rt2x00: Fix the beacon length bug

When setting up a beacon template, the length of the beacon is
calculated with the assumption that the SKB already contains
the Tx descriptor. In the case of beacons it doesn't.

This patch undoes the damage by adding the Tx descriptor length
to the beacon length. This is safe, because the shortest possible
beacon is longer than the Tx header.

Signed-off-by: Iwo Mergler <Iwo@call-direct.com.au>
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/rt2500usb.c b/drivers/net/wireless/rt2x00/rt2500usb.c
index 449c8d3..3078417 100644
--- a/drivers/net/wireless/rt2x00/rt2500usb.c
+++ b/drivers/net/wireless/rt2x00/rt2500usb.c
@@ -1121,6 +1121,7 @@
 	int pipe = usb_sndbulkpipe(usb_dev, 1);
 	int length;
 	u16 reg;
+	u32 word, len;
 
 	/*
 	 * Add the descriptor in front of the skb.
@@ -1130,6 +1131,17 @@
 	skbdesc->desc = entry->skb->data;
 
 	/*
+	 * Adjust the beacon databyte count. The current number is
+	 * calculated before this function gets called, but falsely
+	 * assumes that the descriptor was already present in the SKB.
+	 */
+	rt2x00_desc_read(skbdesc->desc, 0, &word);
+	len  = rt2x00_get_field32(word, TXD_W0_DATABYTE_COUNT);
+	len += skbdesc->desc_len;
+	rt2x00_set_field32(&word, TXD_W0_DATABYTE_COUNT, len);
+	rt2x00_desc_write(skbdesc->desc, 0, word);
+
+	/*
 	 * Disable beaconing while we are reloading the beacon data,
 	 * otherwise we might be sending out invalid data.
 	 */