text: /*
   *  include/linux/ktime.h
   *
   *  ktime_t - nanosecond-resolution time format.
   *
   *   Copyright(C) 2005, Thomas Gleixner <tglx@linutronix.de>
   *   Copyright(C) 2005, Red Hat, Inc., Ingo Molnar
   *
   *  data type definitions, declarations, prototypes and macros.
   *
   *  Started by: Thomas Gleixner and Ingo Molnar
   *
   *  Credits:
   *
   *  	Roman Zippel provided the ideas and primary code snippets of
   *  	the ktime_t union and further simplifications of the original
   *  	code.
   *
   *  For licencing details see kernel-base/COPYING
   */
  #ifndef _LINUX_KTIME_H
  #define _LINUX_KTIME_H
  
  #include <linux/time.h>
  #include <linux/jiffies.h>
  
  /*
   * ktime_t:
   *
   * On 64-bit CPUs a single 64-bit variable is used to store the hrtimers
   * internal representation of time values in scalar nanoseconds. The
   * design plays out best on 64-bit CPUs, where most conversions are
   * NOPs and most arithmetic ktime_t operations are plain arithmetic
   * operations.
   *
   * On 32-bit CPUs an optimized representation of the timespec structure
   * is used to avoid expensive conversions from and to timespecs. The
   * endian-aware order of the tv struct members is chosen to allow
   * mathematical operations on the tv64 member of the union too, which
   * for certain operations produces better code.
   *
   * For architectures with efficient support for 64/32-bit conversions the
   * plain scalar nanosecond based representation can be selected by the
   * config switch CONFIG_KTIME_SCALAR.
   */
  union ktime {
  	s64	tv64;
  #if BITS_PER_LONG != 64 && !defined(CONFIG_KTIME_SCALAR)
  	struct {
  # ifdef __BIG_ENDIAN
  	s32	sec, nsec;
  # else
  	s32	nsec, sec;
  # endif
  	} tv;
  #endif
  };
  
  typedef union ktime ktime_t;		/* Kill this */
  
  /*
   * ktime_t definitions when using the 64-bit scalar representation:
   */
  
  #if (BITS_PER_LONG == 64) || defined(CONFIG_KTIME_SCALAR)
  
  /**
   * ktime_set - Set a ktime_t variable from a seconds/nanoseconds value
   * @secs:	seconds to set
   * @nsecs:	nanoseconds to set
   *
   * Return the ktime_t representation of the value
   */
  static inline ktime_t ktime_set(const long secs, const unsigned long nsecs)
  {
  #if (BITS_PER_LONG == 64)
  	if (unlikely(secs >= KTIME_SEC_MAX))
  		return (ktime_t){ .tv64 = KTIME_MAX };
  #endif
  	return (ktime_t) { .tv64 = (s64)secs * NSEC_PER_SEC + (s64)nsecs };
  }
  
  /* Subtract two ktime_t variables. rem = lhs -rhs: */
  #define ktime_sub(lhs, rhs) \
  		({ (ktime_t){ .tv64 = (lhs).tv64 - (rhs).tv64 }; })
  
  /* Add two ktime_t variables. res = lhs + rhs: */
  #define ktime_add(lhs, rhs) \
  		({ (ktime_t){ .tv64 = (lhs).tv64 + (rhs).tv64 }; })
  
  /*
   * Add a ktime_t variable and a scalar nanosecond value.
   * res = kt + nsval:
   */
  #define ktime_add_ns(kt, nsval) \
  		({ (ktime_t){ .tv64 = (kt).tv64 + (nsval) }; })
  
  /*
   * Subtract a scalar nanosecod from a ktime_t variable
   * res = kt - nsval:
   */
  #define ktime_sub_ns(kt, nsval) \
  		({ (ktime_t){ .tv64 = (kt).tv64 - (nsval) }; })
  
  /* convert a timespec to ktime_t format: */
  static inline ktime_t timespec_to_ktime(struct timespec ts)
  {
  	return ktime_set(ts.tv_sec, ts.tv_nsec);
  }
  
  /* convert a timeval to ktime_t format: */
  static inline ktime_t timeval_to_ktime(struct timeval tv)
  {
  	return ktime_set(tv.tv_sec, tv.tv_usec * NSEC_PER_USEC);
  }
  
