2019-05-27 08:55:21 +02:00
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2016-08-31 12:46:44 +01:00
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2017-11-17 15:27:49 -08:00
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2025-12-16 17:21:53 -08:00
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2025-04-17 18:47:08 +08:00
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Add primitives for manipulating bitfields both in host- and fixed-endian.
The following primitives are defined in linux/bitfield.h:
* u32 le32_get_bits(__le32 val, u32 field) extracts the contents of the
bitfield specified by @field in little-endian 32bit object @val and
converts it to host-endian.
* void le32p_replace_bits(__le32 *p, u32 v, u32 field) replaces
the contents of the bitfield specified by @field in little-endian
32bit object pointed to by @p with the value of @v. New value is
given in host-endian and stored as little-endian.
* __le32 le32_replace_bits(__le32 old, u32 v, u32 field) is equivalent to
({__le32 tmp = old; le32p_replace_bits(&tmp, v, field); tmp;})
In other words, instead of modifying an object in memory, it takes
the initial value and returns the modified one.
* __le32 le32_encode_bits(u32 v, u32 field) is equivalent to
le32_replace_bits(0, v, field). In other words, it returns a little-endian
32bit object with the bitfield specified by @field containing the
value of @v and all bits outside that bitfield being zero.
Such set of helpers is defined for each of little-, big- and host-endian
types; e.g. u64_get_bits(val, field) will return the contents of the bitfield
specified by @field in host-endian 64bit object @val, etc. Of course, for
host-endian no conversion is involved.
Fields to access are specified as GENMASK() values - an N-bit field
starting at bit #M is encoded as GENMASK(M + N - 1, M). Note that
bit numbers refer to endianness of the object we are working with -
e.g. GENMASK(11, 0) in __be16 refers to the second byte and the lower
4 bits of the first byte. In __le16 it would refer to the first byte
and the lower 4 bits of the second byte, etc.
Field specification must be a constant; __builtin_constant_p() doesn't
have to be true for it, but compiler must be able to evaluate it at
build time. If it cannot or if the value does not encode any bitfield,
the build will fail.
If the value being stored in a bitfield is a constant that does not fit
into that bitfield, a warning will be generated at compile time.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2017-12-14 21:27:55 -05:00
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2016-08-31 12:46:44 +01:00
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bitfield: Add non-constant field_{prep,get}() helpers
The existing FIELD_{GET,PREP}() macros are limited to compile-time
constants. However, it is very common to prepare or extract bitfield
elements where the bitfield mask is not a compile-time constant.
To avoid this limitation, the AT91 clock driver and several other
drivers already have their own non-const field_{prep,get}() macros.
Make them available for general use by adding them to
<linux/bitfield.h>, and improve them slightly:
1. Avoid evaluating macro parameters more than once,
2. Replace "ffs() - 1" by "__ffs()",
3. Support 64-bit use on 32-bit architectures,
4. Wire field_{get,prep}() to FIELD_{GET,PREP}() when mask is
actually constant.
This is deliberately not merged into the existing FIELD_{GET,PREP}()
macros, as people expressed the desire to keep stricter variants for
increased safety, or for performance critical paths.
Yury: use __mask withing new macros.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: Crt Mori <cmo@melexis.com>
Acked-by: Nuno Sá <nuno.sa@analog.com>
Acked-by: Richard Genoud <richard.genoud@bootlin.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Reviewed-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
2025-11-06 14:34:01 +01:00
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2016-08-31 12:46:44 +01:00
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2022-03-23 16:05:47 -07:00
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2016-08-31 12:46:44 +01:00
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2025-04-17 18:47:08 +08:00
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2016-08-31 12:46:44 +01:00
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2026-04-27 18:57:05 -04:00
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2016-08-31 12:46:44 +01:00
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2021-11-10 11:01:03 +01:00
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bitfield: Add less-checking __FIELD_{GET,PREP}()
The BUILD_BUG_ON_MSG() check against "~0ull" works only with "unsigned
(long) long" _mask types. For constant masks, that condition is usually
met, as GENMASK() yields an UL value. The few places where the
constant mask is stored in an intermediate variable were fixed by
changing the variable type to u64 (see e.g. [1] and [2]).
However, for non-constant masks, smaller unsigned types should be valid,
too, but currently lead to "result of comparison of constant
18446744073709551615 with expression of type ... is always
false"-warnings with clang and W=1.
