backlight: Catch invalid input in sysfs attributes

Check input properly in backlight, echo > brightness should not turn off
the backlight.

[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: fix printk warning]
Signed-off-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>

drivers/video/backlight/backlight.c

@@ -80,20 +80,18 @@ static ssize_t backlight_show_power(struct device *dev,
 static ssize_t backlight_store_power(struct device *dev,
 		struct device_attribute *attr, const char *buf, size_t count)
 {
-	int rc = -ENXIO;
-	char *endp;
+	int rc;
 	struct backlight_device *bd = to_backlight_device(dev);
-	int power = simple_strtoul(buf, &endp, 0);
-	size_t size = endp - buf;
+	unsigned long power;
 
-	if (*endp && isspace(*endp))
-		size++;
-	if (size != count)
-		return -EINVAL;
+	rc = strict_strtoul(buf, 0, &power);
+	if (rc)
+		return rc;
 
+	rc = -ENXIO;
 	mutex_lock(&bd->ops_lock);
 	if (bd->ops) {
-		pr_debug("backlight: set power to %d\n", power);
+		pr_debug("backlight: set power to %lu\n", power);
 		if (bd->props.power != power) {
 			bd->props.power = power;
 			backlight_update_status(bd);
@@ -116,23 +114,22 @@ static ssize_t backlight_show_brightness(struct device *dev,
 static ssize_t backlight_store_brightness(struct device *dev,
 		struct device_attribute *attr, const char *buf, size_t count)
 {
-	int rc = -ENXIO;
-	char *endp;
+	int rc;
 	struct backlight_device *bd = to_backlight_device(dev);
-	int brightness = simple_strtoul(buf, &endp, 0);
-	size_t size = endp - buf;
+	unsigned long brightness;
 
-	if (*endp && isspace(*endp))
-		size++;
-	if (size != count)
-		return -EINVAL;
+	rc = strict_strtoul(buf, 0, &brightness);
+	if (rc)
+		return rc;
+
+	rc = -ENXIO;
 
 	mutex_lock(&bd->ops_lock);
 	if (bd->ops) {
 		if (brightness > bd->props.max_brightness)
 			rc = -EINVAL;
 		else {
-			pr_debug("backlight: set brightness to %d\n",
+			pr_debug("backlight: set brightness to %lu\n",
 				 brightness);
 			if (bd->props.brightness != brightness) {
 				bd->props.brightness = brightness;