RTC: Properly handle rtc_read_alarm error propagation and fix bug

In reviewing cases where the virtualized interfaces didn't propagate
errors properly, I noticed rtc_read_alarm needed fixing. In doing
so I noticed my RTC rework dropped a memset and that the behavior
of rtc_read_alarm shouldn't be conditionalized on the alarm.enabled
flag (as the alarm may be set, but the irqs may be disabled). So
those were corrected as well.

CC: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
LKML-Reference: <1295565973-14358-2-git-send-email-john.stultz@linaro.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 9 insertions, 3 deletions

diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
index f1ba2c696528..925006d33109 100644
--- a/drivers/rtc/interface.c
+++ b/drivers/rtc/interface.c
@@ -123,12 +123,18 @@ int rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
         err = mutex_lock_interruptible(&rtc->ops_lock);
         if (err)
                 return err;
-        alarm->enabled = rtc->aie_timer.enabled;
-        if (alarm->enabled)
+        if (rtc->ops == NULL)
+                err = -ENODEV;
+        else if (!rtc->ops->read_alarm)
+                err = -EINVAL;
+        else {
+                memset(alarm, 0, sizeof(struct rtc_wkalrm));
+                alarm->enabled = rtc->aie_timer.enabled;
                 alarm->time = rtc_ktime_to_tm(rtc->aie_timer.node.expires);
+        }
         mutex_unlock(&rtc->ops_lock);
 
-        return 0;
+        return err;
 }
 EXPORT_SYMBOL_GPL(rtc_read_alarm);