iio: proximity: isl29501: Fix return type of isl29501_register_writegrafted

isl29501_register_write() was returning a u32 instead of an int.
Since the function returns negative error codes (such as -ERANGE or
return values from i2c_smbus_write_byte_data()), returning an unsigned
integer type prevents callers from correctly checking for negative error
conditions.

Fix this by changing the function return type from u32 to int.

This was found through manual code review.

Fixes: 1c28799257bc ("iio: light: isl29501: Add support for the ISL29501 ToF sensor.")
Signed-off-by: Salah Triki <salah.triki@gmail.com>
Reviewed-by: Joshua Crofts <joshua.crofts1@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>

1 files changed, 211 insertions, 0 deletions

diff --git a/drivers/rtc/lib.c b/drivers/rtc/lib.c
new file mode 100644
index 000000000..f7051592a
--- /dev/null
+++ b/drivers/rtc/lib.c
@@ -0,0 +1,211 @@
+// 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.
+ *		Works for values since at least 1900
+ * @tm:		Pointer to the struct rtc_time.
+ */
+void rtc_time64_to_tm(time64_t time, struct rtc_time *tm)
+{
+	int secs;
+
+	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;
+
+	/*
+	 * The time represented by `time` is given in seconds since 1970-01-01
+	 * (UTC). As the division done below might misbehave for negative
+	 * values, we convert it to seconds since 0000-03-01 and then assume it
+	 * will be non-negative.
+	 * Below we do 4 * udays + 3 which should fit into a 32 bit unsigned
+	 * variable. So the latest date this algorithm works for is 1073741823
+	 * days after 0000-03-01 which is in the year 2939805.
+	 */
+	time += (u64)719468 * 86400;
+
+	udays = div_s64_rem(time, 86400, &secs);
+
+	/*
+	 * day of the week, 0000-03-01 was a Wednesday (in the proleptic
+	 * Gregorian calendar)
+	 */
+	tm->tm_wday = (udays + 3) % 7;
+
+	/*
+	 * The following algorithm is, basically, Figure 12 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] Neri C, Schneider L. Euclidean affine functions and their
+	 *     application to calendar algorithms. Softw Pract Exper.
+	 *     2023;53(4):937-970. doi: 10.1002/spe.3172
+	 *     https://doi.org/10.1002/spe.3172
+	 *
+	 * (*) The numbering of months follows rtc_time more closely and
+	 * thus, is slightly different from [1].
+	 */
+
+	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);