diff options
| author | Yury Norov <ynorov@nvidia.com> | 2026-05-06 13:52:03 -0400 |
|---|---|---|
| committer | Yury Norov <ynorov@nvidia.com> | 2026-05-28 11:39:16 -0400 |
| commit | 00751d655ece97fe85ce9193542ee8396fe98651 (patch) | |
| tree | 4d95cb8b90000b72d4a92bbaf1c6cac29de04c2c /lib | |
| parent | 42d9c75e8b9cae9583c228617be38ab1637fd574 (diff) | |
| download | linux-next-history-00751d655ece97fe85ce9193542ee8396fe98651.tar.gz | |
lib/bitrev: Introduce GENERIC_BITREVERSE
The generic bit reversal implementation is controlled by
!HAVE_ARCH_BITREVERSE. This makes it difficult for architectures to
provide a hardware-accelerated implementation while being able to
fall back to the generic version if needed.
This patch adds GENERIC_BITREVERSE, so bitreverse API is controlled by
BITREVERSE, GENERIC_BITREVERSE and HAVE_ARCH_BITREVERSE options. The
relationship between them is described as follows:
- BITREVERSE is selected by user code; it's required to generate the API;
- Architectures may select HAVE_ARCH_BITREVERSE and provide an arch
implementation in arch/$(ARCH)/include/asm/bitrev.h.
- if HAVE_ARCH_BITREVERSE isn't set, BITREVERSE selects GENERIC_BITREVERSE;
- if GENERIC_BITREVERSE is set and HAVE_ARCH_BITREVERSE is not, the kernel
provides generic implementation only, and wires bitrevXX() to it.
- if HAVE_ARCH_BITREVERSE is set and GENERIC_BITREVERSE is not, the arch
code provides __arch_bitrevXX(), and it is wired to bitrevXX();
- if both GENERIC_BITREVERSE and HAVE_ARCH_BITREVERSE are selected, the kernel
generates generic___bitrev(), but wires bitrev() to the __arch_bitrev().
The last option allows architectures to use generic___bitrev() as a
fallback option.
Drivers and core code should never select GENERIC_BITREVERSE or
HAVE_ARCH_BITREVERSE explicitly.
Architectures that require generic bitreverse API as a fallback should
explicitly enable GENERIC_BITREVERSE together with HAVE_ARCH_BITREVERSE.
Signed-off-by: Yury Norov <ynorov@nvidia.com>
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/Kconfig | 12 | ||||
| -rw-r--r-- | lib/Makefile | 2 | ||||
| -rw-r--r-- | lib/bitrev.c | 3 |
3 files changed, 13 insertions, 4 deletions
diff --git a/lib/Kconfig b/lib/Kconfig index d8e7e89ae3205..a33988adfaa3e 100644 --- a/lib/Kconfig +++ b/lib/Kconfig @@ -54,6 +54,7 @@ config PACKING_KUNIT_TEST config BITREVERSE tristate + select GENERIC_BITREVERSE if !HAVE_ARCH_BITREVERSE config HAVE_ARCH_BITREVERSE bool @@ -63,6 +64,17 @@ config HAVE_ARCH_BITREVERSE This option enables the use of hardware bit-reversal instructions on architectures which support such operations. +config GENERIC_BITREVERSE + tristate + depends on BITREVERSE + help + Generic bit reversal implementation. Drivers should never enable + it explicitly. Instead, enable BITREVERSE. + + Architectures may want to select it as a fall-back option for + HAVE_ARCH_BITREVERSE, when the hardware-accelerated bit reverse + instruction set is optional, like RISC-V ZBKB extension. + config ARCH_HAS_STRNCPY_FROM_USER bool diff --git a/lib/Makefile b/lib/Makefile index f33a24bf1c19a..23e07d19d01c9 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -145,7 +145,7 @@ obj-$(CONFIG_DEBUG_PREEMPT) += smp_processor_id.o obj-$(CONFIG_LIST_HARDENED) += list_debug.o obj-$(CONFIG_DEBUG_OBJECTS) += debugobjects.o -obj-$(CONFIG_BITREVERSE) += bitrev.o +obj-$(CONFIG_GENERIC_BITREVERSE) += bitrev.o obj-$(CONFIG_LINEAR_RANGES) += linear_ranges.o obj-$(CONFIG_PACKING) += packing.o obj-$(CONFIG_PACKING_KUNIT_TEST) += packing_test.o diff --git a/lib/bitrev.c b/lib/bitrev.c index 81b56e0a7f325..05088231f31fd 100644 --- a/lib/bitrev.c +++ b/lib/bitrev.c @@ -1,5 +1,4 @@ // SPDX-License-Identifier: GPL-2.0-only -#ifndef CONFIG_HAVE_ARCH_BITREVERSE #include <linux/types.h> #include <linux/module.h> #include <linux/bitrev.h> @@ -43,5 +42,3 @@ const u8 byte_rev_table[256] = { 0x1f, 0x9f, 0x5f, 0xdf, 0x3f, 0xbf, 0x7f, 0xff, }; EXPORT_SYMBOL_GPL(byte_rev_table); - -#endif /* CONFIG_HAVE_ARCH_BITREVERSE */ |