Linux kernel mirror (for testing)
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1/* SPDX-License-Identifier: MIT */
2/* Copyright © 2026 Intel Corporation */
3
4#ifndef _PICK_H_
5#define _PICK_H_
6
7/*
8 * Given the first two numbers __a and __b of arbitrarily many evenly spaced
9 * numbers, pick the 0-based __index'th value.
10 *
11 * Always prefer this over _PICK() if the numbers are evenly spaced.
12 */
13#define _PICK_EVEN(__index, __a, __b) ((__a) + (__index) * ((__b) - (__a)))
14
15/*
16 * Like _PICK_EVEN(), but supports 2 ranges of evenly spaced address offsets.
17 * @__c_index corresponds to the index in which the second range starts to be
18 * used. Using math interval notation, the first range is used for indexes [ 0,
19 * @__c_index), while the second range is used for [ @__c_index, ... ). Example:
20 *
21 * #define _FOO_A 0xf000
22 * #define _FOO_B 0xf004
23 * #define _FOO_C 0xf008
24 * #define _SUPER_FOO_A 0xa000
25 * #define _SUPER_FOO_B 0xa100
26 * #define FOO(x) _MMIO(_PICK_EVEN_2RANGES(x, 3, \
27 * _FOO_A, _FOO_B, \
28 * _SUPER_FOO_A, _SUPER_FOO_B))
29 *
30 * This expands to:
31 * 0: 0xf000,
32 * 1: 0xf004,
33 * 2: 0xf008,
34 * 3: 0xa000,
35 * 4: 0xa100,
36 * 5: 0xa200,
37 * ...
38 */
39#define _PICK_EVEN_2RANGES(__index, __c_index, __a, __b, __c, __d) \
40 (BUILD_BUG_ON_ZERO(!__is_constexpr(__c_index)) + \
41 ((__index) < (__c_index) ? _PICK_EVEN(__index, __a, __b) : \
42 _PICK_EVEN((__index) - (__c_index), __c, __d)))
43
44/*
45 * Given the arbitrary numbers in varargs, pick the 0-based __index'th number.
46 *
47 * Always prefer _PICK_EVEN() over this if the numbers are evenly spaced.
48 */
49#define _PICK(__index, ...) (((const u32 []){ __VA_ARGS__ })[__index])
50
51#endif