tools/include/linux/bitfield.h

   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);
 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 }
 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