Info/History Screen: use nl80211 signal levels

This now uses the nl80211 signal-level information, if available.
If the hardware does not fill in STA_INFO_SIGNAL{,_AVG} (indicated
by a zero value), it falls back to BSS_SIGNAL; else gives up.

info_scr.c

@@ -45,16 +45,22 @@ void sampling_do_poll(void)
 {
 	iw_getstat(&cur);
 	iw_nl80211_get_linkstat(&ls);
-	iw_cache_update(&cur, &ls);
+	iw_cache_update(&ls);
 }
 
 static void display_levels(void)
 {
+	static float qual, signal, noise, ssnr;
 	char nscale[2]   = { cur.dbm.signal - 20, cur.dbm.signal },
 	     lvlscale[2] = { -40, -20};
 	char tmp[0x100];
-	static float qual, signal, noise, ssnr;
 	int line;
+	bool noise_data_valid = iw_nl80211_have_survey_data(&ls);
+	int sig_level = ls.signal_avg ?: ls.signal;
+
+	/* See comments in iw_cache_update */
+	if (sig_level == 0)
+		sig_level = ls.bss_signal;
 
 	for (line = 1; line <= WH_LEVEL; line++)
 		mvwclrtoborder(w_levels, line, 1);
@@ -68,7 +74,7 @@ static void display_levels(void)
 	line = 1;
 
 	/* Noise data is rare. Use the space for spreading out. */
-	if (!iw_nl80211_have_survey_data(&ls))
+	if (!noise_data_valid)
 		line++;
 
 	if (cur.stat.qual.updated & IW_QUAL_QUAL_INVALID) {
@@ -88,11 +94,11 @@ static void display_levels(void)
 
 	/* Spacer */
 	line++;
-	if (!iw_nl80211_have_survey_data(&ls))
+	if (!noise_data_valid)
 		line++;
 
-	if (!(cur.stat.qual.updated & IW_QUAL_LEVEL_INVALID)) {
-		signal = ewma(signal, cur.dbm.signal, conf.meter_decay / 100.0);
+	if (sig_level != 0) {
+		signal = ewma(signal, sig_level, conf.meter_decay / 100.0);
 
 		mvwaddstr(w_levels, line++, 1, "signal level: ");
 		sprintf(tmp, "%.0f dBm (%s)      ", signal, dbm2units(signal));
@@ -110,7 +116,7 @@ static void display_levels(void)
 
 	line++;
 
-	if (iw_nl80211_have_survey_data(&ls)) {
+	if (noise_data_valid) {
 		noise = ewma(noise, ls.survey.noise, conf.meter_decay / 100.0);
 
 		mvwaddstr(w_levels, line++, 1, "noise level:  ");

iw_if.h

@@ -207,11 +207,7 @@ struct iw_stat {
 /*
  * 	Periodic sampling of wireless statistics via timer alarm
  */
-/* FIXME: remove forward declaration */
-struct iw_nl80211_linkstat;
-
 extern void iw_getstat(struct iw_stat *stat);
-extern void iw_cache_update(struct iw_stat *iw, struct iw_nl80211_linkstat *ls);
 
 extern void sampling_init(void (*sampling_handler)(int));
 extern void sampling_do_poll(void);

iw_nl80211.c

@@ -351,6 +351,14 @@ static int link_handler(struct nl_msg *msg, void *arg)
 	if (!bss[NL80211_BSS_STATUS])
 		return NL_SKIP;
 
+	if (bss[NL80211_BSS_SIGNAL_UNSPEC])
+		ls->bss_signal_qual = nla_get_u8(bss[NL80211_BSS_SIGNAL_UNSPEC]);
+
+	if (bss[NL80211_BSS_SIGNAL_MBM]) {
+		int s = nla_get_u32(bss[NL80211_BSS_SIGNAL_MBM]);
+		ls->bss_signal = s / 100;
+	}
+
 	ls->status = nla_get_u32(bss[NL80211_BSS_STATUS]);
 	switch (ls->status) {
 	case NL80211_BSS_STATUS_ASSOCIATED:	/* apparently no longer used */

