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Define ffs/fls for all architectures

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UBIFS requires fls(), which is not defined for arm (and some other
architectures) and this patch adds it. The implementation is taken from
Linux and is generic. ffs() is also defined for those that miss it.

Signed-off-by: Simon Kagstrom <simon.kagstrom@netinsight.net>
This commit is contained in:
Simon Kagstrom 2009-08-24 09:10:12 +02:00 • committed by Wolfgang Denk
parent 4b15de08fe
commit 52d61227b6
7 changed files with 53 additions and 0 deletions
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45
include/linux/bitops.h
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@ -38,6 +38,43 @@ static inline int generic_ffs(int x)
return r;
}
/**
* fls - find last (most-significant) bit set
* @x: the word to search
*
* This is defined the same way as ffs.
* Note fls(0) = 0, fls(1) = 1, fls(0x80000000) = 32.
*/
static inline int generic_fls(int x)
{
int r = 32;
if (!x)
return 0;
if (!(x & 0xffff0000u)) {
x <<= 16;
r -= 16;
}
if (!(x & 0xff000000u)) {
x <<= 8;
r -= 8;
}
if (!(x & 0xf0000000u)) {
x <<= 4;
r -= 4;
}
if (!(x & 0xc0000000u)) {
x <<= 2;
r -= 2;
}
if (!(x & 0x80000000u)) {
x <<= 1;
r -= 1;
}
return r;
}
/*
* hweightN: returns the hamming weight (i.e. the number
* of bits set) of a N-bit word
@ -82,6 +119,14 @@ static inline unsigned int generic_hweight8(unsigned int w)
# define __clear_bit generic_clear_bit
#endif
#ifndef ffs
# define ffs generic_ffs
#endif
#ifndef fls
# define fls generic_fls
#endif
/**
* __set_bit - Set a bit in memory
* @nr: the bit to set