cfg80211: allow CFG80211_SIGNAL_TYPE_UNSPEC in station_info

The station_info struct had demanded dBm signal values, but the
cfg80211 wireless extensions implementation was also accepting
"unspecified" (i.e. RSSI) unit values while the nl80211 code was
completely unaware of them.  Resolve this by formally allowing the
"unspecified" units while making nl80211 ignore them.
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Reviewed-by: Johannes Berg <johannes@sipsolutions.net>

include/net/cfg80211.h

@@ -619,8 +619,10 @@ struct sta_bss_parameters {
  * @llid: mesh local link id
  * @plid: mesh peer link id
  * @plink_state: mesh peer link state
- * @signal: signal strength of last received packet in dBm
- * @signal_avg: signal strength average in dBm
+ * @signal: the signal strength, type depends on the wiphy's signal_type
+	NOTE: For CFG80211_SIGNAL_TYPE_MBM, value is expressed in _dBm_.
+ * @signal_avg: avg signal strength, type depends on the wiphy's signal_type
+	NOTE: For CFG80211_SIGNAL_TYPE_MBM, value is expressed in _dBm_.
  * @txrate: current unicast bitrate from this station
  * @rxrate: current unicast bitrate to this station
  * @rx_packets: packets received from this station

net/wireless/nl80211.c

@@ -2386,7 +2386,9 @@ static bool nl80211_put_sta_rate(struct sk_buff *msg, struct rate_info *info,
 }
 
 static int nl80211_send_station(struct sk_buff *msg, u32 pid, u32 seq,
-				int flags, struct net_device *dev,
+				int flags,
+				struct cfg80211_registered_device *rdev,
+				struct net_device *dev,
 				const u8 *mac_addr, struct station_info *sinfo)
 {
 	void *hdr;
@@ -2425,12 +2427,18 @@ static int nl80211_send_station(struct sk_buff *msg, u32 pid, u32 seq,
 	if (sinfo->filled & STATION_INFO_PLINK_STATE)
 		NLA_PUT_U8(msg, NL80211_STA_INFO_PLINK_STATE,
 			    sinfo->plink_state);
+	switch (rdev->wiphy.signal_type) {
+	case CFG80211_SIGNAL_TYPE_MBM:
 		if (sinfo->filled & STATION_INFO_SIGNAL)
 			NLA_PUT_U8(msg, NL80211_STA_INFO_SIGNAL,
 				   sinfo->signal);
 		if (sinfo->filled & STATION_INFO_SIGNAL_AVG)
 			NLA_PUT_U8(msg, NL80211_STA_INFO_SIGNAL_AVG,
 				   sinfo->signal_avg);
+		break;
+	default:
+		break;
+	}
 	if (sinfo->filled & STATION_INFO_TX_BITRATE) {
 		if (!nl80211_put_sta_rate(msg, &sinfo->txrate,
 					  NL80211_STA_INFO_TX_BITRATE))
@@ -2523,7 +2531,7 @@ static int nl80211_dump_station(struct sk_buff *skb,
 		if (nl80211_send_station(skb,
 				NETLINK_CB(cb->skb).pid,
 				cb->nlh->nlmsg_seq, NLM_F_MULTI,
-				netdev, mac_addr,
+				dev, netdev, mac_addr,
 				&sinfo) < 0)
 			goto out;
 
@@ -2568,7 +2576,7 @@ static int nl80211_get_station(struct sk_buff *skb, struct genl_info *info)
 		return -ENOMEM;
 
 	if (nl80211_send_station(msg, info->snd_pid, info->snd_seq, 0,
-				 dev, mac_addr, &sinfo) < 0) {
+				 rdev, dev, mac_addr, &sinfo) < 0) {
 		nlmsg_free(msg);
 		return -ENOBUFS;
 	}
@@ -7596,7 +7604,8 @@ void nl80211_send_sta_event(struct cfg80211_registered_device *rdev,
 	if (!msg)
 		return;
 
-	if (nl80211_send_station(msg, 0, 0, 0, dev, mac_addr, sinfo) < 0) {
+	if (nl80211_send_station(msg, 0, 0, 0,
+				 rdev, dev, mac_addr, sinfo) < 0) {
 		nlmsg_free(msg);
 		return;
 	}