Hence refactor the __BF_FIELD_CHECK() helper, and factor out
__FIELD_{GET,PREP}(). The later lack the single problematic check, but
are otherwise identical to FIELD_{GET,PREP}(), and are intended to be
used in the fully non-const variants later.
[1] commit 5c667d5a5a3ec166 ("clk: sp7021: Adjust width of _m in
HWM_FIELD_PREP()")
[2] commit cfd6fb45cfaf46fa ("crypto: ccree - avoid out-of-range
warnings from clang")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://git.kernel.org/torvalds/c/5c667d5a5a3ec166 [1]
Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
2025-11-06 14:34:00 +01:00
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2016-08-31 12:46:44 +01:00
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bitfield: avoid gcc-8 -Wint-in-bool-context warning
Passing an enum into FIELD_GET() produces a long but harmless warning on
newer compilers:
from include/linux/linkage.h:7,
from include/linux/kernel.h:7,
from include/linux/skbuff.h:17,
from include/linux/if_ether.h:23,
from include/linux/etherdevice.h:25,
from drivers/net/wireless/intel/iwlwifi/mvm/rxmq.c:63:
drivers/net/wireless/intel/iwlwifi/mvm/rxmq.c: In function 'iwl_mvm_rx_mpdu_mq':
include/linux/bitfield.h:56:20: error: enum constant in boolean context [-Werror=int-in-bool-context]
BUILD_BUG_ON_MSG(!(_mask), _pfx "mask is zero"); \
^
...
include/linux/bitfield.h:103:3: note: in expansion of macro '__BF_FIELD_CHECK'
__BF_FIELD_CHECK(_mask, _reg, 0U, "FIELD_GET: "); \
^~~~~~~~~~~~~~~~
drivers/net/wireless/intel/iwlwifi/mvm/rxmq.c:1025:21: note: in expansion of macro 'FIELD_GET'
le16_encode_bits(FIELD_GET(IWL_RX_HE_PHY_SIBG_SYM_OR_USER_NUM_MASK,
The problem here is that the caller has no idea how the macro gets
expanding, leading to a false-positive. It can be trivially avoided by
doing a comparison against zero.
This only recently started appearing as the iwlwifi driver was patched
to use FIELD_GET.
Link: http://lkml.kernel.org/r/20180813220950.194841-1-arnd@arndb.de
Fixes: 514c30696fbc ("iwlwifi: add support for IEEE802.11ax")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Jakub Kicinski <jakub.kicinski@netronome.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: David Laight <David.Laight@ACULAB.COM>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-08-17 15:43:36 -07:00
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2016-08-31 12:46:44 +01:00
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2024-02-23 10:01:46 +01:00
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2016-08-31 12:46:44 +01:00
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bitfield: Add less-checking __FIELD_{GET,PREP}()
The BUILD_BUG_ON_MSG() check against "~0ull" works only with "unsigned
(long) long" _mask types. For constant masks, that condition is usually
met, as GENMASK() yields an UL value. The few places where the
constant mask is stored in an intermediate variable were fixed by
changing the variable type to u64 (see e.g. [1] and [2]).
However, for non-constant masks, smaller unsigned types should be valid,
too, but currently lead to "result of comparison of constant
18446744073709551615 with expression of type ... is always
false"-warnings with clang and W=1.
Hence refactor the __BF_FIELD_CHECK() helper, and factor out
__FIELD_{GET,PREP}(). The later lack the single problematic check, but
are otherwise identical to FIELD_{GET,PREP}(), and are intended to be
used in the fully non-const variants later.
[1] commit 5c667d5a5a3ec166 ("clk: sp7021: Adjust width of _m in
HWM_FIELD_PREP()")
[2] commit cfd6fb45cfaf46fa ("crypto: ccree - avoid out-of-range
warnings from clang")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://git.kernel.org/torvalds/c/5c667d5a5a3ec166 [1]
Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
2025-11-06 14:34:00 +01:00
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2020-03-12 11:44:27 -05:00
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2017-02-09 09:17:27 -08:00
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2020-08-10 11:21:11 -07:00
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2017-02-09 09:17:27 -08:00
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2016-08-31 12:46:44 +01:00
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bitfield: Add less-checking __FIELD_{GET,PREP}()
The BUILD_BUG_ON_MSG() check against "~0ull" works only with "unsigned
(long) long" _mask types. For constant masks, that condition is usually
met, as GENMASK() yields an UL value. The few places where the
constant mask is stored in an intermediate variable were fixed by
changing the variable type to u64 (see e.g. [1] and [2]).
