carl9170: allow P2P_GO interface creation after P2P_CLIENT

Janusz Dziedzic reported that after a change in wpa_supplicant
["nl80211: Automatically use concurrent P2P if possible"],
carl9170 was no longer able to host a P2P network.

This patch tackles the problem by allowing GO interfaces to be
registered, long after the P2P_CLIENT interface is brought up.

Reported-by: Janusz Dziedzic <janusz.dziedzic@gmail.com>
Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

diff --git a/drivers/net/wireless/ath/carl9170/main.c b/drivers/net/wireless/ath/carl9170/main.c
index ce8ae1e6bd3b2b2cc6cb03669f0f36c658206d59..95e4bf05e5594a1066319c4791b1a9da6e603685 100644 (file)
--- a/drivers/net/wireless/ath/carl9170/main.c
+++ b/drivers/net/wireless/ath/carl9170/main.c
@@ -580,7 +580,7 @@ static int carl9170_op_add_interface(struct ieee80211_hw *hw,
                                     struct ieee80211_vif *vif)
 {
        struct carl9170_vif_info *vif_priv = (void *) vif->drv_priv;
-       struct ieee80211_vif *main_vif;
+       struct ieee80211_vif *main_vif, *old_main = NULL;
        struct ar9170 *ar = hw->priv;
        int vif_id = -1, err = 0;
 
@@ -602,6 +602,15 @@ static int carl9170_op_add_interface(struct ieee80211_hw *hw,
                goto init;
        }
 
+       /* Because the AR9170 HW's MAC doesn't provide full support for
+        * multiple, independent interfaces [of different operation modes].
+        * We have to select ONE main interface [main mode of HW], but we
+        * can have multiple slaves [AKA: entry in the ACK-table].
+        *
+        * The first (from HEAD/TOP) interface in the ar->vif_list is
+        * always the main intf. All following intfs in this list
+        * are considered to be slave intfs.
+        */
        main_vif = carl9170_get_main_vif(ar);
 
        if (main_vif) {
@@ -610,6 +619,18 @@ static int carl9170_op_add_interface(struct ieee80211_hw *hw,
                        if (vif->type == NL80211_IFTYPE_STATION)
                                break;
 
+                       /* P2P GO [master] use-case
+                        * Because the P2P GO station is selected dynamically
+                        * by all participating peers of a WIFI Direct network,
+                        * the driver has be able to change the main interface
+                        * operating mode on the fly.
+                        */
+                       if (main_vif->p2p && vif->p2p &&
+                           vif->type == NL80211_IFTYPE_AP) {
+                               old_main = main_vif;
+                               break;
+                       }
+
                        err = -EBUSY;
                        rcu_read_unlock();
 
@@ -648,14 +669,41 @@ static int carl9170_op_add_interface(struct ieee80211_hw *hw,
        vif_priv->id = vif_id;
        vif_priv->enable_beacon = false;
        ar->vifs++;
-       list_add_tail_rcu(&vif_priv->list, &ar->vif_list);
+       if (old_main) {
+               /* We end up in here, if the main interface is being replaced.
+                * Put the new main interface at the HEAD of the list and the
+                * previous inteface will automatically become second in line.
+                */
+               list_add_rcu(&vif_priv->list, &ar->vif_list);
+       } else {
+               /* Add new inteface. If the list is empty, it will become the
+                * main inteface, otherwise it will be slave.
+                */
+               list_add_tail_rcu(&vif_priv->list, &ar->vif_list);
+       }
        rcu_assign_pointer(ar->vif_priv[vif_id].vif, vif);
 
 init:
-       if (carl9170_get_main_vif(ar) == vif) {
+       main_vif = carl9170_get_main_vif(ar);
+
+       if (main_vif == vif) {
                rcu_assign_pointer(ar->beacon_iter, vif_priv);
                rcu_read_unlock();
 
+               if (old_main) {
+                       struct carl9170_vif_info *old_main_priv =
+                               (void *) old_main->drv_priv;
+                       /* downgrade old main intf to slave intf.
+                        * NOTE: We are no longer under rcu_read_lock.
+                        * But we are still holding ar->mutex, so the
+                        * vif data [id, addr] is safe.
+                        */
+                       err = carl9170_mod_virtual_mac(ar, old_main_priv->id,
+                                                      old_main->addr);
+                       if (err)
+                               goto unlock;
+               }
+
                err = carl9170_init_interface(ar, vif);
                if (err)
                        goto unlock;