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-rw-r--r--drivers/rtc/lib.c199
1 files changed, 199 insertions, 0 deletions
diff --git a/drivers/rtc/lib.c b/drivers/rtc/lib.c
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index 0000000000..fe36165272
--- /dev/null
+++ b/drivers/rtc/lib.c
@@ -0,0 +1,199 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * rtc and date/time utility functions
+ *
+ * Copyright (C) 2005-06 Tower Technologies
+ * Author: Alessandro Zummo <a.zummo@towertech.it>
+ *
+ * based on arch/arm/common/rtctime.c and other bits
+ *
+ * Author: Cassio Neri <cassio.neri@gmail.com> (rtc_time64_to_tm)
+ */
+
+#include <linux/export.h>
+#include <linux/rtc.h>
+
+static const unsigned char rtc_days_in_month[] = {
+ 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
+};
+
+static const unsigned short rtc_ydays[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 }
+};
+
+/*
+ * The number of days in the month.
+ */
+int rtc_month_days(unsigned int month, unsigned int year)
+{
+ return rtc_days_in_month[month] + (is_leap_year(year) && month == 1);
+}
+EXPORT_SYMBOL(rtc_month_days);
+
+/*
+ * The number of days since January 1. (0 to 365)
+ */
+int rtc_year_days(unsigned int day, unsigned int month, unsigned int year)
+{
+ return rtc_ydays[is_leap_year(year)][month] + day - 1;
+}
+EXPORT_SYMBOL(rtc_year_days);
+
+/**
+ * rtc_time64_to_tm - converts time64_t to rtc_time.
+ *
+ * @time: The number of seconds since 01-01-1970 00:00:00.
+ * (Must be positive.)
+ * @tm: Pointer to the struct rtc_time.
+ */
+void rtc_time64_to_tm(time64_t time, struct rtc_time *tm)
+{
+ unsigned int secs;
+ int days;
+
+ u64 u64tmp;
+ u32 u32tmp, udays, century, day_of_century, year_of_century, year,
+ day_of_year, month, day;
+ bool is_Jan_or_Feb, is_leap_year;
+
+ /* time must be positive */
+ days = div_s64_rem(time, 86400, &secs);
+
+ /* day of the week, 1970-01-01 was a Thursday */
+ tm->tm_wday = (days + 4) % 7;
+
+ /*
+ * The following algorithm is, basically, Proposition 6.3 of Neri
+ * and Schneider [1]. In a few words: it works on the computational
+ * (fictitious) calendar where the year starts in March, month = 2
+ * (*), and finishes in February, month = 13. This calendar is
+ * mathematically convenient because the day of the year does not
+ * depend on whether the year is leap or not. For instance:
+ *
+ * March 1st 0-th day of the year;
+ * ...
+ * April 1st 31-st day of the year;
+ * ...
+ * January 1st 306-th day of the year; (Important!)
+ * ...
+ * February 28th 364-th day of the year;
+ * February 29th 365-th day of the year (if it exists).
+ *
+ * After having worked out the date in the computational calendar
+ * (using just arithmetics) it's easy to convert it to the
+ * corresponding date in the Gregorian calendar.
+ *
+ * [1] "Euclidean Affine Functions and Applications to Calendar
+ * Algorithms". https://arxiv.org/abs/2102.06959
+ *
+ * (*) The numbering of months follows rtc_time more closely and
+ * thus, is slightly different from [1].
+ */
+
+ udays = ((u32) days) + 719468;
+
+ u32tmp = 4 * udays + 3;
+ century = u32tmp / 146097;
+ day_of_century = u32tmp % 146097 / 4;
+
+ u32tmp = 4 * day_of_century + 3;
+ u64tmp = 2939745ULL * u32tmp;
+ year_of_century = upper_32_bits(u64tmp);
+ day_of_year = lower_32_bits(u64tmp) / 2939745 / 4;
+
+ year = 100 * century + year_of_century;
+ is_leap_year = year_of_century != 0 ?
+ year_of_century % 4 == 0 : century % 4 == 0;
+
+ u32tmp = 2141 * day_of_year + 132377;
+ month = u32tmp >> 16;
+ day = ((u16) u32tmp) / 2141;
+
+ /*
+ * Recall that January 01 is the 306-th day of the year in the
+ * computational (not Gregorian) calendar.
+ */
+ is_Jan_or_Feb = day_of_year >= 306;
+
+ /* Converts to the Gregorian calendar. */
+ year = year + is_Jan_or_Feb;
+ month = is_Jan_or_Feb ? month - 12 : month;
+ day = day + 1;
+
+ day_of_year = is_Jan_or_Feb ?
+ day_of_year - 306 : day_of_year + 31 + 28 + is_leap_year;
+
+ /* Converts to rtc_time's format. */
+ tm->tm_year = (int) (year - 1900);
+ tm->tm_mon = (int) month;
+ tm->tm_mday = (int) day;
+ tm->tm_yday = (int) day_of_year + 1;
+
+ tm->tm_hour = secs / 3600;
+ secs -= tm->tm_hour * 3600;
+ tm->tm_min = secs / 60;
+ tm->tm_sec = secs - tm->tm_min * 60;
+
+ tm->tm_isdst = 0;
+}
+EXPORT_SYMBOL(rtc_time64_to_tm);
+
+/*
+ * Does the rtc_time represent a valid date/time?
+ */
+int rtc_valid_tm(struct rtc_time *tm)
+{
+ if (tm->tm_year < 70 ||
+ tm->tm_year > (INT_MAX - 1900) ||
+ ((unsigned int)tm->tm_mon) >= 12 ||
+ tm->tm_mday < 1 ||
+ tm->tm_mday > rtc_month_days(tm->tm_mon,
+ ((unsigned int)tm->tm_year + 1900)) ||
+ ((unsigned int)tm->tm_hour) >= 24 ||
+ ((unsigned int)tm->tm_min) >= 60 ||
+ ((unsigned int)tm->tm_sec) >= 60)
+ return -EINVAL;
+
+ return 0;
+}
+EXPORT_SYMBOL(rtc_valid_tm);
+
+/*
+ * rtc_tm_to_time64 - Converts rtc_time to time64_t.
+ * Convert Gregorian date to seconds since 01-01-1970 00:00:00.
+ */
+time64_t rtc_tm_to_time64(struct rtc_time *tm)
+{
+ return mktime64(((unsigned int)tm->tm_year + 1900), tm->tm_mon + 1,
+ tm->tm_mday, tm->tm_hour, tm->tm_min, tm->tm_sec);
+}
+EXPORT_SYMBOL(rtc_tm_to_time64);
+
+/*
+ * Convert rtc_time to ktime
+ */
+ktime_t rtc_tm_to_ktime(struct rtc_time tm)
+{
+ return ktime_set(rtc_tm_to_time64(&tm), 0);
+}
+EXPORT_SYMBOL_GPL(rtc_tm_to_ktime);
+
+/*
+ * Convert ktime to rtc_time
+ */
+struct rtc_time rtc_ktime_to_tm(ktime_t kt)
+{
+ struct timespec64 ts;
+ struct rtc_time ret;
+
+ ts = ktime_to_timespec64(kt);
+ /* Round up any ns */
+ if (ts.tv_nsec)
+ ts.tv_sec++;
+ rtc_time64_to_tm(ts.tv_sec, &ret);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(rtc_ktime_to_tm);