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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acpi | ||
asm-alpha | ||
asm-arm | ||
asm-arm26 | ||
asm-avr32 | ||
asm-cris | ||
asm-frv | ||
asm-generic | ||
asm-h8300 | ||
asm-i386 | ||
asm-ia64 | ||
asm-m32r | ||
asm-m68k | ||
asm-m68knommu | ||
asm-mips | ||
asm-parisc | ||
asm-powerpc | ||
asm-ppc | ||
asm-s390 | ||
asm-sh | ||
asm-sh64 | ||
asm-sparc | ||
asm-sparc64 | ||
asm-um | ||
asm-v850 | ||
asm-x86_64 | ||
asm-xtensa | ||
crypto | ||
keys | ||
linux | ||
math-emu | ||
media | ||
mtd | ||
net | ||
pcmcia | ||
rdma | ||
rxrpc | ||
scsi | ||
sound | ||
video | ||
Kbuild |