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>,
Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
Jakub Kicinski <kuba@kernel.org>,
Andrew Lunn <andrew+netdev@lunn.ch>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Paolo Abeni <pabeni@redhat.com>,
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=aWFaiEvJyj_35-NK@yury \
--to=ynorov@nvidia.com \
--cc=agordeev@linux.ibm.com \
--cc=airlied@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=andrew+netdev@lunn.ch \
--cc=arnd@arndb.de \
--cc=chris@zankel.net \
--cc=davem@davemloft.net \
--cc=edumazet@google.com \
--cc=fw@strlen.de \
--cc=geert@linux-m68k.org \
--cc=gor@linux.ibm.com \
--cc=hca@linux.ibm.com \
--cc=jcmvbkbc@gmail.com \
--cc=johan.hedberg@gmail.com \
--cc=joro@8bytes.org \
--cc=kuba@kernel.org \
--cc=linmag7@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux@rasmusvillemoes.dk \
--cc=luiz.dentz@gmail.com \
--cc=maarten.lankhorst@linux.intel.com \
--cc=macro@orcam.me.uk \
--cc=maddy@linux.ibm.com \
--cc=marcel@holtmann.org \
--cc=mattst88@gmail.com \
--cc=mpe@ellerman.id.au \
--cc=mripard@kernel.org \
--cc=oliver@neukum.org \
--cc=pabeni@redhat.com \
--cc=pablo@netfilter.org \
--cc=patrik.r.jakobsson@gmail.com \
--cc=ptesarik@suse.com \
--cc=richard.henderson@linaro.org \
--cc=robin.murphy@arm.com \
--cc=simona@ffwll.ch \
--cc=tsbogend@alpha.franken.de \
--cc=tzimmermann@suse.de \
--cc=vgupta@kernel.org \
--cc=visitorckw@gmail.com \
--cc=will@kernel.org \
--cc=yury.norov@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.