[PATCH 3/3] nl80211/mac80211: Report signal average

[Bruno Randolf <br1@einfach.org>]

Extend nl80211 to report an exponential weighted moving average (EWMA) of the
signal value. Since the signal value usually fluctuates between different
packets, an average can be more useful than the value of the last packet.

This uses the recently added generic EWMA library function.

--
v2:	fix ABI breakage and change factor to be a power of 2.

Signed-off-by: Bruno Randolf <br1@einfach.org>
---
 include/linux/nl80211.h |    2 ++
 include/net/cfg80211.h  |    4 ++++
 net/mac80211/Kconfig    |    1 +
 net/mac80211/cfg.c      |    3 ++-
 net/mac80211/rx.c       |    1 +
 net/mac80211/sta_info.c |    2 ++
 net/mac80211/sta_info.h |    3 +++
 net/wireless/nl80211.c  |    3 +++
 8 files changed, 18 insertions(+), 1 deletions(-)

diff --git a/include/linux/nl80211.h b/include/linux/nl80211.h
index 5cfa579..68fc25f 100644
--- a/include/linux/nl80211.h
+++ b/include/linux/nl80211.h
@@ -1183,6 +1183,7 @@ enum nl80211_rate_info {
  *	station)
  * @NL80211_STA_INFO_TX_RETRIES: total retries (u32, to this station)
  * @NL80211_STA_INFO_TX_FAILED: total failed packets (u32, to this station)
+ * @NL80211_STA_INFO_SIGNAL_AVG: signal strength average (u8, dBm)
  */
 enum nl80211_sta_info {
 	__NL80211_STA_INFO_INVALID,
@@ -1198,6 +1199,7 @@ enum nl80211_sta_info {
 	NL80211_STA_INFO_TX_PACKETS,
 	NL80211_STA_INFO_TX_RETRIES,
 	NL80211_STA_INFO_TX_FAILED,
+	NL80211_STA_INFO_SIGNAL_AVG,
 
 	/* keep last */
 	__NL80211_STA_INFO_AFTER_LAST,
diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index 6b2af7a..589c4b1 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -424,6 +424,7 @@ struct station_parameters {
  * @STATION_INFO_TX_RETRIES: @tx_retries filled
  * @STATION_INFO_TX_FAILED: @tx_failed filled
  * @STATION_INFO_RX_DROP_MISC: @rx_dropped_misc filled
+ * @STATION_INFO_SIGNAL_AVG: @signal_avg filled
  */
 enum station_info_flags {
 	STATION_INFO_INACTIVE_TIME	= 1<<0,
@@ -439,6 +440,7 @@ enum station_info_flags {
 	STATION_INFO_TX_RETRIES		= 1<<10,
 	STATION_INFO_TX_FAILED		= 1<<11,
 	STATION_INFO_RX_DROP_MISC	= 1<<12,
+	STATION_INFO_SIGNAL_AVG		= 1<<13,
 };
 
 /**
@@ -485,6 +487,7 @@ struct rate_info {
  * @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
  * @txrate: current unicast bitrate to this station
  * @rx_packets: packets received from this station
  * @tx_packets: packets transmitted to this station
@@ -505,6 +508,7 @@ struct station_info {
 	u16 plid;
 	u8 plink_state;
 	s8 signal;
+	s8 signal_avg;
 	struct rate_info txrate;
 	u32 rx_packets;
 	u32 tx_packets;
diff --git a/net/mac80211/Kconfig b/net/mac80211/Kconfig
index 4d6f865..798d9b9 100644
--- a/net/mac80211/Kconfig
+++ b/net/mac80211/Kconfig
@@ -6,6 +6,7 @@ config MAC80211
 	select CRYPTO_ARC4
 	select CRYPTO_AES
 	select CRC32
+	select AVERAGE
 	---help---
 	  This option enables the hardware independent IEEE 802.11
 	  networking stack.
diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index db134b5..b0e0f6c 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -343,8 +343,9 @@ static void sta_set_sinfo(struct sta_info *sta, struct station_info *sinfo)
 
 	if ((sta->local->hw.flags & IEEE80211_HW_SIGNAL_DBM) ||
 	    (sta->local->hw.flags & IEEE80211_HW_SIGNAL_UNSPEC)) {
-		sinfo->filled |= STATION_INFO_SIGNAL;
+		sinfo->filled |= STATION_INFO_SIGNAL | STATION_INFO_SIGNAL_AVG;
 		sinfo->signal = (s8)sta->last_signal;
+		sinfo->signal_avg = (s8) -ewma_read(&sta->avg_signal);
 	}
 
 	sinfo->txrate.flags = 0;
diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 6289525..2fe8f5f 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -1163,6 +1163,7 @@ ieee80211_rx_h_sta_process(struct ieee80211_rx_data *rx)
 	sta->rx_fragments++;
 	sta->rx_bytes += rx->skb->len;
 	sta->last_signal = status->signal;
+	ewma_add(&sta->avg_signal, -status->signal);
 
 	/*
 	 * Change STA power saving mode only at the end of a frame
diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index eff5857..c426504 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -244,6 +244,8 @@ struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata,
 	sta->local = local;
 	sta->sdata = sdata;
 
+	ewma_init(&sta->avg_signal, 1024, 8);
+
 	if (sta_prepare_rate_control(local, sta, gfp)) {
 		kfree(sta);
 		return NULL;
diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index 05f1130..fdca52c 100644
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -13,6 +13,7 @@
 #include <linux/types.h>
 #include <linux/if_ether.h>
 #include <linux/workqueue.h>
+#include <linux/average.h>
 #include "key.h"
 
 /**
@@ -223,6 +224,7 @@ enum plink_state {
  * @rx_fragments: number of received MPDUs
  * @rx_dropped: number of dropped MPDUs from this STA
  * @last_signal: signal of last received frame from this STA
+ * @avg_signal: moving average of signal of received frames from this STA
  * @last_seq_ctrl: last received seq/frag number from this STA (per RX queue)
  * @tx_filtered_count: number of frames the hardware filtered for this STA
  * @tx_retry_failed: number of frames that failed retry
@@ -291,6 +293,7 @@ struct sta_info {
 	unsigned long rx_fragments;
 	unsigned long rx_dropped;
 	int last_signal;
+	struct ewma avg_signal;
 	__le16 last_seq_ctrl[NUM_RX_DATA_QUEUES];
 
 	/* Updated from TX status path only, no locking requirements */
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 960be4e..45fe06d 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -1874,6 +1874,9 @@ static int nl80211_send_station(struct sk_buff *msg, u32 pid, u32 seq,
 	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);
 	if (sinfo->filled & STATION_INFO_TX_BITRATE) {
 		txrate = nla_nest_start(msg, NL80211_STA_INFO_TX_BITRATE);
 		if (!txrate)