linux/arch/s390
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
..
appldata [PATCH] hotplug CPU: clean up hotcpu_notifier() use 2006-12-07 08:39:39 -08:00
boot [PATCH] use ${CROSS_COMPILE}installkernel in arch/*/boot/install.sh 2005-06-23 09:45:07 -07:00
crypto [S390] Inline assembly cleanup. 2006-09-28 16:56:43 +02:00
hypfs [PATCH] struct path: convert s390 2006-12-08 08:28:49 -08:00
kernel [PATCH] struct path: convert s390 2006-12-08 08:28:49 -08:00
lib [PATCH] mm: pagefault_{disable,enable}() 2006-12-07 08:39:21 -08:00
math-emu [S390] Inline assembly cleanup. 2006-09-28 16:56:43 +02:00
mm [S390] Convert extmem spin_lock into a mutex. 2006-12-04 15:40:51 +01:00
oprofile [PATCH] s390: add oprofile callgraph support 2006-01-06 08:33:50 -08:00
defconfig [S390] revert add_active_range() usage patch. 2006-11-06 10:49:00 +01:00
Kconfig [PATCH] LOG2: Implement a general integer log2 facility in the kernel 2006-12-08 08:28:51 -08:00
Kconfig.debug [PATCH] lockdep: irqtrace subsystem, s390 support 2006-07-03 15:27:03 -07:00
Makefile [S390] set KBUILD_IMAGE. 2006-12-04 15:40:49 +01:00