[PATCH v2 0/2] Implement endianness swap macros for RISC-V

Ignacio Encinas
2025-03-19T21:10:08Z

Motivated by [1]. A couple of things to note:

RISC-V needs a default implementation to fall back on. Such
implementation is available in include/uapi/linux/swab.h in the form of
___constant_swabXX macros. As include/uapi/linux/swab.h can't be
included from arch/riscv/include/asm/swab.h, the default implementation
has been moved into asm-generic in the first patch of the series.

Tested with crc_kunit as pointed out in [2]. I can't provide performance
numbers as I don't have RISC-V hardware yet.

[1] https://lore.kernel.org/all/20250302220426.GC2079@quark.localdomain/
[2] https://lore.kernel.org/all/20250216225530.306980-1-ebiggers@kernel.org/

Signed-off-by: Ignacio Encinas <ignacio@iencinas.com>
---
Changes in v2:
- Introduce first patch factoring out the default implementation into
asm-generic

Patch 2:
- Remove blank line to make checkpatch happy
- Instead of duplicating the default implementation for swap macros,
leverage patch 1 and add an include to asm-generic/swab.h

- Link to v1: https://lore.kernel.org/r/20250310-riscv-swab-v1-1-34652ef1ee96@iencinas.com

---
Ignacio Encinas (2):
include/uapi/linux/swab.h: move default implementation for swab macros into asm-generic
riscv: introduce asm/swab.h

arch/riscv/include/asm/swab.h | 48 +++++++++++++++++++++++++++++++++++++++++
include/uapi/asm-generic/swab.h | 32 +++++++++++++++++++++++++++
include/uapi/linux/swab.h | 33 +---------------------------
3 files changed, 81 insertions(+), 32 deletions(-)
---
base-commit: a7f2e10ecd8f18b83951b0bab47ddaf48f93bf47
change-id: 20250307-riscv-swab-b81b94a9ac1b

Best regards,
--
Ignacio Encinas <ignacio@iencinas.com>