Messages in this thread | | | Date | Sun, 11 Nov 2007 10:28:37 -0800 | From | Randy Dunlap <> | Subject | Re: [PATCH] log2.h: Define order_base_2() macro for convenience. |
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On Sat, 10 Nov 2007 22:53:36 -0500 (EST) Robert P. J. Day wrote:
> > Given a number of places in the tree that need to calculate this value > explicitly, might as well just create a macro for it. > > Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca> > > --- > > run-time tested for the first several values. note that this macro > is defined strictly in terms of rounding *up* -- i've seen no places > in the tree that require this expression to be rounded down, so i'm > not drawing that distinction. > > diff --git a/include/linux/log2.h b/include/linux/log2.h > index c8cf5e8..ed121c0 100644 > --- a/include/linux/log2.h > +++ b/include/linux/log2.h > @@ -190,4 +190,20 @@ unsigned long __rounddown_pow_of_two(unsigned long n) > __rounddown_pow_of_two(n) \ > ) > > +/** > + * order_base_2 - calculate the (rounded up) base 2 order of the argument > + * @n - parameter
* @n: argument
(mostly changing - to :)
> + * > + * The first few values calculated by this routine: > + * ob2(0) = 0 > + * ob2(1) = 0 > + * ob2(2) = 1 > + * ob2(3) = 2 > + * ob2(4) = 2 > + * ob2(5) = 3 > + * ... and so on. > + */ > + > +#define order_base_2(n) ilog2(roundup_pow_of_two(n)) > + > #endif /* _LINUX_LOG2_H */ > > --
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