Messages in this thread | | | Date | Sat, 7 Aug 2004 17:05:03 -0700 | From | "David S. Miller" <> | Subject | Re: [PATCH] b44 1GB DMA workaround (was: b44: add 47xx support) |
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On Sun, 8 Aug 2004 01:40:19 +0300 Pekka Pietikainen <pp@ee.oulu.fi> wrote:
> On Tue, Aug 03, 2004 at 06:39:19PM -0700, David S. Miller wrote: > > Changing skb->data is not legal. Please implement this in > > such a way that skb->data does not get modified. By modifying > > skb->data you will break things such as packet sniffers and > > netfilter, and that's just the tip of the iceberg. :-) > > > Haven't noticed any breakage (tm) but I'm just a x86 weenie :-)
Not an x86 specific problem :-) Just run tcpdump in a shell when one of these TX bounce cases happen, your skb->data modification could will make tcpdump see a corrupt packet.
> Current approach is: > > if(1 (just for testing ;) ) || mapping+len > B44_DMA_MASK) { > /* Chip can't handle DMA to/from >1GB, use bounce buffer */ > pci_unmap_single(bp->pdev, mapping, len,PCI_DMA_TODEVICE); > memcpy(bp->tx_bufs+entry*TX_PKT_BUF_SZ,skb->data,skb->len); > mapping = pci_map_single(bp->pdev,bp->tx_bufs+entry*TX_PKT_BUF_SZ, len, PCI_DMA_TODEVICE); > }
This looks a bit better. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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