Several parts of the kernel contain open-coded and redundant implementations of parity calculation. This patch series introduces a unified helper, parity_odd(), to simplify and standardize these cases.
The first patch renames parity8() to parity_odd(), changes its argument type from u8 to u64 for broader applicability, and updates its return type from int to bool to make its usage and return semantics more intuitive-returning true for odd parity and false for even parity. It also adds __attribute_const__ to enable compiler optimizations. While more efficient implementations may exist, further optimization is postponed until a use case in performance-critical paths arises. Subsequent patches refactor various kernel components to replace open-coded parity logic with the new helper, reducing code duplication and improving consistency. Co-developed-by: Yu-Chun Lin <eleanor...@gmail.com> Signed-off-by: Yu-Chun Lin <eleanor...@gmail.com> Signed-off-by: Kuan-Wei Chiu <visitor...@gmail.com> --- To H. Peter: I understand your preference for a parity8/16/32/64() style interface, and I agree that such a design would better accommodate potential arch-specific implementations. However, I suspect there are very few, if any, users who care about the performance of parity calculations enough to warrant such optimizations. So my inclination is to defer any arch-specific or optimized implementations until we see parity_odd() being used in hot paths. Changes in v4: - Rename parity8() to parity_odd(). - Change the argument type from u8 to u64. - Use a single parity_odd() function. 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 v3: https://lore.kernel.org/lkml/20250306162541.2633025-1-visitor...@gmail.com/ v1: https://lore.kernel.org/lkml/20250223164217.2139331-1-visitor...@gmail.com/ v2: https://lore.kernel.org/lkml/20250301142409.2513835-1-visitor...@gmail.com/ Kuan-Wei Chiu (13): bitops: Change parity8() to parity_odd() with u64 input and bool return type media: media/test_drivers: Replace open-coded parity calculation with parity_odd() media: pci: cx18-av-vbi: Replace open-coded parity calculation with parity_odd() media: saa7115: Replace open-coded parity calculation with parity_odd() serial: max3100: Replace open-coded parity calculation with parity_odd() lib/bch: Replace open-coded parity calculation with parity_odd() Input: joystick - Replace open-coded parity calculation with parity_odd() net: ethernet: oa_tc6: Replace open-coded parity calculation with parity_odd() wifi: brcm80211: Replace open-coded parity calculation with parity_odd() drm/bridge: dw-hdmi: Replace open-coded parity calculation with parity_odd() mtd: ssfdc: Replace open-coded parity calculation with parity_odd() fsi: i2cr: Replace open-coded parity calculation with parity_odd() nfp: bpf: Replace open-coded parity calculation with parity_odd() arch/x86/kernel/bootflag.c | 4 +-- drivers/fsi/fsi-master-i2cr.c | 20 +++------------ .../drm/bridge/synopsys/dw-hdmi-ahb-audio.c | 8 ++---- drivers/hwmon/spd5118.c | 2 +- drivers/i3c/master/dw-i3c-master.c | 2 +- drivers/i3c/master/i3c-master-cdns.c | 2 +- drivers/i3c/master/mipi-i3c-hci/dat_v1.c | 2 +- drivers/input/joystick/grip_mp.c | 17 ++----------- drivers/input/joystick/sidewinder.c | 25 ++++--------------- 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 | 18 ++----------- drivers/tty/serial/max3100.c | 3 ++- include/linux/bitops.h | 19 ++++++++------ lib/bch.c | 14 +---------- 19 files changed, 49 insertions(+), 165 deletions(-) -- 2.34.1
