wl1251: fix null data for IBSS

Fix the WARN below by not calling ieee80211_nullfunc_get() in IBSS mode,
but setting up empty template the same way wl12xx driver does.

WARNING: CPU: 0 PID: 914 at net/mac80211/tx.c:2750 ieee80211_nullfunc_get+0xc0/0xd0 [mac80211]()
Modules linked in: wl1251_sdio wl1251 mac80211 cfg80211
...
[<c00439c0>] (warn_slowpath_null)
[<bf0bdfdc>] (ieee80211_nullfunc_get [mac80211])
[<bf134774>] (wl1251_op_bss_info_changed [wl1251])
[<bf099e14>] (ieee80211_bss_info_change_notify [mac80211])
...

Also perform join command regardless of bss_type as that seems to be
required for proper operation.

Signed-off-by: Grazvydas Ignotas <notasas@gmail.com>
Tested-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ti/wl1251/main.c

@@ -550,6 +550,34 @@ static void wl1251_op_remove_interface(struct ieee80211_hw *hw,
 	mutex_unlock(&wl->mutex);
 }
 
+static int wl1251_build_null_data(struct wl1251 *wl)
+{
+	struct sk_buff *skb = NULL;
+	int size;
+	void *ptr;
+	int ret = -ENOMEM;
+
+	if (wl->bss_type == BSS_TYPE_IBSS) {
+		size = sizeof(struct wl12xx_null_data_template);
+		ptr = NULL;
+	} else {
+		skb = ieee80211_nullfunc_get(wl->hw, wl->vif);
+		if (!skb)
+			goto out;
+		size = skb->len;
+		ptr = skb->data;
+	}
+
+	ret = wl1251_cmd_template_set(wl, CMD_NULL_DATA, ptr, size);
+
+out:
+	dev_kfree_skb(skb);
+	if (ret)
+		wl1251_warning("cmd buld null data failed: %d", ret);
+
+	return ret;
+}
+
 static int wl1251_build_qos_null_data(struct wl1251 *wl)
 {
 	struct ieee80211_qos_hdr template;
@@ -1093,24 +1121,19 @@ static void wl1251_op_bss_info_changed(struct ieee80211_hw *hw,
 		wl->rssi_thold = bss_conf->cqm_rssi_thold;
 	}
 
-	if (changed & BSS_CHANGED_BSSID) {
+	if ((changed & BSS_CHANGED_BSSID) &&
+	    memcmp(wl->bssid, bss_conf->bssid, ETH_ALEN)) {
 		memcpy(wl->bssid, bss_conf->bssid, ETH_ALEN);
 
-		skb = ieee80211_nullfunc_get(wl->hw, wl->vif);
-		if (!skb)
-			goto out_sleep;
-
-		ret = wl1251_cmd_template_set(wl, CMD_NULL_DATA,
-					      skb->data, skb->len);
-		dev_kfree_skb(skb);
-		if (ret < 0)
-			goto out_sleep;
+		if (!is_zero_ether_addr(wl->bssid)) {
+			ret = wl1251_build_null_data(wl);
+			if (ret < 0)
+				goto out_sleep;
 
-		ret = wl1251_build_qos_null_data(wl);
-		if (ret < 0)
-			goto out;
+			ret = wl1251_build_qos_null_data(wl);
+			if (ret < 0)
+				goto out_sleep;
 
-		if (wl->bss_type != BSS_TYPE_IBSS) {
 			ret = wl1251_join(wl, wl->bss_type, wl->channel,
 					  wl->beacon_int, wl->dtim_period);
 			if (ret < 0)