linux/include/linux/ktime.h
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   1/*
   2 *  include/linux/ktime.h
   3 *
   4 *  ktime_t - nanosecond-resolution time format.
   5 *
   6 *   Copyright(C) 2005, Thomas Gleixner <tglx@linutronix.de>
   7 *   Copyright(C) 2005, Red Hat, Inc., Ingo Molnar
   8 *
   9 *  data type definitions, declarations, prototypes and macros.
  10 *
  11 *  Started by: Thomas Gleixner and Ingo Molnar
  12 *
  13 *  Credits:
  14 *
  15 *      Roman Zippel provided the ideas and primary code snippets of
  16 *      the ktime_t union and further simplifications of the original
  17 *      code.
  18 *
  19 *  For licencing details see kernel-base/COPYING
  20 */
  21#ifndef _LINUX_KTIME_H
  22#define _LINUX_KTIME_H
  23
  24#include <linux/time.h>
  25#include <linux/jiffies.h>
  26
  27/*
  28 * ktime_t:
  29 *
  30 * On 64-bit CPUs a single 64-bit variable is used to store the hrtimers
  31 * internal representation of time values in scalar nanoseconds. The
  32 * design plays out best on 64-bit CPUs, where most conversions are
  33 * NOPs and most arithmetic ktime_t operations are plain arithmetic
  34 * operations.
  35 *
  36 * On 32-bit CPUs an optimized representation of the timespec structure
  37 * is used to avoid expensive conversions from and to timespecs. The
  38 * endian-aware order of the tv struct members is chosen to allow
  39 * mathematical operations on the tv64 member of the union too, which
  40 * for certain operations produces better code.
  41 *
  42 * For architectures with efficient support for 64/32-bit conversions the
  43 * plain scalar nanosecond based representation can be selected by the
  44 * config switch CONFIG_KTIME_SCALAR.
  45 */
  46union ktime {
  47        s64     tv64;
  48#if BITS_PER_LONG != 64 && !defined(CONFIG_KTIME_SCALAR)
  49        struct {
  50# ifdef __BIG_ENDIAN
  51        s32     sec, nsec;
  52# else
  53        s32     nsec, sec;
  54# endif
  55        } tv;
  56#endif
  57};
  58
  59typedef union ktime ktime_t;            /* Kill this */
  60
  61/*
  62 * ktime_t definitions when using the 64-bit scalar representation:
  63 */
  64
  65#if (BITS_PER_LONG == 64) || defined(CONFIG_KTIME_SCALAR)
  66
  67/**
  68 * ktime_set - Set a ktime_t variable from a seconds/nanoseconds value
  69 * @secs:       seconds to set
  70 * @nsecs:      nanoseconds to set
  71 *
  72 * Return the ktime_t representation of the value
  73 */
  74static inline ktime_t ktime_set(const long secs, const unsigned long nsecs)
  75{
  76#if (BITS_PER_LONG == 64)
  77        if (unlikely(secs >= KTIME_SEC_MAX))
  78                return (ktime_t){ .tv64 = KTIME_MAX };
  79#endif
  80        return (ktime_t) { .tv64 = (s64)secs * NSEC_PER_SEC + (s64)nsecs };
  81}
  82
  83/* Subtract two ktime_t variables. rem = lhs -rhs: */
  84#define ktime_sub(lhs, rhs) \
  85                ({ (ktime_t){ .tv64 = (lhs).tv64 - (rhs).tv64 }; })
  86
  87/* Add two ktime_t variables. res = lhs + rhs: */
  88#define ktime_add(lhs, rhs) \
  89                ({ (ktime_t){ .tv64 = (lhs).tv64 + (rhs).tv64 }; })
  90
  91/*
  92 * Add a ktime_t variable and a scalar nanosecond value.