  /* Map the ktime_t to timespec conversion to ns_to_timespec function */
  #define ktime_to_timespec(kt)		ns_to_timespec((kt).tv64)
  
  /* Map the ktime_t to timeval conversion to ns_to_timeval function */
  #define ktime_to_timeval(kt)		ns_to_timeval((kt).tv64)
  
  /* Convert ktime_t to nanoseconds - NOP in the scalar storage format: */
  #define ktime_to_ns(kt)			((kt).tv64)
  
  #else	/* !((BITS_PER_LONG == 64) || defined(CONFIG_KTIME_SCALAR)) */
  
  /*
   * Helper macros/inlines to get the ktime_t math right in the timespec
   * representation. The macros are sometimes ugly - their actual use is
   * pretty okay-ish, given the circumstances. We do all this for
   * performance reasons. The pure scalar nsec_t based code was nice and
   * simple, but created too many 64-bit / 32-bit conversions and divisions.
   *
   * Be especially aware that negative values are represented in a way
   * that the tv.sec field is negative and the tv.nsec field is greater
   * or equal to zero but less than nanoseconds per second. This is the
   * same representation which is used by timespecs.
   *
   *   tv.sec < 0 and 0 >= tv.nsec < NSEC_PER_SEC
   */
  
  /* Set a ktime_t variable to a value in sec/nsec representation: */
  static inline ktime_t ktime_set(const long secs, const unsigned long nsecs)
  {
  	return (ktime_t) { .tv = { .sec = secs, .nsec = nsecs } };
  }
  
  /**
   * ktime_sub - subtract two ktime_t variables
   * @lhs:	minuend
   * @rhs:	subtrahend
   *
   * Returns the remainder of the subtraction
   */
  static inline ktime_t ktime_sub(const ktime_t lhs, const ktime_t rhs)
  {
  	ktime_t res;
  
  	res.tv64 = lhs.tv64 - rhs.tv64;
  	if (res.tv.nsec < 0)
  		res.tv.nsec += NSEC_PER_SEC;
  
  	return res;
  }
  
  /**
   * ktime_add - add two ktime_t variables
   * @add1:	addend1
   * @add2:	addend2
   *
   * Returns the sum of @add1 and @add2.
   */
  static inline ktime_t ktime_add(const ktime_t add1, const ktime_t add2)
  {
  	ktime_t res;
  
  	res.tv64 = add1.tv64 + add2.tv64;
  	/*
  	 * performance trick: the (u32) -NSEC gives 0x00000000Fxxxxxxx
  	 * so we subtract NSEC_PER_SEC and add 1 to the upper 32 bit.
  	 *
  	 * it's equivalent to:
  	 *   tv.nsec -= NSEC_PER_SEC
  	 *   tv.sec ++;
  	 */
  	if (res.tv.nsec >= NSEC_PER_SEC)
  		res.tv64 += (u32)-NSEC_PER_SEC;
  
  	return res;
  }
  
  /**
   * ktime_add_ns - Add a scalar nanoseconds value to a ktime_t variable
   * @kt:		addend
   * @nsec:	the scalar nsec value to add
   *
   * Returns the sum of @kt and @nsec in ktime_t format
   */
  extern ktime_t ktime_add_ns(const ktime_t kt, u64 nsec);
  
  /**
   * ktime_sub_ns - Subtract a scalar nanoseconds value from a ktime_t variable
   * @kt:		minuend
   * @nsec:	the scalar nsec value to subtract
   *
   * Returns the subtraction of @nsec from @kt in ktime_t format
   */
  extern ktime_t ktime_sub_ns(const ktime_t kt, u64 nsec);
  
  /**
   * timespec_to_ktime - convert a timespec to ktime_t format
   * @ts:		the timespec variable to convert
   *
   * Returns a ktime_t variable with the converted timespec value
   */
  static inline ktime_t timespec_to_ktime(const struct timespec ts)
  {
  	return (ktime_t) { .tv = { .sec = (s32)ts.tv_sec,
  			   	   .nsec = (s32)ts.tv_nsec } };
  }
  
