LXR linux/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), _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
 107extern void __compiletime_warning("value doesn't fit into mask")
 108__field_overflow(void);
 109extern void __compiletime_error("bad bitfield mask")
 110__bad_mask(void);
 111static __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}
 117static __always_inline u64 field_mask(u64 field)
 118{
 119        return field / field_multiplier(field);
 120}
 121#define ____MAKE_OP(type,base,to,from)                                  \
 122static __always_inline __##type type##_encode_bits(base v, base field)  \
 123{                                                                       \
 124        if (__builtin_constant_p(v) &&  (v & ~field_multiplier(field))) \
 125                            __field_overflow();                         \
 126        return to((v & field_mask(field)) * field_multiplier(field));   \
 127}                                                                       \
 128static __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}                                                                       \
 133static __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}                                                                       \
 138static __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(16)
 147__MAKE_OP(32)
 148__MAKE_OP(64)
 149#undef __MAKE_OP
 150#undef ____MAKE_OP
 151
 152#endif
 153