linux-kernel - Re: [PATCH v12 01/11] bitops: Introduce the for_each_set

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Message-ID: <20190326131854.GA9224@smile.fi.intel.com>
Date:   Tue, 26 Mar 2019 15:18:54 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Lukas Wunner <lukas@...ner.de>
Cc:     William Breathitt Gray <vilhelm.gray@...il.com>,
        linus.walleij@...aro.org, bgolaszewski@...libre.com,
        akpm@...ux-foundation.org, linux-gpio@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux@...musvillemoes.dk, yamada.masahiro@...ionext.com,
        linux-arm-kernel@...ts.infradead.org, linux-pm@...r.kernel.org,
        geert@...ux-m68k.org, preid@...ctromag.com.au,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v12 01/11] bitops: Introduce the for_each_set_clump8 macro

On Tue, Mar 26, 2019 at 02:03:19PM +0100, Lukas Wunner wrote:
> On Tue, Mar 26, 2019 at 07:08:18PM +0900, William Breathitt Gray wrote:
> > On Tue, Mar 26, 2019 at 10:43:45AM +0100, Lukas Wunner wrote:

> > In this case, bitmap_get_value8 could be simplified to something like
> > this:
> > 
> >         index = BIT_WORD(start);
> >         offset = start % BITS_PER_LONG;
> >         return (bitmap[index] >> offset) & 0xFF;
> 

> Hm, shouldn't that be "offset = round_down(start, 8)" ?

No, the index points to the word, the offset points to the offset inside word.

> (I prefer the multi-line version FWIW.)

+1 here.

> > Would it be better to define bitmap_get_value8 as a macro then?
> 
> Or a static inline.

Please, no macro. It disadvantages in terms of type checking. 

-- 
With Best Regards,
Andy Shevchenko