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

[Guenter Roeck]

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