/* 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(x) (__builtin_ffsll(x) - 1)

#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));     \
        })

/**
 * FIELD_MAX() - produce the maximum value representable by a field
 * @_mask: shifted mask defining the field's length and position
 *
 * FIELD_MAX() returns the maximum value that can be held in the field
 * specified by @_mask.
 */
#define FIELD_MAX(_mask)                                                \
        ({                                                              \
                __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_MAX: ");     \
                (typeof(_mask))((_mask) >> __bf_shf(_mask));            \
        })

/**
 * FIELD_FIT() - check if value fits in the field
 * @_mask: shifted mask defining the field's length and position
 * @_val:  value to test against the field
 *
 * Return: true if @_val can fit inside @_mask, false if @_val is too big.
 */
#define FIELD_FIT(_mask, _val)                                          \
        ({                                                              \
                __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_FIT: ");     \
                !((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask)); \
        })

/**
 * FIELD_PREP() - prepare a bitfield element
 * @_mask: shifted mask defining the field's length and position
 * @_val:  value to put in the field
 *
 * FIELD_PREP() masks and shifts up the value.  The result should
 * be combined with other fields of the bitfield using logical OR.
 */
#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)

/**
 * FIELD_PREP_CONST() - prepare a constant bitfield element
 * @_mask: shifted mask defining the field's length and position
 * @_val:  value to put in the field
 *
 * FIELD_PREP_CONST() masks and shifts up the value.  The result should
 * be combined with other fields of the bitfield using logical OR.
 *
 * Unlike FIELD_PREP() this is a constant expression and can therefore
 * be used in initializers. Error checking is less comfortable for this
 * version, and non-constant masks cannot be used.
 */
#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))  \
        )

/**
 * FIELD_GET() - extract a bitfield element
 * @_mask: shifted mask defining the field's length and position
 * @_reg:  value of entire bitfield
 *
 * FIELD_GET() extracts the field specified by @_mask from the
 * bitfield passed in as @_reg by masking and shifting it down.
 */
#define FIELD_GET(_mask, _reg)                                          \
        ({                                                              \
                __BF_FIELD_CHECK_REG(_mask, _reg, "FIELD_GET: ");       \
                __FIELD_GET(_mask, _reg, "FIELD_GET: ");                \
        })

/**
 * FIELD_MODIFY() - modify a bitfield element
 * @_mask: shifted mask defining the field's length and position
 * @_reg_p: pointer to the memory that should be updated
 * @_val: value to store in the bitfield
 *
 * FIELD_MODIFY() modifies the set of bits in @_reg_p specified by @_mask,
 * by replacing them with the bitfield value passed in as @_val.
 */
#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;                            \
        })

/**
 * field_prep() - prepare a bitfield element
 * @mask: shifted mask defining the field's length and position, must be
 *        non-zero
 * @val:  value to put in the field
 *
 * Return: field value masked and shifted to its final destination
 *
 * field_prep() masks and shifts up the value.  The result should be
 * combined with other fields of the bitfield using logical OR.
 * Unlike FIELD_PREP(), @mask is not limited to a compile-time constant.
 * Typical usage patterns are a value stored in a table, or calculated by
 * shifting a constant by a variable number of bits.
 * If you want to ensure that @mask is a compile-time constant, please use
 * FIELD_PREP() directly instead.
 */
#define field_prep(mask, val)                                           \
        (__builtin_constant_p(mask) ? __FIELD_PREP(mask, val, "field_prep: ") \
                                    : __field_prep(mask, val))

/**
 * field_get() - extract a bitfield element
 * @mask: shifted mask defining the field's length and position, must be
 *        non-zero
 * @reg:  value of entire bitfield
 *
 * Return: extracted field value
 *
 * field_get() extracts the field specified by @mask from the
 * bitfield passed in as @reg by masking and shifting it down.
 * Unlike FIELD_GET(), @mask is not limited to a compile-time constant.
 * Typical usage patterns are a value stored in a table, or calculated by
 * shifting a constant by a variable number of bits.
 * If you want to ensure that @mask is a compile-time constant, please use
 * FIELD_GET() directly instead.
 */
#define field_get(mask, reg)                                            \
        (__builtin_constant_p(mask) ? __FIELD_GET(mask, reg, "field_get: ") \
                                    : __field_get(mask, reg))

#endif