  93 * res = kt + nsval:
  94 */
  95#define ktime_add_ns(kt, nsval) \
  96                ({ (ktime_t){ .tv64 = (kt).tv64 + (nsval) }; })
  97
  98/*
  99 * Subtract a scalar nanosecod from a ktime_t variable
 100 * res = kt - nsval:
 101 */
 102#define ktime_sub_ns(kt, nsval) \
 103                ({ (ktime_t){ .tv64 = (kt).tv64 - (nsval) }; })
 104
 105/* convert a timespec to ktime_t format: */
 106static inline ktime_t timespec_to_ktime(struct timespec ts)
 107{
 108        return ktime_set(ts.tv_sec, ts.tv_nsec);
 109}
 110
 111/* convert a timeval to ktime_t format: */
 112static inline ktime_t timeval_to_ktime(struct timeval tv)
 113{
 114        return ktime_set(tv.tv_sec, tv.tv_usec * NSEC_PER_USEC);
 115}
 116
 117/* Map the ktime_t to timespec conversion to ns_to_timespec function */
 118#define ktime_to_timespec(kt)           ns_to_timespec((kt).tv64)
 119
 120/* Map the ktime_t to timeval conversion to ns_to_timeval function */
 121#define ktime_to_timeval(kt)            ns_to_timeval((kt).tv64)
 122
 123/* Convert ktime_t to nanoseconds - NOP in the scalar storage format: */
 124#define ktime_to_ns(kt)                 ((kt).tv64)
 125
 126#else   /* !((BITS_PER_LONG == 64) || defined(CONFIG_KTIME_SCALAR)) */
 127
 128/*
 129 * Helper macros/inlines to get the ktime_t math right in the timespec
 130 * representation. The macros are sometimes ugly - their actual use is
 131 * pretty okay-ish, given the circumstances. We do all this for
 132 * performance reasons. The pure scalar nsec_t based code was nice and
 133 * simple, but created too many 64-bit / 32-bit conversions and divisions.
 134 *
 135 * Be especially aware that negative values are represented in a way
 136 * that the tv.sec field is negative and the tv.nsec field is greater
 137 * or equal to zero but less than nanoseconds per second. This is the
 138 * same representation which is used by timespecs.
 139 *
 140 *   tv.sec < 0 and 0 >= tv.nsec < NSEC_PER_SEC
 141 */
 142
 143/* Set a ktime_t variable to a value in sec/nsec representation: */
 144static inline ktime_t ktime_set(const long secs, const unsigned long nsecs)
 145{
 146        return (ktime_t) { .tv = { .sec = secs, .nsec = nsecs } };
 147}
 148
 149/**
 150 * ktime_sub - subtract two ktime_t variables
 151 * @lhs:        minuend
 152 * @rhs:        subtrahend
 153 *
 154 * Returns the remainder of the subtraction
 155 */
 156static inline ktime_t ktime_sub(const ktime_t lhs, const ktime_t rhs)
 157{
 158        ktime_t res;
 159
 160        res.tv64 = lhs.tv64 - rhs.tv64;
 161        if (res.tv.nsec < 0)
 162                res.tv.nsec += NSEC_PER_SEC;
 163
 164        return res;
 165}
 166
 167/**
 168 * ktime_add - add two ktime_t variables
 169 * @add1:       addend1
 170 * @add2:       addend2
 171 *
 172 * Returns the sum of @add1 and @add2.
 173 */
 174static inline ktime_t ktime_add(const ktime_t add1, const ktime_t add2)
 175{
 176        ktime_t res;
 177
 178        res.tv64 = add1.tv64 + add2.tv64;
 179        /*
 180         * performance trick: the (u32) -NSEC gives 0x00000000Fxxxxxxx
 181         * so we subtract NSEC_PER_SEC and add 1 to the upper 32 bit.
 182         *
 183         * it's equivalent to:
 184         *   tv.nsec -= NSEC_PER_SEC
 185         *   tv.sec ++;
 186         */
 187        if (res.tv.nsec >= NSEC_PER_SEC)
 188                res.tv64 += (u32)-NSEC_PER_SEC;
 189
 190        return res;
 191}
 192
 193/**
 194 * ktime_add_ns - Add a scalar nanoseconds value to a ktime_t variable
 195 * @kt:         addend
 196 * @nsec:       the scalar nsec value to add
 197 *
 198 * Returns the sum of @kt and @nsec in ktime_t format
 199 */
 200extern ktime_t ktime_add_ns(const ktime_t kt, u64 nsec);
 201
 202/**
 203 * ktime_sub_ns - Subtract a scalar nanoseconds value from a ktime_t variable
 204 * @kt:         minuend
 205 * @nsec:       the scalar nsec value to subtract
 206 *
 207 * Returns the subtraction of @nsec from @kt in ktime_t format
 208 */
 209extern ktime_t ktime_sub_ns(const ktime_t kt, u64 nsec);
 210
 211/**
 212 * timespec_to_ktime - convert a timespec to ktime_t format
 213 * @ts:         the timespec variable to convert
