linux-kernel - Re: [PATCH v3 0/6] Add FIELD

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Message-ID: <aAkm79R8f5Vf6TLh@shell.armlinux.org.uk>
Date: Wed, 23 Apr 2025 18:44:15 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Yury Norov <yury.norov@...il.com>
Cc: Marc Zyngier <maz@...nel.org>, Andrew Lunn <andrew@...n.ch>,
	Luo Jie <quic_luoj@...cinc.com>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Julia Lawall <Julia.Lawall@...ia.fr>,
	Nicolas Palix <nicolas.palix@...g.fr>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Oliver Upton <oliver.upton@...ux.dev>,
	Joey Gouly <joey.gouly@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Zenghui Yu <yuzenghui@...wei.com>, linux-kernel@...r.kernel.org,
	cocci@...ia.fr, linux-arm-kernel@...ts.infradead.org,
	kvmarm@...ts.linux.dev, quic_kkumarcs@...cinc.com,
	quic_linchen@...cinc.com, quic_leiwei@...cinc.com,
	quic_suruchia@...cinc.com, quic_pavir@...cinc.com
Subject: Re: [PATCH v3 0/6] Add FIELD_MODIFY() helper

On Fri, Apr 18, 2025 at 11:08:38AM -0400, Yury Norov wrote:
> The _replace_bits() functions return fixed-width values, and intended
> for: "manipulating bitfields both in host- and fixed-endian", as the
> very first line in the commit message says.
> 
> Those using _replace_bits() for something else abuse the API, and
> should switch to FIELD_MODIFY().

Sorry, but please explain this statement, because it means nothing to
me.

FIELD_MODIFY() replaces bits in host endian. _replace_bits() also
replaces bits, but has a wider range of which encompass FIELD_MODIFY().

I see nothing that precludes using using _replace_bits() with
bitfields.

I see nothing that would differentiate the behaviour, other than maybe
religous ideals about C functions vs macros or upper vs lower case.

Please explain why you think there's a difference between the two
because I really can't see any reason not to use one over the other
apart from asthetics.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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