[PATCH] hrtimer: introduce nsec_t type and conversion functions

- introduce the nsec_t type

- basic nsec conversion routines: timespec_to_ns(), timeval_to_ns(),
  ns_to_timespec(), ns_to_timeval().

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 83 insertions, 0 deletions

diff --git a/include/linux/time.h b/include/linux/time.h
index 64e797464589..f639fde29253 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -50,6 +50,12 @@ extern void set_normalized_timespec(struct timespec *ts, time_t sec, long nsec);
 #define timespec_valid(ts) \
         (((ts)->tv_sec >= 0) && (((unsigned) (ts)->tv_nsec) < NSEC_PER_SEC))
 
+/*
+ * 64-bit nanosec type. Large enough to span 292+ years in nanosecond
+ * resolution. Ought to be enough for a while.
+ */
+typedef s64 nsec_t;
+
 extern struct timespec xtime;
 extern struct timespec wall_to_monotonic;
 extern seqlock_t xtime_lock;
@@ -79,6 +85,47 @@ extern void getnstimestamp(struct timespec *ts);
 
 extern struct timespec timespec_trunc(struct timespec t, unsigned gran);
 
+/**
+ * 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 nsec_t timespec_to_ns(const struct timespec *ts)
+{
+        return ((nsec_t) 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 nsec_t timeval_to_ns(const struct timeval *tv)
+{
+        return ((nsec_t) 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 nsec_t 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 nsec_t nsec);
+
 #endif /* __KERNEL__ */
 
 #define NFDBITS                 __NFDBITS
diff --git a/kernel/time.c b/kernel/time.c
index c689b53297cf..cf5a4582a672 100644
--- a/kernel/time.c
+++ b/kernel/time.c
@@ -652,6 +652,42 @@ void set_normalized_timespec(struct timespec *ts, time_t sec, long nsec)
         ts->tv_nsec = nsec;
 }
 
+/**
+ * ns_to_timespec - Convert nanoseconds to timespec
+ * @nsec:       the nanoseconds value to be converted
+ *
+ * Returns the timespec representation of the nsec parameter.
+ */
+inline struct timespec ns_to_timespec(const nsec_t nsec)
+{
+        struct timespec ts;
+
+        if (nsec)
+                ts.tv_sec = div_long_long_rem_signed(nsec, NSEC_PER_SEC,
+                                                     &ts.tv_nsec);
+        else
+                ts.tv_sec = ts.tv_nsec = 0;
+
+        return ts;
+}
+
+/**
+ * ns_to_timeval - Convert nanoseconds to timeval
+ * @nsec:       the nanoseconds value to be converted
+ *
+ * Returns the timeval representation of the nsec parameter.
+ */
+struct timeval ns_to_timeval(const nsec_t nsec)
+{
+        struct timespec ts = ns_to_timespec(nsec);
+        struct timeval tv;
+
+        tv.tv_sec = ts.tv_sec;
+        tv.tv_usec = (suseconds_t) ts.tv_nsec / 1000;
+
+        return tv;
+}
+
 #if (BITS_PER_LONG < 64)
 u64 get_jiffies_64(void)
 {