[KTIME]: Introduce ktime_sub_ns and ktime_sub_us

First user will be the DCCP transport networking protocol.

Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 24 insertions, 0 deletions

diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index c21ca6bfaa66..dc8a4451d79b 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -277,6 +277,30 @@ ktime_t ktime_add_ns(const ktime_t kt, u64 nsec)
 }
 
 EXPORT_SYMBOL_GPL(ktime_add_ns);
+
+/**
+ * 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
+ */
+ktime_t ktime_sub_ns(const ktime_t kt, u64 nsec)
+{
+        ktime_t tmp;
+
+        if (likely(nsec < NSEC_PER_SEC)) {
+                tmp.tv64 = nsec;
+        } else {
+                unsigned long rem = do_div(nsec, NSEC_PER_SEC);
+
+                tmp = ktime_set((long)nsec, rem);
+        }
+
+        return ktime_sub(kt, tmp);
+}
+
+EXPORT_SYMBOL_GPL(ktime_sub_ns);
 # endif /* !CONFIG_KTIME_SCALAR */
 
 /*