net/sonic: Remove redundant next_tx variable

The eol_tx variable is the one that matters to the tx algorithm because
packets are always placed at the end of the list. The next_tx variable
just confuses things so remove it.
Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/natsemi/sonic.c

@@ -300,7 +300,7 @@ static int sonic_send_packet(struct sk_buff *skb, struct net_device *dev)
 
 	spin_lock_irqsave(&lp->lock, flags);
 
-	entry = lp->next_tx;
+	entry = (lp->eol_tx + 1) & SONIC_TDS_MASK;
 
 	sonic_tda_put(dev, entry, SONIC_TD_STATUS, 0);       /* clear status */
 	sonic_tda_put(dev, entry, SONIC_TD_FRAG_COUNT, 1);   /* single fragment */
@@ -321,8 +321,8 @@ static int sonic_send_packet(struct sk_buff *skb, struct net_device *dev)
 				  sonic_tda_get(dev, lp->eol_tx, SONIC_TD_LINK) & ~SONIC_EOL);
 	lp->eol_tx = entry;
 
-	lp->next_tx = (entry + 1) & SONIC_TDS_MASK;
-	if (lp->tx_skb[lp->next_tx] != NULL) {
+	entry = (entry + 1) & SONIC_TDS_MASK;
+	if (lp->tx_skb[entry]) {
 		/* The ring is full, the ISR has yet to process the next TD. */
 		netif_dbg(lp, tx_queued, dev, "%s: stopping queue\n", __func__);
 		netif_stop_queue(dev);
@@ -811,7 +811,7 @@ static int sonic_init(struct net_device *dev)
 
 	SONIC_WRITE(SONIC_UTDA, lp->tda_laddr >> 16);
 	SONIC_WRITE(SONIC_CTDA, lp->tda_laddr & 0xffff);
-	lp->cur_tx = lp->next_tx = 0;
+	lp->cur_tx = 0;
 	lp->eol_tx = SONIC_NUM_TDS - 1;
 
 	/*

drivers/net/ethernet/natsemi/sonic.h

@@ -321,7 +321,6 @@ struct sonic_local {
 	unsigned int cur_tx;           /* first unacked transmit packet */
 	unsigned int eol_rx;
 	unsigned int eol_tx;           /* last unacked transmit packet */
-	unsigned int next_tx;          /* next free TD */
 	int msg_enable;
 	struct device *device;         /* generic device */
 	struct net_device_stats stats;