include/linux/bitfield.h

   1 /*
   2  * Copyright (C) 2014 Felix Fietkau <nbd@nbd.name>
   3  * Copyright (C) 2004 - 2009 Ivo van Doorn <IvDoorn@gmail.com>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2
   7  * as published by the Free Software Foundation
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  */
  14
  15 #ifndef _LINUX_BITFIELD_H
  16 #define _LINUX_BITFIELD_H
  17
  18 #include <linux/build_bug.h>
  19 #include <asm/byteorder.h>
  20
  21 /*
  22  * Bitfield access macros
  23  *
  24  * FIELD_{GET,PREP} macros take as first parameter shifted mask
  25  * from which they extract the base mask and shift amount.
  26  * Mask must be a compilation time constant.
  27  *
  28  * Example:
  29  *
  30  *  #define REG_FIELD_A  GENMASK(6, 0)
  31  *  #define REG_FIELD_B  BIT(7)
  32  *  #define REG_FIELD_C  GENMASK(15, 8)
  33  *  #define REG_FIELD_D  GENMASK(31, 16)
  34  *
  35  * Get:
  36  *  a = FIELD_GET(REG_FIELD_A, reg);
  37  *  b = FIELD_GET(REG_FIELD_B, reg);
  38  *
  39  * Set:
  40  *  reg = FIELD_PREP(REG_FIELD_A, 1) |
  41  *        FIELD_PREP(REG_FIELD_B, 0) |
  42  *        FIELD_PREP(REG_FIELD_C, c) |
  43  *        FIELD_PREP(REG_FIELD_D, 0x40);
  44  *
  45  * Modify:
  46  *  reg &= ~REG_FIELD_C;
  47  *  reg |= FIELD_PREP(REG_FIELD_C, c);
  48  */
  49
  50 #define __bf_shf(x) (__builtin_ffsll(x) - 1)
  51
  52 #define __BF_FIELD_CHECK(_mask, _reg, _val, _pfx)                       \
  53         ({                                                              \
  54                 BUILD_BUG_ON_MSG(!__builtin_constant_p(_mask),          \
  55                                  _pfx "mask is not constant");          \
  56                 BUILD_BUG_ON_MSG((_mask) == 0, _pfx "mask is zero");    \
  57                 BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ?           \
  58                                  ~((_mask) >> __bf_shf(_mask)) & (_val) : 0, \
  59                                  _pfx "value too large for the field"); \
  60                 BUILD_BUG_ON_MSG((_mask) > (typeof(_reg))~0ull,         \
  61                                  _pfx "type of reg too small for mask"); \
  62                 __BUILD_BUG_ON_NOT_POWER_OF_2((_mask) +                 \
  63                                               (1ULL << __bf_shf(_mask))); \
  64         })
  65
  66 /**
  67  * FIELD_FIT() - check if value fits in the field
  68  * @_mask: shifted mask defining the field's length and position
  69  * @_val:  value to test against the field
  70  *
  71  * Return: true if @_val can fit inside @_mask, false if @_val is too big.
  72  */
  73 #define FIELD_FIT(_mask, _val)                                          \
  74         ({                                                              \
  75                 __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_FIT: ");     \
  76                 !((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask)); \
  77         })
  78
  79 /**
  80  * FIELD_PREP() - prepare a bitfield element
  81  * @_mask: shifted mask defining the field's length and position
  82  * @_val:  value to put in the field
  83  *
  84  * FIELD_PREP() masks and shifts up the value.  The result should
  85  * be combined with other fields of the bitfield using logical OR.
  86  */
  87 #define FIELD_PREP(_mask, _val)                                         \
  88         ({                                                              \
  89                 __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: ");    \
  90                 ((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask);   \
  91         })
  92
  93 /**
  94  * FIELD_GET() - extract a bitfield element
  95  * @_mask: shifted mask defining the field's length and position
  96  * @_reg:  value of entire bitfield
  97  *
  98  * FIELD_GET() extracts the field specified by @_mask from the
  99  * bitfield passed in as @_reg by masking and shifting it down.
 100  */
 101 #define FIELD_GET(_mask, _reg)                                          \
 102         ({                                                              \
 103                 __BF_FIELD_CHECK(_mask, _reg, 0U, "FIELD_GET: ");       \
 104                 (typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask)); \
 105         })
 106
 107 extern void __compiletime_error("value doesn't fit into mask")
 108 __field_overflow(void);
 109 extern void __compiletime_error("bad bitfield mask")
 110 __bad_mask(void);
 111 static __always_inline u64 field_multiplier(u64 field)
 112 {
 113         if ((field | (field - 1)) & ((field | (field - 1)) + 1))
 114                 __bad_mask();
 115         return field & -field;
 116 }
 117 static __always_inline u64 field_mask(u64 field)
 118 {
 119         return field / field_multiplier(field);
 120 }
 121 #define ____MAKE_OP(type,base,to,from)                                  \
 122 static __always_inline __##type type##_encode_bits(base v, base field)  \
 123 {                                                                       \
 124         if (__builtin_constant_p(v) && (v & ~field_mask(field)))        \
 125                 __field_overflow();                                     \
 126         return to((v & field_mask(field)) * field_multiplier(field));   \
 127 }                                                                       \
 128 static __always_inline __##type type##_replace_bits(__##type old,       \
 129                                         base val, base field)           \
 130 {                                                                       \
 131         return (old & ~to(field)) | type##_encode_bits(val, field);     \
 132 }                                                                       \
 133 static __always_inline void type##p_replace_bits(__##type *p,           \
 134                                         base val, base field)           \
 135 {                                                                       \
 136         *p = (*p & ~to(field)) | type##_encode_bits(val, field);        \
 137 }                                                                       \
 138 static __always_inline base type##_get_bits(__##type v, base field)     \
 139 {                                                                       \
 140         return (from(v) & field)/field_multiplier(field);               \
 141 }
 142 #define __MAKE_OP(size)                                                 \
 143         ____MAKE_OP(le##size,u##size,cpu_to_le##size,le##size##_to_cpu) \
 144         ____MAKE_OP(be##size,u##size,cpu_to_be##size,be##size##_to_cpu) \
 145         ____MAKE_OP(u##size,u##size,,)
 146 ____MAKE_OP(u8,u8,,)
 147 __MAKE_OP(16)
 148 __MAKE_OP(32)
 149 __MAKE_OP(64)
 150 #undef __MAKE_OP
 151 #undef ____MAKE_OP
 152
 153 #endif