iw_nl80211.h

@@ -16,7 +16,8 @@
 
 #define BIT(x) (1ULL<<(x))		/* from iw:iw.h */
 
-/** struct msg_attribute - attributes to nla_put into the message
+/**
+ * struct msg_attribute - attributes to nla_put into the message
  * @type:	type of the attribute
  * @len:	attribute length
  * @data:	pointer to data area of length @len
@@ -119,12 +120,14 @@ extern void iw_nl80211_get_survey(struct iw_nl80211_survey *sd);
  * @beacon_int:	      beacon interval in Time Units of 1024usec
  * @dtim_period:      DTIM period for beaconing
  * @beacon_avg_sig:   average beacon signal (in dBm)
- * @beacons:	      number of beacons received
+ * @beacons:          number of beacons received
  * @beacon_loss:      count of times beacon loss was detected
- * @signal:           signal strength in dBm
- * @signal_avg:	      average signal strength in dBm
- * @tx_bitrate:	      string describing current TX bitrate
- * @rx_bitrate:	      string describing current RX bitrate
+ * @signal:           signal strength in dBm (0 if not present)
+ * @signal_avg:       average signal strength in dBm
+ * @bss_signal:       signal strength of BSS probe in dBm (or 0)
+ * @bss_signal_qual:  unitless signal strength of BSS probe, 0..100
+ * @tx_bitrate:       string describing current TX bitrate
+ * @rx_bitrate:       string describing current RX bitrate
  * @authorized:       FIXME
  * @authenticated:    FIXME
  * @long_preamble:    whether using long or short preamble
@@ -161,6 +164,9 @@ struct iw_nl80211_linkstat {
 	int8_t			signal,
 				signal_avg;
 
+	int8_t			bss_signal;
+	uint8_t			bss_signal_qual;
+
 	char			tx_bitrate[100],
 				rx_bitrate[100];
 
@@ -177,6 +183,7 @@ struct iw_nl80211_linkstat {
 	struct iw_nl80211_survey	survey;
 };
 extern void iw_nl80211_get_linkstat(struct iw_nl80211_linkstat *ls);
+extern void iw_cache_update(struct iw_nl80211_linkstat *ls);
 
 /* Indicate whether @ls contains usable channel survey data */
 static inline bool iw_nl80211_have_survey_data(struct iw_nl80211_linkstat *ls)

lhist_scr.c

@@ -118,24 +118,34 @@ static struct iw_levelstat iw_cache_get(const uint32_t index)
 	return iw_stats_cache[(count - index) % IW_STACKSIZE];
 }
 
-// XXX FIXME: rewrite in terms of struct iw_nl80211_linkstat
-void iw_cache_update(struct iw_stat *iw,
-		     struct iw_nl80211_linkstat *ls)
+void iw_cache_update(struct iw_nl80211_linkstat *ls)
 {
 	static struct iw_levelstat prev, avg = IW_LSTAT_INIT;
 	static int slot;
+	int sig_level = ls->signal_avg ?: ls->signal;
 
-	if (! (iw->stat.qual.updated & IW_QUAL_LEVEL_INVALID)) {
+	/*
+	 * If hardware does not support dBm signal level, it will not
+	 * be filled in, and show up as 0. Try to fall back to the BSS
+	 * probe where again a 0 dBm value reflects 'not initialized'.
+	 */
+	if (sig_level == 0)
+		sig_level = ls->bss_signal;
+
+	if (sig_level == 0) {
+		avg.flags  |= IW_QUAL_LEVEL_INVALID;
+	} else {
 		avg.flags  &= ~IW_QUAL_LEVEL_INVALID;
-		avg.signal += iw->dbm.signal / conf.slotsize;
-		track_extrema(iw->dbm.signal, &e_signal);
+		avg.signal += (float)sig_level / conf.slotsize;
+		track_extrema(sig_level, &e_signal);
 	}
 
 	if (iw_nl80211_have_survey_data(ls)) {
 		avg.flags  &= ~IW_QUAL_NOISE_INVALID;
 		avg.noise += (float)ls->survey.noise / conf.slotsize;
 		track_extrema(ls->survey.noise, &e_noise);
-		track_extrema(iw->dbm.signal - ls->survey.noise, &e_snr);
+		if (! (avg.flags & IW_QUAL_LEVEL_INVALID))
+			track_extrema(sig_level - ls->survey.noise, &e_snr);
 	}
 
 	if (++slot >= conf.slotsize) {