From: Yury Norov <ynorov@nvidia.com>
To: Petr Tesarik <ptesarik@suse.com>
Cc: Yury Norov <yury.norov@gmail.com>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Richard Henderson <richard.henderson@linaro.org>,
Matt Turner <mattst88@gmail.com>,
Magnus Lindholm <linmag7@gmail.com>,
Vineet Gupta <vgupta@kernel.org>,
Geert Uytterhoeven <geert@linux-m68k.org>,
"Maciej W. Rozycki" <macro@orcam.me.uk>,
Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
Madhavan Srinivasan <maddy@linux.ibm.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Heiko Carstens <hca@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>,
Alexander Gordeev <agordeev@linux.ibm.com>,
Chris Zankel <chris@zankel.net>,
Max Filippov <jcmvbkbc@gmail.com>,
Patrik Jakobsson <patrik.r.jakobsson@gmail.com>,
Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
Maxime Ripard <mripard@kernel.org>,
Thomas Zimmermann <tzimmermann@suse.de>,
David Airlie <airlied@gmail.com>, Simona Vetter <simona@ffwll.ch>,
Robin Murphy <robin.murphy@arm.com>,
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Jakub Kicinski <kuba@kernel.org>,
Andrew Lunn <andrew+netdev@lunn.ch>,
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Eric Dumazet <edumazet@google.com>,
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Oliver Neukum <oliver@neukum.org>, Arnd Bergmann <arnd@arndb.de>,
Kuan-Wei Chiu <visitorckw@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Marcel Holtmann <marcel@holtmann.org>,
Johan Hedberg <johan.hedberg@gmail.com>,
Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
Pablo Neira Ayuso <pablo@netfilter.org>,
Florian Westphal <fw@strlen.de>,
linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 1/2] bits: introduce ffs_val()
Date: Fri, 9 Jan 2026 14:44:08 -0500 [thread overview]
Message-ID: <aWFaiEvJyj_35-NK@yury> (raw)
In-Reply-To: <20260109202711.5f356b3e@mordecai>
On Fri, Jan 09, 2026 at 08:27:11PM +0100, Petr Tesarik wrote:
> On Fri, 9 Jan 2026 13:26:30 -0500
> Yury Norov <ynorov@nvidia.com> wrote:
...
> > In bitops world, something_mask() has a very clear meaning. Consider
> > GENMASK(), BITMAP_FIRST_BYTE_MASK(), __BF_FIELD_CHECK_MASK(), and so
> > on.
> >
> > lsb_mask(), or LSB_MASK() if you prefer, is just right.
>
> I assume you mean BITMAP_FIRST_WORD_MASK(), not btrfs-specific
> BITMAP_FIRST_BYTE_MASK(), defined in fs/btrfs/extent_io.h.
>
> But then it nicely illustrate exactly what I mean:
They all have a consistent meaning:
> BIT_MASK(4) = 0x0000000000000010
A mask constructed from bit #4.
> GENMASK(4, 0) = 0x000000000000001f
A mask constructed from bits #0..4.
> BITMAP_FIRST_WORD_MASK(4) == 0xfffffffffffffff0
A mask constructed from all bits starting #4.
Don't see any misalignment here.
> > > The only issue is that LSB may also refer to least-significant BYTE. :-(
> >
> > It will never mean byte because it hosts in bitops.h, not byteops.h
>
> I'm afraid that identifiers from various sources end up next to each
> other and they do not carry tags where each of them came from...
You can name it lsb_bitmask() if you want, either way works. But to me
shorter is better.
next prev parent reply other threads:[~2026-01-09 19:44 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-09 16:41 [RFC PATCH 0/2] Helper to isolate least-significant bit Petr Tesarik
2026-01-09 16:37 ` [RFC PATCH 1/2] bits: introduce ffs_val() Petr Tesarik
2026-01-09 17:01 ` Arnd Bergmann
2026-01-09 23:54 ` David Laight
2026-01-09 17:16 ` Yury Norov
2026-01-09 17:46 ` Petr Tesarik
2026-01-09 18:26 ` Yury Norov
2026-01-09 19:27 ` Petr Tesarik
2026-01-09 19:44 ` Yury Norov [this message]
2026-01-09 18:50 ` Arnd Bergmann
2026-01-10 10:50 ` David Laight
2026-01-12 8:15 ` Thomas Zimmermann
2026-01-12 8:58 ` Petr Tesarik
2026-01-12 11:22 ` David Laight
2026-01-13 1:40 ` Maciej W. Rozycki
2026-01-09 16:37 ` [RFC PATCH 2/2] treewide, bits: use ffs_val() where it is open-coded Petr Tesarik
2026-01-09 18:19 ` Yury Norov
2026-01-09 19:32 ` Petr Tesarik
2026-01-09 20:19 ` Yury Norov
2026-01-10 10:36 ` Maciej W. Rozycki
2026-01-10 11:54 ` David Laight
2026-01-11 3:15 ` Maciej W. Rozycki
2026-01-11 10:40 ` David Laight
2026-01-11 21:22 ` Maciej W. Rozycki
2026-01-11 23:57 ` David Laight
2026-01-12 11:21 ` Maciej W. Rozycki
2026-01-12 13:23 ` David Laight
2026-01-10 16:42 ` Kuan-Wei Chiu
2026-01-10 22:23 ` David Laight
2026-01-11 14:41 ` Kuan-Wei Chiu
2026-01-11 21:22 ` Maciej W. Rozycki
2026-01-09 17:20 ` [RFC PATCH 0/2] Helper to isolate least-significant bit Kuan-Wei Chiu
2026-01-09 18:59 ` Petr Tesarik
2026-01-09 19:26 ` Andrew Cooper
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