However, for non-constant masks, smaller unsigned types should be valid,
too, but currently lead to "result of comparison of constant
18446744073709551615 with expression of type ... is always
false"-warnings with clang and W=1.
Hence refactor the __BF_FIELD_CHECK() helper, and factor out
__FIELD_{GET,PREP}(). The later lack the single problematic check, but
are otherwise identical to FIELD_{GET,PREP}(), and are intended to be
used in the fully non-const variants later.
[1] commit 5c667d5a5a3ec166 ("clk: sp7021: Adjust width of _m in
HWM_FIELD_PREP()")
[2] commit cfd6fb45cfaf46fa ("crypto: ccree - avoid out-of-range
warnings from clang")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://git.kernel.org/torvalds/c/5c667d5a5a3ec166 [1]
Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
2025-11-06 14:34:00 +01:00
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2016-08-31 12:46:44 +01:00
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2023-01-18 14:26:53 +01:00
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2016-08-31 12:46:44 +01:00
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2017-10-03 16:16:04 -07:00
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2016-08-31 12:46:44 +01:00
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bitfield: Add less-checking __FIELD_{GET,PREP}()
The BUILD_BUG_ON_MSG() check against "~0ull" works only with "unsigned
(long) long" _mask types. For constant masks, that condition is usually
met, as GENMASK() yields an UL value. The few places where the
constant mask is stored in an intermediate variable were fixed by
changing the variable type to u64 (see e.g. [1] and [2]).
However, for non-constant masks, smaller unsigned types should be valid,
too, but currently lead to "result of comparison of constant
18446744073709551615 with expression of type ... is always
false"-warnings with clang and W=1.
Hence refactor the __BF_FIELD_CHECK() helper, and factor out
__FIELD_{GET,PREP}(). The later lack the single problematic check, but
are otherwise identical to FIELD_{GET,PREP}(), and are intended to be
used in the fully non-const variants later.
[1] commit 5c667d5a5a3ec166 ("clk: sp7021: Adjust width of _m in
HWM_FIELD_PREP()")
[2] commit cfd6fb45cfaf46fa ("crypto: ccree - avoid out-of-range
warnings from clang")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://git.kernel.org/torvalds/c/5c667d5a5a3ec166 [1]
Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
2025-11-06 14:34:00 +01:00
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2016-08-31 12:46:44 +01:00
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bitfield: add FIELD_GET_SIGNED()
The bitfields are designed in assumption that fields contain unsigned
integer values, thus extracting the values from the field implies
zero-extending.
Some drivers need to sign-extend their fields, and currently do it like:
dc_re += sign_extend32(FIELD_GET(0xfff000, tmp), 11);
dc_im += sign_extend32(FIELD_GET(0xfff, tmp), 11);
It's error-prone because it relies on user to provide the correct
index of the most significant bit and proper 32 vs 64 function flavor.
Thus, introduce a FIELD_GET_SIGNED(). With the new API, the above
snippet turns into the more convenient:
dc_re += FIELD_GET_SIGNED(0xfff000, tmp);
dc_im += FIELD_GET_SIGNED(0xfff, tmp);
It compiles (on x86_64) into just a couple instructions: shl and sar.
When the mask includes MSB, the '<< __builtin_clzll(mask)' part becomes
a NOP, and the compiler only emits a single sar:
long long foo(long long reg)
{
10: f3 0f 1e fa endbr64
return FIELD_GET_SIGNED(GENMASK_ULL(63, 60), reg);
14: 48 89 f8 mov %rdi,%rax
17: 48 c1 f8 3c sar $0x3c,%rax
}
32-bit code generation is equally well. On arm32:
long long foo(long long reg)
{
return FIELD_GET_SIGNED(0x00f00000ULL, reg);
}
generates:
foo(long long):
lsls r1, r0, #8
asrs r0, r1, #28
asrs r1, r1, #31
bx lr
Signed-off-by: Yury Norov <ynorov@nvidia.com>
2026-04-27 17:41:18 -04:00
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2025-04-17 18:47:08 +08:00
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2018-06-20 08:58:28 +02:00
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Add primitives for manipulating bitfields both in host- and fixed-endian.
The following primitives are defined in linux/bitfield.h:
* u32 le32_get_bits(__le32 val, u32 field) extracts the contents of the
bitfield specified by @field in little-endian 32bit object @val and
converts it to host-endian.
