pegasus: Use heap buffers for all register access

Allocating USB buffers on the stack is not portable, and no longer
works on x86_64 (with VMAP_STACK enabled as per default).

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
References: https://bugs.debian.org/852556
Reported-by: Lisandro Damián Nicanor Pérez Meyer <lisandro@debian.org>
Tested-by: Lisandro Damián Nicanor Pérez Meyer <lisandro@debian.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
static netdev_tx_t pegasus_start_xmit(struct sk_buff *skb,
					    struct net_device *net)
{
	pegasus_t *pegasus = netdev_priv(net);
	int count = ((skb->len + 2) & 0x3f) ? skb->len + 2 : skb->len + 3;
	int res;
	__u16 l16 = skb->len;

	netif_stop_queue(net);

	((__le16 *) pegasus->tx_buff)[0] = cpu_to_le16(l16);
	skb_copy_from_linear_data(skb, pegasus->tx_buff + 2, skb->len);
	usb_fill_bulk_urb(pegasus->tx_urb, pegasus->usb,
			  usb_sndbulkpipe(pegasus->usb, 2),
			  pegasus->tx_buff, count,
			  write_bulk_callback, pegasus);
	if ((res = usb_submit_urb(pegasus->tx_urb, GFP_ATOMIC))) {
		netif_warn(pegasus, tx_err, net, "fail tx, %d\n", res);
		switch (res) {
		case -EPIPE:		/* stall, or disconnect from TT */
			/* cleanup should already have been scheduled */
			break;
		case -ENODEV:		/* disconnect() upcoming */
		case -EPERM:
			netif_device_detach(pegasus->net);
			break;
		default:
			pegasus->stats.tx_errors++;
			netif_start_queue(net);
		}
	} else {
		pegasus->stats.tx_packets++;
		pegasus->stats.tx_bytes += skb->len;
	}
	dev_kfree_skb(skb);

	return NETDEV_TX_OK;
}

static netdev_tx_t pegasus_start_xmit(struct sk_buff *skb,
					    struct net_device *net)
{
	pegasus_t *pegasus = netdev_priv(net);
	int count = ((skb->len + 2) & 0x3f) ? skb->len + 2 : skb->len + 3;
	int res;
	__u16 l16 = skb->len;

	netif_stop_queue(net);

	((__le16 *) pegasus->tx_buff)[0] = cpu_to_le16(l16);
	skb_copy_from_linear_data(skb, pegasus->tx_buff + 2, skb->len);
	usb_fill_bulk_urb(pegasus->tx_urb, pegasus->usb,
			  usb_sndbulkpipe(pegasus->usb, 2),
			  pegasus->tx_buff, count,
			  write_bulk_callback, pegasus);
	if ((res = usb_submit_urb(pegasus->tx_urb, GFP_ATOMIC))) {
		netif_warn(pegasus, tx_err, net, "fail tx, %d\n", res);
		switch (res) {
		case -EPIPE:		/* stall, or disconnect from TT */
			/* cleanup should already have been scheduled */
			break;
		case -ENODEV:		/* disconnect() upcoming */
		case -EPERM:
			netif_device_detach(pegasus->net);
			break;
		default:
			pegasus->stats.tx_errors++;
			netif_start_queue(net);
		}
	} else {
		pegasus->stats.tx_packets++;
		pegasus->stats.tx_bytes += skb->len;
	}
	dev_kfree_skb(skb);

	return NETDEV_TX_OK;
}
