diff options
Diffstat (limited to 'drivers/rtc/rtc-sysfs.c')
| -rw-r--r-- | drivers/rtc/rtc-sysfs.c | 19 |
1 files changed, 13 insertions, 6 deletions
diff --git a/drivers/rtc/rtc-sysfs.c b/drivers/rtc/rtc-sysfs.c index 2ae0e8304d3..4d27ccc4fc0 100644 --- a/drivers/rtc/rtc-sysfs.c +++ b/drivers/rtc/rtc-sysfs.c @@ -17,6 +17,13 @@ /* device attributes */ +/* + * NOTE: RTC times displayed in sysfs use the RTC's timezone. That's + * ideally UTC. However, PCs that also boot to MS-Windows normally use + * the local time and change to match daylight savings time. That affects + * attributes including date, time, since_epoch, and wakealarm. + */ + static ssize_t rtc_sysfs_show_name(struct device *dev, struct device_attribute *attr, char *buf) @@ -113,13 +120,13 @@ rtc_sysfs_show_wakealarm(struct device *dev, struct device_attribute *attr, unsigned long alarm; struct rtc_wkalrm alm; - /* Don't show disabled alarms; but the RTC could leave the - * alarm enabled after it's already triggered. Alarms are - * conceptually one-shot, even though some common hardware - * (PCs) doesn't actually work that way. + /* Don't show disabled alarms. For uniformity, RTC alarms are + * conceptually one-shot, even though some common RTCs (on PCs) + * don't actually work that way. * - * REVISIT maybe we should require RTC implementations to - * disable the RTC alarm after it triggers, for uniformity. + * NOTE: RTC implementations where the alarm doesn't match an + * exact YYYY-MM-DD HH:MM[:SS] date *must* disable their RTC + * alarms after they trigger, to ensure one-shot semantics. */ retval = rtc_read_alarm(to_rtc_device(dev), &alm); if (retval == 0 && alm.enabled) { |