[PATCH] drivers/rtc/interface.c: check the validation of rtc_time in __rtc_read_time

[Hyogi Gim <ciogenis@gmail.com>]

Some of rtc devices always return '0' when rtc_class_ops.read_time is called.
So if rtc_time isn't verified in callback, rtc interface cannot know whether
rtc_time is valid.

Check rtc_time by using 'rtc_valid_tm' in '__rtc_read_time'. And add the
message for debugging.

Signed-off-by: Hyogi Gim <hyogi.gim@lge.com>
---
 drivers/rtc/interface.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
index 5b2717f..818ea97 100644
--- a/drivers/rtc/interface.c
+++ b/drivers/rtc/interface.c
@@ -30,6 +30,14 @@ static int __rtc_read_time(struct rtc_device *rtc, struct rtc_time *tm)
 	else {
 		memset(tm, 0, sizeof(struct rtc_time));
 		err = rtc->ops->read_time(rtc->dev.parent, tm);
+		if (err < 0) {
+			dev_err(&rtc->dev, "read_time: fail to read\n");
+			return err;
+		}
+
+		err = rtc_valid_tm(tm);
+		if (err < 0)
+			dev_err(&rtc->dev, "read_time: rtc_time isn't valid\n");
 	}
 	return err;
 }
-- 
1.8.3.2