[PATCH 02/17] bitops: Add generic parity calculation for u64
From: Kuan-Wei Chiu <visitorckw@gmail.com>
Date: 2025-02-23 16:43:13
Also in:
bpf, dri-devel, linux-input, linux-media, linux-serial, linux-wireless, lkml
Subsystem:
bitops api, the rest · Maintainers:
Yury Norov, Linus Torvalds
Several parts of the kernel open-code parity calculations using different methods. Add a generic parity64() helper implemented with the same efficient approach as parity8(). Co-developed-by: Yu-Chun Lin <redacted> Signed-off-by: Yu-Chun Lin <redacted> Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com> --- include/linux/bitops.h | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+)
diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index fb13dedad7aa..67677057f5e2 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h@@ -281,6 +281,28 @@ static inline int parity32(u32 val) return (0x6996 >> (val & 0xf)) & 1; } +/** + * parity64 - get the parity of an u64 value + * @value: the value to be examined + * + * Determine the parity of the u64 argument. + * + * Returns: + * 0 for even parity, 1 for odd parity + */ +static inline int parity64(u64 val) +{ + /* + * One explanation of this algorithm: + * https://funloop.org/codex/problem/parity/README.html + */ + val ^= val >> 32; + val ^= val >> 16; + val ^= val >> 8; + val ^= val >> 4; + return (0x6996 >> (val & 0xf)) & 1; +} + /** * __ffs64 - find first set bit in a 64 bit word * @word: The 64 bit word
--
2.34.1