#ifndef _LINUX_TIME_H
  #define _LINUX_TIME_H
  
  # include <linux/cache.h>
  # include <linux/seqlock.h>
  # include <linux/math64.h>
  #include <uapi/linux/time.h>
  
  extern struct timezone sys_tz;
  
  /* Parameters used to convert the timespec values: */
  #define MSEC_PER_SEC	1000L
  #define USEC_PER_MSEC	1000L
  #define NSEC_PER_USEC	1000L
  #define NSEC_PER_MSEC	1000000L
  #define USEC_PER_SEC	1000000L
  #define NSEC_PER_SEC	1000000000L
  #define FSEC_PER_SEC	1000000000000000LL
  
  #define TIME_T_MAX	(time_t)((1UL << ((sizeof(time_t) << 3) - 1)) - 1)
  
  static inline int timespec_equal(const struct timespec *a,
                                   const struct timespec *b)
  {
  	return (a->tv_sec == b->tv_sec) && (a->tv_nsec == b->tv_nsec);
  }
  
  /*
   * lhs < rhs:  return <0
   * lhs == rhs: return 0
   * lhs > rhs:  return >0
   */
  static inline int timespec_compare(const struct timespec *lhs, const struct timespec *rhs)
  {
  	if (lhs->tv_sec < rhs->tv_sec)
  		return -1;
  	if (lhs->tv_sec > rhs->tv_sec)
  		return 1;
  	return lhs->tv_nsec - rhs->tv_nsec;
  }
  
  static inline int timeval_compare(const struct timeval *lhs, const struct timeval *rhs)
  {
  	if (lhs->tv_sec < rhs->tv_sec)
  		return -1;
  	if (lhs->tv_sec > rhs->tv_sec)
  		return 1;
  	return lhs->tv_usec - rhs->tv_usec;
  }
  
  extern unsigned long mktime(const unsigned int year, const unsigned int mon,
  			    const unsigned int day, const unsigned int hour,
  			    const unsigned int min, const unsigned int sec);
  
  extern void set_normalized_timespec(struct timespec *ts, time_t sec, s64 nsec);
  
  /*
   * timespec_add_safe assumes both values are positive and checks
   * for overflow. It will return TIME_T_MAX if the reutrn would be
   * smaller then either of the arguments.
   */
  extern struct timespec timespec_add_safe(const struct timespec lhs,
  					 const struct timespec rhs);
  
  
  static inline struct timespec timespec_add(struct timespec lhs,
  						struct timespec rhs)
  {
  	struct timespec ts_delta;
  	set_normalized_timespec(&ts_delta, lhs.tv_sec + rhs.tv_sec,
  				lhs.tv_nsec + rhs.tv_nsec);
  	return ts_delta;
  }
  
  /*
   * sub = lhs - rhs, in normalized form
   */
  static inline struct timespec timespec_sub(struct timespec lhs,
  						struct timespec rhs)
  {
  	struct timespec ts_delta;
  	set_normalized_timespec(&ts_delta, lhs.tv_sec - rhs.tv_sec,
  				lhs.tv_nsec - rhs.tv_nsec);
  	return ts_delta;
  }
  
  #define KTIME_MAX			((s64)~((u64)1 << 63))
  #if (BITS_PER_LONG == 64)
  # define KTIME_SEC_MAX			(KTIME_MAX / NSEC_PER_SEC)
  #else
  # define KTIME_SEC_MAX			LONG_MAX
  #endif
  
  /*
   * Returns true if the timespec is norm, false if denorm:
   */
  static inline bool timespec_valid(const struct timespec *ts)
  {
  	/* Dates before 1970 are bogus */
  	if (ts->tv_sec < 0)
  		return false;
  	/* Can't have more nanoseconds then a second */
  	if ((unsigned long)ts->tv_nsec >= NSEC_PER_SEC)
  		return false;
  	return true;
  }
  
  static inline bool timespec_valid_strict(const struct timespec *ts)
  {
  	if (!timespec_valid(ts))
  		return false;
  	/* Disallow values that could overflow ktime_t */
  	if ((unsigned long long)ts->tv_sec >= KTIME_SEC_MAX)
  		return false;
  	return true;
  }
  
  extern bool persistent_clock_exist;
  
  static inline bool has_persistent_clock(void)
  {
  	return persistent_clock_exist;
  }
  
  extern void read_persistent_clock(struct timespec *ts);
  extern void read_boot_clock(struct timespec *ts);
  extern int persistent_clock_is_local;
  extern int update_persistent_clock(struct timespec now);
  void timekeeping_init(void);
  extern int timekeeping_suspended;
  
  unsigned long get_seconds(void);
  struct timespec current_kernel_time(void);
  struct timespec __current_kernel_time(void); /* does not take xtime_lock */
  struct timespec get_monotonic_coarse(void);
  void get_xtime_and_monotonic_and_sleep_offset(struct timespec *xtim,
  				struct timespec *wtom, struct timespec *sleep);
  void timekeeping_inject_sleeptime(struct timespec *delta);
  
  #define CURRENT_TIME		(current_kernel_time())
  #define CURRENT_TIME_SEC	((struct timespec) { get_seconds(), 0 })
  
