Merge branch 'drm-intel-next' of git://git.kernel.org/pub/scm/linux/kernel/git/anholt...

[pandora-kernel.git] / drivers / rtc / rtc-sysfs.c

diff --git a/drivers/rtc/rtc-sysfs.c b/drivers/rtc/rtc-sysfs.c
index 6cad084..2531ce4 100644 (file)
--- 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) {
@@ -138,6 +145,8 @@ rtc_sysfs_set_wakealarm(struct device *dev, struct device_attribute *attr,
        unsigned long now, alarm;
        struct rtc_wkalrm alm;
        struct rtc_device *rtc = to_rtc_device(dev);
+       char *buf_ptr;
+       int adjust = 0;
 
        /* Only request alarms that trigger in the future.  Disable them
         * by writing another time, e.g. 0 meaning Jan 1 1970 UTC.
@@ -147,7 +156,15 @@ rtc_sysfs_set_wakealarm(struct device *dev, struct device_attribute *attr,
                return retval;
        rtc_tm_to_time(&alm.time, &now);
 
-       alarm = simple_strtoul(buf, NULL, 0);
+       buf_ptr = (char *)buf;
+       if (*buf_ptr == '+') {
+               buf_ptr++;
+               adjust = 1;
+       }
+       alarm = simple_strtoul(buf_ptr, NULL, 0);
+       if (adjust) {
+               alarm += now;
+       }
        if (alarm > now) {
                /* Avoid accidentally clobbering active alarms; we can't
                 * entirely prevent that here, without even the minimal
@@ -200,9 +217,8 @@ void rtc_sysfs_add_device(struct rtc_device *rtc)
 
        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)