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

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Message-ID: <1d70b1c8-f5f7-4027-a0cb-b1638e309a48@quicinc.com>
Date: Wed, 23 Apr 2025 21:19:43 +0800
From: Jie Luo <quic_luoj@...cinc.com>
To: Yury Norov <yury.norov@...il.com>, Marc Zyngier <maz@...nel.org>
CC: Andrew Lunn <andrew@...n.ch>, 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 4/19/2025 1:04 AM, Yury Norov wrote:
>>>> I think a bunch of people have found them, tooling notwithstanding.
>>>>
>>>> As for the documentation, the commit message in 00b0c9b82663ac would
>>>> be advantageously promoted to full-fledged kernel-doc.
>>> The FIELD_MODIFY() and uxx_replace_bits() are simply different things.
>>>
>>> FIELD_MODIFY() employs __BF_FIELD_CHECK(), which allows strict
>>> parameters checking at compile time. And people like it. See
>>> recent fixed-size GENMASK() series:
>>>
>>> https://patchwork.kernel.org/comment/26283604/
>> I don't care much for what people like or not. I don't see this
>> FIELD_MODIFY() as a particular improvement on *_replace_bits().
> Sad to hear that. Those people are all kernel engineers, and they
> deserve some respect.
> 
> We are talking about tooling here. People use tools only if they like
> them. Luo likes FIELD_MODIFY() over (yes, undocumented and ungreppable)
> xx_replace_bits() for the reasons he described very clearly. He's going
> to use it in his driver shortly, and this arm64 detour has been made
> after my request.
> 
>  From my perspective, both functions have their right to live in kernel.
> They are similar but not identical.
> 
> I'll take patch #1 in my branch. Regarding ARM64 part - it's up to you
> either to switch to FIELD_MODIFY(), _replace_bits(), or do nothing.
> 
> Thanks,
> Yury

Thank you for reviewing and discussing this patch series. The newly
added macro FIELD_MODIFY() will be utilized by the Qualcomm PPE (Packet
Processing Engine) Ethernet driver. Regarding the ARM64 core files,
could you please provide guidance on the preferred approach?