linux-kernel - [PATCH 4/6] time: Add time64_to

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Date:	Mon, 20 Jun 2016 12:56:23 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	lkml <linux-kernel@...r.kernel.org>
Cc:	Deepa Dinamani <deepa.kernel@...il.com>,
	Prarit Bhargava <prarit@...hat.com>,
	Richard Cochran <richardcochran@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	John Stultz <john.stultz@...aro.org>
Subject: [PATCH 4/6] time: Add time64_to_tm()

From: Deepa Dinamani <deepa.kernel@...il.com>

time_to_tm() takes time_t as an argument.
time_t is not y2038 safe.
Add time64_to_tm() that takes time64_t as an argument
which is y2038 safe.
The plan is to eventually replace all calls to time_to_tm()
by time64_to_tm().

Cc: Prarit Bhargava <prarit@...hat.com>
Cc: Richard Cochran <richardcochran@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Deepa Dinamani <deepa.kernel@...il.com>
Signed-off-by: John Stultz <john.stultz@...aro.org>
---
 include/linux/time.h   | 15 ++++++++++++++-
 kernel/time/timeconv.c | 11 ++++++-----
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/include/linux/time.h b/include/linux/time.h
index 297f09f..4cea09d 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -205,7 +205,20 @@ struct tm {
 	int tm_yday;
 };
 
-void time_to_tm(time_t totalsecs, int offset, struct tm *result);
+void time64_to_tm(time64_t totalsecs, int offset, struct tm *result);
+
+/**
+ * time_to_tm - converts the calendar time to local broken-down time
+ *
+ * @totalsecs	the number of seconds elapsed since 00:00:00 on January 1, 1970,
+ *		Coordinated Universal Time (UTC).
+ * @offset	offset seconds adding to totalsecs.
+ * @result	pointer to struct tm variable to receive broken-down time
+ */
+static inline void time_to_tm(time_t totalsecs, int offset, struct tm *result)
+{
+	time64_to_tm(totalsecs, offset, result);
+}
 
 /**
  * timespec_to_ns - Convert timespec to nanoseconds
diff --git a/kernel/time/timeconv.c b/kernel/time/timeconv.c
index 86628e7..7142580 100644
--- a/kernel/time/timeconv.c
+++ b/kernel/time/timeconv.c
@@ -67,20 +67,21 @@ static const unsigned short __mon_yday[2][13] = {
 #define SECS_PER_DAY	(SECS_PER_HOUR * 24)
 
 /**
- * time_to_tm - converts the calendar time to local broken-down time
+ * time64_to_tm - converts the calendar time to local broken-down time
  *
  * @totalsecs	the number of seconds elapsed since 00:00:00 on January 1, 1970,
  *		Coordinated Universal Time (UTC).
  * @offset	offset seconds adding to totalsecs.
  * @result	pointer to struct tm variable to receive broken-down time
  */
-void time_to_tm(time_t totalsecs, int offset, struct tm *result)
+void time64_to_tm(time64_t totalsecs, int offset, struct tm *result)
 {
 	long days, rem, y;
+	int remainder;
 	const unsigned short *ip;
 
-	days = totalsecs / SECS_PER_DAY;
-	rem = totalsecs % SECS_PER_DAY;
+	days = div_s64_rem(totalsecs, SECS_PER_DAY, &remainder);
+	rem = remainder;
 	rem += offset;
 	while (rem < 0) {
 		rem += SECS_PER_DAY;
@@ -124,4 +125,4 @@ void time_to_tm(time_t totalsecs, int offset, struct tm *result)
 	result->tm_mon = y;
 	result->tm_mday = days + 1;
 }
-EXPORT_SYMBOL(time_to_tm);
+EXPORT_SYMBOL(time64_to_tm);
-- 
1.9.1