1 /* SPDX-License-Identifier: GPL-2.0-only */ 2 /* 3 * Copyright (C) 2014 Felix Fietkau <nbd@nbd.name> 4 * Copyright (C) 2004 - 2009 Ivo van Doorn <IvDoorn@gmail.com> 5 */ 6 7 #ifndef _LINUX_BITFIELD_H 8 #define _LINUX_BITFIELD_H 9 10 #include <linux/build_bug.h> 11 #include <linux/kernel.h> 12 #include <linux/bitfield-fix-width.h> 13 14 /* 15 * Bitfield access macros 16 * 17 * FIELD_{GET,PREP} macros take as first parameter shifted mask 18 * from which they extract the base mask and shift amount. 19 * Mask must be a compilation time constant. 20 * 21 * Example: 22 * 23 * #define REG_FIELD_A GENMASK(6, 0) 24 * #define REG_FIELD_B BIT(7) 25 * #define REG_FIELD_C GENMASK(15, 8) 26 * #define REG_FIELD_D GENMASK(31, 16) 27 * 28 * Get: 29 * a = FIELD_GET(REG_FIELD_A, reg); 30 * b = FIELD_GET(REG_FIELD_B, reg); 31 * 32 * Set: 33 * reg = FIELD_PREP(REG_FIELD_A, 1) | 34 * FIELD_PREP(REG_FIELD_B, 0) | 35 * FIELD_PREP(REG_FIELD_C, c) | 36 * FIELD_PREP(REG_FIELD_D, 0x40); 37 * 38 * Modify: 39 * reg &= ~REG_FIELD_C; 40 * reg |= FIELD_PREP(REG_FIELD_C, c); 41 */ 42 43 #define __bf_shf(x) (__builtin_ffsll(x) - 1) 44 45 #define __scalar_type_to_unsigned_cases(type) \ 46 unsigned type: (unsigned type)0, \ 47 signed type: (unsigned type)0 48 49 #define __unsigned_scalar_typeof(x) typeof( \ 50 _Generic((x), \ 51 char: (unsigned char)0, \ 52 __scalar_type_to_unsigned_cases(char), \ 53 __scalar_type_to_unsigned_cases(short), \ 54 __scalar_type_to_unsigned_cases(int), \ 55 __scalar_type_to_unsigned_cases(long), \ 56 __scalar_type_to_unsigned_cases(long long), \ 57 default: (x))) 58 59 #define __bf_cast_unsigned(type, x) ((__unsigned_scalar_typeof(type))(x)) 60 61 #define __BF_FIELD_CHECK(_mask, _reg, _val, _pfx) \ 62 ({ \ 63 BUILD_BUG_ON_MSG(!__builtin_constant_p(_mask), \ 64 _pfx "mask is not constant"); \ 65 BUILD_BUG_ON_MSG((_mask) == 0, _pfx "mask is zero"); \ 66 BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ? \ 67 ~((_mask) >> __bf_shf(_mask)) & (_val) : 0, \ 68 _pfx "value too large for the field"); \ 69 BUILD_BUG_ON_MSG(__bf_cast_unsigned(_mask, _mask) > \ 70 __bf_cast_unsigned(_reg, ~0ull), \ 71 _pfx "type of reg too small for mask"); \ 72 __BUILD_BUG_ON_NOT_POWER_OF_2((_mask) + \ 73 (1ULL << __bf_shf(_mask))); \ 74 }) 75 76 /** 77 * FIELD_MAX() - produce the maximum value representable by a field 78 * @_mask: shifted mask defining the field's length and position 79 * 80 * FIELD_MAX() returns the maximum value that can be held in the field 81 * specified by @_mask. 82 */ 83 #define FIELD_MAX(_mask) \ 84 ({ \ 85 __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_MAX: "); \ 86 (typeof(_mask))((_mask) >> __bf_shf(_mask)); \ 87 }) 88 89 /** 90 * FIELD_FIT() - check if value fits in the field 91 * @_mask: shifted mask defining the field's length and position 92 * @_val: value to test against the field 93 * 94 * Return: true if @_val can fit inside @_mask, false if @_val is too big. 95 */ 96 #define FIELD_FIT(_mask, _val) \ 97 ({ \ 98 __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_FIT: "); \ 99 !((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask)); \ 100 }) 101 102 /** 103 * FIELD_PREP() - prepare a bitfield element 104 * @_mask: shifted mask defining the field's length and position 105 * @_val: value to put in the field 106 * 107 * FIELD_PREP() masks and shifts up the value. The result should 108 * be combined with other fields of the bitfield using logical OR. 109 */ 110 #define FIELD_PREP(_mask, _val) \ 111 ({ \ 112 __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: "); \ 113 ((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask); \ 114 }) 115 116 /** 117 * FIELD_GET() - extract a bitfield element 118 * @_mask: shifted mask defining the field's length and position 119 * @_reg: value of entire bitfield 120 * 121 * FIELD_GET() extracts the field specified by @_mask from the 122 * bitfield passed in as @_reg by masking and shifting it down. 123 */ 124 #define FIELD_GET(_mask, _reg) \ 125 ({ \ 126 __BF_FIELD_CHECK(_mask, _reg, 0U, "FIELD_GET: "); \ 127 (typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask)); \ 128 }) 129 130 #endif 131