1 files changed, 91 insertions, 11 deletions

diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
index 7e3ad4f3b343..58b7336640ff 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);