forked from mirrors/linux
416eb60317
There's a somewhat common pattern of using FIELD_PREP()
even for single bits, e.g.
cmd->info1 |= FIELD_PREP(HTT_SRNG_SETUP_CMD_INFO1_RING_FLAGS_MSI_SWAP,
!!(params.flags & HAL_SRNG_FLAGS_MSI_SWAP));
which might as well be written as
if (params.flags & HAL_SRNG_FLAGS_MSI_SWAP)
cmd->info1 |= HTT_SRNG_SETUP_CMD_INFO1_RING_FLAGS_MSI_SWAP;
(since info1 is fully initialized to start with), but in
a long chain of FIELD_PREP() this really seems fine.
However, it triggers a sparse warning, in the check in
the macro for whether a constant value fits into the mask,
as this contains a "& (_val)". In this case, this really
is always intentional, so just suppress the warning by
adding "0+" to the expression, indicating explicitly that
this is correct.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/20240223100146.d243b6b1a9a1.I033828b1187c6bccf086e31400f7e933bb8373e7@changeid
206 lines
6.4 KiB
C
206 lines
6.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright (C) 2014 Felix Fietkau <nbd@nbd.name>
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* Copyright (C) 2004 - 2009 Ivo van Doorn <IvDoorn@gmail.com>
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*/
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#ifndef _LINUX_BITFIELD_H
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#define _LINUX_BITFIELD_H
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#include <linux/build_bug.h>
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#include <asm/byteorder.h>
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/*
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* Bitfield access macros
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*
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* FIELD_{GET,PREP} macros take as first parameter shifted mask
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* from which they extract the base mask and shift amount.
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* Mask must be a compilation time constant.
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*
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* Example:
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*
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* #include <linux/bitfield.h>
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* #include <linux/bits.h>
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*
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* #define REG_FIELD_A GENMASK(6, 0)
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* #define REG_FIELD_B BIT(7)
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* #define REG_FIELD_C GENMASK(15, 8)
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* #define REG_FIELD_D GENMASK(31, 16)
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*
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* Get:
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* a = FIELD_GET(REG_FIELD_A, reg);
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* b = FIELD_GET(REG_FIELD_B, reg);
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*
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* Set:
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* reg = FIELD_PREP(REG_FIELD_A, 1) |
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* FIELD_PREP(REG_FIELD_B, 0) |
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* FIELD_PREP(REG_FIELD_C, c) |
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* FIELD_PREP(REG_FIELD_D, 0x40);
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*
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* Modify:
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* reg &= ~REG_FIELD_C;
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* reg |= FIELD_PREP(REG_FIELD_C, c);
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*/
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#define __bf_shf(x) (__builtin_ffsll(x) - 1)
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#define __scalar_type_to_unsigned_cases(type) \
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unsigned type: (unsigned type)0, \
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signed type: (unsigned type)0
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#define __unsigned_scalar_typeof(x) typeof( \
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_Generic((x), \
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char: (unsigned char)0, \
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__scalar_type_to_unsigned_cases(char), \
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__scalar_type_to_unsigned_cases(short), \
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__scalar_type_to_unsigned_cases(int), \
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__scalar_type_to_unsigned_cases(long), \
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__scalar_type_to_unsigned_cases(long long), \
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default: (x)))
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#define __bf_cast_unsigned(type, x) ((__unsigned_scalar_typeof(type))(x))
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#define __BF_FIELD_CHECK(_mask, _reg, _val, _pfx) \
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({ \
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BUILD_BUG_ON_MSG(!__builtin_constant_p(_mask), \
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_pfx "mask is not constant"); \
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BUILD_BUG_ON_MSG((_mask) == 0, _pfx "mask is zero"); \
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BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ? \
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~((_mask) >> __bf_shf(_mask)) & \
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(0 + (_val)) : 0, \
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_pfx "value too large for the field"); \
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BUILD_BUG_ON_MSG(__bf_cast_unsigned(_mask, _mask) > \
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__bf_cast_unsigned(_reg, ~0ull), \
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_pfx "type of reg too small for mask"); \
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__BUILD_BUG_ON_NOT_POWER_OF_2((_mask) + \
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(1ULL << __bf_shf(_mask))); \
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})
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/**
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* FIELD_MAX() - produce the maximum value representable by a field
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* @_mask: shifted mask defining the field's length and position
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*
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* FIELD_MAX() returns the maximum value that can be held in the field
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* specified by @_mask.
