[NET]: Remove gratuitous use of skb->tail in network drivers.

Many drivers use skb->tail unnecessarily.

In these situations, the code roughly looks like:

	dev = dev_alloc_skb(...);

	[optional] skb_reserve(skb, ...);

	... skb->tail ...

But even if the skb_reserve() happens, skb->data equals
skb->tail.  So it doesn't make any sense to use anything
other than skb->data in these cases.

Another case was the s2io.c driver directly mucking with
the skb->data and skb->tail pointers.  It really just wanted
to do an skb_reserve(), so that's what the code was changed
to do instead.

Another reason I'm making this change as it allows some SKB
cleanups I have planned simpler to merge.  In those cleanups,
skb->head, skb->tail, and skb->end pointers are removed, and
replaced with skb->head_room and skb->tail_room integers.

Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Jeff Garzik <jgarzik@pobox.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/net/tulip/xircom_tulip_cb.c b/drivers/net/tulip/xircom_tulip_cb.c
index b8a9b395c5ea..887d7245fe7b 100644
--- a/drivers/net/tulip/xircom_tulip_cb.c
+++ b/drivers/net/tulip/xircom_tulip_cb.c
@@ -899,7 +899,7 @@ static void xircom_init_ring(struct net_device *dev)
 			break;
 		skb->dev = dev;			/* Mark as being used by this device. */
 		tp->rx_ring[i].status = Rx0DescOwned;	/* Owned by Xircom chip */
-		tp->rx_ring[i].buffer1 = virt_to_bus(skb->tail);
+		tp->rx_ring[i].buffer1 = virt_to_bus(skb->data);
 	}
 	tp->dirty_rx = (unsigned int)(i - RX_RING_SIZE);
 
@@ -1291,7 +1291,7 @@ xircom_rx(struct net_device *dev)
 			if (skb == NULL)
 				break;
 			skb->dev = dev;			/* Mark as being used by this device. */
-			tp->rx_ring[entry].buffer1 = virt_to_bus(skb->tail);
+			tp->rx_ring[entry].buffer1 = virt_to_bus(skb->data);
 			work_done++;
 		}
 		tp->rx_ring[entry].status = Rx0DescOwned;