linux-kernel - Re: [PATCH 01/20] bitfield: introduce HWORD

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Message-ID: <22744779.EfDdHjke4D@workhorse>
Date: Thu, 12 Jun 2025 21:50:12 +0200
From: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Yury Norov <yury.norov@...il.com>,
 Rasmus Villemoes <linux@...musvillemoes.dk>,
 Jaehoon Chung <jh80.chung@...sung.com>, Ulf Hansson <ulf.hansson@...aro.org>,
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Subject: Re: [PATCH 01/20] bitfield: introduce HWORD_UPDATE bitfield macros

On Thursday, 12 June 2025 21:44:15 Central European Summer Time Jakub Kicinski wrote:
> On Thu, 12 Jun 2025 20:56:03 +0200 Nicolas Frattaroli wrote:
> > Hardware of various vendors, but very notably Rockchip, often uses
> > 32-bit registers where the upper 16-bit half of the register is a
> > write-enable mask for the lower half.
> 
> Please limit the spread of this weirdness to a rockchip or "hiword"
> specific header. To a normal reader of bitfield.h these macros will
> be equally confusing and useless.
> 

That is how this change started out, and then a different maintainer told
me that this is a commonly used thing (see: the sunplus patch), and
Rockchip just happens to have a lot of these with consistent naming.

I believe normal readers of bitfield.h will be much more confused by the
undocumented concatenating macro soup at the end, but maybe that's just
me.

Best regards,
Nicolas Frattaroli