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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| .. | ||
| a.out.h | ||
| atomic.h | ||
| auxvec.h | ||
| ax88796.h | ||
| bitops.h | ||
| bug.h | ||
| bugs.h | ||
| busctl-regs.h | ||
| byteorder.h | ||
| cache.h | ||
| cacheflush.h | ||
| checksum.h | ||
| cpu-irqs.h | ||
| cpumask.h | ||
| cputime.h | ||
| current.h | ||
| delay.h | ||
| device.h | ||
| div64.h | ||
| dm9000.h | ||
| dma-mapping.h | ||
| dma.h | ||
| elf.h | ||
| emergency-restart.h | ||
| errno.h | ||
| fcntl.h | ||
| fpu.h | ||
| futex.h | ||
| gdb-stub.h | ||
| gpio-regs.h | ||
| hardirq.h | ||
| highmem.h | ||
| hw_irq.h | ||
| ide.h | ||
| init.h | ||
| io.h | ||
| ioctl.h | ||
| ioctls.h | ||
| ipc.h | ||
| ipcbuf.h | ||
| irc-regs.h | ||
| irq_regs.h | ||
| irq.h | ||
| Kbuild | ||
| kmap_types.h | ||
| linkage.h | ||
| local.h | ||
| math-emu.h | ||
| mb86943a.h | ||
| mb93091-fpga-irqs.h | ||
| mb93093-fpga-irqs.h | ||
| mb93493-irqs.h | ||
| mb93493-regs.h | ||
| mb-regs.h | ||
| mc146818rtc.h | ||
| mem-layout.h | ||
| mman.h | ||
| mmu_context.h | ||
| mmu.h | ||
| module.h | ||
| msgbuf.h | ||
| mutex.h | ||
| namei.h | ||
| page.h | ||
| param.h | ||
| pci.h | ||
| percpu.h | ||
| pgalloc.h | ||
| pgtable.h | ||
| poll.h | ||
| posix_types.h | ||
| processor.h | ||
| ptrace.h | ||
| registers.h | ||
| resource.h | ||
| scatterlist.h | ||
| sections.h | ||
| segment.h | ||
| semaphore.h | ||
| sembuf.h | ||
| serial-regs.h | ||
| serial.h | ||
| setup.h | ||
| shmbuf.h | ||
| shmparam.h | ||
| sigcontext.h | ||
| siginfo.h | ||
| signal.h | ||
| smp.h | ||
| socket.h | ||
| sockios.h | ||
| spinlock.h | ||
| spr-regs.h | ||
| stat.h | ||
| statfs.h | ||
| string.h | ||
| suspend.h | ||
| system.h | ||
| termbits.h | ||
| termios.h | ||
| thread_info.h | ||
| timer-regs.h | ||
| timex.h | ||
| tlb.h | ||
| tlbflush.h | ||
| topology.h | ||
| types.h | ||
| uaccess.h | ||
| ucontext.h | ||
| unaligned.h | ||
| unistd.h | ||
| user.h | ||
| vga.h | ||
| virtconvert.h | ||
| xor.h | ||