linux-kernel - Re: [PATCH] Introduce a boolean "single_bit

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Date:	Fri, 24 Apr 2009 10:46:51 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Robert P. J. Day" <rpjday@...shcourse.ca>
Cc:	David Daney <ddaney@...iumnetworks.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Introduce a boolean "single_bit_set" function.

On Fri, 24 Apr 2009 06:40:39 -0400 (EDT) "Robert P. J. Day" <rpjday@...shcourse.ca> wrote:

>   so it would be a simple matter to define the bit set boolean in
> terms of hweight_long(), yes?  so what about, in bitops.h:
> 
>   static inline bool
>   exactly_one_bit_set(unsigned long w)
>   {
> 	return hweight_long(w) == 1;
>   }
> 
>   static inline bool
>   more_than_one_bit_set(unsigned long w)
>   {
> 	return hweight_long(w) > 1;
>   }
> 
> or something to that effect, *if* people think it's worth it.
> obviously, none of the above is strictly necessary, but it would make
> a lot of code semantically cleaner.
> 

Doing plain old

	if (hweight32(foo) == 1)

(say) at the call sites quite clearly expresses what the code is trying
to do.

> rday
> 
> p.s.  i notice that, even in a single header file like bitops.h, there
> is a mixture of both "inline" and "__inline__".  what's the
> recommended choice these days?

`inline'.  Or uninline the function ;)
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