[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, 3 insertions, 3 deletions

diff --git a/drivers/net/tulip/winbond-840.c b/drivers/net/tulip/winbond-840.c
index db4b32c2369a..5b1af3986abf 100644
--- a/drivers/net/tulip/winbond-840.c
+++ b/drivers/net/tulip/winbond-840.c
@@ -849,7 +849,7 @@ static void init_rxtx_rings(struct net_device *dev)
                 if (skb == NULL)
                         break;
                 skb->dev = dev;                 /* Mark as being used by this device. */
-                np->rx_addr[i] = pci_map_single(np->pci_dev,skb->tail,
+                np->rx_addr[i] = pci_map_single(np->pci_dev,skb->data,
                                         skb->len,PCI_DMA_FROMDEVICE);
 
                 np->rx_ring[i].buffer1 = np->rx_addr[i];
@@ -1269,7 +1269,7 @@ static int netdev_rx(struct net_device *dev)
                                 pci_dma_sync_single_for_cpu(np->pci_dev,np->rx_addr[entry],
                                                             np->rx_skbuff[entry]->len,
                                                             PCI_DMA_FROMDEVICE);
-                                eth_copy_and_sum(skb, np->rx_skbuff[entry]->tail, pkt_len, 0);
+                                eth_copy_and_sum(skb, np->rx_skbuff[entry]->data, pkt_len, 0);
                                 skb_put(skb, pkt_len);
                                 pci_dma_sync_single_for_device(np->pci_dev,np->rx_addr[entry],
                                                                np->rx_skbuff[entry]->len,
@@ -1315,7 +1315,7 @@ static int netdev_rx(struct net_device *dev)
                                 break;                  /* Better luck next round. */
                         skb->dev = dev;                 /* Mark as being used by this device. */
                         np->rx_addr[entry] = pci_map_single(np->pci_dev,
-                                                        skb->tail,
+                                                        skb->data,
                                                         skb->len, PCI_DMA_FROMDEVICE);
                         np->rx_ring[entry].buffer1 = np->rx_addr[entry];
                 }