Re: [PATCH v4 01/13] bitops: Change parity8() to parity_odd() with u64 input and bool return type

Guenter Roeck
2025-05-15T09:20:30Z

On 4/9/25 11:25, Kuan-Wei Chiu wrote:
> On Wed, Apr 09, 2025 at 12:59:14PM -0400, Yury Norov wrote:
>> On Wed, Apr 09, 2025 at 11:43:44PM +0800, Kuan-Wei Chiu wrote:
>>> Redesign the parity8() helper as parity_odd(), changing its input type
>>> from u8 to u64 to support broader use cases and its return type from
>>> int to bool to clearly reflect the function's binary output. The
>>> function now returns true for odd parity and false for even parity,
>>> making its behavior more intuitive based on the name.
>>>
>>> Also mark the function with __attribute_const__ to enable better
>>> compiler optimization, as the result depends solely on its input and
>>> has no side effects.
>>>
>>> While more efficient implementations may exist, further optimization is
>>> postponed until a use case in performance-critical paths arises.
>>>
>>> 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>
>>> ---
>>> arch/x86/kernel/bootflag.c | 4 ++--
>>> 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 +-
>>> include/linux/bitops.h | 19 ++++++++++++-------
>>> 6 files changed, 18 insertions(+), 13 deletions(-)
>>>
>>> diff --git a/arch/x86/kernel/bootflag.c b/arch/x86/kernel/bootflag.c
>>> index 73274d76ce16..86aae4b2bfd5 100644
>>> --- a/arch/x86/kernel/bootflag.c
>>> +++ b/arch/x86/kernel/bootflag.c
>>> @@ -26,7 +26,7 @@ static void __init sbf_write(u8 v)
>>> unsigned long flags;
>>>
>>> if (sbf_port != -1) {
>>> - if (!parity8(v))
>>> + if (!parity_odd(v))

What is the benefit of this change all over the place instead of
adding parity_odd() as new API and keeping the old one (just letting
it call the new API) ?

A simple

static inline int parity8(u8 val)
{
return parity_odd(val);
}

would have done the trick and be much less invasive.

Guenter