mac80211: only create default STA interface if supported

Drivers will support this, obviously, but this forces them to
set it up properly.

(This includes the fix posted as "mac80211: fix ifmodes check" and
tested in wireless-testing by Hin-Tak and others. -- JWL)

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Reported-by: Larry Finger <Larry.Finger@lwfinger.net>
Tested-by: Hin-Tak Leung <htl10@users.sourceforge.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/main.c

@@ -886,12 +886,14 @@ int ieee80211_register_hw(struct ieee80211_hw *hw)
 
 	local->mdev->select_queue = ieee80211_select_queue;
 
-	/* add one default STA interface */
-	result = ieee80211_if_add(local, "wlan%d", NULL,
-				  NL80211_IFTYPE_STATION, NULL);
-	if (result)
-		printk(KERN_WARNING "%s: Failed to add default virtual iface\n",
-		       wiphy_name(local->hw.wiphy));
+	/* add one default STA interface if supported */
+	if (local->hw.wiphy->interface_modes & BIT(NL80211_IFTYPE_STATION)) {
+		result = ieee80211_if_add(local, "wlan%d", NULL,
+					  NL80211_IFTYPE_STATION, NULL);
+		if (result)
+			printk(KERN_WARNING "%s: Failed to add default virtual iface\n",
+			       wiphy_name(local->hw.wiphy));
+	}
 
 	rtnl_unlock();