linux-kernel - Re: [PATCH V6 4/7] mfd: da9061: MFD core support

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Message-ID: <20170329083058.6pcslbsq3qnifwjv@dell>
Date:   Wed, 29 Mar 2017 09:30:58 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Steve Twiss <stwiss.opensource@...semi.com>,
        kbuild test robot <lkp@...el.com>,
        "kbuild-all@...org" <kbuild-all@...org>,
        LINUX-KERNEL <linux-kernel@...r.kernel.org>,
        DEVICETREE <devicetree@...r.kernel.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Eduardo Valentin <edubezval@...il.com>,
        Guenter Roeck <linux@...ck-us.net>,
        LINUX-INPUT <linux-input@...r.kernel.org>,
        LINUX-PM <linux-pm@...r.kernel.org>,
        LINUX-WATCHDOG <linux-watchdog@...r.kernel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Support Opensource <Support.Opensource@...semi.com>,
        Wim Van Sebroeck <wim@...ana.be>,
        Zhang Rui <rui.zhang@...el.com>
Subject: Re: [PATCH V6 4/7] mfd: da9061: MFD core support

On Tue, 28 Mar 2017, Geert Uytterhoeven wrote:

> Hi Steve,
> 
> On Tue, Mar 28, 2017 at 12:42 PM, Steve Twiss
> <stwiss.opensource@...semi.com> wrote:
> > On 28 March 2017 09:37, Geert Uytterhoeven wrote:
> >> Subject: Re: [PATCH V6 4/7] mfd: da9061: MFD core support
> >> On Tue, Mar 28, 2017 at 10:21 AM, Lee Jones <lee.jones@...aro.org> wrote:
> >> >> [auto build test WARNING on ljones-mfd/for-mfd-next]
> >> >> [also build test WARNING on v4.11-rc4 next-20170327]
> >> >> base:   https://git.kernel.org/pub/scm/linux/kernel/git/lee/mfd.git for-mfd-next
> >> >> config: x86_64-randconfig-x009-201713 (attached as .config)
> >> >> compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
> >> >> reproduce:
> >> >>         # save the attached .config to linux build tree
> >> >>         make ARCH=x86_64
> >> >>
> >> >> All warnings (new ones prefixed by >>):
> >> >>
> >> >>    drivers//mfd/da9062-core.c: In function 'da9062_i2c_probe':
> >> >> >> drivers//mfd/da9062-core.c:845:21: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
> >> >>       chip->chip_type = (int)match->data;
> >> >>                        ^
> >> >
> >> > Please use longs or enums.
> >>
> >> Enums would still give a warning on 64-bit.
> >> The simple fix is change the cast from (int) to (uintptr_t).
> >
> > Hi Lee and Geert,
> >
> > How about this? Fix by redefining the enum chip_type to be an int.
> > Then, just use substitution:
> > #define COMPAT_TYPE_DA9061  1
> > #define COMPAT_TYPE_DA9062  2
> >
> > That would be simple.
> > Are there any reasons this would not be acceptable?
> 
> I don't see how that can help.
> The warning is caused by casting the "void *" (which is either 32-bit or
> 64-bit) in of_device_if.data to an integer or enum (which is always 32-bit).
> 
> The right fix is to cast it to uintptr_t intead of int, like other drivers do.

That's a hack though, isn't it?  chip->chip_type is not of type
uintptr_t, so all you're doing here is making the compiler happy.

I see people using (int)(uintptr_t), which I guess keeps the
compiler happy in the first instance and actually culminates in a
correct cast to the right type.

So how about something like (enum da9062_compatible_types)(long)?

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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