cfg80211: Add a function to iterate all BSS entries

Add a function that iterates over the BSS entries associated with a
given wiphy and calls a callback for each iterated BSS. This can be
used by drivers in various ways, e.g., to evaluate some property for
all the BSSs in the medium.
Signed-off-by: Ilan Peer <ilan.peer@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/cfg80211.h

@@ -5750,6 +5750,26 @@ void cfg80211_put_bss(struct wiphy *wiphy, struct cfg80211_bss *bss);
  */
 void cfg80211_unlink_bss(struct wiphy *wiphy, struct cfg80211_bss *bss);
 
+/**
+ * cfg80211_bss_iter - iterate all BSS entries
+ *
+ * This function iterates over the BSS entries associated with the given wiphy
+ * and calls the callback for the iterated BSS. The iterator function is not
+ * allowed to call functions that might modify the internal state of the BSS DB.
+ *
+ * @wiphy: the wiphy
+ * @chandef: if given, the iterator function will be called only if the channel
+ *     of the currently iterated BSS is a subset of the given channel.
+ * @iter: the iterator function to call
+ * @iter_data: an argument to the iterator function
+ */
+void cfg80211_bss_iter(struct wiphy *wiphy,
+		       struct cfg80211_chan_def *chandef,
+		       void (*iter)(struct wiphy *wiphy,
+				    struct cfg80211_bss *bss,
+				    void *data),
+		       void *iter_data);
+
 static inline enum nl80211_bss_scan_width
 cfg80211_chandef_to_scan_width(const struct cfg80211_chan_def *chandef)
 {

net/wireless/scan.c

@@ -1974,6 +1974,27 @@ void cfg80211_unlink_bss(struct wiphy *wiphy, struct cfg80211_bss *pub)
 }
 EXPORT_SYMBOL(cfg80211_unlink_bss);
 
+void cfg80211_bss_iter(struct wiphy *wiphy,
+		       struct cfg80211_chan_def *chandef,
+		       void (*iter)(struct wiphy *wiphy,
+				    struct cfg80211_bss *bss,
+				    void *data),
+		       void *iter_data)
+{
+	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wiphy);
+	struct cfg80211_internal_bss *bss;
+
+	spin_lock_bh(&rdev->bss_lock);
+
+	list_for_each_entry(bss, &rdev->bss_list, list) {
+		if (!chandef || cfg80211_is_sub_chan(chandef, bss->pub.channel))
+			iter(wiphy, &bss->pub, iter_data);
+	}
+
+	spin_unlock_bh(&rdev->bss_lock);
+}
+EXPORT_SYMBOL(cfg80211_bss_iter);
+
 #ifdef CONFIG_CFG80211_WEXT
 static struct cfg80211_registered_device *
 cfg80211_get_dev_from_ifindex(struct net *net, int ifindex)