| Message ID | 20250223164217.2139331-3-visitorckw@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Introduce and use generic parity32/64 helper | expand |
On 23. 02. 25, 17:42, Kuan-Wei Chiu wrote: > 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 <eleanor15x@gmail.com> > Signed-off-by: Yu-Chun Lin <eleanor15x@gmail.com> > 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; Do we need all these implementations? Can't we simply use parity64() for any 8, 16 and 32-bit values too? I.e. have one parity(). > + 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
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