/* 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)
return retval;
}
+static ssize_t
+rtc_sysfs_show_max_user_freq(struct device *dev, struct device_attribute *attr,
+ char *buf)
+{
+ return sprintf(buf, "%d\n", to_rtc_device(dev)->max_user_freq);
+}
+
+static ssize_t
+rtc_sysfs_set_max_user_freq(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t n)
+{
+ struct rtc_device *rtc = to_rtc_device(dev);
+ unsigned long val = simple_strtoul(buf, NULL, 0);
+
+ if (val >= 4096 || val == 0)
+ return -EINVAL;
+
+ rtc->max_user_freq = (int)val;
+
+ return n;
+}
+
static struct device_attribute rtc_attrs[] = {
__ATTR(name, S_IRUGO, rtc_sysfs_show_name, NULL),
__ATTR(date, S_IRUGO, rtc_sysfs_show_date, NULL),
__ATTR(time, S_IRUGO, rtc_sysfs_show_time, NULL),
__ATTR(since_epoch, S_IRUGO, rtc_sysfs_show_since_epoch, NULL),
+ __ATTR(max_user_freq, S_IRUGO | S_IWUSR, rtc_sysfs_show_max_user_freq,
+ rtc_sysfs_set_max_user_freq),
{ },
};
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)