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

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Message-ID: <315b4c75-a596-4509-99f7-921ebda2fed9@roeck-us.net>
Date: Wed, 9 Apr 2025 11:39:22 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Kuan-Wei Chiu <visitorckw@...il.com>, Yury Norov <yury.norov@...il.com>
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 Yu-Chun Lin <eleanor15x@...il.com>
Subject: Re: [PATCH v4 01/13] bitops: Change parity8() to parity_odd() with
 u64 input and bool return type

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@...il.com>
>>> Signed-off-by: Yu-Chun Lin <eleanor15x@...il.com>
>>> Signed-off-by: Kuan-Wei Chiu <visitorckw@...il.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