From a90788cb44227a1618bc7341cd179c115047ab13 Mon Sep 17 00:00:00 2001
From: Hubertus Franke <frankeh@us.ibm.com>
Date: Wed, 29 Jun 2016 17:29:15 -0400
Subject: [PATCH] support for kevent type timer resolutions

add documentation for timer resolution
---
 include/sys/event.h |  9 +++++++++
 kqueue.2            | 16 +++++++++++++++-
 src/linux/timer.c   | 34 ++++++++++++++++++++++++++++------
 3 files changed, 52 insertions(+), 7 deletions(-)

diff --git a/include/sys/event.h b/include/sys/event.h
index 610ab449..087917df 100644
--- a/include/sys/event.h
+++ b/include/sys/event.h
@@ -168,6 +168,15 @@ struct kevent {
                                    program */
 #define VQ_NOTRESPLOCK  0x0080  /* server lockd down */
 
+/*
+ * data/hint flags for EVFILT_TIMER as suported and defined in kevent64
+ */
+#define NOTE_SECONDS    0x0001  /* time specified in seconds */
+#define NOTE_USECONDS   0x0002  /* time specified in micro seconds */
+#define NOTE_NSECONDS   0x0004  /* time specified in nano seconds */
+#define NOTE_ABSOLUTE   0x0008  /* data is an absolute timeout */
+
+
 
 #ifndef __KERNEL__
 #ifdef  __cplusplus
diff --git a/kqueue.2 b/kqueue.2
index 22cca6cc..d8b5414f 100644
--- a/kqueue.2
+++ b/kqueue.2
@@ -364,7 +364,21 @@ Establishes an arbitrary timer identified by
 .Va ident .
 When adding a timer,
 .Va data
-specifies the timeout period in milliseconds.
+specifies the timeout period and
+.Va fflags
+can be set to one of the following:
+.Bl -tag -width XXNOTE_RENAME
+.It NOTE_SECONDS
+data is in seconds
+.It NOTE_USECONDS
+data is in microseconds
+.It NOTE_NSECONDS
+data is in nanoseconds
+.It NOTE_ABSOLUTE
+data is an absolute timeout
+.El
+.Pp
+If fflags is not set, the default is milliseconds.
 The timer will be periodic unless EV_ONESHOT is specified.
 On return,
 .Va data
diff --git a/src/linux/timer.c b/src/linux/timer.c
index 7cd48c5d..06ddfc8b 100644
--- a/src/linux/timer.c
+++ b/src/linux/timer.c
@@ -79,14 +79,33 @@ itimerspec_dump(struct itimerspec *ts)
 }
 #endif
 
-/* Convert milliseconds into seconds+nanoseconds */
+/* Convert time data into seconds+nanoseconds */
+
+#define NOTE_TIMER_MASK (NOTE_ABSOLUTE-1)
+
 static void
-convert_msec_to_itimerspec(struct itimerspec *dst, int src, int oneshot)
+convert_timedata_to_itimerspec(struct itimerspec *dst, long src,
+						       unsigned int flags, int oneshot)
 {
     time_t sec, nsec;
 
-    sec = src / 1000;
-    nsec = (src % 1000) * 1000000;
+	switch (flags & NOTE_TIMER_MASK) {
+	case NOTE_USECONDS:
+        sec = src / 1000000;
+        nsec = (src % 1000000);
+        break;
+	case NOTE_NSECONDS:
+        sec = src / 1000000000;
+        nsec = (src % 1000000000);
+        break;
+	case NOTE_SECONDS:
+        sec = src;
+        nsec = 0;
+        break;
+	default: /* milliseconds */
+        sec = src / 1000;
+        nsec = (src % 1000) * 1000000;
+	}
 
     /* Set the interval */
     if (oneshot) {
@@ -133,6 +152,7 @@ evfilt_timer_knote_create(struct filter *filt, struct knote *kn)
     struct epoll_event ev;
     struct itimerspec ts;
     int tfd;
+    int flags;
 
     kn->kev.flags |= EV_CLEAR;
 
@@ -143,8 +163,10 @@ evfilt_timer_knote_create(struct filter *filt, struct knote *kn)
     }
     dbg_printf("created timerfd %d", tfd);
 
-    convert_msec_to_itimerspec(&ts, kn->kev.data, kn->kev.flags & EV_ONESHOT);
-    if (timerfd_settime(tfd, 0, &ts, NULL) < 0) {
+    convert_timedata_to_itimerspec(&ts, kn->kev.data, kn->kev.fflags,
+								   kn->kev.flags & EV_ONESHOT);
+	flags = (kn->kev.fflags & NOTE_ABSOLUTE) ? TFD_TIMER_ABSTIME : 0;
+    if (timerfd_settime(tfd, flags, &ts, NULL) < 0) {
         dbg_printf("timerfd_settime(2): %s", strerror(errno));
         close(tfd);
         return (-1);