linux/arch/powerpc
David Howells f0d1b0b30d [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>
2006-12-08 08:28:51 -08:00
..
boot [POWERPC] ps3: add a default zImage target 2006-12-05 11:28:17 +11:00
configs [POWERPC] Linkstation / kurobox support 2006-12-04 20:42:08 +11:00
kernel [PATCH] struct path: convert powerpc 2006-12-08 08:28:48 -08:00
lib [POWERPC] Disallow kprobes on emulate_step and branch_taken 2006-11-01 15:14:12 +11:00
math-emu [POWERPC] ppc math-emu needs -fno-builtin-fabs for math.c and fabs.c 2006-09-26 15:24:35 +10:00
mm [PATCH] slab: remove kmem_cache_t 2006-12-07 08:39:25 -08:00
oprofile [POWERPC] ps3: multiplatform build fixes 2006-12-04 20:41:16 +11:00
platforms [PATCH] struct path: convert powerpc 2006-12-08 08:28:48 -08:00
sysdev [POWERPC] Replace kmalloc+memset with kzalloc 2006-12-04 20:42:09 +11:00
xmon [POWERPC] Allow xmon to build on legacy iSeries 2006-12-04 20:41:56 +11:00
.gitignore [POWERPC] Add files build to .gitignore 2006-12-04 20:41:29 +11:00
Kconfig [PATCH] LOG2: Implement a general integer log2 facility in the kernel 2006-12-08 08:28:51 -08:00
Kconfig.debug [POWERPC] Allow CONFIG_BOOTX_TEXT on iSeries 2006-12-04 20:41:58 +11:00
Makefile [POWERPC] Create a "wrapper" script and use it in arch/powerpc/boot 2006-09-28 14:30:02 +10:00