cfg80211: add reg_get_dfs_region()

This can be used outside of the regulatory context for any checks
on the DFS region. The central cfg80211 dfs_region is always used
and if it does not match with the wiphy a debug print is issued.
Signed-off-by: Luis R. Rodriguez <mcgrof@do-not-panic.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/reg.c

@@ -135,6 +135,33 @@ static const char *reg_dfs_region_str(enum nl80211_dfs_regions dfs_region)
 	return "Unknown";
 }
 
+enum nl80211_dfs_regions reg_get_dfs_region(struct wiphy *wiphy)
+{
+	const struct ieee80211_regdomain *regd = NULL;
+	const struct ieee80211_regdomain *wiphy_regd = NULL;
+
+	regd = get_cfg80211_regdom();
+	if (!wiphy)
+		goto out;
+
+	wiphy_regd = get_wiphy_regdom(wiphy);
+	if (!wiphy_regd)
+		goto out;
+
+	if (wiphy_regd->dfs_region == regd->dfs_region)
+		goto out;
+
+	REG_DBG_PRINT("%s: device specific dfs_region "
+		      "(%s) disagrees with cfg80211's "
+		      "central dfs_region (%s)\n",
+		      dev_name(&wiphy->dev),
+		      reg_dfs_region_str(wiphy_regd->dfs_region),
+		      reg_dfs_region_str(regd->dfs_region));
+
+out:
+	return regd->dfs_region;
+}
+
 static void rcu_free_regdom(const struct ieee80211_regdomain *r)
 {
 	if (!r)

net/wireless/reg.h

@@ -21,6 +21,7 @@ extern const struct ieee80211_regdomain __rcu *cfg80211_regdomain;
 bool reg_is_valid_request(const char *alpha2);
 bool is_world_regdom(const char *alpha2);
 bool reg_supported_dfs_region(enum nl80211_dfs_regions dfs_region);
+enum nl80211_dfs_regions reg_get_dfs_region(struct wiphy *wiphy);
 
 int regulatory_hint_user(const char *alpha2,
 			 enum nl80211_user_reg_hint_type user_reg_hint_type);