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authorDavid Howells <dhowells@redhat.com>2006-12-08 02:37:49 -0800
committerLinus Torvalds <torvalds@woody.osdl.org>2006-12-08 08:28:51 -0800
commitf0d1b0b30d250a07627ad8b9fbbb5c7cc08422e8 (patch)
tree0aa5379150574374351fb92af7881a48dbfcf2ce /arch/sparc
parentb3d7ae5f47a58a9f7b152deeaf7daa1fc558a8f1 (diff)
downloadlinux-linaro-stable-f0d1b0b30d250a07627ad8b9fbbb5c7cc08422e8.tar.gz
[PATCH] LOG2: Implement a general integer log2 facility in the kernel
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>
Diffstat (limited to 'arch/sparc')
-rw-r--r--arch/sparc/Kconfig8
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index 92a7c8a636d3..d0dec1ea2eed 100644
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -166,6 +166,14 @@ config ARCH_MAY_HAVE_PC_FDC
bool
default y
+config ARCH_HAS_ILOG2_U32
+ bool
+ default n
+
+config ARCH_HAS_ILOG2_U64
+ bool
+ default n
+
config SUN_PM
bool
default y