diff options
Diffstat (limited to 'drivers/rtc')
| -rw-r--r-- | drivers/rtc/interface.c | 102 |
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); |