 214 *
 215 * Returns a ktime_t variable with the converted timespec value
 216 */
 217static inline ktime_t timespec_to_ktime(const struct timespec ts)
 218{
 219        return (ktime_t) { .tv = { .sec = (s32)ts.tv_sec,
 220                                   .nsec = (s32)ts.tv_nsec } };
 221}
 222
 223/**
 224 * timeval_to_ktime - convert a timeval to ktime_t format
 225 * @tv:         the timeval variable to convert
 226 *
 227 * Returns a ktime_t variable with the converted timeval value
 228 */
 229static inline ktime_t timeval_to_ktime(const struct timeval tv)
 230{
 231        return (ktime_t) { .tv = { .sec = (s32)tv.tv_sec,
 232                                   .nsec = (s32)tv.tv_usec * 1000 } };
 233}
 234
 235/**
 236 * ktime_to_timespec - convert a ktime_t variable to timespec format
 237 * @kt:         the ktime_t variable to convert
 238 *
 239 * Returns the timespec representation of the ktime value
 240 */
 241static inline struct timespec ktime_to_timespec(const ktime_t kt)
 242{
 243        return (struct timespec) { .tv_sec = (time_t) kt.tv.sec,
 244                                   .tv_nsec = (long) kt.tv.nsec };
 245}
 246
 247/**
 248 * ktime_to_timeval - convert a ktime_t variable to timeval format
 249 * @kt:         the ktime_t variable to convert
 250 *
 251 * Returns the timeval representation of the ktime value
 252 */
 253static inline struct timeval ktime_to_timeval(const ktime_t kt)
 254{
 255        return (struct timeval) {
 256                .tv_sec = (time_t) kt.tv.sec,
 257                .tv_usec = (suseconds_t) (kt.tv.nsec / NSEC_PER_USEC) };
 258}
 259
 260/**
 261 * ktime_to_ns - convert a ktime_t variable to scalar nanoseconds
 262 * @kt:         the ktime_t variable to convert
 263 *
 264 * Returns the scalar nanoseconds representation of @kt
 265 */
 266static inline s64 ktime_to_ns(const ktime_t kt)
 267{
 268        return (s64) kt.tv.sec * NSEC_PER_SEC + kt.tv.nsec;
 269}
 270
 271#endif  /* !((BITS_PER_LONG == 64) || defined(CONFIG_KTIME_SCALAR)) */
 272
 273/**
 274 * ktime_equal - Compares two ktime_t variables to see if they are equal
 275 * @cmp1:       comparable1
 276 * @cmp2:       comparable2
 277 *
 278 * Compare two ktime_t variables, returns 1 if equal
 279 */
 280static inline int ktime_equal(const ktime_t cmp1, const ktime_t cmp2)
 281{
 282        return cmp1.tv64 == cmp2.tv64;
 283}
 284
 285static inline s64 ktime_to_us(const ktime_t kt)
 286{
 287        struct timeval tv = ktime_to_timeval(kt);
 288        return (s64) tv.tv_sec * USEC_PER_SEC + tv.tv_usec;
 289}
 290
 291static inline s64 ktime_to_ms(const ktime_t kt)
 292{
 293        struct timeval tv = ktime_to_timeval(kt);
 294        return (s64) tv.tv_sec * MSEC_PER_SEC + tv.tv_usec / USEC_PER_MSEC;
 295}
 296
 297static inline s64 ktime_us_delta(const ktime_t later, const ktime_t earlier)
 298{
 299       return ktime_to_us(ktime_sub(later, earlier));
 300}
 301
 302static inline ktime_t ktime_add_us(const ktime_t kt, const u64 usec)
 303{
 304        return ktime_add_ns(kt, usec * 1000);
 305}
 306
 307static inline ktime_t ktime_sub_us(const ktime_t kt, const u64 usec)
 308{
 309        return ktime_sub_ns(kt, usec * 1000);
 310}
 311
 312extern ktime_t ktime_add_safe(const ktime_t lhs, const ktime_t rhs);
 313
 314/*
 315 * The resolution of the clocks. The resolution value is returned in
 316 * the clock_getres() system call to give application programmers an
 317 * idea of the (in)accuracy of timers. Timer values are rounded up to
 318 * this resolution values.
 319 */
 320#define LOW_RES_NSEC            TICK_NSEC
 321#define KTIME_LOW_RES           (ktime_t){ .tv64 = LOW_RES_NSEC }
 322
 323/* Get the monotonic time in timespec format: */
 324extern void ktime_get_ts(struct timespec *ts);
 325
 326/* Get the real (wall-) time in timespec format: */
 327#define ktime_get_real_ts(ts)   getnstimeofday(ts)
 328
 329static inline ktime_t ns_to_ktime(u64 ns)
 330{
 331        static const ktime_t ktime_zero = { .tv64 = 0 };
 332        return ktime_add_ns(ktime_zero, ns);
 333}
 334
 335#endif
 336
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