cfg80211/mac80211: re-add get_channel operation

This essentially reverts commit 2e165b8184 but
introduces the get_channel operation with a new
wireless_dev argument so that you can retrieve
the channel per interface. This is necessary as
even though we can track all interface channels
(except monitor) we can't track the channel type
used.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/nl80211.c

@@ -1759,11 +1759,17 @@ static int nl80211_send_iface(struct sk_buff *msg, u32 pid, u32 seq, int flags,
 			(cfg80211_rdev_list_generation << 2)))
 		goto nla_put_failure;
 
-	if (rdev->monitor_channel) {
-		if (nla_put_u32(msg, NL80211_ATTR_WIPHY_FREQ,
-				rdev->monitor_channel->center_freq) ||
-		    nla_put_u32(msg, NL80211_ATTR_WIPHY_CHANNEL_TYPE,
-				rdev->monitor_channel_type))
+	if (rdev->ops->get_channel) {
+		struct ieee80211_channel *chan;
+		enum nl80211_channel_type channel_type;
+
+		chan = rdev->ops->get_channel(&rdev->wiphy, wdev,
+					      &channel_type);
+		if (chan &&
+		    (nla_put_u32(msg, NL80211_ATTR_WIPHY_FREQ,
+				 chan->center_freq) ||
+		     nla_put_u32(msg, NL80211_ATTR_WIPHY_CHANNEL_TYPE,
+				 channel_type)))
 			goto nla_put_failure;
 	}