bitfield.h

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/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * Copyright (C) 2014 Felix Fietkau <nbd@nbd.name>
 * Copyright (C) 2004 - 2009 Ivo van Doorn <IvDoorn@gmail.com>
 */
 
#ifndef _LINUX_BITFIELD_H
#define _LINUX_BITFIELD_H
 
#include <linux/build_bug.h>
#include <linux/compiler.h>
#include <linux/typecheck.h>
#include <asm/byteorder.h>
 
/*
 * Bitfield access macros
 *
 * FIELD_{GET,PREP} macros take as first parameter shifted mask
 * from which they extract the base mask and shift amount.
 * Mask must be a compilation time constant.
 * field_{get,prep} are variants that take a non-const mask.
 *
 * Example:
 *
 *  #include <linux/bitfield.h>
 *  #include <linux/bits.h>
 *
 *  #define REG_FIELD_A  GENMASK(6, 0)
 *  #define REG_FIELD_B  BIT(7)
 *  #define REG_FIELD_C  GENMASK(15, 8)
 *  #define REG_FIELD_D  GENMASK(31, 16)
 *
 * Get:
 *  a = FIELD_GET(REG_FIELD_A, reg);
 *  b = FIELD_GET(REG_FIELD_B, reg);
 *
 * Set:
 *  reg = FIELD_PREP(REG_FIELD_A, 1) |
 *    FIELD_PREP(REG_FIELD_B, 0) |
 *    FIELD_PREP(REG_FIELD_C, c) |
 *    FIELD_PREP(REG_FIELD_D, 0x40);
 *
 * Modify:
 *  FIELD_MODIFY(REG_FIELD_C, &reg, c);
 */
 
#define __bf_shf __builtin_ctzll
 
#define __scalar_type_to_unsigned_cases(type)               \
        unsigned type:  (unsigned type)0,           \
        signed type:    (unsigned type)0
 
#define __unsigned_scalar_typeof(x) typeof(             \
        _Generic((x),                       \
            char:   (unsigned char)0,           \
            __scalar_type_to_unsigned_cases(char),      \
            __scalar_type_to_unsigned_cases(short),     \
            __scalar_type_to_unsigned_cases(int),       \
            __scalar_type_to_unsigned_cases(long),      \
            __scalar_type_to_unsigned_cases(long long), \
            default: (x)))
 
#define __bf_cast_unsigned(type, x) ((__unsigned_scalar_typeof(type))(x))
 
#define __BF_FIELD_CHECK_MASK(_mask, _val, _pfx)            \
    ({                              \
        BUILD_BUG_ON_MSG(!__builtin_constant_p(_mask),      \
                 _pfx "mask is not constant");      \
        BUILD_BUG_ON_MSG((_mask) == 0, _pfx "mask is zero");    \
        BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ?       \
                 ~((_mask) >> __bf_shf(_mask)) &    \
                    (0 + (_val)) : 0,       \
                 _pfx "value too large for the field"); \
        __BUILD_BUG_ON_NOT_POWER_OF_2((_mask) +         \
                          (1ULL << __bf_shf(_mask))); \
    })
 
#define __BF_FIELD_CHECK_REG(mask, reg, pfx)                \
    BUILD_BUG_ON_MSG(__bf_cast_unsigned(mask, mask) >       \
             __bf_cast_unsigned(reg, ~0ull),        \
             pfx "type of reg too small for mask")
 
#define __BF_FIELD_CHECK(mask, reg, val, pfx)               \
    ({                              \
        __BF_FIELD_CHECK_MASK(mask, val, pfx);          \
        __BF_FIELD_CHECK_REG(mask, reg, pfx);           \
    })
 
#define __FIELD_PREP(mask, val, pfx)                    \
    ({                              \
        __BF_FIELD_CHECK_MASK(mask, val, pfx);          \
        ((typeof(mask))(val) << __bf_shf(mask)) & (mask);   \
    })
 
#define __FIELD_GET(mask, reg, pfx)                 \
    ({                              \
        __BF_FIELD_CHECK_MASK(mask, 0U, pfx);           \
        (typeof(mask))(((reg) & (mask)) >> __bf_shf(mask)); \
    })
 
#define FIELD_MAX(_mask)                        \
    ({                              \
        __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_MAX: "); \
        (typeof(_mask))((_mask) >> __bf_shf(_mask));        \
    })
 
#define FIELD_FIT(_mask, _val)                      \
    ({                              \
        __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_FIT: "); \
        !((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask)); \
    })
 
#define FIELD_PREP(_mask, _val)                     \
    ({                              \
        __BF_FIELD_CHECK_REG(_mask, 0ULL, "FIELD_PREP: ");  \
        __FIELD_PREP(_mask, _val, "FIELD_PREP: ");      \
    })
 
