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https://github.com/brain-hackers/u-boot-brain
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83d290c56f
When U-Boot started using SPDX tags we were among the early adopters and there weren't a lot of other examples to borrow from. So we picked the area of the file that usually had a full license text and replaced it with an appropriate SPDX-License-Identifier: entry. Since then, the Linux Kernel has adopted SPDX tags and they place it as the very first line in a file (except where shebangs are used, then it's second line) and with slightly different comment styles than us. In part due to community overlap, in part due to better tag visibility and in part for other minor reasons, switch over to that style. This commit changes all instances where we have a single declared license in the tag as both the before and after are identical in tag contents. There's also a few places where I found we did not have a tag and have introduced one. Signed-off-by: Tom Rini <trini@konsulko.com>
205 lines
5.0 KiB
C
205 lines
5.0 KiB
C
/* SPDX-License-Identifier: GPL-2.0+ */
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/* Integer base 2 logarithm calculation
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*
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* Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*/
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#ifndef _LINUX_LOG2_H
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#define _LINUX_LOG2_H
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#include <linux/types.h>
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#include <linux/bitops.h>
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/*
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* deal with unrepresentable constant logarithms
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*/
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extern __attribute__((const, noreturn))
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int ____ilog2_NaN(void);
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/*
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* non-constant log of base 2 calculators
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* - the arch may override these in asm/bitops.h if they can be implemented
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* more efficiently than using fls() and fls64()
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* - the arch is not required to handle n==0 if implementing the fallback
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*/
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#ifndef CONFIG_ARCH_HAS_ILOG2_U32
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static inline __attribute__((const))
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int __ilog2_u32(u32 n)
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{
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return fls(n) - 1;
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}
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#endif
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#ifndef CONFIG_ARCH_HAS_ILOG2_U64
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static inline __attribute__((const))
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int __ilog2_u64(u64 n)
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{
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return fls64(n) - 1;
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}
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#endif
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/*
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* Determine whether some value is a power of two, where zero is
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* *not* considered a power of two.
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*/
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static inline __attribute__((const))
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bool is_power_of_2(unsigned long n)
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{
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return (n != 0 && ((n & (n - 1)) == 0));
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}
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/*
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* round up to nearest power of two
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*/
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static inline __attribute__((const))
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unsigned long __roundup_pow_of_two(unsigned long n)
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{
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return 1UL << fls_long(n - 1);
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}
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/*
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* round down to nearest power of two
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*/
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static inline __attribute__((const))
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unsigned long __rounddown_pow_of_two(unsigned long n)
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{
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return 1UL << (fls_long(n) - 1);
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}
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/**
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* ilog2 - log of base 2 of 32-bit or a 64-bit unsigned value
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* @n - parameter
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*
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* constant-capable log of base 2 calculation
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* - this can be used to initialise global variables from constant data, hence
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* the massive ternary operator construction
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*
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* selects the appropriately-sized optimised version depending on sizeof(n)
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*/
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#define ilog2(n) \
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( \
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__builtin_constant_p(n) ? ( \
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(n) < 1 ? ____ilog2_NaN() : \
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(n) & (1ULL << 63) ? 63 : \
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(n) & (1ULL << 62) ? 62 : \
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(n) & (1ULL << 61) ? 61 : \
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(n) & (1ULL << 60) ? 60 : \
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(n) & (1ULL << 59) ? 59 : \
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(n) & (1ULL << 58) ? 58 : \
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(n) & (1ULL << 57) ? 57 : \
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(n) & (1ULL << 56) ? 56 : \
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(n) & (1ULL << 55) ? 55 : \
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(n) & (1ULL << 54) ? 54 : \
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(n) & (1ULL << 53) ? 53 : \
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(n) & (1ULL << 52) ? 52 : \
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(n) & (1ULL << 51) ? 51 : \
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(n) & (1ULL << 50) ? 50 : \
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(n) & (1ULL << 49) ? 49 : \
