cfg80211: add P2P Device abstraction

In order to support using a different MAC address
for the P2P Device address we must first have a
P2P Device abstraction that can be assigned a MAC
address.

This abstraction will also be useful to support
offloading P2P operations to the device, e.g.
periodic listen for discoverability.

Currently, the driver is responsible for assigning
a MAC address to the P2P Device, but this could be
changed by allowing a MAC address to be given to
the NEW_INTERFACE command.

As it has no associated netdev, a P2P Device can
only be identified by its wdev identifier but the
previous patches allowed using the wdev identifier
in various APIs, e.g. remain-on-channel.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/wireless/chan.c b/net/wireless/chan.c
index d355f67..2f876b9 100644
--- a/net/wireless/chan.c
+++ b/net/wireless/chan.c
@@ -105,7 +105,7 @@
 
 	ASSERT_WDEV_LOCK(wdev);
 
-	if (!netif_running(wdev->netdev))
+	if (wdev->netdev && !netif_running(wdev->netdev))
 		return;
 
 	switch (wdev->iftype) {
@@ -143,6 +143,11 @@
 	case NL80211_IFTYPE_WDS:
 		/* these interface types don't really have a channel */
 		return;
+	case NL80211_IFTYPE_P2P_DEVICE:
+		if (wdev->wiphy->features &
+				NL80211_FEATURE_P2P_DEVICE_NEEDS_CHANNEL)
+			*chanmode = CHAN_MODE_EXCLUSIVE;
+		return;
 	case NL80211_IFTYPE_UNSPECIFIED:
 	case NUM_NL80211_IFTYPES:
 		WARN_ON(1);