#define __BF_CHECK_POW2(n)  BUILD_BUG_ON_ZERO(((n) & ((n) - 1)) != 0)
 
#define FIELD_PREP_CONST(_mask, _val)                   \
    (                               \
        /* mask must be non-zero */             \
        BUILD_BUG_ON_ZERO((_mask) == 0) +           \
        /* check if value fits */               \
        BUILD_BUG_ON_ZERO(~((_mask) >> __bf_shf(_mask)) & (_val)) + \
        /* check if mask is contiguous */           \
        __BF_CHECK_POW2((_mask) + (1ULL << __bf_shf(_mask))) +  \
        /* and create the value */              \
        (((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask))  \
    )
 
#define FIELD_GET(_mask, _reg)                      \
    ({                              \
        __BF_FIELD_CHECK_REG(_mask, _reg, "FIELD_GET: ");   \
        __FIELD_GET(_mask, _reg, "FIELD_GET: ");        \
    })
 
#define FIELD_GET_SIGNED(mask, reg)                 \
    ({                              \
        __BF_FIELD_CHECK(mask, reg, 0U, "FIELD_GET_SIGNED: ");  \
         ((__signed_scalar_typeof(mask))            \
          (((long long)(reg) << __builtin_clzll(mask)) >>   \
           (__builtin_clzll(mask) + __builtin_ctzll(mask))));   \
    })
 
#define FIELD_MODIFY(_mask, _reg_p, _val)                       \
    ({                                      \
        typecheck_pointer(_reg_p);                      \
        __BF_FIELD_CHECK(_mask, *(_reg_p), _val, "FIELD_MODIFY: ");     \
        *(_reg_p) &= ~(_mask);                          \
        *(_reg_p) |= (((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask));    \
    })
 
extern void __compiletime_error("value doesn't fit into mask")
__field_overflow(void);
extern void __compiletime_error("bad bitfield mask")
__bad_mask(void);
static __always_inline u64 field_multiplier(u64 field)
{
    if ((field | (field - 1)) & ((field | (field - 1)) + 1))
        __bad_mask();
    return field & -field;
}
static __always_inline u64 field_mask(u64 field)
{
    return field / field_multiplier(field);
}
#define field_max(field)    ((typeof(field))field_mask(field))
#define ____MAKE_OP(type,base,to,from)                  \
static __always_inline __##type __must_check type##_encode_bits(base v, base field) \
{                                   \
    if (__builtin_constant_p(v) && (v & ~field_mask(field)))    \
        __field_overflow();                 \
    return to((v & field_mask(field)) * field_multiplier(field));   \
}                                   \
static __always_inline __##type __must_check type##_replace_bits(__##type old,  \
                            base val, base field)   \
{                                   \
    return (old & ~to(field)) | type##_encode_bits(val, field); \
}                                   \
static __always_inline void type##p_replace_bits(__##type *p,       \
                    base val, base field)       \
{                                   \
    *p = (*p & ~to(field)) | type##_encode_bits(val, field);    \
}                                   \
static __always_inline base __must_check type##_get_bits(__##type v, base field)    \
{                                   \
    return (from(v) & field)/field_multiplier(field);       \
}
#define __MAKE_OP(size)                         \
    ____MAKE_OP(le##size,u##size,cpu_to_le##size,le##size##_to_cpu) \
    ____MAKE_OP(be##size,u##size,cpu_to_be##size,be##size##_to_cpu) \
    ____MAKE_OP(u##size,u##size,,)
____MAKE_OP(u8,u8,,)
__MAKE_OP(16)
__MAKE_OP(32)
__MAKE_OP(64)
#undef __MAKE_OP
#undef ____MAKE_OP
 
#define __field_prep(mask, val)                     \
    ({                              \
        auto __mask = (mask);                   \
        typeof(__mask) __val = (val);               \
        unsigned int __shift = BITS_PER_TYPE(__mask) <= 32 ?    \
                       __ffs(__mask) : __ffs64(__mask); \
        (__val << __shift) & __mask;                \
    })
 
#define __field_get(mask, reg)                      \
    ({                              \
        auto __mask = (mask);                   \
        typeof(__mask) __reg =  (reg);              \
        unsigned int __shift = BITS_PER_TYPE(__mask) <= 32 ?    \
                       __ffs(__mask) : __ffs64(__mask); \
        (__reg & __mask) >> __shift;                \
    })
 
#define field_prep(mask, val)                       \
    (__builtin_constant_p(mask) ? __FIELD_PREP(mask, val, "field_prep: ") \
                    : __field_prep(mask, val))
 
#define field_get(mask, reg)                        \
    (__builtin_constant_p(mask) ? __FIELD_GET(mask, reg, "field_get: ") \
                    : __field_get(mask, reg))
 
#endif