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[PATCH] fix natsemi PCI mapping

To: Netdev <netdev@xxxxxxxxxxx>, Tim Hockin <thockin@xxxxxxx>
Subject: [PATCH] fix natsemi PCI mapping
From: Jeff Garzik <jgarzik@xxxxxxxxx>
Date: Tue, 16 Mar 2004 13:06:31 -0500
Cc: Linux Kernel <linux-kernel@xxxxxxxxxxxxxxx>, ralf@xxxxxxxxxxxxxx, sjhill@xxxxxxxxxxxxxxxxxx
Sender: netdev-bounce@xxxxxxxxxxx
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.4) Gecko/20030703

Somebody wanna review and/or test?

Changes:
* Define RX_OFFSET constant (value==2) for uses related to SKB allocation and skb_reserve() calls

* RX skb's are always allocated maximally-sized, since we don't know the size of an RX packet in advance. This means that we always alloc and map RX skbs based on "np->rx_buf_sz + RX_OFFSET". natsemi got this really wrong in refill_rx(), where it mapped skb->len just after dev_alloc_skb(), which was very incorrect.

* call skb_reserve() in refill_rx(), our main skb allocation function, just after dev_alloc_skb() returns successfully


===== drivers/net/natsemi.c 1.58 vs edited =====
--- 1.58/drivers/net/natsemi.c  Sun Mar 14 01:54:58 2004
+++ edited/drivers/net/natsemi.c        Tue Mar 16 13:02:04 2004
@@ -175,6 +175,8 @@
 #define DRV_VERSION    "1.07+LK1.0.17"
 #define DRV_RELDATE    "Sep 27, 2002"
 
+#define RX_OFFSET      2
+
 /* Updated to recommendations in pci-skeleton v2.03. */
 
 /* The user-configurable values.
@@ -1467,13 +1469,16 @@
                struct sk_buff *skb;
                int entry = np->dirty_rx % RX_RING_SIZE;
                if (np->rx_skbuff[entry] == NULL) {
-                       skb = dev_alloc_skb(np->rx_buf_sz);
+                       unsigned int buflen = np->rx_buf_sz + RX_OFFSET;
+                       skb = dev_alloc_skb(buflen);
                        np->rx_skbuff[entry] = skb;
                        if (skb == NULL)
                                break; /* Better luck next round. */
                        skb->dev = dev; /* Mark as being used by this device. */
+                       /* 16 byte align the IP header */
+                       skb_reserve(skb, RX_OFFSET);
                        np->rx_dma[entry] = pci_map_single(np->pci_dev,
-                               skb->data, skb->len, PCI_DMA_FROMDEVICE);
+                               skb->tail, buflen, PCI_DMA_FROMDEVICE);
                        np->rx_ring[entry].addr = 
cpu_to_le32(np->rx_dma[entry]);
                }
                np->rx_ring[entry].cmd_status = cpu_to_le32(np->rx_buf_sz);
@@ -1543,6 +1548,7 @@
 static void drain_ring(struct net_device *dev)
 {
        struct netdev_private *np = dev->priv;
+       unsigned int buflen = np->rx_buf_sz + RX_OFFSET;
        int i;
 
        /* Free all the skbuffs in the Rx queue. */
@@ -1551,7 +1557,7 @@
                np->rx_ring[i].addr = 0xBADF00D0; /* An invalid address. */
                if (np->rx_skbuff[i]) {
                        pci_unmap_single(np->pci_dev,
-                               np->rx_dma[i], np->rx_skbuff[i]->len,
+                               np->rx_dma[i], buflen,
                                PCI_DMA_FROMDEVICE);
                        dev_kfree_skb(np->rx_skbuff[i]);
                }
@@ -1747,6 +1753,7 @@
        int entry = np->cur_rx % RX_RING_SIZE;
        int boguscnt = np->dirty_rx + RX_RING_SIZE - np->cur_rx;
        s32 desc_status = le32_to_cpu(np->rx_head_desc->cmd_status);
+       unsigned int buflen = np->rx_buf_sz + RX_OFFSET;
 
        /* If the driver owns the next entry it's a new packet. Send it up. */
        while (desc_status < 0) { /* e.g. & DescOwn */
@@ -1785,13 +1792,13 @@
                        /* Check if the packet is long enough to accept
                         * without copying to a minimally-sized skbuff. */
                        if (pkt_len < rx_copybreak
-                           && (skb = dev_alloc_skb(pkt_len + 2)) != NULL) {
+                           && (skb = dev_alloc_skb(pkt_len + RX_OFFSET)) != 
NULL) {
                                skb->dev = dev;
                                /* 16 byte align the IP header */
-                               skb_reserve(skb, 2);
+                               skb_reserve(skb, RX_OFFSET);
                                pci_dma_sync_single_for_cpu(np->pci_dev,
                                        np->rx_dma[entry],
-                                       np->rx_skbuff[entry]->len,
+                                       buflen,
                                        PCI_DMA_FROMDEVICE);
 #if HAS_IP_COPYSUM
                                eth_copy_and_sum(skb,
@@ -1803,12 +1810,11 @@
 #endif
                                pci_dma_sync_single_for_device(np->pci_dev,
                                        np->rx_dma[entry],
-                                       np->rx_skbuff[entry]->len,
+                                       buflen,
                                        PCI_DMA_FROMDEVICE);
                        } else {
                                pci_unmap_single(np->pci_dev, np->rx_dma[entry],
-                                       np->rx_skbuff[entry]->len,
-                                       PCI_DMA_FROMDEVICE);
+                                       buflen, PCI_DMA_FROMDEVICE);
                                skb_put(skb = np->rx_skbuff[entry], pkt_len);
                                np->rx_skbuff[entry] = NULL;
                        }
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