LXR linux/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
 112extern void __compiletime_error("value doesn't fit into mask")
 113__field_overflow(void);
 114extern void __compiletime_error("bad bitfield mask")
 115__bad_mask(void);
 116static __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}
 122static __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)                                  \
 128static __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}                                                                       \
 134static __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}                                                                       \
 139static __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}                                                                       \
 144static __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
 160