[PATCH] rt2x00: Add get_tx_data_len callback function

The TX datalen must always be converted to a value rt73 and rt2500usb
understand. Both require to use a different size then skb->len.
First off this is required because the descriptor must be added,
but the second is because the value must be a multiple of either 2 or 4,
and it should not be a multiple of the USB packetmax

Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/rt2x00/rt73usb.c b/drivers/net/wireless/rt2x00/rt73usb.c
index 919cca5..4a78ca7 100644
--- a/drivers/net/wireless/rt2x00/rt73usb.c
+++ b/drivers/net/wireless/rt2x00/rt73usb.c
@@ -1286,6 +1286,21 @@
 	rt2x00_desc_write(txd, 0, word);
 }
 
+static int rt73usb_get_tx_data_len(struct rt2x00_dev *rt2x00dev,
+				   int maxpacket, struct sk_buff *skb)
+{
+	int length;
+
+	/*
+	 * The length _must_ be a multiple of 4,
+	 * but it must _not_ be a multiple of the USB packet size.
+	 */
+	length = roundup(skb->len, 4);
+	length += (4 * !(length % maxpacket));
+
+	return length;
+}
+
 /*
  * TX data initialization
  */
@@ -2012,6 +2027,7 @@
 	.link_tuner		= rt73usb_link_tuner,
 	.write_tx_desc		= rt73usb_write_tx_desc,
 	.write_tx_data		= rt2x00usb_write_tx_data,
+	.get_tx_data_len	= rt73usb_get_tx_data_len,
 	.kick_tx_queue		= rt73usb_kick_tx_queue,
 	.fill_rxdone		= rt73usb_fill_rxdone,
 	.config_mac_addr	= rt73usb_config_mac_addr,