linux-kernel - Re: [PATCH 3/3] rtc: stm32: use 32-bit cast for BIT() macro

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Date:   Fri, 13 Jan 2017 17:48:49 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Amelie DELAUNAY <amelie.delaunay@...com>
Cc:     Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
        Mark Brown <broonie@...nel.org>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre TORGUE <alexandre.torgue@...com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        "rtc-linux@...glegroups.com" <rtc-linux@...glegroups.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] rtc: stm32: use 32-bit cast for BIT() macro

On Fri, Jan 13, 2017 at 4:56 PM, Amelie DELAUNAY <amelie.delaunay@...com> wrote:
> On 01/13/2017 04:32 PM, Arnd Bergmann wrote:
>>
>> Using the ~ operator on a BIT() constant results in a large 'unsigned
>> long'
>> constant that won't fit into an 'unsigned int' function argument on 64-bit
>> architectures, resulting in a harmless build warning in x86 allmodconfig:
>>
>> drivers/rtc/rtc-stm32.c: In function 'stm32_rtc_probe':
>> drivers/rtc/rtc-stm32.c:651:51: error: large integer implicitly truncated
>> to unsigned type [-Werror=overflow]
>>   regmap_update_bits(rtc->dbp, PWR_CR, PWR_CR_DBP, ~PWR_CR_DBP);
>
> I thought I would fix this warning by replacing all ~PWR_CR_DBP by 0,
> because the mask PWR_CR_DBP prevents other bits to be cleared.
> In this way, I avoid the ugly cast...

Good idea, much nicer than mine! Can you send that patch?

    Arnd