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*/
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#define FIELD_MAX(_mask) \
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({ \
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__BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_MAX: "); \
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(typeof(_mask))((_mask) >> __bf_shf(_mask)); \
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})
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/**
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* FIELD_FIT() - check if value fits in the field
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* @_mask: shifted mask defining the field's length and position
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* @_val: value to test against the field
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*
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* Return: true if @_val can fit inside @_mask, false if @_val is too big.
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*/
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#define FIELD_FIT(_mask, _val) \
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({ \
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__BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_FIT: "); \
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!((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask)); \
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})
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/**
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* FIELD_PREP() - prepare a bitfield element
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* @_mask: shifted mask defining the field's length and position
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* @_val: value to put in the field
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*
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* FIELD_PREP() masks and shifts up the value. The result should
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* be combined with other fields of the bitfield using logical OR.
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*/
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#define FIELD_PREP(_mask, _val) \
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({ \
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__BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: "); \
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((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask); \
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})
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#define __BF_CHECK_POW2(n) BUILD_BUG_ON_ZERO(((n) & ((n) - 1)) != 0)
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/**
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* FIELD_PREP_CONST() - prepare a constant bitfield element
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* @_mask: shifted mask defining the field's length and position
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* @_val: value to put in the field
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*
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* FIELD_PREP_CONST() masks and shifts up the value. The result should
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* be combined with other fields of the bitfield using logical OR.
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*
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* Unlike FIELD_PREP() this is a constant expression and can therefore
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* be used in initializers. Error checking is less comfortable for this
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* version, and non-constant masks cannot be used.
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*/
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#define FIELD_PREP_CONST(_mask, _val) \
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( \
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/* mask must be non-zero */ \
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BUILD_BUG_ON_ZERO((_mask) == 0) + \
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/* check if value fits */ \
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BUILD_BUG_ON_ZERO(~((_mask) >> __bf_shf(_mask)) & (_val)) + \
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/* check if mask is contiguous */ \
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__BF_CHECK_POW2((_mask) + (1ULL << __bf_shf(_mask))) + \
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/* and create the value */ \
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(((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask)) \
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)
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/**
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* FIELD_GET() - extract a bitfield element
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* @_mask: shifted mask defining the field's length and position
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* @_reg: value of entire bitfield
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*
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* FIELD_GET() extracts the field specified by @_mask from the
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* bitfield passed in as @_reg by masking and shifting it down.
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*/
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#define FIELD_GET(_mask, _reg) \
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({ \
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__BF_FIELD_CHECK(_mask, _reg, 0U, "FIELD_GET: "); \
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(typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask)); \
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})
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extern void __compiletime_error("value doesn't fit into mask")
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__field_overflow(void);
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extern void __compiletime_error("bad bitfield mask")
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__bad_mask(void);
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static __always_inline u64 field_multiplier(u64 field)
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{
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if ((field | (field - 1)) & ((field | (field - 1)) + 1))
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__bad_mask();
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return field & -field;
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}
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static __always_inline u64 field_mask(u64 field)
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{
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return field / field_multiplier(field);
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}
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#define field_max(field) ((typeof(field))field_mask(field))
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#define ____MAKE_OP(type,base,to,from) \
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static __always_inline __##type type##_encode_bits(base v, base field) \
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{ \
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if (__builtin_constant_p(v) && (v & ~field_mask(field))) \
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__field_overflow(); \
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return to((v & field_mask(field)) * field_multiplier(field)); \
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} \
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static __always_inline __##type type##_replace_bits(__##type old, \
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base val, base field) \
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{ \
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return (old & ~to(field)) | type##_encode_bits(val, field); \
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} \
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static __always_inline void type##p_replace_bits(__##type *p, \
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base val, base field) \
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{ \
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*p = (*p & ~to(field)) | type##_encode_bits(val, field); \
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} \
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static __always_inline base type##_get_bits(__##type v, base field) \
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{ \
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return (from(v) & field)/field_multiplier(field); \
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}
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#define __MAKE_OP(size) \
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____MAKE_OP(le##size,u##size,cpu_to_le##size,le##size##_to_cpu) \
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____MAKE_OP(be##size,u##size,cpu_to_be##size,be##size##_to_cpu) \
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____MAKE_OP(u##size,u##size,,)
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____MAKE_OP(u8,u8,,)
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__MAKE_OP(16)
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__MAKE_OP(32)
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__MAKE_OP(64)
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#undef __MAKE_OP
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#undef ____MAKE_OP
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#endif
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