timespec: Add timespec_to_msec helper

Paralleling timespec_to_nsec, converts to milliseconds.

Signed-off-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
[Pekka: added doc about flooring]
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>

libweston/compositor.c

@@ -2388,7 +2388,7 @@ weston_output_finish_frame(struct weston_output *output,
 						  output->msc,
 						  presented_flags);
 
-	output->frame_time = stamp->tv_sec * 1000 + stamp->tv_nsec / 1000000;
+	output->frame_time = timespec_to_msec(stamp);
 
 	weston_compositor_read_presentation_clock(compositor, &now);
 	timespec_sub(&gone, &now, stamp);

shared/timespec-util.h

@@ -93,6 +93,19 @@ timespec_to_nsec(const struct timespec *a)
 	return (int64_t)a->tv_sec * NSEC_PER_SEC + a->tv_nsec;
 }
 
+/* Convert timespec to milliseconds
+ *
+ * \param a timespec
+ * \return milliseconds
+ *
+ * Rounding to integer milliseconds happens always down (floor()).
+ */
+static inline int64_t
+timespec_to_msec(const struct timespec *a)
+{
+	return (int64_t)a->tv_sec * 1000 + a->tv_nsec / 1000000;
+}
+
 /* Convert milli-Hertz to nanoseconds
  *
  * \param mhz frequency in mHz, not zero

tests/timespec-test.c

@@ -60,6 +60,15 @@ ZUC_TEST(timespec_test, timespec_to_nsec)
 	ZUC_ASSERT_EQ(timespec_to_nsec(&a), (NSEC_PER_SEC * 4ULL) + 4);
 }
 
+ZUC_TEST(timespec_test, timespec_to_msec)
+{
+	struct timespec a;
+
+	a.tv_sec = 4;
+	a.tv_nsec = 4000000;
+	ZUC_ASSERT_EQ(timespec_to_msec(&a), (4000ULL) + 4);
+}
+
 ZUC_TEST(timespec_test, millihz_to_nsec)
 {
 	ZUC_ASSERT_EQ(millihz_to_nsec(60000), 16666666);