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From:   Jani Nikula <jani.nikula@linux.intel.com>
To:     Arnd Bergmann <arnd@arndb.de>,
        Alejandro Colomar <alx.manpages@gmail.com>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        Kees Cook <keescook@chromium.org>,
        Joe Perches <joe@perches.com>
Subject: Re: [PATCH v2 18/20] linux/power_of_2.h: Add __IS_POWER_OF_2(n) and
 __IS_POWER_OF_2_OR_0(n) macros
In-Reply-To: <CAK8P3a0b7_yMExXEiH-4sKnN2Smh+BDB+=dyNvPWVcLvR_zG5w@mail.gmail.com>
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References: <20211119113644.1600-1-alx.manpages@gmail.com>
 <20211120130104.185699-1-alx.manpages@gmail.com>
 <20211120130104.185699-20-alx.manpages@gmail.com>
 <CAK8P3a0b7_yMExXEiH-4sKnN2Smh+BDB+=dyNvPWVcLvR_zG5w@mail.gmail.com>
Date:   Mon, 22 Nov 2021 10:55:28 +0200
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On Sun, 21 Nov 2021, Arnd Bergmann <arnd@arndb.de> wrote:
> On Sat, Nov 20, 2021 at 2:01 PM Alejandro Colomar
> <alx.manpages@gmail.com> wrote:
>> +
>> +#define __IS_POWER_OF_2_OR_0(n)  (((n) & ((n) - 1)) == 0)
>> +#define __IS_POWER_OF_2(n)       (__IS_POWER_OF_2_OR_0(n) && ((n) != 0))
>> +
>
> There is already is_power_of_2() in include/linux/log2.h, which would
> be preferred
> in most cases. If you need a macro version, put it in the same file
> and explain why it's
> needed.

Also, the macro argument n is evaluated 2-3 times. Please use
checkpatch.pl --strict argument on the patches, and it'll give you hints
about this stuff too.

BR,
Jani.


-- 
Jani Nikula, Intel Open Source Graphics Center