linux-kernel - Re: [PATCH v3 00/20] BYEWORD_UPDATE: unifying (most) HIWORD

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Message-ID: <aLeMJjfhisYSIEph@yury>
Date: Tue, 2 Sep 2025 20:30:30 -0400
From: Yury Norov <yury.norov@...il.com>
To: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>
Cc: Rasmus Villemoes <linux@...musvillemoes.dk>,
	Jaehoon Chung <jh80.chung@...sung.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
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	Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
Subject: Re: [PATCH v3 00/20] BYEWORD_UPDATE: unifying (most) HIWORD_UPDATE
 macros

On Mon, Aug 25, 2025 at 10:28:20AM +0200, Nicolas Frattaroli wrote:
> This series was spawned by [1], where I was asked to move every instance
> of HIWORD_UPDATE et al that I could find to a common macro in the same
> series that I am introducing said common macro.
> 
> The first patch of the series introduces a new header file,
> hw_bitfield.h, which contains two new macros: FIELD_PREP_WM16 and
> FIELD_PREP_WM16_CONST. The latter can be used in initializers.
> 
> I've cheekily added the hw_bitfield.h header to the BITMAP API section
> of the MAINTAINERS file.
> 
> This macro definition checks that the mask fits, and that the value fits
> in the mask. Like FIELD_PREP, it also shifts the value up to the mask,
> so turning off a bit does not require using the mask as a value. Masks
> are also required to be contiguous, like with FIELD_PREP.
> 
> For each definition of such a macro, the driver(s) that used it were
> evaluated for three different treatments:
>  - full conversion to the new macro, for cases where replacing the
>    implementation of the old macro wouldn't have worked, or where the
>    conversion was trivial. These are the most complex patches in this
>    series, as they sometimes have to pull apart definitions of masks
>    and values due to the new semantics, which require a contiguous
>    mask and shift the value for us.
>  - replacing the implementation of the old macro with an instance of the
>    new macro, done where I felt it made the patch much easier to review
>    because I didn't want to drop a big diff on people.
>  - skipping conversion entirely, usually because the mask is
>    non-constant and it's not trivial to make it constant. Sometimes an
>    added complication is that said non-constant mask is either used in a
>    path where runtime overhead may not be desirable, or in an
>    initializer.

Applied in bitmap-for-next for testing.

Thanks,
Yury