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time: add function to convert between calendar time and broken-down t…

…ime for universal use

There are many similar code in kernel for one object: convert time between
calendar time and broken-down time.

Here is some source I found:
  fs/ncpfs/dir.c
  fs/smbfs/proc.c
  fs/fat/misc.c
  fs/udf/udftime.c
  fs/cifs/netmisc.c
  net/netfilter/xt_time.c
  drivers/scsi/ips.c
  drivers/input/misc/hp_sdc_rtc.c
  drivers/rtc/rtc-lib.c
  arch/ia64/hp/sim/boot/fw-emu.c
  arch/m68k/mac/misc.c
  arch/powerpc/kernel/time.c
  arch/parisc/include/asm/rtc.h
  ...

We can make a common function for this type of conversion, At least we
can get following benefit:

1: Make kernel simple and unify
2: Easy to fix bug in converting code
3: Reduce clone of code in future
   For example, I'm trying to make ftrace display walltime,
   this patch will make me easy.

This code is based on code from glibc-2.6

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  • Loading branch information...
commit 57f1f0874f426a9bdfc5cd3f886113dd5cd17834 1 parent ef1ff6b
Zhaolei authored committed
28 include/linux/time.h
View
@@ -155,6 +155,34 @@ extern void timekeeping_leap_insert(int leapsecond);
struct tms;
extern void do_sys_times(struct tms *);
+/*
+ * Similar to the struct tm in userspace <time.h>, but it needs to be here so
+ * that the kernel source is self contained.
+ */
+struct tm {
+ /*
+ * the number of seconds after the minute, normally in the range
+ * 0 to 59, but can be up to 60 to allow for leap seconds
+ */
+ int tm_sec;
+ /* the number of minutes after the hour, in the range 0 to 59*/
+ int tm_min;
+ /* the number of hours past midnight, in the range 0 to 23 */
+ int tm_hour;
+ /* the day of the month, in the range 1 to 31 */
+ int tm_mday;
+ /* the number of months since January, in the range 0 to 11 */
+ int tm_mon;
+ /* the number of years since 1900 */
+ long tm_year;
+ /* the number of days since Sunday, in the range 0 to 6 */
+ int tm_wday;
+ /* the number of days since January 1, in the range 0 to 365 */
+ int tm_yday;
+};
+
+void time_to_tm(time_t totalsecs, int offset, struct tm *result);
+
/**
* timespec_to_ns - Convert timespec to nanoseconds
* @ts: pointer to the timespec variable to be converted
2  kernel/time/Makefile
View
@@ -1,4 +1,4 @@
-obj-y += timekeeping.o ntp.o clocksource.o jiffies.o timer_list.o timecompare.o
+obj-y += timekeeping.o ntp.o clocksource.o jiffies.o timer_list.o timecompare.o timeconv.o
obj-$(CONFIG_GENERIC_CLOCKEVENTS_BUILD) += clockevents.o
obj-$(CONFIG_GENERIC_CLOCKEVENTS) += tick-common.o
127 kernel/time/timeconv.c
View
@@ -0,0 +1,127 @@
+/*
+ * Copyright (C) 1993, 1994, 1995, 1996, 1997 Free Software Foundation, Inc.
+ * This file is part of the GNU C Library.
+ * Contributed by Paul Eggert (eggert@twinsun.com).
+ *
+ * The GNU C Library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * The GNU C Library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with the GNU C Library; see the file COPYING.LIB. If not,
+ * write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+/*
+ * Converts the calendar time to broken-down time representation
+ * Based on code from glibc-2.6
+ *
+ * 2009-7-14:
+ * Moved from glibc-2.6 to kernel by Zhaolei<zhaolei@cn.fujitsu.com>
+ */
+
+#include <linux/time.h>
+#include <linux/module.h>
+
+/*
+ * Nonzero if YEAR is a leap year (every 4 years,
+ * except every 100th isn't, and every 400th is).
+ */
+static int __isleap(long year)
+{
+ return (year) % 4 == 0 && ((year) % 100 != 0 || (year) % 400 == 0);
+}
+
+/* do a mathdiv for long type */
+static long math_div(long a, long b)
+{
+ return a / b - (a % b < 0);
+}
+
+/* How many leap years between y1 and y2, y1 must less or equal to y2 */
+static long leaps_between(long y1, long y2)
+{
+ long leaps1 = math_div(y1 - 1, 4) - math_div(y1 - 1, 100)
+ + math_div(y1 - 1, 400);
+ long leaps2 = math_div(y2 - 1, 4) - math_div(y2 - 1, 100)
+ + math_div(y2 - 1, 400);
+ return leaps2 - leaps1;
+}
+
+/* How many days come before each month (0-12). */
+static const unsigned short __mon_yday[2][13] = {
+ /* Normal years. */
+ {0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365},
+ /* Leap years. */
+ {0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366}
+};
+
+#define SECS_PER_HOUR (60 * 60)
+#define SECS_PER_DAY (SECS_PER_HOUR * 24)
+
+/**
+ * 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
+ */
+void time_to_tm(time_t totalsecs, int offset, struct tm *result)
+{
+ long days, rem, y;
+ const unsigned short *ip;
+
+ days = totalsecs / SECS_PER_DAY;
+ rem = totalsecs % SECS_PER_DAY;
+ rem += offset;
+ while (rem < 0) {
+ rem += SECS_PER_DAY;
+ --days;
+ }
+ while (rem >= SECS_PER_DAY) {
+ rem -= SECS_PER_DAY;
+ ++days;
+ }
+
+ result->tm_hour = rem / SECS_PER_HOUR;
+ rem %= SECS_PER_HOUR;
+ result->tm_min = rem / 60;
+ result->tm_sec = rem % 60;
+
+ /* January 1, 1970 was a Thursday. */
+ result->tm_wday = (4 + days) % 7;
+ if (result->tm_wday < 0)
+ result->tm_wday += 7;
+
+ y = 1970;
+
+ while (days < 0 || days >= (__isleap(y) ? 366 : 365)) {
+ /* Guess a corrected year, assuming 365 days per year. */
+ long yg = y + math_div(days, 365);
+
+ /* Adjust DAYS and Y to match the guessed year. */
+ days -= (yg - y) * 365 + leaps_between(y, yg);
+ y = yg;
+ }
+
+ result->tm_year = y - 1900;
+
+ result->tm_yday = days;
+
+ ip = __mon_yday[__isleap(y)];
+ for (y = 11; days < ip[y]; y--)
+ continue;
+ days -= ip[y];
+
+ result->tm_mon = y;
+ result->tm_mday = days + 1;
+}
+EXPORT_SYMBOL(time_to_tm);
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