Re: [PATCH 14/14] [media] fix warning on v4l2_subdev_call() result interpreted as bool

From: Arnd Bergmann <arnd@arndb.de>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: devel@driverdev.osuosl.org,
	Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
	"Linux Media Mailing List" <linux-media@vger.kernel.org>,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"Daeseok Youn" <daeseok.youn@gmail.com>,
	"Linus Torvalds" <torvalds@linux-foundation.org>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	adi-buildroot-devel@lists.sourceforge.net,
	"Hans Verkuil" <hverkuil@xs4all.nl>,
	IDE-ML <linux-ide@vger.kernel.org>,
	"Guenter Roeck" <linux@roeck-us.net>,
	"Niklas Söderlund" <niklas.soderlund@ragnatech.se>,
	"Tejun Heo" <tj@kernel.org>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Mauro Carvalho Chehab" <mchehab@kernel.org>,
	"Robert Jarzmik" <robert.jarzmik@free.fr>,
	"Linux ARM" <linux-arm-kernel@lists.infradead.org>,
	"Alan Cox" <alan@linux.intel.com>
Subject: Re: [PATCH 14/14] [media] fix warning on v4l2_subdev_call() result interpreted as bool
Date: Fri, 14 Jul 2017 14:27:19 +0200	[thread overview]
Message-ID: <CAK8P3a0f84OPcCK1r3P9inGYDJC2KaAO4mjE2vn+vCws-oo_bw@mail.gmail.com> (raw)
In-Reply-To: <20170714120512.ioe67nnloqivtbr7@mwanda>

On Fri, Jul 14, 2017 at 2:05 PM, Dan Carpenter <dan.carpenter@oracle.com> wrote:
> Changing:
>
> - if (!frob()) {
> + if (frob() == 0) {
>
> is a totally pointless change.  They're both bad, because they're doing
> success testing instead of failure testing, but probably the second one
> is slightly worse.
>
> This warning seems dumb.  I can't imagine it has even a 10% success rate
> at finding real bugs.  Just disable it.
>
> Changing the code to propagate error codes, is the right thing of course
> so long as it doesn't introduce bugs.

It found a two of bugs that I fixed earlier:

f0e8faa7a5e8 ("ARM: ux500: fix prcmu_is_cpu_in_wfi() calculation")
af15769ffab1 ("scsi: mvsas: fix command_active typo")

plus three patches from this series:

1. staging:iio:resolver:ad2s1210 fix negative IIO_ANGL_VEL read
2. isdn: isdnloop: suppress a gcc-7 warning (my patch is wrong,
   as Joe pointed out there is a real bug)
3. drm/vmwgfx: avoid gcc-7 parentheses (here, Linus had a better
   analysis of the problem, so we should consider that a bug as well)

I would estimate around 25% success rate here, which isn't that
bad for a new warning.

I agree that most of the false positives are really dumb though.

       Arnd
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