Merge branch 'misc-vlan-cleanups'

Gal Pressman says:

====================
Misc vlan cleanups

This patch series addresses compilation issues with objtool when VLAN
support is disabled (CONFIG_VLAN_8021Q=n) and makes related improvements
to the VLAN infrastructure.

When CONFIG_VLAN_8021Q=n, CONFIG_OBJTOOL=y, and CONFIG_OBJTOOL_WERROR=y,
the following compilation error occurs:

drivers/net/ethernet/mellanox/mlx5/core/mlx5_core.o: error: objtool: parse_mirred.isra.0+0x370: mlx5e_tc_act_vlan_add_push_action() missing __noreturn in .c/.h or NORETURN() in noreturns.h

The error occurs because objtool cannot determine that unreachable BUG()
calls in VLAN code paths are actually dead code when VLAN support is
disabled.

First patch makes is_vlan_dev() a stub when VLAN is not configured,
allows compile-out of VLAN-dependent dead code paths and resolves the
objtool compilation error.

Second patch replaces BUG() calls with WARN_ON_ONCE(), as the usage of
BUG() should be avoided.

Third patch uses the "kernel" way of testing whether an option is
configured as builtin/module, instead of open-coding it.

v2: https://lore.kernel.org/[e-mail]/
====================

Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

include/linux/if_vlan.h

···
 /* found in socket.c */
 extern void vlan_ioctl_set(int (*hook)(struct net *, void __user *));
 
-static inline bool is_vlan_dev(const struct net_device *dev)
-{
-        return dev->priv_flags & IFF_802_1Q_VLAN;
-}
-
 #define skb_vlan_tag_present(__skb)	(!!(__skb)->vlan_all)
 #define skb_vlan_tag_get(__skb)		((__skb)->vlan_tci)
 #define skb_vlan_tag_get_id(__skb)	((__skb)->vlan_tci & VLAN_VID_MASK)
···
 	u32			tx_dropped;
 };
 
-#if defined(CONFIG_VLAN_8021Q) || defined(CONFIG_VLAN_8021Q_MODULE)
+#if IS_ENABLED(CONFIG_VLAN_8021Q)
 
 extern struct net_device *__vlan_find_dev_deep_rcu(struct net_device *real_dev,
 					       __be16 vlan_proto, u16 vlan_id);
···
 #endif
 };
 
+static inline bool is_vlan_dev(const struct net_device *dev)
+{
+	return dev->priv_flags & IFF_802_1Q_VLAN;
+}
+
 static inline struct vlan_dev_priv *vlan_dev_priv(const struct net_device *dev)
 {
 	return netdev_priv(dev);
···
 extern bool vlan_uses_dev(const struct net_device *dev);
 
 #else
+static inline bool is_vlan_dev(const struct net_device *dev)
+{
+	return false;
+}
+
 static inline struct net_device *
 __vlan_find_dev_deep_rcu(struct net_device *real_dev,
 		     __be16 vlan_proto, u16 vlan_id)
···
 
 static inline struct net_device *vlan_dev_real_dev(const struct net_device *dev)
 {
-	BUG();
+	WARN_ON_ONCE(1);
 	return NULL;
 }
 
 static inline u16 vlan_dev_vlan_id(const struct net_device *dev)
 {
-	BUG();
+	WARN_ON_ONCE(1);
 	return 0;
 }
 
 static inline __be16 vlan_dev_vlan_proto(const struct net_device *dev)
 {
-	BUG();
+	WARN_ON_ONCE(1);
 	return 0;
 }