Fix roundup_pow_of_two(1)
1 is a power of two, therefore roundup_pow_of_two(1) should return 1. It does
in case the argument is a variable but in case it's a constant it behaves
wrong and returns 0. Probably nobody ever did it so this was never noticed.
Signed-off-by: Rolf Eike Beer <[email protected]>
---
commit 01ceeffac83011f0b5021013cc4abd1c4f291df5
tree 7da59df51617d7cebd55e4361019181645a17e10
parent ab35916f807eb4f2019a208e96cb0bddbb91dfc3
author Rolf Eike Beer <[email protected]> Thu, 17 May 2007 23:43:54 +0200
committer Rolf Eike Beer <[email protected]> Thu, 17 May 2007 23:43:54 +0200
include/linux/log2.h | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/include/linux/log2.h b/include/linux/log2.h
index 57e641e..1b8a2c1 100644
--- a/include/linux/log2.h
+++ b/include/linux/log2.h
@@ -159,7 +159,7 @@ unsigned long __roundup_pow_of_two(unsigned long n)
#define roundup_pow_of_two(n) \
( \
__builtin_constant_p(n) ? ( \
- (n == 1) ? 0 : \
+ (n == 1) ? 1 : \
(1UL << (ilog2((n) - 1) + 1)) \
) : \
__roundup_pow_of_two(n) \
On Thu, May 17, 2007 at 11:56:56PM +0200, Rolf Eike Beer wrote:
> Fix roundup_pow_of_two(1)
>
> 1 is a power of two, therefore roundup_pow_of_two(1) should return 1. It does
> in case the argument is a variable but in case it's a constant it behaves
> wrong and returns 0. Probably nobody ever did it so this was never noticed.
I'm not getting the problem.
2^0 = 1
> Signed-off-by: Rolf Eike Beer <[email protected]>
>
> ---
> commit 01ceeffac83011f0b5021013cc4abd1c4f291df5
> tree 7da59df51617d7cebd55e4361019181645a17e10
> parent ab35916f807eb4f2019a208e96cb0bddbb91dfc3
> author Rolf Eike Beer <[email protected]> Thu, 17 May 2007 23:43:54 +0200
> committer Rolf Eike Beer <[email protected]> Thu, 17 May 2007 23:43:54 +0200
>
> include/linux/log2.h | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/include/linux/log2.h b/include/linux/log2.h
> index 57e641e..1b8a2c1 100644
> --- a/include/linux/log2.h
> +++ b/include/linux/log2.h
> @@ -159,7 +159,7 @@ unsigned long __roundup_pow_of_two(unsigned long n)
> #define roundup_pow_of_two(n) \
> ( \
> __builtin_constant_p(n) ? ( \
> - (n == 1) ? 0 : \
> + (n == 1) ? 1 : \
> (1UL << (ilog2((n) - 1) + 1)) \
> ) : \
> __roundup_pow_of_two(n) \
cu
Adrian
--
"Is there not promise of rain?" Ling Tan asked suddenly out
of the darkness. There had been need of rain for many days.
"Only a promise," Lao Er said.
Pearl S. Buck - Dragon Seed
Adrian Bunk wrote:
> On Thu, May 17, 2007 at 11:56:56PM +0200, Rolf Eike Beer wrote:
> > Fix roundup_pow_of_two(1)
> >
> > 1 is a power of two, therefore roundup_pow_of_two(1) should return 1. It
> > does in case the argument is a variable but in case it's a constant it
> > behaves wrong and returns 0. Probably nobody ever did it so this was
> > never noticed.
>
> I'm not getting the problem.
> 2^0 = 1
Yes. But it returned 0 (not 1 << 0).
Eike
On Mon, 4 Jun 2007, Adrian Bunk wrote:
> > 1 is a power of two, therefore roundup_pow_of_two(1) should return 1. It does
> > in case the argument is a variable but in case it's a constant it behaves
> > wrong and returns 0. Probably nobody ever did it so this was never noticed.
> I'm not getting the problem.
> 2^0 = 1
Adrian,
that's of course true, but unrelated to the patch in question :)
You simply want roundup_pow_of_two(1) to be 1, and not 0. That's what the
patch does, and that's correct.
--
Jiri Kosina
On Mon, Jun 04, 2007 at 02:13:11PM +0200, Rolf Eike Beer wrote:
> Adrian Bunk wrote:
> > On Thu, May 17, 2007 at 11:56:56PM +0200, Rolf Eike Beer wrote:
> > > Fix roundup_pow_of_two(1)
> > >
> > > 1 is a power of two, therefore roundup_pow_of_two(1) should return 1. It
> > > does in case the argument is a variable but in case it's a constant it
> > > behaves wrong and returns 0. Probably nobody ever did it so this was
> > > never noticed.
> >
> > I'm not getting the problem.
> > 2^0 = 1
>
> Yes. But it returned 0 (not 1 << 0).
Sorry, I had a thinko and you are right.
> Eike
cu
Adrian
--
"Is there not promise of rain?" Ling Tan asked suddenly out
of the darkness. There had been need of rain for many days.
"Only a promise," Lao Er said.
Pearl S. Buck - Dragon Seed