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>

1 files changed, 51 insertions, 3 deletions

diff --git a/drivers/net/wireless/ath/carl9170/main.c b/drivers/net/wireless/ath/carl9170/main.c
index ce8ae1e6bd3b..95e4bf05e559 100644
--- 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;