1. 根目录:
2. include
3. linux
4. 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	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;
}

/*
 * 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 void read_persistent_clock(struct timespec *ts);
extern void read_boot_clock(struct timespec *ts);
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);
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);

#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);
#else
static inline u32 arch_gettimeoffset(void) { return 0; }
#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 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 void timekeeping_leap_insert(int leapsecond);
extern int timekeeping_inject_offset(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 /* __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
#define CLOCK_REALTIME_COARSE		5
#define CLOCK_MONOTONIC_COARSE		6
#define CLOCK_BOOTTIME			7

/*
 * 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