sys/dev/drm/include/linux/log2.h

   1 /*-
   2  * Copyright (c) 2010 Isilon Systems, Inc.
   3  * Copyright (c) 2010 iX Systems, Inc.
   4  * Copyright (c) 2010 Panasas, Inc.
   5  * Copyright (c) 2013, 2014 Mellanox Technologies, Ltd.
   6  * All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice unmodified, this list of conditions, and the following
  13  *    disclaimer.
  14  * 2. Redistributions in binary form must reproduce the above copyright
  15  *    notice, this list of conditions and the following disclaimer in the
  16  *    documentation and/or other materials provided with the distribution.
  17  *
  18  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  19  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  20  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  21  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  22  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  23  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  24  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  25  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  26  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  27  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  28  */
  29
  30 #ifndef _LINUX_LOG2_H_
  31 #define _LINUX_LOG2_H_
  32
  33 #include <linux/types.h>
  34
  35 #include <sys/libkern.h>
  36
  37 static inline unsigned long
  38 roundup_pow_of_two(unsigned long x)
  39 {
  40         return (1UL << flsl(x - 1));
  41 }
  42
  43 static inline int
  44 is_power_of_2(unsigned long n)
  45 {
  46         return (n == roundup_pow_of_two(n));
  47 }
  48
  49 static inline unsigned long
  50 rounddown_pow_of_two(unsigned long x)
  51 {
  52         return (1UL << (flsl(x) - 1));
  53 }
  54
  55
  56 /*
  57  * deal with unrepresentable constant logarithms
  58  */
  59 extern __attribute__((const, noreturn))
  60 int ____ilog2_NaN(void);
  61
  62 /*
  63  * non-constant log of base 2 calculators
  64  * - the arch may override these in asm/bitops.h if they can be implemented
  65  *   more efficiently than using fls() and fls64()
  66  * - the arch is not required to handle n==0 if implementing the fallback
  67  */
  68 #ifndef CONFIG_ARCH_HAS_ILOG2_U32
  69 static inline __attribute__((const))
  70 int __ilog2_u32(u32 n)
  71 {
  72         return flsl(n) - 1;
  73 }
  74 #endif
  75
  76 #ifndef CONFIG_ARCH_HAS_ILOG2_U64
  77 static inline __attribute__((const))
  78 int __ilog2_u64(u64 n)
  79 {
  80         return flsl(n) - 1;
  81 }
  82 #endif
  83
  84
  85 /**
  86  * ilog2 - log of base 2 of 32-bit or a 64-bit unsigned value
  87  * @n - parameter
  88  *
  89  * constant-capable log of base 2 calculation
  90  * - this can be used to initialise global variables from constant data, hence
  91  *   the massive ternary operator construction
  92  *
  93  * selects the appropriately-sized optimised version depending on sizeof(n)
  94  */
  95 #define ilog2(n)                                \
  96 (                                               \
  97         __builtin_constant_p(n) ? (             \
  98                 (n) < 1 ? ____ilog2_NaN() :     \
  99                 (n) & (1ULL << 63) ? 63 :       \
 100                 (n) & (1ULL << 62) ? 62 :       \
 101                 (n) & (1ULL << 61) ? 61 :       \
 102                 (n) & (1ULL << 60) ? 60 :       \
 103                 (n) & (1ULL << 59) ? 59 :       \
 104                 (n) & (1ULL << 58) ? 58 :       \
 105                 (n) & (1ULL << 57) ? 57 :       \
 106                 (n) & (1ULL << 56) ? 56 :       \
 107                 (n) & (1ULL << 55) ? 55 :       \
 108                 (n) & (1ULL << 54) ? 54 :       \
 109                 (n) & (1ULL << 53) ? 53 :       \
 110                 (n) & (1ULL << 52) ? 52 :       \
 111                 (n) & (1ULL << 51) ? 51 :       \
 112                 (n) & (1ULL << 50) ? 50 :       \
 113                 (n) & (1ULL << 49) ? 49 :       \
 114                 (n) & (1ULL << 48) ? 48 :       \
 115                 (n) & (1ULL << 47) ? 47 :       \
 116                 (n) & (1ULL << 46) ? 46 :       \
 117                 (n) & (1ULL << 45) ? 45 :       \
 118                 (n) & (1ULL << 44) ? 44 :       \
 119                 (n) & (1ULL << 43) ? 43 :       \
 120                 (n) & (1ULL << 42) ? 42 :       \
 121                 (n) & (1ULL << 41) ? 41 :       \
 122                 (n) & (1ULL << 40) ? 40 :       \
 123                 (n) & (1ULL << 39) ? 39 :       \
 124                 (n) & (1ULL << 38) ? 38 :       \
 125                 (n) & (1ULL << 37) ? 37 :       \
 126                 (n) & (1ULL << 36) ? 36 :       \
 127                 (n) & (1ULL << 35) ? 35 :       \
 128                 (n) & (1ULL << 34) ? 34 :       \
 129                 (n) & (1ULL << 33) ? 33 :       \
 130                 (n) & (1ULL << 32) ? 32 :       \
 131                 (n) & (1ULL << 31) ? 31 :       \
 132                 (n) & (1ULL << 30) ? 30 :       \
 133                 (n) & (1ULL << 29) ? 29 :       \
 134                 (n) & (1ULL << 28) ? 28 :       \
 135                 (n) & (1ULL << 27) ? 27 :       \
 136                 (n) & (1ULL << 26) ? 26 :       \
 137                 (n) & (1ULL << 25) ? 25 :       \
 138                 (n) & (1ULL << 24) ? 24 :       \
 139                 (n) & (1ULL << 23) ? 23 :       \
 140                 (n) & (1ULL << 22) ? 22 :       \
 141                 (n) & (1ULL << 21) ? 21 :       \
 142                 (n) & (1ULL << 20) ? 20 :       \
 143                 (n) & (1ULL << 19) ? 19 :       \
 144                 (n) & (1ULL << 18) ? 18 :       \
 145                 (n) & (1ULL << 17) ? 17 :       \
 146                 (n) & (1ULL << 16) ? 16 :       \
 147                 (n) & (1ULL << 15) ? 15 :       \
 148                 (n) & (1ULL << 14) ? 14 :       \
 149                 (n) & (1ULL << 13) ? 13 :       \
 150                 (n) & (1ULL << 12) ? 12 :       \
 151                 (n) & (1ULL << 11) ? 11 :       \
 152                 (n) & (1ULL << 10) ? 10 :       \
 153                 (n) & (1ULL <<  9) ?  9 :       \
 154                 (n) & (1ULL <<  8) ?  8 :       \
 155                 (n) & (1ULL <<  7) ?  7 :       \
 156                 (n) & (1ULL <<  6) ?  6 :       \
 157                 (n) & (1ULL <<  5) ?  5 :       \
 158                 (n) & (1ULL <<  4) ?  4 :       \
 159                 (n) & (1ULL <<  3) ?  3 :       \
 160                 (n) & (1ULL <<  2) ?  2 :       \
 161                 (n) & (1ULL <<  1) ?  1 :       \
 162                 (n) & (1ULL <<  0) ?  0 :       \
 163                 ____ilog2_NaN()                 \
 164                                    ) :          \
 165         (sizeof(n) <= 4) ?                      \
 166         __ilog2_u32(n) :                        \
 167         __ilog2_u64(n)                          \
 168  )
 169
 170 #define order_base_2(n) ilog2(roundup_pow_of_two(n))
 171
 172 #endif  /* _LINUX_LOG2_H_ */