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

[Kuan-Wei Chiu]

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@xxxxxxxxx>
Signed-off-by: Yu-Chun Lin <eleanor15x@xxxxxxxxx>
Signed-off-by: Kuan-Wei Chiu <visitorckw@xxxxxxxxx>
---
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@xxxxxxxxx/
v2: https://lore.kernel.org/lkml/20250301142409.2513835-1-visitorckw@xxxxxxxxx/

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