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f0d1b0b30d
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>
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| .. | ||
| boot | ||
| common | ||
| configs | ||
| kernel | ||
| lib | ||
| mach-aaec2000 | ||
| mach-at91rm9200 | ||
| mach-clps711x | ||
| mach-clps7500 | ||
| mach-ebsa110 | ||
| mach-ep93xx | ||
| mach-footbridge | ||
| mach-h720x | ||
| mach-imx | ||
| mach-integrator | ||
| mach-iop13xx | ||
| mach-iop32x | ||
| mach-iop33x | ||
| mach-ixp4xx | ||
| mach-ixp23xx | ||
| mach-ixp2000 | ||
| mach-l7200 | ||
| mach-lh7a40x | ||
| mach-netx | ||
| mach-omap1 | ||
| mach-omap2 | ||
| mach-pnx4008 | ||
| mach-pxa | ||
| mach-realview | ||
| mach-rpc | ||
| mach-s3c2410 | ||
| mach-sa1100 | ||
| mach-shark | ||
| mach-versatile | ||
| mm | ||
| nwfpe | ||
| oprofile | ||
| plat-iop | ||
| plat-omap | ||
| tools | ||
| vfp | ||
| Kconfig | ||
| Kconfig-nommu | ||
| Kconfig.debug | ||
| Makefile | ||