From: Petr Tesarik <ptesarik@suse.com>
To: Yury Norov <yury.norov@gmail.com>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: 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, Petr Tesarik <ptesarik@suse.com>
Subject: [RFC PATCH 0/2] Helper to isolate least-significant bit
Date: Fri, 9 Jan 2026 17:37:55 +0100 [thread overview]
Message-ID: <cover.1767974455.git.ptesarik@suse.com> (raw)
Isolation of the least significant bit can be achieved with 3 basic
ALU operations which are already open-coded in various places in the
kernel.
However, since other places less efficient constructs, for example
`1UL << ffs(x)`, I assume the trick is known only to some authors, and
it's worth adding a helper to promote its use.
Petr Tesarik (2):
bits: introduce ffs_val()
treewide, bits: use ffs_val() where it is open-coded
arch/alpha/include/asm/bitops.h | 2 +-
arch/alpha/kernel/core_cia.c | 2 +-
arch/alpha/kernel/smp.c | 2 +-
arch/arc/include/asm/bitops.h | 2 +-
arch/m68k/include/asm/bitops.h | 12 +++++------
arch/mips/dec/ecc-berr.c | 2 +-
arch/mips/include/asm/bitops.h | 4 ++--
arch/mips/pci/pci-malta.c | 4 ++--
arch/powerpc/include/asm/bitops.h | 4 ++--
arch/powerpc/kvm/e500_mmu_host.c | 2 +-
arch/powerpc/lib/sstep.c | 2 +-
arch/powerpc/xmon/ppc-dis.c | 3 ++-
arch/powerpc/xmon/ppc-opc.c | 6 +++---
arch/s390/include/asm/bitops.h | 2 +-
arch/xtensa/include/asm/bitops.h | 6 +++---
arch/xtensa/kernel/traps.c | 2 +-
drivers/gpu/drm/gma500/psb_intel_sdvo.c | 2 +-
drivers/iommu/dma-iommu.c | 2 +-
drivers/net/ethernet/netronome/nfp/bpf/jit.c | 2 +-
drivers/net/usb/cdc_ncm.c | 4 ++--
include/asm-generic/div64.h | 4 ++--
include/linux/bitfield.h | 3 ++-
include/linux/bitops.h | 1 +
include/linux/ffs_val.h | 21 ++++++++++++++++++++
include/linux/log2.h | 2 +-
include/linux/min_heap.h | 5 +++--
lib/math/gcd.c | 4 ++--
lib/sort.c | 3 ++-
net/bluetooth/mgmt.c | 2 +-
net/netfilter/nft_set_pipapo.c | 2 +-
30 files changed, 70 insertions(+), 44 deletions(-)
create mode 100644 include/linux/ffs_val.h
--
2.52.0
next reply other threads:[~2026-01-09 16:38 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-09 16:37 Petr Tesarik [this message]
2026-01-09 19:11 ` [RFC PATCH 0/2] Helper to isolate least-significant bit Geert Uytterhoeven
-- strict thread matches above, loose matches on Subject: below --
2026-01-09 16:41 Petr Tesarik
2026-01-09 17:20 ` 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=cover.1767974455.git.ptesarik@suse.com \
--to=ptesarik@suse.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=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.