net: mac802154: Follow the count of ongoing transmissions

In order to create a synchronous API for MLME command purposes, we need
to be able to track the end of the ongoing transmissions. Let's
introduce an atomic variable which is incremented when a transmission
starts and decremented when relevant so that we know at any moment
whether there is an ongoing transmission.

The counter gets decremented in the following situations:
- The operation is asynchronous and there was a failure during the
  offloading process.
- The operation is synchronous and the synchronous operation failed.
- The operation finished, either successfully or not.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Alexander Aring <aahringo@redhat.com>
Link: https://lore.kernel.org/r/20220519150516.443078-5-miquel.raynal@bootlin.com
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>

include/net/cfg802154.h

@@ -214,6 +214,9 @@ struct wpan_phy {
 	/* the network namespace this phy lives in currently */
 	possible_net_t _net;
 
+	/* Transmission monitoring */
+	atomic_t ongoing_txs;
+
 	char priv[] __aligned(NETDEV_ALIGN);
 };
 

net/mac802154/tx.c

@@ -44,6 +44,7 @@ void ieee802154_xmit_sync_worker(struct work_struct *work)
 err_tx:
 	/* Restart the netif queue on each sub_if_data object. */
 	ieee802154_wake_queue(&local->hw);
+	atomic_dec(&local->phy->ongoing_txs);
 	kfree_skb(skb);
 	netdev_dbg(dev, "transmission failed\n");
 }
@@ -75,6 +76,7 @@ ieee802154_tx(struct ieee802154_local *local, struct sk_buff *skb)
 
 	/* Stop the netif queue on each sub_if_data object. */
 	ieee802154_stop_queue(&local->hw);
+	atomic_inc(&local->phy->ongoing_txs);
 
 	/* Drivers should preferably implement the async callback. In some rare
 	 * cases they only provide a sync callback which we will use as a
@@ -98,6 +100,7 @@ ieee802154_tx(struct ieee802154_local *local, struct sk_buff *skb)
 
 err_wake_netif_queue:
 	ieee802154_wake_queue(&local->hw);
+	atomic_dec(&local->phy->ongoing_txs);
 err_free_skb:
 	kfree_skb(skb);
 	return NETDEV_TX_OK;

net/mac802154/util.c

@@ -88,6 +88,7 @@ void ieee802154_xmit_complete(struct ieee802154_hw *hw, struct sk_buff *skb,
 	}
 
 	dev_consume_skb_any(skb);
+	atomic_dec(&hw->phy->ongoing_txs);
 }
 EXPORT_SYMBOL(ieee802154_xmit_complete);
 
@@ -99,6 +100,7 @@ void ieee802154_xmit_error(struct ieee802154_hw *hw, struct sk_buff *skb,
 	local->tx_result = reason;
 	ieee802154_wake_queue(hw);
 	dev_kfree_skb_any(skb);
+	atomic_dec(&hw->phy->ongoing_txs);
 }
 EXPORT_SYMBOL(ieee802154_xmit_error);