linux-kernel - Re: [PATCH 1/4] bitops: Add single_bit

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Message-ID: <YZuUUGvVjcHk79k0@smile.fi.intel.com>
Date:   Mon, 22 Nov 2021 15:00:00 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     "Vaittinen, Matti" <Matti.Vaittinen@...rohmeurope.com>
Cc:     Matti Vaittinen <mazziesaccount@...il.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Jiri Kosina <trivial@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Yury Norov <yury.norov@...il.com>,
        Kumar Kartikeya Dwivedi <memxor@...il.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/4] bitops: Add single_bit_set()

On Mon, Nov 22, 2021 at 02:57:27PM +0200, Andy Shevchenko wrote:
> On Mon, Nov 22, 2021 at 12:42:21PM +0000, Vaittinen, Matti wrote:
> > On 11/22/21 13:28, Andy Shevchenko wrote:

...

> > I think I actually tried using hweight() at some point but don't really 
> > remember why I rolled the single_bit_set. (I remember the hweight() 
> > usage because I had to do some googling as I had never heard term 
> > hamming weight before).
> 
> Oh, it should be a very good reason not to use hweight() since on some
> architectures it might become just one assembly instruction.

(for the sake of educational purposes to us both)
https://vaibhavsagar.com/blog/2019/09/08/popcount/

-- 
With Best Regards,
Andy Shevchenko