linux/include/linux/time.h

#ifndef _LINUX_TIME_H
#define _LINUX_TIME_H

#include <linux/types.h>

#ifdef __KERNEL__
# include <linux/cache.h>
# include <linux/seqlock.h>
# include <linux/math64.h>
#endif

#ifndef _STRUCT_TIMESPEC
#define _STRUCT_TIMESPEC
struct timespec {
	__kernel_time_t	tv_sec;			/* seconds */
	long		tv_nsec;		/* nanoseconds */
};
#endif

struct timeval {
	__kernel_time_t		tv_sec;		/* seconds */
	__kernel_suseconds_t	tv_usec;	/* microseconds */
};

struct timezone {
	int	tz_minuteswest;	/* minutes west of Greenwich */
	int	tz_dsttime;	/* type of dst correction */
};

#ifdef __KERNEL__

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	1000000000000000L

#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, long nsec);
extern struct timespec timespec_add_safe(const struct timespec lhs,
					 const struct timespec rhs);

/*
 * 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;
}

/*
 * Returns true if the timespec is norm, false if denorm:
 */
#define timespec_valid(ts) \
	(((ts)->tv_sec >= 0) && (((unsigned long) (ts)->tv_nsec) < NSEC_PER_SEC))

extern struct timespec xtime;
extern struct timespec wall_to_monotonic;
extern seqlock_t xtime_lock;

extern unsigned long read_persistent_clock(void);
extern int update_persistent_clock(struct timespec now);
extern int no_sync_cmos_clock __read_mostly;
void timekeeping_init(void);
extern int timekeeping_suspended;

unsigned long get_seconds(void);
struct timespec current_kernel_time(void);

#define CURRENT_TIME		(current_kernel_time())
#define CURRENT_TIME_SEC	((struct timespec) { get_seconds(), 0 })

extern void do_gettimeofday(struct timeval *tv);
extern int do_settimeofday(struct timespec *tv);
extern int do_sys_settimeofday(struct timespec *tv, struct timezone *tz);
#define do_posix_clock_monotonic_gettime(ts) ktime_get_ts(ts)
extern long do_utimes(int dfd, 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 void getnstimeofday(struct timespec *tv);
extern void getrawmonotonic(struct timespec *ts);
extern void getboottime(struct timespec *ts);
extern void monotonic_to_bootbased(struct timespec *ts);

extern struct timespec timespec_trunc(struct timespec t, unsigned gran);
extern int timekeeping_valid_for_hres(void);
extern void update_wall_time(void);
extern void update_xtime_cache(u64 nsec);

struct tms;
extern void do_sys_times(struct tms *);

/**
 * 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 /* __KERNEL__ */

#define NFDBITS			__NFDBITS

#define FD_SETSIZE		__FD_SETSIZE
#define FD_SET(fd,fdsetp)	__FD_SET(fd,fdsetp)
#define FD_CLR(fd,fdsetp)	__FD_CLR(fd,fdsetp)
#define FD_ISSET(fd,fdsetp)	__FD_ISSET(fd,fdsetp)
#define FD_ZERO(fdsetp)		__FD_ZERO(fdsetp)

/*
 * Names of the interval timers, and structure
 * defining a timer setting:
 */
#define	ITIMER_REAL		0
#define	ITIMER_VIRTUAL		1
#define	ITIMER_PROF		2

struct itimerspec {
	struct timespec it_interval;	/* timer period */
	struct timespec it_value;	/* timer expiration */
};

struct itimerval {
	struct timeval it_interval;	/* timer interval */
	struct timeval it_value;	/* current value */
};

/*
 * The IDs of the various system clocks (for POSIX.1b interval timers):
 */
#define CLOCK_REALTIME			0
#define CLOCK_MONOTONIC			1
#define CLOCK_PROCESS_CPUTIME_ID	2
#define CLOCK_THREAD_CPUTIME_ID		3
#define CLOCK_MONOTONIC_RAW		4

/*
 * The IDs of various hardware clocks:
 */
#define CLOCK_SGI_CYCLE			10
#define MAX_CLOCKS			16
#define CLOCKS_MASK			(CLOCK_REALTIME | CLOCK_MONOTONIC)
#define CLOCKS_MONO			CLOCK_MONOTONIC

/*
 * The various flags for setting POSIX.1b interval timers:
 */
#define TIMER_ABSTIME			0x01

#endif