  /* Some architectures do not supply their own clocksource.
   * This is mainly the case in architectures that get their
   * inter-tick times by reading the counter on their interval
   * timer. Since these timers wrap every tick, they're not really
   * useful as clocksources. Wrapping them to act like one is possible
   * but not very efficient. So we provide a callout these arches
   * can implement for use with the jiffies clocksource to provide
   * finer then tick granular time.
   */
  #ifdef CONFIG_ARCH_USES_GETTIMEOFFSET
  extern u32 (*arch_gettimeoffset)(void);
  #endif
  
  extern void do_gettimeofday(struct timeval *tv);
  extern int do_settimeofday(const struct timespec *tv);
  extern int do_sys_settimeofday(const struct timespec *tv,
  			       const struct timezone *tz);
  #define do_posix_clock_monotonic_gettime(ts) ktime_get_ts(ts)
  extern long do_utimes(int dfd, const char __user *filename, struct timespec *times, int flags);
  struct itimerval;
  extern int do_setitimer(int which, struct itimerval *value,
  			struct itimerval *ovalue);
  extern unsigned int alarm_setitimer(unsigned int seconds);
  extern int do_getitimer(int which, struct itimerval *value);
  extern int __getnstimeofday(struct timespec *tv);
  extern void getnstimeofday(struct timespec *tv);
  extern void getrawmonotonic(struct timespec *ts);
  extern void getnstime_raw_and_real(struct timespec *ts_raw,
  		struct timespec *ts_real);
  extern void getboottime(struct timespec *ts);
  extern void monotonic_to_bootbased(struct timespec *ts);
  extern void get_monotonic_boottime(struct timespec *ts);
  
  extern struct timespec timespec_trunc(struct timespec t, unsigned gran);
  extern int timekeeping_valid_for_hres(void);
  extern u64 timekeeping_max_deferment(void);
  extern int timekeeping_inject_offset(struct timespec *ts);
  extern s32 timekeeping_get_tai_offset(void);
  extern void timekeeping_set_tai_offset(s32 tai_offset);
  extern void timekeeping_clocktai(struct timespec *ts);
  
  struct tms;
  extern void do_sys_times(struct tms *);
  
  /*
   * Similar to the struct tm in userspace <time.h>, but it needs to be here so
   * that the kernel source is self contained.
   */
  struct tm {
  	/*
  	 * the number of seconds after the minute, normally in the range
  	 * 0 to 59, but can be up to 60 to allow for leap seconds
  	 */
  	int tm_sec;
  	/* the number of minutes after the hour, in the range 0 to 59*/
  	int tm_min;
  	/* the number of hours past midnight, in the range 0 to 23 */
  	int tm_hour;
  	/* the day of the month, in the range 1 to 31 */
  	int tm_mday;
  	/* the number of months since January, in the range 0 to 11 */
  	int tm_mon;
  	/* the number of years since 1900 */
  	long tm_year;
  	/* the number of days since Sunday, in the range 0 to 6 */
  	int tm_wday;
  	/* the number of days since January 1, in the range 0 to 365 */
  	int tm_yday;
  };
  
  void time_to_tm(time_t totalsecs, int offset, struct tm *result);
  
  /**
   * timespec_to_ns - Convert timespec to nanoseconds
   * @ts:		pointer to the timespec variable to be converted
   *
   * Returns the scalar nanosecond representation of the timespec
   * parameter.
   */
  static inline s64 timespec_to_ns(const struct timespec *ts)
  {
  	return ((s64) ts->tv_sec * NSEC_PER_SEC) + ts->tv_nsec;
  }
  
  /**
   * timeval_to_ns - Convert timeval to nanoseconds
   * @ts:		pointer to the timeval variable to be converted
   *
   * Returns the scalar nanosecond representation of the timeval
   * parameter.
   */
  static inline s64 timeval_to_ns(const struct timeval *tv)
  {
  	return ((s64) tv->tv_sec * NSEC_PER_SEC) +
  		tv->tv_usec * NSEC_PER_USEC;
  }
  
  /**
   * ns_to_timespec - Convert nanoseconds to timespec
   * @nsec:	the nanoseconds value to be converted
   *
   * Returns the timespec representation of the nsec parameter.
   */
  extern struct timespec ns_to_timespec(const s64 nsec);
  
  /**
   * ns_to_timeval - Convert nanoseconds to timeval
   * @nsec:	the nanoseconds value to be converted
   *
   * Returns the timeval representation of the nsec parameter.
   */
  extern struct timeval ns_to_timeval(const s64 nsec);
  
  /**
   * timespec_add_ns - Adds nanoseconds to a timespec
   * @a:		pointer to timespec to be incremented
   * @ns:		unsigned nanoseconds value to be added
   *
   * This must always be inlined because its used from the x86-64 vdso,
   * which cannot call other kernel functions.
   */
  static __always_inline void timespec_add_ns(struct timespec *a, u64 ns)
  {
  	a->tv_sec += __iter_div_u64_rem(a->tv_nsec + ns, NSEC_PER_SEC, &ns);
  	a->tv_nsec = ns;
  }
  
  #endif