* void le32p_replace_bits(__le32 *p, u32 v, u32 field) replaces
the contents of the bitfield specified by @field in little-endian
32bit object pointed to by @p with the value of @v. New value is
given in host-endian and stored as little-endian.
* __le32 le32_replace_bits(__le32 old, u32 v, u32 field) is equivalent to
({__le32 tmp = old; le32p_replace_bits(&tmp, v, field); tmp;})
In other words, instead of modifying an object in memory, it takes
the initial value and returns the modified one.
* __le32 le32_encode_bits(u32 v, u32 field) is equivalent to
le32_replace_bits(0, v, field). In other words, it returns a little-endian
32bit object with the bitfield specified by @field containing the
value of @v and all bits outside that bitfield being zero.
Such set of helpers is defined for each of little-, big- and host-endian
types; e.g. u64_get_bits(val, field) will return the contents of the bitfield
specified by @field in host-endian 64bit object @val, etc. Of course, for
host-endian no conversion is involved.
Fields to access are specified as GENMASK() values - an N-bit field
starting at bit #M is encoded as GENMASK(M + N - 1, M). Note that
bit numbers refer to endianness of the object we are working with -
e.g. GENMASK(11, 0) in __be16 refers to the second byte and the lower
4 bits of the first byte. In __le16 it would refer to the first byte
and the lower 4 bits of the second byte, etc.
Field specification must be a constant; __builtin_constant_p() doesn't
have to be true for it, but compiler must be able to evaluate it at
build time. If it cannot or if the value does not encode any bitfield,
the build will fail.
If the value being stored in a bitfield is a constant that does not fit
into that bitfield, a warning will be generated at compile time.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2017-12-14 21:27:55 -05:00
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2020-03-12 11:44:27 -05:00
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Add primitives for manipulating bitfields both in host- and fixed-endian.
The following primitives are defined in linux/bitfield.h:
* u32 le32_get_bits(__le32 val, u32 field) extracts the contents of the
bitfield specified by @field in little-endian 32bit object @val and
converts it to host-endian.
* void le32p_replace_bits(__le32 *p, u32 v, u32 field) replaces
the contents of the bitfield specified by @field in little-endian
32bit object pointed to by @p with the value of @v. New value is
given in host-endian and stored as little-endian.
* __le32 le32_replace_bits(__le32 old, u32 v, u32 field) is equivalent to
({__le32 tmp = old; le32p_replace_bits(&tmp, v, field); tmp;})
In other words, instead of modifying an object in memory, it takes
the initial value and returns the modified one.
* __le32 le32_encode_bits(u32 v, u32 field) is equivalent to
le32_replace_bits(0, v, field). In other words, it returns a little-endian
32bit object with the bitfield specified by @field containing the
value of @v and all bits outside that bitfield being zero.
Such set of helpers is defined for each of little-, big- and host-endian
types; e.g. u64_get_bits(val, field) will return the contents of the bitfield
specified by @field in host-endian 64bit object @val, etc. Of course, for
host-endian no conversion is involved.
Fields to access are specified as GENMASK() values - an N-bit field
starting at bit #M is encoded as GENMASK(M + N - 1, M). Note that
bit numbers refer to endianness of the object we are working with -
e.g. GENMASK(11, 0) in __be16 refers to the second byte and the lower
4 bits of the first byte. In __le16 it would refer to the first byte
and the lower 4 bits of the second byte, etc.
Field specification must be a constant; __builtin_constant_p() doesn't
have to be true for it, but compiler must be able to evaluate it at
build time. If it cannot or if the value does not encode any bitfield,
the build will fail.
If the value being stored in a bitfield is a constant that does not fit
into that bitfield, a warning will be generated at compile time.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2017-12-14 21:27:55 -05:00
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2025-07-09 10:38:08 +01:00
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Add primitives for manipulating bitfields both in host- and fixed-endian.
The following primitives are defined in linux/bitfield.h:
* u32 le32_get_bits(__le32 val, u32 field) extracts the contents of the
bitfield specified by @field in little-endian 32bit object @val and
converts it to host-endian.
* void le32p_replace_bits(__le32 *p, u32 v, u32 field) replaces
the contents of the bitfield specified by @field in little-endian
32bit object pointed to by @p with the value of @v. New value is
given in host-endian and stored as little-endian.
