iwlegacy: add flush callback

Dump implementation of flush, which just wait until all TX queues
become empty.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/iwlegacy/common.c b/drivers/net/wireless/iwlegacy/common.c
index 7e16d10..56b8021 100644
--- a/drivers/net/wireless/iwlegacy/common.c
+++ b/drivers/net/wireless/iwlegacy/common.c
@@ -4707,6 +4707,42 @@
 }
 EXPORT_SYMBOL(il_mac_change_interface);
 
+void
+il_mac_flush(struct ieee80211_hw *hw, bool drop)
+{
+	struct il_priv *il = hw->priv;
+	unsigned long timeout = jiffies + msecs_to_jiffies(500);
+	int i;
+
+	mutex_lock(&il->mutex);
+	D_MAC80211("enter\n");
+
+	if (il->txq == NULL)
+		goto out;
+
+	for (i = 0; i < il->hw_params.max_txq_num; i++) {
+		struct il_queue *q;
+
+		if (i == il->cmd_queue)
+			continue;
+
+		q = &il->txq[i].q;
+		if (q->read_ptr == q->write_ptr)
+			continue;
+
+		if (time_after(jiffies, timeout)) {
+			IL_ERR("Failed to flush queue %d\n", q->id);
+			break;
+		}
+
+		msleep(20);
+	}
+out:
+	D_MAC80211("leave\n");
+	mutex_unlock(&il->mutex);
+}
+EXPORT_SYMBOL(il_mac_flush);
+
 /*
  * On every watchdog tick we check (latest) time stamp. If it does not
  * change during timeout period and queue is not empty we reset firmware.