From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Johannes Berg <johannes@sipsolutions.net>
Cc: Joe Perches <joe@perches.com>,
Andrew Morton <akpm@linux-foundation.org>,
Patrick Venture <venture@google.com>,
Nancy Yuen <yuenn@google.com>,
Benjamin Fair <benjaminfair@google.com>,
Andrew Jeffery <andrew@aj.id.au>,
openbmc@lists.ozlabs.org, linux-kernel@vger.kernel.org,
linux-aspeed@lists.ozlabs.org,
linux-arm-kernel@lists.infradead.org,
linux-amlogic@lists.infradead.org, netdev@vger.kernel.org,
linux-mediatek@lists.infradead.org,
linux-stm32@st-md-mailman.stormreply.com,
linux-wireless@vger.kernel.org, linux-media@vger.kernel.org,
linux-iio@vger.kernel.org, devel@driverdev.osuosl.org,
alsa-devel@alsa-project.org, linux-mmc@vger.kernel.org,
dri-devel@lists.freedesktop.org
Subject: Re: [PATCH 00/12] treewide: Fix GENMASK misuses
Date: Wed, 10 Jul 2019 10:43:37 +0100 [thread overview]
Message-ID: <20190710094337.wf2lftxzfjq2etro@shell.armlinux.org.uk> (raw)
In-Reply-To: <5fa1fa6998332642c49e2d5209193ffe2713f333.camel@sipsolutions.net>
On Wed, Jul 10, 2019 at 11:17:31AM +0200, Johannes Berg wrote:
> On Tue, 2019-07-09 at 22:04 -0700, Joe Perches wrote:
> > These GENMASK uses are inverted argument order and the
> > actual masks produced are incorrect. Fix them.
> >
> > Add checkpatch tests to help avoid more misuses too.
> >
> > Joe Perches (12):
> > checkpatch: Add GENMASK tests
>
> IMHO this doesn't make a lot of sense as a checkpatch test - just throw
> in a BUILD_BUG_ON()?
My personal take on this is that GENMASK() is really not useful, it's
just pure obfuscation and leads to exactly these kinds of mistakes.
Yes, I fully understand the argument that you can just specify the
start and end bits, and it _in theory_ makes the code more readable.
However, the problem is when writing code. GENMASK(a, b). Is a the
starting bit or ending bit? Is b the number of bits? It's confusing
and causes mistakes resulting in incorrect code. A BUILD_BUG_ON()
can catch some of the cases, but not all of them.
For example:
GENMASK(6, 2)
would satisify the requirement that a > b, so a BUILD_BUG_ON() will
not trigger, but was the author meaning 0x3c or 0xc0?
Personally, I've decided I am _not_ going to use GENMASK() in my code
because I struggle to get the macro arguments correct - I'm _much_
happier, and it is way more reliable for me to write the mask in hex
notation.
I think this is where use of a ternary operator would come in use. The
normal way of writing a number of bits tends to be "a:b", so if GENMASK
took something like GENMASK(6:2), then I'd have less issue with it,
because it's argument is then in a familiar notation.
Yes, I'm sure that someone will point out that the GENMASK arguments
are just in the same order, but that doesn't prevent _me_ frequently
getting it wrong - and that's the point. The macro seems to me to
cause more problems than it solves.
