rt2x00usb: Zero USB padding before sending URB

When USB driver requires padding at the end of frame or URB it will report
this need by increasing return value of get_tx_data_len callback. Common
USB code uses that return value as desired URB length.

Ensure that appropriate part of skb's tailroom exists and is zeroed.

Signed-off-by: Jakub Kicinski <kubakici@wp.pl>
Acked-by: Ivo van Doorn <IvDoorn@gmail.com>
--
 drivers/net/wireless/rt2x00/rt2x00usb.c |   16 +++++++++++++---
 1 files changed, 13 insertions(+), 3 deletions(-)
Signed-off-by: Gertjan van Wingerde <gwingerde@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 13 insertions, 3 deletions

diff --git a/drivers/net/wireless/rt2x00/rt2x00usb.c b/drivers/net/wireless/rt2x00/rt2x00usb.c
index 1e31050dafc9..2eea3866504d 100644
--- a/drivers/net/wireless/rt2x00/rt2x00usb.c
+++ b/drivers/net/wireless/rt2x00/rt2x00usb.c
@@ -298,12 +298,22 @@ static bool rt2x00usb_kick_tx_entry(struct queue_entry *entry, void* data)
                 return false;
 
         /*
-         * USB devices cannot blindly pass the skb->len as the
-         * length of the data to usb_fill_bulk_urb. Pass the skb
-         * to the driver to determine what the length should be.
+         * USB devices require certain padding at the end of each frame
+         * and urb. Those paddings are not included in skbs. Pass entry
+         * to the driver to determine what the overall length should be.
          */
         length = rt2x00dev->ops->lib->get_tx_data_len(entry);
 
+        status = skb_padto(entry->skb, length);
+        if (unlikely(status)) {
+                /* TODO: report something more appropriate than IO_FAILED. */
+                WARNING(rt2x00dev, "TX SKB padding error, out of memory\n");
+                set_bit(ENTRY_DATA_IO_FAILED, &entry->flags);
+                rt2x00lib_dmadone(entry);
+
+                return false;
+        }
+
         usb_fill_bulk_urb(entry_priv->urb, usb_dev,
                           usb_sndbulkpipe(usb_dev, entry->queue->usb_endpoint),
                           entry->skb->data, length,