* __le32 le32_replace_bits(__le32 old, u32 v, u32 field) is equivalent to
({__le32 tmp = old; le32p_replace_bits(&tmp, v, field); tmp;})
In other words, instead of modifying an object in memory, it takes
the initial value and returns the modified one.
* __le32 le32_encode_bits(u32 v, u32 field) is equivalent to
le32_replace_bits(0, v, field). In other words, it returns a little-endian
32bit object with the bitfield specified by @field containing the
value of @v and all bits outside that bitfield being zero.
Such set of helpers is defined for each of little-, big- and host-endian
types; e.g. u64_get_bits(val, field) will return the contents of the bitfield
specified by @field in host-endian 64bit object @val, etc. Of course, for
host-endian no conversion is involved.
Fields to access are specified as GENMASK() values - an N-bit field
starting at bit #M is encoded as GENMASK(M + N - 1, M). Note that
bit numbers refer to endianness of the object we are working with -
e.g. GENMASK(11, 0) in __be16 refers to the second byte and the lower
4 bits of the first byte. In __le16 it would refer to the first byte
and the lower 4 bits of the second byte, etc.
Field specification must be a constant; __builtin_constant_p() doesn't
have to be true for it, but compiler must be able to evaluate it at
build time. If it cannot or if the value does not encode any bitfield,
the build will fail.
If the value being stored in a bitfield is a constant that does not fit
into that bitfield, a warning will be generated at compile time.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2017-12-14 21:27:55 -05:00
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2018-06-20 08:58:28 +02:00
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Add primitives for manipulating bitfields both in host- and fixed-endian.
The following primitives are defined in linux/bitfield.h:
* u32 le32_get_bits(__le32 val, u32 field) extracts the contents of the
bitfield specified by @field in little-endian 32bit object @val and
converts it to host-endian.
* void le32p_replace_bits(__le32 *p, u32 v, u32 field) replaces
the contents of the bitfield specified by @field in little-endian
32bit object pointed to by @p with the value of @v. New value is
given in host-endian and stored as little-endian.
* __le32 le32_replace_bits(__le32 old, u32 v, u32 field) is equivalent to
({__le32 tmp = old; le32p_replace_bits(&tmp, v, field); tmp;})
In other words, instead of modifying an object in memory, it takes
the initial value and returns the modified one.
* __le32 le32_encode_bits(u32 v, u32 field) is equivalent to
le32_replace_bits(0, v, field). In other words, it returns a little-endian
32bit object with the bitfield specified by @field containing the
value of @v and all bits outside that bitfield being zero.
Such set of helpers is defined for each of little-, big- and host-endian
types; e.g. u64_get_bits(val, field) will return the contents of the bitfield
specified by @field in host-endian 64bit object @val, etc. Of course, for
host-endian no conversion is involved.
Fields to access are specified as GENMASK() values - an N-bit field
starting at bit #M is encoded as GENMASK(M + N - 1, M). Note that
bit numbers refer to endianness of the object we are working with -
e.g. GENMASK(11, 0) in __be16 refers to the second byte and the lower
4 bits of the first byte. In __le16 it would refer to the first byte
and the lower 4 bits of the second byte, etc.
Field specification must be a constant; __builtin_constant_p() doesn't
have to be true for it, but compiler must be able to evaluate it at
build time. If it cannot or if the value does not encode any bitfield,
the build will fail.
If the value being stored in a bitfield is a constant that does not fit
into that bitfield, a warning will be generated at compile time.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2017-12-14 21:27:55 -05:00
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2025-07-09 10:38:08 +01:00
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|
Add primitives for manipulating bitfields both in host- and fixed-endian.
The following primitives are defined in linux/bitfield.h:
* u32 le32_get_bits(__le32 val, u32 field) extracts the contents of the
bitfield specified by @field in little-endian 32bit object @val and
converts it to host-endian.
* void le32p_replace_bits(__le32 *p, u32 v, u32 field) replaces
the contents of the bitfield specified by @field in little-endian
32bit object pointed to by @p with the value of @v. New value is
given in host-endian and stored as little-endian.
* __le32 le32_replace_bits(__le32 old, u32 v, u32 field) is equivalent to
({__le32 tmp = old; le32p_replace_bits(&tmp, v, field); tmp;})
In other words, instead of modifying an object in memory, it takes
the initial value and returns the modified one.
