wl1251: add get_survey callback in order to get channel noise

Signed-off-by: John W. Linville <linville@tuxdriver.com>
Acked-by: Kalle Valo <kvalo@adurom.com>

drivers/net/wireless/wl12xx/wl1251.h

@@ -381,6 +381,9 @@ struct wl1251 {
 
 	u32 chip_id;
 	char fw_ver[21];
+
+	/* Most recently reported noise in dBm */
+	s8 noise;
 };
 
 int wl1251_plt_start(struct wl1251 *wl);

drivers/net/wireless/wl12xx/wl1251_main.c

@@ -1172,6 +1172,22 @@ static int wl1251_op_conf_tx(struct ieee80211_hw *hw, u16 queue,
 	return ret;
 }
 
+static int wl1251_op_get_survey(struct ieee80211_hw *hw, int idx,
+				struct survey_info *survey)
+{
+	struct wl1251 *wl = hw->priv;
+	struct ieee80211_conf *conf = &hw->conf;
+
+	if (idx != 0)
+		return -ENOENT;
+
+	survey->channel = conf->channel;
+	survey->filled = SURVEY_INFO_NOISE_DBM;
+	survey->noise = wl->noise;
+
+	return 0;
+}
+
 /* can't be const, mac80211 writes to this */
 static struct ieee80211_supported_band wl1251_band_2ghz = {
 	.channels = wl1251_channels,
@@ -1193,6 +1209,7 @@ static const struct ieee80211_ops wl1251_ops = {
 	.bss_info_changed = wl1251_op_bss_info_changed,
 	.set_rts_threshold = wl1251_op_set_rts_threshold,
 	.conf_tx = wl1251_op_conf_tx,
+	.get_survey = wl1251_op_get_survey,
 };
 
 static int wl1251_read_eeprom_byte(struct wl1251 *wl, off_t offset, u8 *data)

drivers/net/wireless/wl12xx/wl1251_rx.c

@@ -74,6 +74,12 @@ static void wl1251_rx_status(struct wl1251 *wl,
 
 	status->signal = desc->rssi;
 
+	/*
+	 * FIXME: guessing that snr needs to be divided by two, otherwise
+	 * the values don't make any sense
+	 */
+	wl->noise = desc->rssi - desc->snr / 2;
+
 	status->freq = ieee80211_channel_to_frequency(desc->channel);
 
 	status->flag |= RX_FLAG_TSFT;