linux-kernel - [PATCH 1/3] kernel/time: Add new helpers to convert ktime to/from jiffies

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Date:	Thu, 02 Jan 2014 22:30:46 +0400
From:	Alexey Perevalov <a.perevalov@...sung.com>
To:	linux-kernel@...r.kernel.org, john.stultz@...aro.org
Cc:	Anton Vorontsov <anton@...msg.org>, kyungmin.park@...sung.com,
	akpm@...ux-foundation.org,
	Anton Vorontsov <anton.vorontsov@...aro.org>,
	Alexey Perevalov <a.perevalov@...sung.com>
Subject: [PATCH 1/3] kernel/time: Add new helpers to convert ktime to/from
 jiffies

From: Anton Vorontsov <anton@...msg.org>

Two new functions: jiffies_to_ktime() and ktime_to_jiffies(), we'll use
them for timerfd deferred timers handling.

We fully reuse the logic from timespec implementations, so the functions
are pretty straightforward.

The only tricky part is in headers: we have to include jiffies.h after
we defined ktime_t, this is because ktime.h needs some declarations from
jiffies.h (e.g. TICK_NSEC).

Signed-off-by: Anton Vorontsov <anton.vorontsov@...aro.org>
Signed-off-by: Alexey Perevalov <a.perevalov@...sung.com>
---
 include/linux/jiffies.h |    4 +++-
 include/linux/ktime.h   |    3 ++-
 kernel/time.c           |   23 +++++++++++++++++++++++
 3 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/include/linux/jiffies.h b/include/linux/jiffies.h
index d235e88..1ba02ae 100644
--- a/include/linux/jiffies.h
+++ b/include/linux/jiffies.h
@@ -6,6 +6,7 @@
 #include <linux/types.h>
 #include <linux/time.h>
 #include <linux/timex.h>
+#include <linux/ktime.h>
 #include <asm/param.h>			/* for HZ */
 
 /*
@@ -302,7 +303,8 @@ extern void jiffies_to_timespec(const unsigned long jiffies,
 extern unsigned long timeval_to_jiffies(const struct timeval *value);
 extern void jiffies_to_timeval(const unsigned long jiffies,
 			       struct timeval *value);
-
+extern unsigned long ktime_to_jiffies(ktime_t *value);
+extern void jiffies_to_ktime(const unsigned long jiffies, ktime_t *value);
 extern clock_t jiffies_to_clock_t(unsigned long x);
 static inline clock_t jiffies_delta_to_clock_t(long delta)
 {
diff --git a/include/linux/ktime.h b/include/linux/ktime.h
index 31c0cd1..e8ed619 100644
--- a/include/linux/ktime.h
+++ b/include/linux/ktime.h
@@ -22,7 +22,6 @@
 #define _LINUX_KTIME_H
 
 #include <linux/time.h>
-#include <linux/jiffies.h>
 
 /*
  * ktime_t:
@@ -58,6 +57,8 @@ union ktime {
 
 typedef union ktime ktime_t;		/* Kill this */
 
+#include <linux/jiffies.h>
+
 /*
  * ktime_t definitions when using the 64-bit scalar representation:
  */
diff --git a/kernel/time.c b/kernel/time.c
index 7c7964c..22580a0 100644
--- a/kernel/time.c
+++ b/kernel/time.c
@@ -29,6 +29,7 @@
 
 #include <linux/export.h>
 #include <linux/timex.h>
+#include <linux/ktime.h>
 #include <linux/capability.h>
 #include <linux/timekeeper_internal.h>
 #include <linux/errno.h>
@@ -575,6 +576,28 @@ void jiffies_to_timeval(const unsigned long jiffies, struct timeval *value)
 }
 EXPORT_SYMBOL(jiffies_to_timeval);
 
+unsigned long ktime_to_jiffies(ktime_t *value)
+{
+	struct timespec ts = ktime_to_timespec(*value);
+
+	/*
+	 * nsecs_to_jiffies(ktime_to_ns(*ktime)) is unsafe as nsecs_to_jiffies
+	 * doesn't handle MAX_JIFFY_OFFSET. So we reuse the logic from the
+	 * timespec to jiffies conversion function.
+	 */
+	return timespec_to_jiffies(&ts);
+}
+EXPORT_SYMBOL(ktime_to_jiffies);
+
+void jiffies_to_ktime(const unsigned long jiffies, ktime_t *value)
+{
+	struct timespec ts;
+
+	jiffies_to_timespec(jiffies, &ts);
+	*value = timespec_to_ktime(ts);
+}
+EXPORT_SYMBOL(jiffies_to_ktime);
+
 /*
  * Convert jiffies/jiffies_64 to clock_t and back.
  */
-- 
1.7.9.5

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