* __le32 le32_encode_bits(u32 v, u32 field) is equivalent to
le32_replace_bits(0, v, field). In other words, it returns a little-endian
32bit object with the bitfield specified by @field containing the
value of @v and all bits outside that bitfield being zero.
Such set of helpers is defined for each of little-, big- and host-endian
types; e.g. u64_get_bits(val, field) will return the contents of the bitfield
specified by @field in host-endian 64bit object @val, etc. Of course, for
host-endian no conversion is involved.
Fields to access are specified as GENMASK() values - an N-bit field
starting at bit #M is encoded as GENMASK(M + N - 1, M). Note that
bit numbers refer to endianness of the object we are working with -
e.g. GENMASK(11, 0) in __be16 refers to the second byte and the lower
4 bits of the first byte. In __le16 it would refer to the first byte
and the lower 4 bits of the second byte, etc.
Field specification must be a constant; __builtin_constant_p() doesn't
have to be true for it, but compiler must be able to evaluate it at
build time. If it cannot or if the value does not encode any bitfield,
the build will fail.
If the value being stored in a bitfield is a constant that does not fit
into that bitfield, a warning will be generated at compile time.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2017-12-14 21:27:55 -05:00
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2025-07-09 10:38:08 +01:00
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Add primitives for manipulating bitfields both in host- and fixed-endian.
The following primitives are defined in linux/bitfield.h:
* u32 le32_get_bits(__le32 val, u32 field) extracts the contents of the
bitfield specified by @field in little-endian 32bit object @val and
converts it to host-endian.
* void le32p_replace_bits(__le32 *p, u32 v, u32 field) replaces
the contents of the bitfield specified by @field in little-endian
32bit object pointed to by @p with the value of @v. New value is
given in host-endian and stored as little-endian.
* __le32 le32_replace_bits(__le32 old, u32 v, u32 field) is equivalent to
({__le32 tmp = old; le32p_replace_bits(&tmp, v, field); tmp;})
In other words, instead of modifying an object in memory, it takes
the initial value and returns the modified one.
* __le32 le32_encode_bits(u32 v, u32 field) is equivalent to
le32_replace_bits(0, v, field). In other words, it returns a little-endian
32bit object with the bitfield specified by @field containing the
value of @v and all bits outside that bitfield being zero.
Such set of helpers is defined for each of little-, big- and host-endian
types; e.g. u64_get_bits(val, field) will return the contents of the bitfield
specified by @field in host-endian 64bit object @val, etc. Of course, for
host-endian no conversion is involved.
Fields to access are specified as GENMASK() values - an N-bit field
starting at bit #M is encoded as GENMASK(M + N - 1, M). Note that
bit numbers refer to endianness of the object we are working with -
e.g. GENMASK(11, 0) in __be16 refers to the second byte and the lower
4 bits of the first byte. In __le16 it would refer to the first byte
and the lower 4 bits of the second byte, etc.
Field specification must be a constant; __builtin_constant_p() doesn't
have to be true for it, but compiler must be able to evaluate it at
build time. If it cannot or if the value does not encode any bitfield,
the build will fail.
If the value being stored in a bitfield is a constant that does not fit
into that bitfield, a warning will be generated at compile time.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2017-12-14 21:27:55 -05:00
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2018-06-20 08:58:29 +02:00
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Add primitives for manipulating bitfields both in host- and fixed-endian.
The following primitives are defined in linux/bitfield.h:
* u32 le32_get_bits(__le32 val, u32 field) extracts the contents of the
bitfield specified by @field in little-endian 32bit object @val and
converts it to host-endian.
* void le32p_replace_bits(__le32 *p, u32 v, u32 field) replaces
the contents of the bitfield specified by @field in little-endian
32bit object pointed to by @p with the value of @v. New value is
given in host-endian and stored as little-endian.
* __le32 le32_replace_bits(__le32 old, u32 v, u32 field) is equivalent to
({__le32 tmp = old; le32p_replace_bits(&tmp, v, field); tmp;})
In other words, instead of modifying an object in memory, it takes
the initial value and returns the modified one.
* __le32 le32_encode_bits(u32 v, u32 field) is equivalent to
le32_replace_bits(0, v, field). In other words, it returns a little-endian
32bit object with the bitfield specified by @field containing the
value of @v and all bits outside that bitfield being zero.
Such set of helpers is defined for each of little-, big- and host-endian
types; e.g. u64_get_bits(val, field) will return the contents of the bitfield
specified by @field in host-endian 64bit object @val, etc. Of course, for
host-endian no conversion is involved.