  /**
   * timeval_to_ktime - convert a timeval to ktime_t format
   * @tv:		the timeval variable to convert
   *
   * Returns a ktime_t variable with the converted timeval value
   */
  static inline ktime_t timeval_to_ktime(const struct timeval tv)
  {
  	return (ktime_t) { .tv = { .sec = (s32)tv.tv_sec,
  				   .nsec = (s32)tv.tv_usec * 1000 } };
  }
  
  /**
   * ktime_to_timespec - convert a ktime_t variable to timespec format
   * @kt:		the ktime_t variable to convert
   *
   * Returns the timespec representation of the ktime value
   */
  static inline struct timespec ktime_to_timespec(const ktime_t kt)
  {
  	return (struct timespec) { .tv_sec = (time_t) kt.tv.sec,
  				   .tv_nsec = (long) kt.tv.nsec };
  }
  
  /**
   * ktime_to_timeval - convert a ktime_t variable to timeval format
   * @kt:		the ktime_t variable to convert
   *
   * Returns the timeval representation of the ktime value
   */
  static inline struct timeval ktime_to_timeval(const ktime_t kt)
  {
  	return (struct timeval) {
  		.tv_sec = (time_t) kt.tv.sec,
  		.tv_usec = (suseconds_t) (kt.tv.nsec / NSEC_PER_USEC) };
  }
  
  /**
   * ktime_to_ns - convert a ktime_t variable to scalar nanoseconds
   * @kt:		the ktime_t variable to convert
   *
   * Returns the scalar nanoseconds representation of @kt
   */
  static inline s64 ktime_to_ns(const ktime_t kt)
  {
  	return (s64) kt.tv.sec * NSEC_PER_SEC + kt.tv.nsec;
  }
  
  #endif	/* !((BITS_PER_LONG == 64) || defined(CONFIG_KTIME_SCALAR)) */
  
  /**
   * ktime_equal - Compares two ktime_t variables to see if they are equal
   * @cmp1:	comparable1
   * @cmp2:	comparable2
   *
   * Compare two ktime_t variables, returns 1 if equal
   */
  static inline int ktime_equal(const ktime_t cmp1, const ktime_t cmp2)
  {
  	return cmp1.tv64 == cmp2.tv64;
  }
  
  static inline s64 ktime_to_us(const ktime_t kt)
  {
  	struct timeval tv = ktime_to_timeval(kt);
  	return (s64) tv.tv_sec * USEC_PER_SEC + tv.tv_usec;
  }
  
  static inline s64 ktime_to_ms(const ktime_t kt)
  {
  	struct timeval tv = ktime_to_timeval(kt);
  	return (s64) tv.tv_sec * MSEC_PER_SEC + tv.tv_usec / USEC_PER_MSEC;
  }
  
  static inline s64 ktime_us_delta(const ktime_t later, const ktime_t earlier)
  {
         return ktime_to_us(ktime_sub(later, earlier));
  }
  
  static inline ktime_t ktime_add_us(const ktime_t kt, const u64 usec)
  {
  	return ktime_add_ns(kt, usec * 1000);
  }
  
  static inline ktime_t ktime_sub_us(const ktime_t kt, const u64 usec)
  {
  	return ktime_sub_ns(kt, usec * 1000);
  }
  
  extern ktime_t ktime_add_safe(const ktime_t lhs, const ktime_t rhs);
  
  /*
   * The resolution of the clocks. The resolution value is returned in
   * the clock_getres() system call to give application programmers an
   * idea of the (in)accuracy of timers. Timer values are rounded up to
   * this resolution values.
   */
  #define LOW_RES_NSEC		TICK_NSEC
  #define KTIME_LOW_RES		(ktime_t){ .tv64 = LOW_RES_NSEC }
  
  /* Get the monotonic time in timespec format: */
  extern void ktime_get_ts(struct timespec *ts);
  
  /* Get the real (wall-) time in timespec format: */
  #define ktime_get_real_ts(ts)	getnstimeofday(ts)
  
  static inline ktime_t ns_to_ktime(u64 ns)
  {
  	static const ktime_t ktime_zero = { .tv64 = 0 };
  	return ktime_add_ns(ktime_zero, ns);
  }
  
  #endif
  