linux-kernel - Re: [RFC PATCH 2/2] treewide, bits: use ffs

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Message-ID: <20260109203250.08b6f746@mordecai>
Date: Fri, 9 Jan 2026 20:32:50 +0100
From: Petr Tesarik <ptesarik@...e.com>
To: Yury Norov <ynorov@...dia.com>
Cc: Yury Norov <yury.norov@...il.com>, Rasmus Villemoes
 <linux@...musvillemoes.dk>, Richard Henderson
 <richard.henderson@...aro.org>, Matt Turner <mattst88@...il.com>, Magnus
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 Madhavan Srinivasan <maddy@...ux.ibm.com>, Michael Ellerman
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 <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>,
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 <luiz.dentz@...il.com>, Pablo Neira Ayuso <pablo@...filter.org>, Florian
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Subject: Re: [RFC PATCH 2/2] treewide, bits: use ffs_val() where it is
 open-coded

On Fri, 9 Jan 2026 13:19:25 -0500
Yury Norov <ynorov@...dia.com> wrote:

>[...]
> --
> 
> OK, let me stop here.
> 
> Can you please instead of mechanical rework check each case
> individually and find the best replacement to highlight the intention?
> 
> Can you also split this patch to a series according to subsystems, so
> that corresponding maintainers will have better access to their changes?

Well, then it makes more sense to start by identifying the intention in
every place and getting them fixed one by one. Whatever remains should
be converted to use the new macro.

In fact, I can do both in parallel, converting the places where the
result of ffs() is immediately used as a shift count.

Then no tree-wide change is necessary, as long as we can first get the
helper (under whichever name) into bitops.h. But it will be rejected
without an in-tree user. I somehow feel caught by Catch XXII.

Advice welcome. Non-ironically.

Petr T