linux-kernel - Re: [PATCH v2 2/3] lib/find_bit: create find_first_zero_bit

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Message-ID: <CAHp75VdxXVezM90AdCn=1HnNY9uDbg5OzWDL5RS66yGppZCQ_A@mail.gmail.com>
Date:   Wed, 24 Aug 2022 12:24:11 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Yury Norov <yury.norov@...il.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Dennis Zhou <dennis@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Alexey Klimov <aklimov@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Andy Whitcroft <apw@...onical.com>
Subject: Re: [PATCH v2 2/3] lib/find_bit: create find_first_zero_bit_le()

On Wed, Aug 24, 2022 at 12:22 PM Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
> On Wed, Aug 24, 2022 at 5:17 AM Yury Norov <yury.norov@...il.com> wrote:

...

> > +#define word_op swab
> > +#include "find_bit.h"
>
> Looking at this, I would rather always require to define __ffs_word_op
> (or whatever name) in the user and replace #ifndef in the find_bit.h
> with
> #error "The __ffs_word_op must be defined before including find_bit.h!"

The rationale is that the missed definition may give wrong results
while being compiled with no errors. With the above, the developer
must think about what they are doing.

-- 
With Best Regards,
Andy Shevchenko