[PATCH v2] backport: add ktime_get_raw_ts64() backport for < 3.19

[Luca Coelho <luca@coelho.fi>]

From: Luca Coelho <luciano.coelho@intel.com>

The getrawmonotonic64() function that is used by the
ktime_get_raw_ts64() backport was only introduced in 3.19.  To fix
compilation with earlier kernels, do the convertion from
getrawmonotonic() manually if the kernel is < 3.19.

Additionally, add timespec_to_timespec64() that we need for this
conversion (and which was only introduced in 3.17).

Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
---
 backport/backport-include/linux/timekeeping.h | 29 +++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/backport/backport-include/linux/timekeeping.h b/backport/backport-include/linux/timekeeping.h
index aebb00ca366b..718715316a1d 100644
--- a/backport/backport-include/linux/timekeeping.h
+++ b/backport/backport-include/linux/timekeeping.h
@@ -55,11 +55,40 @@ static inline void ktime_get_ts64(struct timespec64 *ts)
 }
 #endif
 
+#if LINUX_VERSION_IS_LESS(3,17,0)
+/* This was introduced in 4.15, but we only need it in the
+ * ktime_get_raw_ts64 backport() for < 3.17.
+ */
+#if __BITS_PER_LONG == 64
+static inline struct timespec64 timespec_to_timespec64(const struct timespec ts)
+{
+	return *(const struct timespec64 *)&ts;
+}
+
+#else
+static inline struct timespec64 timespec_to_timespec64(const struct timespec ts)
+{
+	struct timespec64 ret;
+
+	ret.tv_sec = ts.tv_sec;
+	ret.tv_nsec = ts.tv_nsec;
+	return ret;
+}
+#endif
+#endif /* < 3.17 */
+
 #if LINUX_VERSION_IS_LESS(4,18,0)
 #define ktime_get_raw_ts64 LINUX_BACKPORT(ktime_get_raw_ts64)
 static inline void ktime_get_raw_ts64(struct timespec64 *ts)
 {
+#if LINUX_VERSION_IS_LESS(3,19,0)
+	struct timespec64 ts64;
+
+	getrawmonotonic(&ts64);
+	*ts = timespec_to_timespec64(ts64);
+#else
 	return getrawmonotonic64(ts);
+#endif /* < 3.19 */
 }
 #endif
 
-- 
2.19.0

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