wifi: mac80211: add netdev per-link debugfs data and driver hook

This adds the infrastructure to have netdev specific per-link data both
for mac80211 and the driver in debugfs. For the driver, a new callback
is added which is only used if MLO is supported.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230301115906.fb4c947e4df8.I69b3516ddf4c8a7501b395f652d6063444ecad63@changeidSigned-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/mac80211.h

@@ -3844,6 +3844,12 @@ struct ieee80211_prep_tx_info {
  *	the station. See @sta_pre_rcu_remove if needed.
  *	This callback can sleep.
  *
+ * @link_add_debugfs: Drivers can use this callback to add debugfs files
+ *	when a link is added to a mac80211 vif. This callback should be within
+ *	a CONFIG_MAC80211_DEBUGFS conditional. This callback can sleep.
+ *	For non-MLO the callback will be called once for the default bss_conf
+ *	with the vif's directory rather than a separate subdirectory.
+ *
  * @sta_add_debugfs: Drivers can use this callback to add debugfs files
  *	when a station is added to mac80211's station list. This callback
  *	should be within a CONFIG_MAC80211_DEBUGFS conditional. This
@@ -4325,6 +4331,10 @@ struct ieee80211_ops {
 	int (*sta_remove)(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
 			  struct ieee80211_sta *sta);
 #ifdef CONFIG_MAC80211_DEBUGFS
+	void (*link_add_debugfs)(struct ieee80211_hw *hw,
+				 struct ieee80211_vif *vif,
+				 struct ieee80211_bss_conf *link_conf,
+				 struct dentry *dir);
 	void (*sta_add_debugfs)(struct ieee80211_hw *hw,
 				struct ieee80211_vif *vif,
 				struct ieee80211_sta *sta,

net/mac80211/debugfs_netdev.h

@@ -10,6 +10,12 @@
 void ieee80211_debugfs_add_netdev(struct ieee80211_sub_if_data *sdata);
 void ieee80211_debugfs_remove_netdev(struct ieee80211_sub_if_data *sdata);
 void ieee80211_debugfs_rename_netdev(struct ieee80211_sub_if_data *sdata);
+
+void ieee80211_link_debugfs_add(struct ieee80211_link_data *link);
+void ieee80211_link_debugfs_remove(struct ieee80211_link_data *link);
+
+void ieee80211_link_debugfs_drv_add(struct ieee80211_link_data *link);
+void ieee80211_link_debugfs_drv_remove(struct ieee80211_link_data *link);
 #else
 static inline void ieee80211_debugfs_add_netdev(
 	struct ieee80211_sub_if_data *sdata)
@@ -20,6 +26,16 @@ static inline void ieee80211_debugfs_remove_netdev(
 static inline void ieee80211_debugfs_rename_netdev(
 	struct ieee80211_sub_if_data *sdata)
 {}
+
+static inline void ieee80211_link_debugfs_add(struct ieee80211_link_data *link)
+{}
+static inline void ieee80211_link_debugfs_remove(struct ieee80211_link_data *link)
+{}
+
+static inline void ieee80211_link_debugfs_drv_add(struct ieee80211_link_data *link)
+{}
+static inline void ieee80211_link_debugfs_drv_remove(struct ieee80211_link_data *link)
+{}
 #endif
 
 #endif /* __IEEE80211_DEBUGFS_NETDEV_H */

net/mac80211/driver-ops.c

@@ -8,6 +8,7 @@
 #include "trace.h"
 #include "driver-ops.h"
 #include "debugfs_sta.h"
+#include "debugfs_netdev.h"
 
 int drv_start(struct ieee80211_local *local)
 {
@@ -477,6 +478,10 @@ int drv_change_vif_links(struct ieee80211_local *local,
 			 u16 old_links, u16 new_links,
 			 struct ieee80211_bss_conf *old[IEEE80211_MLD_MAX_NUM_LINKS])
 {
+	struct ieee80211_link_data *link;
+	unsigned long links_to_add;
+	unsigned long links_to_rem;
+	unsigned int link_id;
 	int ret = -EOPNOTSUPP;
 
 	might_sleep();
@@ -487,13 +492,31 @@ int drv_change_vif_links(struct ieee80211_local *local,
 	if (old_links == new_links)
 		return 0;
 
+	links_to_add = ~old_links & new_links;
+	links_to_rem = old_links & ~new_links;
+
+	for_each_set_bit(link_id, &links_to_rem, IEEE80211_MLD_MAX_NUM_LINKS) {
+		link = rcu_access_pointer(sdata->link[link_id]);
+
+		ieee80211_link_debugfs_drv_remove(link);
+	}
+
 	trace_drv_change_vif_links(local, sdata, old_links, new_links);
 	if (local->ops->change_vif_links)
 		ret = local->ops->change_vif_links(&local->hw, &sdata->vif,
 						   old_links, new_links, old);
 	trace_drv_return_int(local, ret);
 
-	return ret;
+	if (ret)
+		return ret;
+
+	for_each_set_bit(link_id, &links_to_add, IEEE80211_MLD_MAX_NUM_LINKS) {
+		link = rcu_access_pointer(sdata->link[link_id]);
+
+		ieee80211_link_debugfs_drv_add(link);
+	}
+
+	return 0;
 }
 
 int drv_change_sta_links(struct ieee80211_local *local,

net/mac80211/driver-ops.h

@@ -465,6 +465,22 @@ static inline void drv_sta_remove(struct ieee80211_local *local,
 }
 
 #ifdef CONFIG_MAC80211_DEBUGFS
+static inline void drv_link_add_debugfs(struct ieee80211_local *local,
+					struct ieee80211_sub_if_data *sdata,
+					struct ieee80211_bss_conf *link_conf,
+					struct dentry *dir)
+{
+	might_sleep();
+
+	sdata = get_bss_sdata(sdata);
+	if (!check_sdata_in_driver(sdata))
+		return;
+
+	if (local->ops->link_add_debugfs)
+		local->ops->link_add_debugfs(&local->hw, &sdata->vif,
+					     link_conf, dir);
+}
+
 static inline void drv_sta_add_debugfs(struct ieee80211_local *local,
 				       struct ieee80211_sub_if_data *sdata,
 				       struct ieee80211_sta *sta,

net/mac80211/ieee80211_i.h

@@ -999,6 +999,10 @@ struct ieee80211_link_data {
 	struct ieee80211_tx_queue_params tx_conf[IEEE80211_NUM_ACS];
 
 	struct ieee80211_bss_conf *conf;
+
+#ifdef CONFIG_MAC80211_DEBUGFS
+	struct dentry *debugfs_dir;
+#endif
 };
 
 struct ieee80211_sub_if_data {

net/mac80211/link.c

@@ -10,6 +10,7 @@
 #include "ieee80211_i.h"
 #include "driver-ops.h"
 #include "key.h"
+#include "debugfs_netdev.h"
 
 void ieee80211_link_setup(struct ieee80211_link_data *link)
 {
@@ -61,6 +62,8 @@ void ieee80211_link_init(struct ieee80211_sub_if_data *sdata,
 		default:
 			WARN_ON(1);
 		}
+
+		ieee80211_link_debugfs_add(link);
 	}
 }
 
@@ -94,6 +97,7 @@ static void ieee80211_tear_down_links(struct ieee80211_sub_if_data *sdata,
 		if (WARN_ON(!link))
 			continue;
 		ieee80211_remove_link_keys(link, &keys);
+		ieee80211_link_debugfs_remove(link);
 		ieee80211_link_stop(link);
 	}