Subject: [PATCH net-next v2] net: ifdefy the wireless pointers in struct net_device

From: Jakub Kicinski <[email-masked]>
Date: Wed, 18 May 2022 11:18:07 -0700

Most protocol-specific pointers in struct net_device are under
a respective ifdef. Wireless is the notable exception. Since
there's a sizable number of custom-built kernels for datacenter
workloads which don't build wireless it seems reasonable to
ifdefy those pointers as well.

While at it move IPv4 and IPv6 pointers up, those are special
for obvious reasons.

Acked-by: Stefan Schmidt <[email-masked]> # ieee802154
Signed-off-by: Jakub Kicinski <[email-masked]>
---
v1: https://lore.kernel.org/all/[email-masked]/
v2: - CONFIG_WIRELESS -> CONFIG_CFG80211 (this needs a bit of
      untangling in sysfs)
    - keep cfg80211_unregister_netdevice in the header

CC: [email-masked]
CC: [email-masked]
CC: [email-masked]
CC: [email-masked]
CC: [email-masked]
CC: [email-masked]
CC: [email-masked]
CC: [email-masked]
CC: [email-masked]
---
 include/linux/netdevice.h       |  8 ++++++--
 include/net/cfg80211.h          |  2 ++
 include/net/cfg802154.h         |  2 ++
 net/batman-adv/hard-interface.c |  2 ++
 net/core/net-sysfs.c            | 21 ++++++++++++++-------
 5 files changed, 26 insertions(+), 9 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index cbaf312e365b..3ff4a654f1f0 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2119,6 +2119,8 @@ struct net_device {
 
 	/* Protocol-specific pointers */
 
+	struct in_device __rcu	*ip_ptr;
+	struct inet6_dev __rcu	*ip6_ptr;
 #if IS_ENABLED(CONFIG_VLAN_8021Q)
 	struct vlan_info __rcu	*vlan_info;
 #endif
@@ -2131,16 +2133,18 @@ struct net_device {
 #if IS_ENABLED(CONFIG_ATALK)
 	void 			*atalk_ptr;
 #endif
-	struct in_device __rcu	*ip_ptr;
 #if IS_ENABLED(CONFIG_DECNET)
 	struct dn_dev __rcu     *dn_ptr;
 #endif
-	struct inet6_dev __rcu	*ip6_ptr;
 #if IS_ENABLED(CONFIG_AX25)
 	void			*ax25_ptr;
 #endif
+#if IS_ENABLED(CONFIG_CFG80211)
 	struct wireless_dev	*ieee80211_ptr;
+#endif
+#if IS_ENABLED(CONFIG_IEEE802154) || IS_ENABLED(CONFIG_6LOWPAN)
 	struct wpan_dev		*ieee802154_ptr;
+#endif
 #if IS_ENABLED(CONFIG_MPLS_ROUTING)
 	struct mpls_dev __rcu	*mpls_ptr;
 #endif
diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index 68713388b617..d523b1e49d1e 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -8006,7 +8006,9 @@ int cfg80211_register_netdevice(struct net_device *dev);
  */
 static inline void cfg80211_unregister_netdevice(struct net_device *dev)
 {
+#if IS_ENABLED(CONFIG_CFG80211)
 	cfg80211_unregister_wdev(dev->ieee80211_ptr);
+#endif
 }
 
 /**
diff --git a/include/net/cfg802154.h b/include/net/cfg802154.h
index 85f9e8417688..d8d8719315fd 100644
--- a/include/net/cfg802154.h
+++ b/include/net/cfg802154.h
@@ -373,6 +373,7 @@ struct wpan_dev {
 
 #define to_phy(_dev)	container_of(_dev, struct wpan_phy, dev)
 
+#if IS_ENABLED(CONFIG_IEEE802154) || IS_ENABLED(CONFIG_6LOWPAN)
 static inline int
 wpan_dev_hard_header(struct sk_buff *skb, struct net_device *dev,
 		     const struct ieee802154_addr *daddr,
@@ -383,6 +384,7 @@ wpan_dev_hard_header(struct sk_buff *skb, struct net_device *dev,
 
 	return wpan_dev->header_ops->create(skb, dev, daddr, saddr, len);
 }
+#endif
 
 struct wpan_phy *
 wpan_phy_new(const struct cfg802154_ops *ops, size_t priv_size);
diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c
index 83fb51b6e299..b8f8da7ee3de 100644
--- a/net/batman-adv/hard-interface.c
+++ b/net/batman-adv/hard-interface.c
@@ -307,9 +307,11 @@ static bool batadv_is_cfg80211_netdev(struct net_device *net_device)
 	if (!net_device)
 		return false;
 
+#if IS_ENABLED(CONFIG_CFG80211)
 	/* cfg80211 drivers have to set ieee80211_ptr */
 	if (net_device->ieee80211_ptr)
 		return true;
+#endif
 
 	return false;
 }
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 4980c3a50475..99d737b1c720 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -757,6 +757,19 @@ static const struct attribute_group wireless_group = {
 };
 #endif
 
+static bool wireless_group_needed(struct net_device *ndev)
+{
+#if IS_ENABLED(CONFIG_CFG80211)
+	if (ndev->ieee80211_ptr)
+		return true;
+#endif
+#if IS_ENABLED(CONFIG_WIRELESS_EXT)
+	if (ndev->wireless_handlers)
+		return true;
+#endif
+	return false;
+}
+
 #else /* CONFIG_SYSFS */
 #define net_class_groups	NULL
 #endif /* CONFIG_SYSFS */
@@ -1996,14 +2009,8 @@ int netdev_register_kobject(struct net_device *ndev)
 
 	*groups++ = &netstat_group;
 
-#if IS_ENABLED(CONFIG_WIRELESS_EXT) || IS_ENABLED(CONFIG_CFG80211)
-	if (ndev->ieee80211_ptr)
-		*groups++ = &wireless_group;
-#if IS_ENABLED(CONFIG_WIRELESS_EXT)
-	else if (ndev->wireless_handlers)
+	if (wireless_group_needed(ndev))
 		*groups++ = &wireless_group;
-#endif
-#endif
 #endif /* CONFIG_SYSFS */
 
 	error = device_add(dev);
-- 
2.34.3