linux-toradex.git/include/linux/log2.h, branch v2.6.26-rc5

log2.h: Define order_base_2() macro for convenience.

2008-02-06T18:41:03+00:00

Given a number of places in the tree that need to calculate this value
explicitly, might as well just create a macro for it.

(akpm: must be implemented as a macro for callee typeof() usage)

Signed-off-by: Robert P. J. Day 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Add a "rounddown_pow_of_two" routine to log2.h

2007-10-17T15:42:56+00:00

To go along with the existing "roundup_pow_of_two" routine, add one for
rounding down since that operation appears to crop up on a regular basis in
the source tree.

[m.kozlowski@tuxland.pl: fix unbalanced parentheses]
Signed-off-by: Robert P. J. Day 
Signed-off-by: Mariusz Kozlowski 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Fix roundup_pow_of_two(1)

2007-05-19T03:46:30+00:00

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 
Signed-off-by: Linus Torvalds

Correct trivial typo in log2.h.

2007-02-17T18:17:37+00:00

Single typo correction in include/linux/log2.h.

Signed-off-by: Robert P. J. Day 
Signed-Off-By: David Howells 
Signed-off-by: Adrian Bunk

[POWERPC] Add "is_power_of_2" checking to log2.h.

2007-02-07T03:03:19+00:00

Add the inline function "is_power_of_2()" to log2.h, where the value
zero is *not* considered to be a power of two.

Signed-off-by: Robert P. J. Day 
Acked-by: Kumar Gala 
Signed-off-by: Paul Mackerras

[PATCH] LOG2: Alter roundup_pow_of_two() so that it can use a ilog2() on a constant

2006-12-08T16:28:51+00:00

Alter roundup_pow_of_two() so that it can make use of ilog2() on a constant to
produce a constant value, retaining the ability for an arch to override it in
the non-const case.

This permits the function to be used to initialise variables.

Signed-off-by: David Howells 
Cc: Benjamin Herrenschmidt 
Cc: Paul Mackerras 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] LOG2: Implement a general integer log2 facility in the kernel

2006-12-08T16:28:51+00:00

This facility provides three entry points:

	ilog2()		Log base 2 of unsigned long
	ilog2_u32()	Log base 2 of u32
	ilog2_u64()	Log base 2 of u64

These facilities can either be used inside functions on dynamic data:

	int do_something(long q)
	{
		...;
		y = ilog2(x)
		...;
	}

Or can be used to statically initialise global variables with constant values:

	unsigned n = ilog2(27);

When performing static initialisation, the compiler will report "error:
initializer element is not constant" if asked to take a log of zero or of
something not reducible to a constant.  They treat negative numbers as
unsigned.

When not dealing with a constant, they fall back to using fls() which permits
them to use arch-specific log calculation instructions - such as BSR on
x86/x86_64 or SCAN on FRV - if available.

[akpm@osdl.org: MMC fix]
Signed-off-by: David Howells 
Cc: Benjamin Herrenschmidt 
Cc: Paul Mackerras 
Cc: Herbert Xu 
Cc: David Howells 
Cc: Wojtek Kaniewski 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds