/* 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)
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) {
err = device_create_file(&rtc->dev, &dev_attr_wakealarm);
if (err)
- dev_err(rtc->dev.parent, "failed to create "
- "alarm attribute, %d",
- err);
+ dev_err(rtc->dev.parent,
+ "failed to create alarm attribute, %d\n", err);
}
void rtc_sysfs_del_device(struct rtc_device *rtc)