drivers/video/backlight/adp5520_bl.c: check strict_strtoul() return value

It should check if strict_strtoul() succeeds.

[akpm@linux-foundation.org: don't override strict_strtoul() return value]
Signed-off-by: Liu Yuan <tailai.ly@taobao.com>
Acked-by: Michael Hennerich <michael.hennerich@analog.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/video/backlight/adp5520_bl.c

@@ -211,8 +211,12 @@ static ssize_t adp5520_bl_daylight_max_store(struct device *dev,
 			const char *buf, size_t count)
 {
 	struct adp5520_bl *data = dev_get_drvdata(dev);
+	int ret;
+
+	ret = strict_strtoul(buf, 10, &data->cached_daylight_max);
+	if (ret < 0)
+		return ret;
 
-	strict_strtoul(buf, 10, &data->cached_daylight_max);
 	return adp5520_store(dev, buf, count, ADP5520_DAYLIGHT_MAX);
 }
 static DEVICE_ATTR(daylight_max, 0664, adp5520_bl_daylight_max_show,