+/**
+ * zd_usb_disable_tx - disable transmission
+ * @usb: the zd1211rw-private USB structure
+ *
+ * Frees all URBs in the free list and marks the transmission as disabled.
+ */
+void zd_usb_disable_tx(struct zd_usb *usb)
+{
+ struct zd_usb_tx *tx = &usb->tx;
+ unsigned long flags;
+ struct list_head *pos, *n;
+
+ spin_lock_irqsave(&tx->lock, flags);
+ list_for_each_safe(pos, n, &tx->free_urb_list) {
+ list_del(pos);
+ usb_free_urb(list_entry(pos, struct urb, urb_list));
+ }
+ tx->enabled = 0;
+ tx->submitted_urbs = 0;
+ /* The stopped state is ignored, relying on ieee80211_wake_queues()
+ * in a potentionally following zd_usb_enable_tx().
+ */
+ spin_unlock_irqrestore(&tx->lock, flags);
+}
+
+/**
+ * zd_usb_enable_tx - enables transmission
+ * @usb: a &struct zd_usb pointer
+ *
+ * This function enables transmission and prepares the &zd_usb_tx data
+ * structure.
+ */
+void zd_usb_enable_tx(struct zd_usb *usb)
+{
+ unsigned long flags;
+ struct zd_usb_tx *tx = &usb->tx;
+
+ spin_lock_irqsave(&tx->lock, flags);
+ tx->enabled = 1;
+ tx->submitted_urbs = 0;
+ ieee80211_wake_queues(zd_usb_to_hw(usb));
+ tx->stopped = 0;
+ spin_unlock_irqrestore(&tx->lock, flags);
+}
+
+/**
+ * alloc_tx_urb - provides an tx URB
+ * @usb: a &struct zd_usb pointer
+ *
+ * Allocates a new URB. If possible takes the urb from the free list in
+ * usb->tx.
+ */
+static struct urb *alloc_tx_urb(struct zd_usb *usb)
+{
+ struct zd_usb_tx *tx = &usb->tx;
+ unsigned long flags;
+ struct list_head *entry;
+ struct urb *urb;
+
+ spin_lock_irqsave(&tx->lock, flags);
+ if (list_empty(&tx->free_urb_list)) {
+ urb = usb_alloc_urb(0, GFP_ATOMIC);
+ goto out;
+ }
+ entry = tx->free_urb_list.next;
+ list_del(entry);
+ urb = list_entry(entry, struct urb, urb_list);
+out:
+ spin_unlock_irqrestore(&tx->lock, flags);
+ return urb;
+}
+
+/**
+ * free_tx_urb - frees a used tx URB
+ * @usb: a &struct zd_usb pointer
+ * @urb: URB to be freed
+ *
+ * Frees the the transmission URB, which means to put it on the free URB
+ * list.
+ */
+static void free_tx_urb(struct zd_usb *usb, struct urb *urb)
+{
+ struct zd_usb_tx *tx = &usb->tx;
+ unsigned long flags;
+
+ spin_lock_irqsave(&tx->lock, flags);
+ if (!tx->enabled) {
+ usb_free_urb(urb);
+ goto out;
+ }
+ list_add(&urb->urb_list, &tx->free_urb_list);
+out:
+ spin_unlock_irqrestore(&tx->lock, flags);
+}
+
+static void tx_dec_submitted_urbs(struct zd_usb *usb)
+{
+ struct zd_usb_tx *tx = &usb->tx;
+ unsigned long flags;
+
+ spin_lock_irqsave(&tx->lock, flags);
+ --tx->submitted_urbs;
+ if (tx->stopped && tx->submitted_urbs <= ZD_USB_TX_LOW) {
+ ieee80211_wake_queues(zd_usb_to_hw(usb));
+ tx->stopped = 0;
+ }
+ spin_unlock_irqrestore(&tx->lock, flags);
+}
+
+static void tx_inc_submitted_urbs(struct zd_usb *usb)
+{
+ struct zd_usb_tx *tx = &usb->tx;
+ unsigned long flags;
+
+ spin_lock_irqsave(&tx->lock, flags);
+ ++tx->submitted_urbs;
+ if (!tx->stopped && tx->submitted_urbs > ZD_USB_TX_HIGH) {
+ ieee80211_stop_queues(zd_usb_to_hw(usb));
+ tx->stopped = 1;
+ }
+ spin_unlock_irqrestore(&tx->lock, flags);
+}
+
+/**
+ * tx_urb_complete - completes the execution of an URB
+ * @urb: a URB
+ *
+ * This function is called if the URB has been transferred to a device or an
+ * error has happened.
+ */