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path: root/include/linux/log2.h
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2008-02-06log2.h: Define order_base_2() macro for convenience.Robert P. J. Day
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 <rpjday@crashcourse.ca> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-10-17Add a "rounddown_pow_of_two" routine to log2.hRobert P. J. Day
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 <rpjday@mindspring.com> Signed-off-by: Mariusz Kozlowski <m.kozlowski@tuxland.pl> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-05-18Fix roundup_pow_of_two(1)Rolf Eike Beer
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 <eike-kernel@sf-tec.de> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-02-17Correct trivial typo in log2.h.Robert P. J. Day
Single typo correction in include/linux/log2.h. Signed-off-by: Robert P. J. Day <rpjday@mindspring.com> Signed-Off-By: David Howells <dhowells@redhat.com> Signed-off-by: Adrian Bunk <bunk@stusta.de>
2007-02-07[POWERPC] Add "is_power_of_2" checking to log2.h.Robert P. J. Day
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 <rpjday@mindspring.com> Acked-by: Kumar Gala <galak@kernel.crashing.org> Signed-off-by: Paul Mackerras <paulus@samba.org>
2006-12-08[PATCH] LOG2: Alter roundup_pow_of_two() so that it can use a ilog2() on a ↵David Howells
constant 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 <dhowells@redhat.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-08[PATCH] LOG2: Implement a general integer log2 facility in the kernelDavid Howells
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 <dhowells@redhat.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: David Howells <dhowells@redhat.com> Cc: Wojtek Kaniewski <wojtekka@toxygen.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>