diff options
Diffstat (limited to 'drivers/rtc/interface.c')
| -rw-r--r-- | drivers/rtc/interface.c | 180 |
1 files changed, 180 insertions, 0 deletions
diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c index cb2f072..8ec6b06 100644 --- a/drivers/rtc/interface.c +++ b/drivers/rtc/interface.c @@ -116,6 +116,186 @@ int rtc_set_mmss(struct rtc_device *rtc, unsigned long secs) } EXPORT_SYMBOL_GPL(rtc_set_mmss); +static int rtc_read_alarm_internal(struct rtc_device *rtc, struct rtc_wkalrm *alarm) +{ + int err; + + err = mutex_lock_interruptible(&rtc->ops_lock); + if (err) + return err; + + if (rtc->ops == NULL) + err = -ENODEV; + else if (!rtc->ops->read_alarm) + err = -EINVAL; + else { + memset(alarm, 0, sizeof(struct rtc_wkalrm)); + err = rtc->ops->read_alarm(rtc->dev.parent, alarm); + } + + mutex_unlock(&rtc->ops_lock); + 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; + unsigned long 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) + 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 = now.tm_mday; + missing = day; + } + if (alarm->time.tm_mon == -1) { + 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; + } + + /* 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) != 0); + break; + + default: + dev_warn(&rtc->dev, "alarm rollover not handled\n"); + } + +done: + return 0; +} + int rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm) { int err; |