static int __rtc_read_time(struct rtc_device *rtc, struct rtc_time *tm)
{
int err;
if (!rtc->ops) {
err = -ENODEV;
} else if (!rtc->ops->read_time) {
err = -EINVAL;
} else {
memset(tm, 0, sizeof(struct rtc_time));
err = rtc->ops->read_time(rtc->dev.parent, tm);
if (err < 0) {
dev_dbg(&rtc->dev, "read_time: fail to read: %d\n",
err);
return err;
}
rtc_add_offset(rtc, tm);
err = rtc_valid_tm(tm);
if (err < 0)
dev_dbg(&rtc->dev, "read_time: rtc_time isn't valid\n");
}
return err;
}
int __rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
{
int err;
struct rtc_time before, now;
int first_time = 1;
time64_t t_now, t_alm;
enum { none, day, month, year } missing = none;
unsigned days;
/* 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,
* which would lead to us inserting inconsistent values in place
* of the -1 fields.
*
* Reading the alarm and timestamp in the reverse sequence
* would have the same race condition, and not solve the issue.
*
* So, we must first read the RTC timestamp,
* then read the RTC alarm value,
* and then read a second RTC timestamp.
*
* If any fields of the second timestamp have changed
* when compared with the first timestamp, then we know
* our timestamp may be inconsistent with that used by
* the low-level rtc_read_alarm_internal() function.
*
* So, when the two timestamps disagree, we just loop and do
* the process again to get a fully consistent set of values.
*
* This could all instead be done in the lower level driver,
* but since more than one lower level RTC implementation needs it,
* then it's probably best best to do it here instead of there..
*/
/* Get the "before" timestamp */
err = rtc_read_time(rtc, &before);
if (err < 0)
return err;
do {
if (!first_time)
memcpy(&before, &now, sizeof(struct rtc_time));
first_time = 0;
/* get the RTC alarm values, which may be incomplete */
err = rtc_read_alarm_internal(rtc, alarm);
if (err)
return err;
/* full-function RTCs won't have such missing fields */
if (rtc_valid_tm(&alarm->time) == 0) {
rtc_add_offset(rtc, &alarm->time);
return 0;
}
/* get the "after" timestamp, to detect wrapped fields */
err = rtc_read_time(rtc, &now);
if (err < 0)
return err;
/* note that tm_sec is a "don't care" value here: */
} 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);
/* 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;
/* For simplicity, only support date rollover for now */
if (alarm->time.tm_mday < 1 || alarm->time.tm_mday > 31) {
alarm->time.tm_mday = now.tm_mday;
missing = day;
}
if ((unsigned)alarm->time.tm_mon >= 12) {
alarm->time.tm_mon = now.tm_mon;
if (missing == none)
missing = month;
}
if (alarm->time.tm_year == -1) {
alarm->time.tm_year = now.tm_year;
if (missing == none)
missing = year;
}
/* Can't proceed if alarm is still invalid after replacing
* missing fields.
*/
err = rtc_valid_tm(&alarm->time);
if (err)
goto done;
/* with luck, no rollover is needed */
t_now = rtc_tm_to_time64(&now);
t_alm = rtc_tm_to_time64(&alarm->time);
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_time64_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 (!is_leap_year(alarm->time.tm_year + 1900)
&& rtc_valid_tm(&alarm->time) != 0);
break;
default:
dev_warn(&rtc->dev, "alarm rollover not handled\n");
}
err = rtc_valid_tm(&alarm->time);
done:
if (err) {
dev_warn(&rtc->dev, "invalid alarm value: %d-%d-%d %d:%d:%d\n",
alarm->time.tm_year + 1900, alarm->time.tm_mon + 1,
alarm->time.tm_mday, alarm->time.tm_hour, alarm->time.tm_min,
alarm->time.tm_sec);
}
return err;
}