Fields to access are specified as GENMASK() values - an N-bit field
starting at bit #M is encoded as GENMASK(M + N - 1, M). Note that
bit numbers refer to endianness of the object we are working with -
e.g. GENMASK(11, 0) in __be16 refers to the second byte and the lower
4 bits of the first byte. In __le16 it would refer to the first byte
and the lower 4 bits of the second byte, etc.
Field specification must be a constant; __builtin_constant_p() doesn't
have to be true for it, but compiler must be able to evaluate it at
build time. If it cannot or if the value does not encode any bitfield,
the build will fail.
If the value being stored in a bitfield is a constant that does not fit
into that bitfield, a warning will be generated at compile time.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2017-12-14 21:27:55 -05:00
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bitfield: Add non-constant field_{prep,get}() helpers
The existing FIELD_{GET,PREP}() macros are limited to compile-time
constants. However, it is very common to prepare or extract bitfield
elements where the bitfield mask is not a compile-time constant.
To avoid this limitation, the AT91 clock driver and several other
drivers already have their own non-const field_{prep,get}() macros.
Make them available for general use by adding them to
<linux/bitfield.h>, and improve them slightly:
1. Avoid evaluating macro parameters more than once,
2. Replace "ffs() - 1" by "__ffs()",
3. Support 64-bit use on 32-bit architectures,
4. Wire field_{get,prep}() to FIELD_{GET,PREP}() when mask is
actually constant.
This is deliberately not merged into the existing FIELD_{GET,PREP}()
macros, as people expressed the desire to keep stricter variants for
increased safety, or for performance critical paths.
Yury: use __mask withing new macros.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: Crt Mori <cmo@melexis.com>
Acked-by: Nuno Sá <nuno.sa@analog.com>
Acked-by: Richard Genoud <richard.genoud@bootlin.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Reviewed-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
2025-11-06 14:34:01 +01:00
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2025-12-16 17:21:53 -08:00
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bitfield: Add non-constant field_{prep,get}() helpers
The existing FIELD_{GET,PREP}() macros are limited to compile-time
constants. However, it is very common to prepare or extract bitfield
elements where the bitfield mask is not a compile-time constant.
To avoid this limitation, the AT91 clock driver and several other
drivers already have their own non-const field_{prep,get}() macros.
Make them available for general use by adding them to
<linux/bitfield.h>, and improve them slightly:
1. Avoid evaluating macro parameters more than once,
2. Replace "ffs() - 1" by "__ffs()",
3. Support 64-bit use on 32-bit architectures,
4. Wire field_{get,prep}() to FIELD_{GET,PREP}() when mask is
actually constant.
This is deliberately not merged into the existing FIELD_{GET,PREP}()
macros, as people expressed the desire to keep stricter variants for
increased safety, or for performance critical paths.
Yury: use __mask withing new macros.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: Crt Mori <cmo@melexis.com>
Acked-by: Nuno Sá <nuno.sa@analog.com>
Acked-by: Richard Genoud <richard.genoud@bootlin.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Reviewed-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
2025-11-06 14:34:01 +01:00
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2025-12-16 17:21:53 -08:00
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bitfield: Add non-constant field_{prep,get}() helpers
The existing FIELD_{GET,PREP}() macros are limited to compile-time
constants. However, it is very common to prepare or extract bitfield
elements where the bitfield mask is not a compile-time constant.
To avoid this limitation, the AT91 clock driver and several other
drivers already have their own non-const field_{prep,get}() macros.
Make them available for general use by adding them to
<linux/bitfield.h>, and improve them slightly:
1. Avoid evaluating macro parameters more than once,
2. Replace "ffs() - 1" by "__ffs()",
3. Support 64-bit use on 32-bit architectures,
4. Wire field_{get,prep}() to FIELD_{GET,PREP}() when mask is
actually constant.
This is deliberately not merged into the existing FIELD_{GET,PREP}()
macros, as people expressed the desire to keep stricter variants for
increased safety, or for performance critical paths.
Yury: use __mask withing new macros.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: Crt Mori <cmo@melexis.com>
Acked-by: Nuno Sá <nuno.sa@analog.com>
Acked-by: Richard Genoud <richard.genoud@bootlin.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Reviewed-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
2025-11-06 14:34:01 +01:00
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2016-08-31 12:46:44 +01:00
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