linux-kernel - Re: [PATCH] Add the macro to test if "exactly_one_bit

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Message-ID: <Pine.LNX.4.64.0711061352520.29701@localhost.localdomain>
Date:	Tue, 6 Nov 2007 13:53:29 -0500 (EST)
From:	"Robert P. J. Day" <rpjday@...shcourse.ca>
To:	Boaz Harrosh <bharrosh@...asas.com>
cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...l.org>, matthew@....cx
Subject: Re: [PATCH] Add the macro to test if "exactly_one_bit_set" to log2.h.

On Tue, 6 Nov 2007, Boaz Harrosh wrote:

> On Tue, Nov 06 2007 at 18:38 +0200, "Robert P. J. Day" <rpjday@...shcourse.ca> wrote:
> > While this macro is defined in terms of "is_power_of_2" and is
> > therefore functionally equivalent, the visual semantics are sometimes
> > more appropriate for what is actually being tested.
> >
> > Signed-off-by: Robert P. J. Day <rpjday@...shcourse.ca>
> >
> > ---
> >
> > diff --git a/include/linux/log2.h b/include/linux/log2.h
> > index c8cf5e8..d0d324e 100644
> > --- a/include/linux/log2.h
> > +++ b/include/linux/log2.h
> > @@ -55,6 +55,12 @@ bool is_power_of_2(unsigned long n)
> >  }
> >
> >  /*
> > + *  And for folks who want slightly different semantics ...
> > + */
> > +
> > +#define exactly_one_bit_set is_power_of_2
>
> at_most_one_bit_set No?

no, it really is *exactly* one bit set.  zero is not considered a
power of two.

rday
-- 
========================================================================
Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry
Waterloo, Ontario, CANADA

http://crashcourse.ca
========================================================================
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