false) problem a (don't care, true, false) or a
46 * (don't care true, false).  Then we can use a variadic macro to only select
47 * the always well known and defined argument #2.  And that seems to be
48 * exactly what we need.  Use 1 for true and 0 for false to also allow
49 * #if IS_*() checks pre-compiler checks which do not like #if true.
50 */
51#define ___XAB_1		dontcare,
52#define ___IS_XAB(_ignore, _x, ...)	(_x)
53#define	__IS_XAB(_x)		___IS_XAB(_x 1, 0)
54#define	_IS_XAB(_x)		__IS_XAB(__CONCAT(___XAB_, _x))
55
56/* This is if CONFIG_ccc=y. */
57#define	IS_BUILTIN(_x)		_IS_XAB(_x)
58/* This is if CONFIG_ccc=m. */
59#define	IS_MODULE(_x)		_IS_XAB(_x ## _MODULE)
60/* This is if CONFIG_ccc is compiled in(=y) or a module(=m). */
61#define	IS_ENABLED(_x)		(IS_BUILTIN(_x) || IS_MODULE(_x))
62/*
63 * This is weird case.  If the CONFIG_ccc is builtin (=y) this returns true;
64 * or if the CONFIG_ccc is a module (=m) and the caller is built as a module
65 * (-DMODULE defined) this returns true, but if the callers is not a module
66 * (-DMODULE not defined, which means caller is BUILTIN) then it returns
67 * false.  In other words, a module can reach the kernel, a module can reach
68 * a module, but the kernel cannot reach a module, and code never compiled
69 * cannot be reached either.
70 * XXX -- I'd hope the module-to-module case would be handled by a proper
71 * module dependency definition (MODULE_DEPEND() in FreeBSD).
72 */
73#define	IS_REACHABLE(_x)	(IS_BUILTIN(_x) || \
74				    (IS_MODULE(_x) && IS_BUILTIN(MODULE)))
75
76#endif /* _LINUXKPI_LINUX_KCONFIG_H_ */
77