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path: root/drivers/rtc/rtc-sysfs.c
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Diffstat (limited to 'drivers/rtc/rtc-sysfs.c')
-rw-r--r--drivers/rtc/rtc-sysfs.c103
1 files changed, 101 insertions, 2 deletions
diff --git a/drivers/rtc/rtc-sysfs.c b/drivers/rtc/rtc-sysfs.c
index 2ddd0cf0714..899ab8c514f 100644
--- a/drivers/rtc/rtc-sysfs.c
+++ b/drivers/rtc/rtc-sysfs.c
@@ -78,6 +78,92 @@ static struct attribute_group rtc_attr_group = {
.attrs = rtc_attrs,
};
+
+static ssize_t
+rtc_sysfs_show_wakealarm(struct class_device *dev, char *buf)
+{
+ ssize_t retval;
+ 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.
+ *
+ * REVISIT maybe we should require RTC implementations to
+ * disable the RTC alarm after it triggers, for uniformity.
+ */
+ retval = rtc_read_alarm(dev, &alm);
+ if (retval == 0 && alm.enabled) {
+ rtc_tm_to_time(&alm.time, &alarm);
+ retval = sprintf(buf, "%lu\n", alarm);
+ }
+
+ return retval;
+}
+
+static ssize_t
+rtc_sysfs_set_wakealarm(struct class_device *dev, const char *buf, size_t n)
+{
+ ssize_t retval;
+ unsigned long now, alarm;
+ struct rtc_wkalrm alm;
+
+ /* Only request alarms that trigger in the future. Disable them
+ * by writing another time, e.g. 0 meaning Jan 1 1970 UTC.
+ */
+ retval = rtc_read_time(dev, &alm.time);
+ if (retval < 0)
+ return retval;
+ rtc_tm_to_time(&alm.time, &now);
+
+ alarm = simple_strtoul(buf, NULL, 0);
+ if (alarm > now) {
+ /* Avoid accidentally clobbering active alarms; we can't
+ * entirely prevent that here, without even the minimal
+ * locking from the /dev/rtcN api.
+ */
+ retval = rtc_read_alarm(dev, &alm);
+ if (retval < 0)
+ return retval;
+ if (alm.enabled)
+ return -EBUSY;
+
+ alm.enabled = 1;
+ } else {
+ alm.enabled = 0;
+
+ /* Provide a valid future alarm time. Linux isn't EFI,
+ * this time won't be ignored when disabling the alarm.
+ */
+ alarm = now + 300;
+ }
+ rtc_time_to_tm(alarm, &alm.time);
+
+ retval = rtc_set_alarm(dev, &alm);
+ return (retval < 0) ? retval : n;
+}
+static const CLASS_DEVICE_ATTR(wakealarm, S_IRUGO | S_IWUSR,
+ rtc_sysfs_show_wakealarm, rtc_sysfs_set_wakealarm);
+
+
+/* The reason to trigger an alarm with no process watching it (via sysfs)
+ * is its side effect: waking from a system state like suspend-to-RAM or
+ * suspend-to-disk. So: no attribute unless that side effect is possible.
+ * (Userspace may disable that mechanism later.)
+ */
+static inline int rtc_does_wakealarm(struct class_device *class_dev)
+{
+ struct rtc_device *rtc;
+
+ if (!device_can_wakeup(class_dev->dev))
+ return 0;
+ rtc = to_rtc_device(class_dev);
+ return rtc->ops->set_alarm != NULL;
+}
+
+
static int rtc_sysfs_add_device(struct class_device *class_dev,
struct class_interface *class_intf)
{
@@ -87,8 +173,18 @@ static int rtc_sysfs_add_device(struct class_device *class_dev,
err = sysfs_create_group(&class_dev->kobj, &rtc_attr_group);
if (err)
- dev_err(class_dev->dev,
- "failed to create sysfs attributes\n");
+ dev_err(class_dev->dev, "failed to create %s\n",
+ "sysfs attributes");
+ else if (rtc_does_wakealarm(class_dev)) {
+ /* not all RTCs support both alarms and wakeup */
+ err = class_device_create_file(class_dev,
+ &class_device_attr_wakealarm);
+ if (err) {
+ dev_err(class_dev->dev, "failed to create %s\n",
+ "alarm attribute");
+ sysfs_remove_group(&class_dev->kobj, &rtc_attr_group);
+ }
+ }
return err;
}
@@ -96,6 +192,9 @@ static int rtc_sysfs_add_device(struct class_device *class_dev,
static void rtc_sysfs_remove_device(struct class_device *class_dev,
struct class_interface *class_intf)
{
+ if (rtc_does_wakealarm(class_dev))
+ class_device_remove_file(class_dev,
+ &class_device_attr_wakealarm);
sysfs_remove_group(&class_dev->kobj, &rtc_attr_group);
}