From: Joe Perches <joe@perches.com>
To: Robin Murphy <robin.murphy@arm.com>,
LKML <linux-kernel@vger.kernel.org>,
Jiri Kosina <trivial@kernel.org>
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Will Deacon <will@kernel.org>
Subject: Re: [trivial PATCH] treewide: Convert switch/case fallthrough; to break;
Date: Thu, 10 Sep 2020 21:19:35 -0700 [thread overview]
Message-ID: <f4ad706519917d493a0af32ea2da8565227cc74a.camel@perches.com> (raw)
In-Reply-To: <9372456a-8dcf-2735-57a4-e126aa5df3a6@arm.com>
On Thu, 2020-09-10 at 15:21 +0100, Robin Murphy wrote:
> On 2020-09-09 21:06, Joe Perches wrote:
> > fallthrough to a separate case/default label break; isn't very readable.
> >
> > Convert pseudo-keyword fallthrough; statements to a simple break; when
> > the next label is case or default and the only statement in the next
> > label block is break;
> >
> > Found using:
> >
> > $ grep-2.5.4 -rP --include=*.[ch] -n "fallthrough;(\s*(case\s+\w+|default)\s*:\s*){1,7}break;" *
> >
> > Miscellanea:
> >
> > o Move or coalesce a couple label blocks above a default: block.
> >
> > Signed-off-by: Joe Perches <joe@perches.com>
> > ---
> >
> > Compiled allyesconfig x86-64 only.
> > A few files for other arches were not compiled.
> >
>
> [...]
> > diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> > index c192544e874b..743db1abec40 100644
> > --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> > +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> > @@ -3777,7 +3777,7 @@ static int arm_smmu_device_hw_probe(struct arm_smmu_device *smmu)
> > switch (FIELD_GET(IDR0_TTF, reg)) {
> > case IDR0_TTF_AARCH32_64:
> > smmu->ias = 40;
> > - fallthrough;
> > + break;
> > case IDR0_TTF_AARCH64:
> > break;
> > default:
>
> I have to say I don't really agree with the readability argument for
> this one - a fallthrough is semantically correct here, since the first
> case is a superset of the second. It just happens that anything we would
> do for the common subset is implicitly assumed (there are other
> potential cases we simply haven't added support for at the moment), thus
> the second case is currently empty.
> This change actively obfuscates that distinction.
Then perhaps comments should be added to usefully
describe the mechanisms.
case IDR0_TTF_AARCH32_64:
smmu->ias = 40;
fallthrough; /* and still do the 64 bit processing */
case IDR0_TTF_AARCH64:
/* Nothing specific yet */
break;
> Robin.
next prev parent reply other threads:[~2020-09-11 4:20 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-09 20:06 [trivial PATCH] treewide: Convert switch/case fallthrough; to break; Joe Perches
2020-09-09 20:38 ` Gustavo A. R. Silva
2020-09-09 20:55 ` Keith Busch
2020-09-17 19:40 ` Jacob Keller
2020-09-09 22:36 ` Jason Gunthorpe
2020-09-09 22:47 ` Joe Perches
2020-09-10 6:28 ` Mauro Carvalho Chehab
2020-09-10 6:53 ` Wolfram Sang
2020-09-10 8:24 ` Nicolas.Ferre
2020-09-10 8:47 ` Felipe Balbi
2020-09-10 9:18 ` Steffen Maier
2020-09-10 9:24 ` Ilya Dryomov
2020-09-10 10:16 ` Matthias Brugger
2020-09-10 14:21 ` Robin Murphy
2020-09-11 4:19 ` Joe Perches [this message]
2020-09-15 9:06 ` [Intel-gfx] " Jani Nikula
2020-09-15 9:19 ` Miquel Raynal
2020-09-17 8:03 ` [oss-drivers] " Simon Horman
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