linux-kernel - Re: [PATCH 13/14] iopoll: avoid -Wint-in-bool-context warning

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Date:   Fri, 14 Jul 2017 12:22:00 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Joe Perches <joe@...ches.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mark Brown <broonie@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Tejun Heo <tj@...nel.org>, Guenter Roeck <linux@...ck-us.net>,
        IDE-ML <linux-ide@...r.kernel.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
Subject: Re: [PATCH 13/14] iopoll: avoid -Wint-in-bool-context warning

On Fri, Jul 14, 2017 at 11:55 AM, Joe Perches <joe@...ches.com> wrote:
> On Fri, 2017-07-14 at 11:31 +0200, Arnd Bergmann wrote:
>> When we pass the result of a multiplication as the timeout, we
>> can get a warning:
>>
>> drivers/mmc/host/bcm2835.c:596:149: error: '*' in boolean context, suggest '&&' instead [-Werror=int-in-bool-context]
>> drivers/mfd/arizona-core.c:247:195: error: '*' in boolean context, suggest '&&' instead [-Werror=int-in-bool-context]
>>
>> This is easy to avoid by comparing the timeout to zero instead,
>> making it a boolean expression.
>
> Perhaps this is better as != 0 if the multiply is signed.

I thought about that, but decided that as a negative timeout_us already
gives us rather random behavior (ktime_add_us() takes an unsigned
argument), the '>' comparison gives a more well-defined result by
ignoring the timeout.

         Arnd