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 __BF_FIELD_CHECK(_mask, _reg, _val, _pfx)                       \
  45         ({                                                              \
  46                 BUILD_BUG_ON_MSG(!__builtin_constant_p(_mask),          \
  47                                  _pfx "mask is not constant");          \
  48                 BUILD_BUG_ON_MSG((_mask) == 0, _pfx "mask is zero");    \
  49                 BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ?           \
  50                                  ~((_mask) >> __bf_shf(_mask)) & (_val) : 0, \
  51                                  _pfx "value too large for the field"); \
  52                 BUILD_BUG_ON_MSG((_mask) > (typeof(_reg))~0ull,         \
  53                                  _pfx "type of reg too small for mask"); \
  54                 __BUILD_BUG_ON_NOT_POWER_OF_2((_mask) +                 \
  55                                               (1ULL << __bf_shf(_mask))); \
  56         })
  57
  58 /**
  59  * FIELD_MAX() - produce the maximum value representable by a field
  60  * @_mask: shifted mask defining the field's length and position
  61  *
  62  * FIELD_MAX() returns the maximum value that can be held in the field
  63  * specified by @_mask.
  64  */
  65 #define FIELD_MAX(_mask)                                                \
  66         ({                                                              \
  67                 __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_MAX: ");     \
  68                 (typeof(_mask))((_mask) >> __bf_shf(_mask));            \
  69         })
  70
  71 /**
  72  * FIELD_FIT() - check if value fits in the field
  73  * @_mask: shifted mask defining the field's length and position
  74  * @_val:  value to test against the field
  75  *
  76  * Return: true if @_val can fit inside @_mask, false if @_val is too big.
  77  */
  78 #define FIELD_FIT(_mask, _val)                                          \
  79         ({                                                              \
  80                 __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_FIT: ");     \
  81                 !((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask)); \
  82         })
  83
  84 /**
  85  * FIELD_PREP() - prepare a bitfield element
  86  * @_mask: shifted mask defining the field's length and position
  87  * @_val:  value to put in the field
  88  *
  89  * FIELD_PREP() masks and shifts up the value.  The result should
  90  * be combined with other fields of the bitfield using logical OR.
  91  */
  92 #define FIELD_PREP(_mask, _val)                                         \
  93         ({                                                              \
  94                 __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: ");    \
  95                 ((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask);   \
  96         })
  97
  98 /**
  99  * FIELD_GET() - extract a bitfield element
 100  * @_mask: shifted mask defining the field's length and position
 101  * @_reg:  value of entire bitfield
 102  *
 103  * FIELD_GET() extracts the field specified by @_mask from the
 104  * bitfield passed in as @_reg by masking and shifting it down.
 105  */
 106 #define FIELD_GET(_mask, _reg)                                          \
 107         ({                                                              \
 108                 __BF_FIELD_CHECK(_mask, _reg, 0U, "FIELD_GET: ");       \
 109                 (typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask)); \
 110         })
 111
 112 extern void __compiletime_error("value doesn't fit into mask")
 113 __field_overflow(void);
 114 extern void __compiletime_error("bad bitfield mask")
 115 __bad_mask(void);
 116 static __always_inline u64 field_multiplier(u64 field)
 117 {
 118         if ((field | (field - 1)) & ((field | (field - 1)) + 1))
 119                 __bad_mask();
 120         return field & -field;
 121 }
 122 static __always_inline u64 field_mask(u64 field)
 123 {
 124         return field / field_multiplier(field);
 125 }
 126 #define field_max(field)        ((typeof(field))field_mask(field))
 127 #define ____MAKE_OP(type,base,to,from)                                  \
 128 static __always_inline __##type type##_encode_bits(base v, base field)  \
 129 {                                                                       \
 130         if (__builtin_constant_p(v) && (v & ~field_mask(field)))        \
 131                 __field_overflow();                                     \
 132         return to((v & field_mask(field)) * field_multiplier(field));   \
 133 }                                                                       \
 134 static __always_inline __##type type##_replace_bits(__##type old,       \
 135                                         base val, base field)           \
 136 {                                                                       \
 137         return (old & ~to(field)) | type##_encode_bits(val, field);     \
 138 }                                                                       \
 139 static __always_inline void type##p_replace_bits(__##type *p,           \
 140                                         base val, base field)           \
 141 {                                                                       \
 142         *p = (*p & ~to(field)) | type##_encode_bits(val, field);        \
 143 }                                                                       \
 144 static __always_inline base type##_get_bits(__##type v, base field)     \
 145 {                                                                       \
 146         return (from(v) & field)/field_multiplier(field);               \
 147 }
 148 #define __MAKE_OP(size)                                                 \
 149         ____MAKE_OP(le##size,u##size,cpu_to_le##size,le##size##_to_cpu) \
 150         ____MAKE_OP(be##size,u##size,cpu_to_be##size,be##size##_to_cpu) \
 151         ____MAKE_OP(u##size,u##size,,)
 152 ____MAKE_OP(u8,u8,,)
 153 __MAKE_OP(16)
 154 __MAKE_OP(32)
 155 __MAKE_OP(64)
 156 #undef __MAKE_OP
 157 #undef ____MAKE_OP
 158
 159 #endif