07 Feb, 2008

1 commit

• de9330d13   log2.h: Define order_base_2() macro for convenience. ... Browse Code »

  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

  Robert P. J. Day

  2008-02-07 02:41:03 +0800  

17 Oct, 2007

1 commit

• b311e921b   Add a "rounddown_pow_of_two" routine to log2.h ... Browse Code »

  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

  Robert P. J. Day

  2007-10-17 23:42:56 +0800  

19 May, 2007

1 commit

• 1a06a52ee   Fix roundup_pow_of_two(1) ... Browse Code »

  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
  Signed-off-by: Linus Torvalds

  Rolf Eike Beer

  2007-05-19 11:46:30 +0800  

18 Feb, 2007

1 commit

• 6fb189c2a   Correct trivial typo in log2.h. ... Browse Code »

  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

  Robert P. J. Day

  2007-02-18 02:17:37 +0800  

07 Feb, 2007

1 commit

• 63c2f782e   [POWERPC] Add "is_power_of_2" checking to log2.h. ... Browse Code »

  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

  Robert P. J. Day

  2007-02-07 11:03:19 +0800  

09 Dec, 2006

2 commits

• 312a0c170   [PATCH] LOG2: Alter roundup_pow_of_two() so that it can use a ilog2() on a constant ... Browse Code »

  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

  David Howells

  2006-12-09 00:28:51 +0800  
• f0d1b0b30   [PATCH] LOG2: Implement a general integer log2 facility in the kernel ... Browse Code »

  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

  David Howells

  2006-12-09 00:28:51 +0800