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 <asm/byteorder.h> 12 13 /* 14 * Bitfield access macros 15 * 16 * FIELD_{GET,PREP} macros take as first parameter shifted mask 17 * from which they extract the base mask and shift amount. 18 * Mask must be a compilation time constant. 19 * 20 * Example: 21 * 22 * #define REG_FIELD_A GENMASK(6, 0) 23 * #define REG_FIELD_B BIT(7) 24 * #define REG_FIELD_C GENMASK(15, 8) 25 * #define REG_FIELD_D GENMASK(31, 16) 26 * 27 * Get: 28 * a = FIELD_GET(REG_FIELD_A, reg); 29 * b = FIELD_GET(REG_FIELD_B, reg); 30 * 31 * Set: 32 * reg = FIELD_PREP(REG_FIELD_A, 1) | 33 * FIELD_PREP(REG_FIELD_B, 0) | 34 * FIELD_PREP(REG_FIELD_C, c) | 35 * FIELD_PREP(REG_FIELD_D, 0x40); 36 * 37 * Modify: 38 * reg &= ~REG_FIELD_C; 39 * reg |= FIELD_PREP(REG_FIELD_C, c); 40 */ 41 42 #define __bf_shf(x) (__builtin_ffsll(x) - 1) 43 44 #define __scalar_type_to_unsigned_cases(type) \ 45 unsigned type: (unsigned type)0, \ 46 signed type: (unsigned type)0 47 48 #define __unsigned_scalar_typeof(x) typeof( \ 49 _Generic((x), \ 50 char: (unsigned char)0, \ 51 __scalar_type_to_unsigned_cases(char), \ 52 __scalar_type_to_unsigned_cases(short), \ 53 __scalar_type_to_unsigned_cases(int), \ 54 __scalar_type_to_unsigned_cases(long), \ 55 __scalar_type_to_unsigned_cases(long long), \ 56 default: (x))) 57 58 #define __bf_cast_unsigned(type, x) ((__unsigned_scalar_typeof(type))(x)) 59 60 #define __BF_FIELD_CHECK(_mask, _reg, _val, _pfx) \ 61 ({ \ 62 BUILD_BUG_ON_MSG(!__builtin_constant_p(_mask), \ 63 _pfx "mask is not constant"); \ 64 BUILD_BUG_ON_MSG((_mask) == 0, _pfx "mask is zero"); \ 65 BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ? \ 66 ~((_mask) >> __bf_shf(_mask)) & (_val) : 0, \ 67 _pfx "value too large for the field"); \ 68 BUILD_BUG_ON_MSG(__bf_cast_unsigned(_mask, _mask) > \ 69 __bf_cast_unsigned(_reg, ~0ull), \ 70 _pfx "type of reg too small for mask"); \ 71 __BUILD_BUG_ON_NOT_POWER_OF_2((_mask) + \ 72 (1ULL << __bf_shf(_mask))); \ 73 }) 74 75 /** 76 * FIELD_MAX() - produce the maximum value representable by a field 77 * @_mask: shifted mask defining the field's length and position 78 * 79 * FIELD_MAX() returns the maximum value that can be held in the field 80 * specified by @_mask. 81 */ 82 #define FIELD_MAX(_mask) \ 83 ({ \ 84 __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_MAX: "); \ 85 (typeof(_mask))((_mask) >> __bf_shf(_mask)); \ 86 }) 87 88 /** 89 * FIELD_FIT() - check if value fits in the field 90 * @_mask: shifted mask defining the field's length and position 91 * @_val: value to test against the field 92 * 93 * Return: true if @_val can fit inside @_mask, false if @_val is too big. 94 */ 95 #define FIELD_FIT(_mask, _val) \ 96 ({ \ 97 __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_FIT: "); \ 98 !((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask)); \ 99 }) 100 101 /** 102 * FIELD_PREP() - prepare a bitfield element 103 * @_mask: shifted mask defining the field's length and position 104 * @_val: value to put in the field 105 * 106 * FIELD_PREP() masks and shifts up the value. The result should 107 * be combined with other fields of the bitfield using logical OR. 108 */ 109 #define FIELD_PREP(_mask, _val) \ 110 ({ \ 111 __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: "); \ 112 ((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask); \ 113 }) 114 115 /** 116 * FIELD_GET() - extract a bitfield element 117 * @_mask: shifted mask defining the field's length and position 118 * @_reg: value of entire bitfield 119 * 120 * FIELD_GET() extracts the field specified by @_mask from the 121 * bitfield passed in as @_reg by masking and shifting it down. 122 */ 123 #define FIELD_GET(_mask, _reg) \ 124 ({ \ 125 __BF_FIELD_CHECK(_mask, _reg, 0U, "FIELD_GET: "); \ 126 (typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask)); \ 127 }) 128 129 extern void __compiletime_error("value doesn't fit into mask") 130 __field_overflow(void); 131 extern void __compiletime_error("bad bitfield mask") 132 __bad_mask(void); field_multiplier(u64 field)133 static __always_inline u64 field_multiplier(u64 field) 134 { 135 if ((field | (field - 1)) & ((field | (field - 1)) + 1)) 136 __bad_mask(); 137 return field & -field; 138 } field_mask(u64 field)139 static __always_inline u64 field_mask(u64 field) 140 { 141 return field / field_multiplier(field); 142 } 143 #define field_max(field) ((typeof(field))field_mask(field)) 144 #define ____MAKE_OP(type,base,to,from) \ 145 static __always_inline __##type type##_encode_bits(base v, base field) \ 146 { \ 147 if (__builtin_constant_p(v) && (v & ~field_mask(field))) \ 148 __field_overflow(); \ 149 return to((v & field_mask(field)) * field_multiplier(field)); \ 150 } \ 151 static __always_inline __##type type##_replace_bits(__##type old, \ 152 base val, base field) \ 153 { \ 154 return (old & ~to(field)) | type##_encode_bits(val, field); \ 155 } \ 156 static __always_inline void type##p_replace_bits(__##type *p, \ 157 base val, base field) \ 158 { \ 159 *p = (*p & ~to(field)) | type##_encode_bits(val, field); \ 160 } \ 161 static __always_inline base type##_get_bits(__##type v, base field) \ 162 { \ 163 return (from(v) & field)/field_multiplier(field); \ 164 } 165 #define __MAKE_OP(size) \ 166 ____MAKE_OP(le##size,u##size,cpu_to_le##size,le##size##_to_cpu) \ 167 ____MAKE_OP(be##size,u##size,cpu_to_be##size,be##size##_to_cpu) \ 168 ____MAKE_OP(u##size,u##size,,) 169 ____MAKE_OP(u8,u8,,) 170 __MAKE_OP(16) 171 __MAKE_OP(32) 172 __MAKE_OP(64) 173 #undef __MAKE_OP 174 #undef ____MAKE_OP 175 176 #endif 177