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(n) & (1ULL << 48) ? 48 : \
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(n) & (1ULL << 47) ? 47 : \
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(n) & (1ULL << 46) ? 46 : \
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(n) & (1ULL << 45) ? 45 : \
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(n) & (1ULL << 44) ? 44 : \
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(n) & (1ULL << 43) ? 43 : \
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(n) & (1ULL << 42) ? 42 : \
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(n) & (1ULL << 41) ? 41 : \
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(n) & (1ULL << 40) ? 40 : \
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(n) & (1ULL << 39) ? 39 : \
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(n) & (1ULL << 38) ? 38 : \
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(n) & (1ULL << 37) ? 37 : \
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(n) & (1ULL << 36) ? 36 : \
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(n) & (1ULL << 35) ? 35 : \
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(n) & (1ULL << 34) ? 34 : \
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(n) & (1ULL << 33) ? 33 : \
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(n) & (1ULL << 32) ? 32 : \
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(n) & (1ULL << 31) ? 31 : \
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(n) & (1ULL << 30) ? 30 : \
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(n) & (1ULL << 29) ? 29 : \
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(n) & (1ULL << 28) ? 28 : \
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(n) & (1ULL << 27) ? 27 : \
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(n) & (1ULL << 26) ? 26 : \
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(n) & (1ULL << 25) ? 25 : \
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(n) & (1ULL << 24) ? 24 : \
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(n) & (1ULL << 23) ? 23 : \
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(n) & (1ULL << 22) ? 22 : \
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(n) & (1ULL << 21) ? 21 : \
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(n) & (1ULL << 20) ? 20 : \
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(n) & (1ULL << 19) ? 19 : \
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(n) & (1ULL << 18) ? 18 : \
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(n) & (1ULL << 17) ? 17 : \
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(n) & (1ULL << 16) ? 16 : \
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(n) & (1ULL << 15) ? 15 : \
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(n) & (1ULL << 14) ? 14 : \
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(n) & (1ULL << 13) ? 13 : \
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(n) & (1ULL << 12) ? 12 : \
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(n) & (1ULL << 11) ? 11 : \
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(n) & (1ULL << 10) ? 10 : \
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(n) & (1ULL << 9) ? 9 : \
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(n) & (1ULL << 8) ? 8 : \
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(n) & (1ULL << 7) ? 7 : \
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(n) & (1ULL << 6) ? 6 : \
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(n) & (1ULL << 5) ? 5 : \
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(n) & (1ULL << 4) ? 4 : \
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(n) & (1ULL << 3) ? 3 : \
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(n) & (1ULL << 2) ? 2 : \
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(n) & (1ULL << 1) ? 1 : \
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(n) & (1ULL << 0) ? 0 : \
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____ilog2_NaN() \
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) : \
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(sizeof(n) <= 4) ? \
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__ilog2_u32(n) : \
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__ilog2_u64(n) \
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)
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/**
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* roundup_pow_of_two - round the given value up to nearest power of two
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* @n - parameter
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*
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* round the given value up to the nearest power of two
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* - the result is undefined when n == 0
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* - this can be used to initialise global variables from constant data
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*/
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#define roundup_pow_of_two(n) \
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( \
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__builtin_constant_p(n) ? ( \
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(n == 1) ? 1 : \
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(1UL << (ilog2((n) - 1) + 1)) \
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) : \
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__roundup_pow_of_two(n) \
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)
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/**
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* rounddown_pow_of_two - round the given value down to nearest power of two
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* @n - parameter
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*
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* round the given value down to the nearest power of two
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* - the result is undefined when n == 0
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* - this can be used to initialise global variables from constant data
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*/
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#define rounddown_pow_of_two(n) \
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( \
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__builtin_constant_p(n) ? ( \
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(1UL << ilog2(n))) : \
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__rounddown_pow_of_two(n) \
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)
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/**
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* order_base_2 - calculate the (rounded up) base 2 order of the argument
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* @n: parameter
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*
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* The first few values calculated by this routine:
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* ob2(0) = 0
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* ob2(1) = 0
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* ob2(2) = 1
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* ob2(3) = 2
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* ob2(4) = 2
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* ob2(5) = 3
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* ... and so on.
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*/
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#define order_base_2(n) ilog2(roundup_pow_of_two(n))
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#endif /* _LINUX_LOG2_H */
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