linux-kernel - Re: [RFC PATCH 1/2] bitops: add generic parity calculation for u8

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Message-ID: <Z2EzKErhR2MomNz+@visitorckw-System-Product-Name>
Date: Tue, 17 Dec 2024 16:15:36 +0800
From: Kuan-Wei Chiu <visitorckw@...il.com>
To: Wolfram Sang <wsa+renesas@...g-engineering.com>
Cc: linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-hwmon@...r.kernel.org, Yury Norov <yury.norov@...il.com>,
	Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: Re: [RFC PATCH 1/2] bitops: add generic parity calculation for u8

On Sat, Dec 14, 2024 at 09:58:31AM +0100, Wolfram Sang wrote:
> There are multiple open coded implementations for getting the parity of
> a byte in the kernel, even using different approaches. Take the pretty
> efficient version from SPD5118 driver and make it generally available by
> putting it into the bitops header. As long as there is just one parity
> calculation helper, the creation of a distinct 'parity.h' header was
> discarded. Also, the usage of hweight8() for architectures having a
> popcnt instruction is postponed until a use case within hot paths is
> desired. The motivation for this patch is the frequent use of odd parity
> in the I3C specification and to simplify drivers there.
> 
> Changes compared to the original SPD5118 version are the addition of
> kernel documentation, switching the return type from bool to int, and
> renaming the argument of the function.
> 
> Signed-off-by: Wolfram Sang <wsa+renesas@...g-engineering.com>

Compare the results with hweight8(x) & 1 for correctness when x is in
the range [0, 255].

Reviewed-by: Kuan-Wei Chiu <visitorckw@...il.com>
Tested-by: Kuan-Wei Chiu <visitorckw@...il.com>

Regards,
Kuan-Wei