[PATCH v3 00/16] Introduce and use generic parity16/32/64 helper

Kuan-Wei Chiu
2025-03-06T16:28:10Z

Several parts of the kernel contain redundant implementations of parity
calculations for 16/32/64-bit values. Introduces generic
parity16/32/64() helpers in bitops.h, providing a standardized
and optimized implementation.

Subsequent patches refactor various kernel components to replace
open-coded parity calculations with the new helpers, reducing code
duplication and improving maintainability.

Co-developed-by: Yu-Chun Lin <eleanor15x@gmail.com>
Signed-off-by: Yu-Chun Lin <eleanor15x@gmail.com>
Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
---
In v3, I use parityXX() instead of the parity() macro since the
parity() macro may generate suboptimal code and requires special hacks
to make GCC happy. If anyone still prefers a single parity() macro,
please let me know.

Additionally, I changed parityXX() << y users to !!parityXX() << y
because, unlike C++, C does not guarantee that true casts to int as 1.

Changes in v3:
- Avoid using __builtin_parity.
- Change return type to bool.
- Drop parity() macro.
- Change parityXX() << y to !!parityXX() << y.

Changes in v2:
- Provide fallback functions for __builtin_parity() when the compiler
decides not to inline it
- Use __builtin_parity() when no architecture-specific implementation
is available
- Optimize for constant folding when val is a compile-time constant
- Add a generic parity() macro
- Drop the x86 bootflag conversion patch since it has been merged into
the tip tree

v1: https://lore.kernel.org/lkml/20250223164217.2139331-1-visitorckw@gmail.com/
v2: https://lore.kernel.org/lkml/20250301142409.2513835-1-visitorckw@gmail.com/

Kuan-Wei Chiu (16):
bitops: Change parity8() return type to bool
bitops: Add parity16(), parity32(), and parity64() helpers
media: media/test_drivers: Replace open-coded parity calculation with
parity8()
media: pci: cx18-av-vbi: Replace open-coded parity calculation with
parity8()
media: saa7115: Replace open-coded parity calculation with parity8()
serial: max3100: Replace open-coded parity calculation with parity8()
lib/bch: Replace open-coded parity calculation with parity32()
Input: joystick - Replace open-coded parity calculation with
parity32()
net: ethernet: oa_tc6: Replace open-coded parity calculation with
parity32()
wifi: brcm80211: Replace open-coded parity calculation with parity32()
drm/bridge: dw-hdmi: Replace open-coded parity calculation with
parity32()
mtd: ssfdc: Replace open-coded parity calculation with parity32()
fsi: i2cr: Replace open-coded parity calculation with parity32()
fsi: i2cr: Replace open-coded parity calculation with parity64()
Input: joystick - Replace open-coded parity calculation with
parity64()
nfp: bpf: Replace open-coded parity calculation with parity64()

drivers/fsi/fsi-master-i2cr.c | 18 ++-----
.../drm/bridge/synopsys/dw-hdmi-ahb-audio.c | 8 +--
drivers/input/joystick/grip_mp.c | 17 +-----
drivers/input/joystick/sidewinder.c | 24 ++-------
drivers/media/i2c/saa7115.c | 12 +----
drivers/media/pci/cx18/cx18-av-vbi.c | 12 +----
.../media/test-drivers/vivid/vivid-vbi-gen.c | 8 +--
drivers/mtd/ssfdc.c | 20 ++-----
drivers/net/ethernet/netronome/nfp/nfp_asm.c | 7 +--
drivers/net/ethernet/oa_tc6.c | 19 ++-----
.../broadcom/brcm80211/brcmsmac/dma.c | 16 +-----
drivers/tty/serial/max3100.c | 3 +-
include/linux/bitops.h | 52 +++++++++++++++++--
lib/bch.c | 14 +----
14 files changed, 77 insertions(+), 153 deletions(-)

--
2.34.1