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up
According to speedtest.net: 11.9Mbps down 500kbps up
next prev parent reply other threads:[~2019-07-10 9:44 UTC|newest]
Thread overview: 109+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20190710050444epcas1p250f7aa0f8798a7757df51d66f5970c2a@epcas1p2.samsung.com>
2019-07-10 5:04 ` [PATCH 00/12] treewide: Fix GENMASK misuses Joe Perches
2019-07-10 5:04 ` [PATCH 01/12] checkpatch: Add GENMASK tests Joe Perches
2019-07-24 18:03 ` Joe Perches
2019-07-10 5:04 ` [PATCH 02/12] clocksource/drivers/npcm: Fix misuse of GENMASK macro Joe Perches
2019-07-10 9:10 ` [tip:timers/urgent] " tip-bot for Joe Perches
2019-07-15 10:00 ` [PATCH 02/12] " Avi Fishman
2019-07-10 5:04 ` [PATCH 03/12] drm: aspeed_gfx: " Joe Perches
2019-07-24 17:16 ` Joe Perches
2019-07-25 1:10 ` Andrew Jeffery
2019-07-25 1:18 ` Joe Perches
2019-07-25 2:52 ` Joel Stanley
2019-07-25 14:37 ` Joe Perches
2019-07-10 5:04 ` [PATCH 04/12] iio: adc: max9611: " Joe Perches
2019-07-14 11:54 ` Jonathan Cameron
2019-07-14 12:19 ` Joe Perches
2019-07-14 14:37 ` Jacopo Mondi
2019-07-29 21:52 ` Jacopo Mondi
2019-07-31 8:37 ` Jonathan Cameron
2019-07-10 5:04 ` [PATCH 05/12] irqchip/gic-v3-its: " Joe Perches
2019-07-10 8:28 ` Marc Zyngier
2019-07-10 9:07 ` [tip:irq/urgent] " tip-bot for Joe Perches
2019-07-10 5:04 ` [PATCH 06/12] mmc: meson-mx-sdio: " Joe Perches
2019-07-22 7:23 ` Neil Armstrong
2019-07-22 13:43 ` Ulf Hansson
2019-07-10 5:04 ` [PATCH 07/12] net: ethernet: mediatek: Fix misuses " Joe Perches
2019-07-10 5:04 ` [PATCH 08/12] net: stmmac: " Joe Perches
2019-07-10 10:33 ` Jose Abreu
2019-07-10 5:04 ` [PATCH 09/12] rtw88: Fix misuse " Joe Perches
2019-07-10 5:07 ` Tony Chuang
2019-07-24 11:48 ` Kalle Valo
2019-07-10 5:04 ` [PATCH 10/12] phy: amlogic: G12A: " Joe Perches
2019-07-22 7:23 ` Neil Armstrong
2019-08-23 2:41 ` Kishon Vijay Abraham I
2019-08-23 4:59 ` Joe Perches
2019-07-10 5:04 ` [PATCH 11/12] staging: media: cedrus: " Joe Perches
2019-07-10 7:23 ` Paul Kocialkowski
2019-07-24 17:09 ` Joe Perches
2019-07-24 18:35 ` Greg Kroah-Hartman
2019-07-24 18:39 ` Joe Perches
2019-07-24 18:55 ` Greg Kroah-Hartman
2019-07-25 6:46 ` Hans Verkuil
2019-07-10 5:04 ` [PATCH 12/12] ASoC: wcd9335: " Joe Perches
2019-07-22 12:22 ` Applied "ASoC: wcd9335: Fix misuse of GENMASK macro" to the asoc tree Mark Brown
2019-07-10 9:17 ` [PATCH 00/12] treewide: Fix GENMASK misuses Johannes Berg
2019-07-10 9:43 ` Russell King - ARM Linux admin [this message]
2019-07-10 15:45 ` Joe Perches
2019-07-10 16:01 ` Joe Perches
2019-07-27 19:54 ` Rikard Falkeborn
2019-07-28 23:45 ` Joe Perches
2019-07-31 19:03 ` [PATCH] linux/bits.h: Add compile time sanity check of GENMASK inputs Rikard Falkeborn
2019-07-31 19:27 ` Joe Perches
2019-08-01 23:03 ` Rikard Falkeborn
2019-08-02 1:40 ` Masahiro Yamada
2019-08-02 3:13 ` Joe Perches
2019-08-02 3:25 ` Masahiro Yamada
2019-08-02 18:18 ` Rikard Falkeborn
2019-08-03 3:03 ` Masahiro Yamada
2019-08-03 3:12 ` Masahiro Yamada
2019-08-03 18:36 ` Rikard Falkeborn
2019-08-04 6:45 ` Masahiro Yamada
2019-08-05 19:55 ` Rikard Falkeborn
2019-08-06 15:19 ` Masahiro Yamada
2019-08-06 19:27 ` Rikard Falkeborn
2019-08-06 21:15 ` Joe Perches
