nl80211: vendor command support

Add support for vendor-specific commands to nl80211. This is
intended to be used for really vendor-specific functionality
that can't be implemented in a generic fashion for any reason.
It's *NOT* intended to be used for any normal/generic feature
or any optimisations that could be implemented across drivers.

Currently, only vendor commands (with replies) are supported,
no dump operations or vendor-specific notifications.

Also add a function wdev_to_ieee80211_vif() to mac80211 which
is needed for mac80211-based drivers wanting to implement any
vendor commands.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index 06265d7..4a376a7 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -642,6 +642,17 @@
 }
 EXPORT_SYMBOL_GPL(ieee80211_iterate_active_interfaces_rtnl);
 
+struct ieee80211_vif *wdev_to_ieee80211_vif(struct wireless_dev *wdev)
+{
+	struct ieee80211_sub_if_data *sdata = IEEE80211_WDEV_TO_SUB_IF(wdev);
+
+	if (!ieee80211_sdata_running(sdata) ||
+	    !(sdata->flags & IEEE80211_SDATA_IN_DRIVER))
+		return NULL;
+	return &sdata->vif;
+}
+EXPORT_SYMBOL_GPL(wdev_to_ieee80211_vif);
+
 /*
  * Nothing should have been stuffed into the workqueue during
  * the suspend->resume cycle. If this WARN is seen then there