1 files changed, 91 insertions, 11 deletions

diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
index 7e3ad4f..58b7336 100644
--- a/drivers/rtc/interface.c
+++ b/drivers/rtc/interface.c
@@ -126,12 +126,25 @@ int rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
 	int err;
 	struct rtc_time before, now;
 	int first_time = 1;
+	unsigned long t_now, t_alm;
+	enum { none, day, month, year } missing = none;
+	unsigned days;
 
-	/* The lower level RTC driver may not be capable of filling
-	 * in all fields of the rtc_time struct (eg. rtc-cmos),
-	 * and so might instead return -1 in some fields.
-	 * We deal with that here by grabbing a current RTC timestamp
-	 * and using values from that for any missing (-1) values.
+	/* The lower level RTC driver may return -1 in some fields,
+	 * creating invalid alarm->time values, for reasons like:
+	 *
+	 *   - The hardware may not be capable of filling them in;
+	 *     many alarms match only on time-of-day fields, not
+	 *     day/month/year calendar data.
+	 *
+	 *   - Some hardware uses illegal values as "wildcard" match
+	 *     values, which non-Linux firmware (like a BIOS) may try
+	 *     to set up as e.g. "alarm 15 minutes after each hour".
+	 *     Linux uses only oneshot alarms.
+	 *
+	 * When we see that here, we deal with it by using values from
+	 * a current RTC timestamp for any missing (-1) values.  The
+	 * RTC driver prevents "periodic alarm" modes.
 	 *
 	 * But this can be racey, because some fields of the RTC timestamp
 	 * may have wrapped in the interval since we read the RTC alarm,
@@ -174,6 +187,10 @@ int rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
 		if (!alarm->enabled)
 			return 0;
 
+		/* full-function RTCs won't have such missing fields */
+		if (rtc_valid_tm(&alarm->time) == 0)
+			return 0;
+
 		/* get the "after" timestamp, to detect wrapped fields */
 		err = rtc_read_time(rtc, &now);
 		if (err < 0)
@@ -183,22 +200,85 @@ int rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
 	} while (   before.tm_min   != now.tm_min
 		 || before.tm_hour  != now.tm_hour
 		 || before.tm_mon   != now.tm_mon
-		 || before.tm_year  != now.tm_year
-		 || before.tm_isdst != now.tm_isdst);
+		 || before.tm_year  != now.tm_year);
 
-	/* Fill in any missing alarm fields using the timestamp */
+	/* Fill in the missing alarm fields using the timestamp; we
+	 * know there's at least one since alarm->time is invalid.
+	 */
 	if (alarm->time.tm_sec == -1)
 		alarm->time.tm_sec = now.tm_sec;
 	if (alarm->time.tm_min == -1)
 		alarm->time.tm_min = now.tm_min;
 	if (alarm->time.tm_hour == -1)
 		alarm->time.tm_hour = now.tm_hour;
-	if (alarm->time.tm_mday == -1)
+
+	/* For simplicity, only support date rollover for now */
+	if (alarm->time.tm_mday == -1) {
 		alarm->time.tm_mday = now.tm_mday;
-	if (alarm->time.tm_mon == -1)
+		missing = day;
+	}
+	if (alarm->time.tm_mon == -1) {
 		alarm->time.tm_mon = now.tm_mon;
-	if (alarm->time.tm_year == -1)
+		if (missing == none)
+			missing = month;
+	}
+	if (alarm->time.tm_year == -1) {
 		alarm->time.tm_year = now.tm_year;
+		if (missing == none)
+			missing = year;
+	}
+
+	/* with luck, no rollover is needed */
+	rtc_tm_to_time(&now, &t_now);
+	rtc_tm_to_time(&alarm->time, &t_alm);
+	if (t_now < t_alm)
+		goto done;
+
+	switch (missing) {
+
+	/* 24 hour rollover ... if it's now 10am Monday, an alarm that
+	 * that will trigger at 5am will do so at 5am Tuesday, which
+	 * could also be in the next month or year.  This is a common
+	 * case, especially for PCs.
+	 */
+	case day:
+		dev_dbg(&rtc->dev, "alarm rollover: %s\n", "day");
+		t_alm += 24 * 60 * 60;
+		rtc_time_to_tm(t_alm, &alarm->time);
+		break;
+
+	/* Month rollover ... if it's the 31th, an alarm on the 3rd will
+	 * be next month.  An alarm matching on the 30th, 29th, or 28th
+	 * may end up in the month after that!  Many newer PCs support
+	 * this type of alarm.
+	 */
+	case month:
+		dev_dbg(&rtc->dev, "alarm rollover: %s\n", "month");
+		do {
+			if (alarm->time.tm_mon < 11)
+				alarm->time.tm_mon++;
+			else {
+				alarm->time.tm_mon = 0;
+				alarm->time.tm_year++;
+			}
+			days = rtc_month_days(alarm->time.tm_mon,
+					alarm->time.tm_year);
+		} while (days < alarm->time.tm_mday);
+		break;
+
+	/* Year rollover ... easy except for leap years! */
+	case year:
+		dev_dbg(&rtc->dev, "alarm rollover: %s\n", "year");
+		do {
+			alarm->time.tm_year++;
+		} while (!rtc_valid_tm(&alarm->time));
+		break;
+
+	default:
+		dev_warn(&rtc->dev, "alarm rollover not handled\n");
+	}
+
+done:
 	return 0;
 }
 EXPORT_SYMBOL_GPL(rtc_read_alarm);