2019-08-07 20:53 ` Rikard Falkeborn
2019-08-01 2:50 ` Masahiro Yamada
2019-08-01 2:57 ` Joe Perches
2019-08-01 23:03 ` Rikard Falkeborn
2019-08-01 23:03 ` [PATCH v2 1/2] linux/bits.h: Clarify macro argument names Rikard Falkeborn
2019-08-01 23:03 ` [PATCH v2 2/2] linux/bits.h: Add compile time sanity check of GENMASK inputs Rikard Falkeborn
2019-08-01 23:14 ` Joe Perches
2019-08-07 14:27 ` Guenter Roeck
2019-08-07 14:55 ` Masahiro Yamada
2019-08-07 16:52 ` Guenter Roeck
2019-08-07 20:07 ` Rikard Falkeborn
2019-08-08 0:07 ` Joe Perches
2019-08-08 0:58 ` Guenter Roeck
2019-08-08 1:08 ` Joe Perches
2019-08-08 1:53 ` Guenter Roeck
2019-08-08 2:44 ` kbuild test robot
2019-08-08 2:44 ` kbuild test robot
2019-08-08 3:46 ` [PATCH v2 1/2] linux/bits.h: Clarify macro argument names Masahiro Yamada
2019-08-10 18:43 ` Rikard Falkeborn
2019-08-10 19:20 ` Joe Perches
2019-08-11 18:49 ` [PATCH v3 0/3] Add compile time sanity check of GENMASK inputs Rikard Falkeborn
2019-08-11 18:49 ` [PATCH v3 1/3] x86/boot: Use common BUILD_BUG_ON Rikard Falkeborn
2019-08-12 18:19 ` [tip:x86/boot] " tip-bot for Rikard Falkeborn
2019-08-16 12:19 ` tip-bot for Rikard Falkeborn
2019-08-11 18:49 ` [PATCH v3 2/3] linux/build_bug.h: Change type to int Rikard Falkeborn
2019-10-06 2:26 ` Masahiro Yamada
2019-08-11 18:49 ` [PATCH v3 3/3] linux/bits.h: Add compile time sanity check of GENMASK inputs Rikard Falkeborn
2019-10-06 2:30 ` Masahiro Yamada
2019-10-08 7:23 ` Geert Uytterhoeven
2019-10-08 7:44 ` Masahiro Yamada
2019-10-08 7:52 ` Masahiro Yamada
2019-10-08 19:06 ` Rikard Falkeborn
2019-08-12 17:58 ` [PATCH v3 0/3] " Kees Cook
2019-10-05 19:46 ` Rikard Falkeborn
2019-10-09 21:45 ` [Patch v4 0/2] " Rikard Falkeborn
2019-10-09 21:45 ` [Patch v4 1/2] linux/build_bug.h: Change type to int Rikard Falkeborn
2019-10-09 21:45 ` [Patch v4 2/2] linux/bits.h: Add compile time sanity check of GENMASK inputs Rikard Falkeborn
2019-10-10 2:24 ` Masahiro Yamada
2019-10-12 2:27 ` Andrew Morton
2019-10-22 19:53 ` Rikard Falkeborn
2019-11-01 21:28 ` Rikard Falkeborn
2020-03-08 19:39 ` [PATCH v5] " Rikard Falkeborn
2020-03-09 16:40 ` Kees Cook
2019-07-11 21:30 ` [PATCH 00/12] treewide: Fix GENMASK misuses David Miller
2019-07-12 12:54 ` Andrzej Hajda
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=20190710094337.wf2lftxzfjq2etro@shell.armlinux.org.uk \
--to=linux@armlinux.org.uk \
--cc=akpm@linux-foundation.org \
--cc=alsa-devel@alsa-project.org \
--cc=andrew@aj.id.au \
--cc=benjaminfair@google.com \
--cc=devel@driverdev.osuosl.org \
--cc=dri-devel@lists.freedesktop.org \
--cc=joe@perches.com \
--cc=johannes@sipsolutions.net \
--cc=linux-amlogic@lists.infradead.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-aspeed@lists.ozlabs.org \
--cc=linux-iio@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-media@vger.kernel.org \
--cc=linux-mediatek@lists.infradead.org \
--cc=linux-mmc@vger.kernel.org \
--cc=linux-stm32@st-md-mailman.stormreply.com \
--cc=linux-wireless@vger.kernel.org \
--cc=netdev@vger.kernel.org \
--cc=openbmc@lists.ozlabs.org \
--cc=venture@google.com \
--cc=yuenn@google.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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).