tun: use DEVICE_ATTR_RO macro

Use DEVICE_ATTR_RO helper instead of plain DEVICE_ATTR,
which makes the code a bit shorter and easier to read.
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/tun.c

@@ -2559,15 +2559,15 @@ static int tun_flags(struct tun_struct *tun)
 	return tun->flags & (TUN_FEATURES | IFF_PERSIST | IFF_TUN | IFF_TAP);
 }
 
-static ssize_t tun_show_flags(struct device *dev, struct device_attribute *attr,
+static ssize_t tun_flags_show(struct device *dev, struct device_attribute *attr,
 			      char *buf)
 {
 	struct tun_struct *tun = netdev_priv(to_net_dev(dev));
 	return sprintf(buf, "0x%x\n", tun_flags(tun));
 }
 
-static ssize_t tun_show_owner(struct device *dev, struct device_attribute *attr,
-			      char *buf)
+static ssize_t owner_show(struct device *dev, struct device_attribute *attr,
+			  char *buf)
 {
 	struct tun_struct *tun = netdev_priv(to_net_dev(dev));
 	return uid_valid(tun->owner)?
@@ -2576,8 +2576,8 @@ static ssize_t tun_show_owner(struct device *dev, struct device_attribute *attr,
 		sprintf(buf, "-1\n");
 }
 
-static ssize_t tun_show_group(struct device *dev, struct device_attribute *attr,
-			      char *buf)
+static ssize_t group_show(struct device *dev, struct device_attribute *attr,
+			  char *buf)
 {
 	struct tun_struct *tun = netdev_priv(to_net_dev(dev));
 	return gid_valid(tun->group) ?
@@ -2586,9 +2586,9 @@ static ssize_t tun_show_group(struct device *dev, struct device_attribute *attr,
 		sprintf(buf, "-1\n");
 }
 
-static DEVICE_ATTR(tun_flags, 0444, tun_show_flags, NULL);
-static DEVICE_ATTR(owner, 0444, tun_show_owner, NULL);
-static DEVICE_ATTR(group, 0444, tun_show_group, NULL);
+static DEVICE_ATTR_RO(tun_flags);
+static DEVICE_ATTR_RO(owner);
+static DEVICE_ATTR_RO(group);
 
 static struct attribute *tun_dev_attrs[] = {
 	&dev_attr_tun_flags.attr,