Stephen Hemminger wrote:

On Tue, 19 Jan 2010 20:01:10 -0500
Michael Breuer [off-list ref] wrote:

quoted

On 1/19/2010 5:45 PM, Jarek Poplawski wrote:

[...]

quoted

quoted

--- a/drivers/net/sky2.c
+++ b/drivers/net/sky2.c

@@ -2252,12 +2252,14 @@ static struct sk_buff *receive_copy(struct sky2_port *sky2,
  	skb = netdev_alloc_skb_ip_align(sky2->netdev, length);
  	if (likely(skb)) {
  		pci_dma_sync_single_for_cpu(sky2->hw->pdev, re->data_addr,
-					    length, PCI_DMA_FROMDEVICE);
+					    pci_unmap_len(re, data_size),
+					    PCI_DMA_FROMDEVICE);
  		skb_copy_from_linear_data(re->skb, skb->data, length);
  		skb->ip_summed = re->skb->ip_summed;
  		skb->csum = re->skb->csum;
  		pci_dma_sync_single_for_device(sky2->hw->pdev, re->data_addr,
-					       length, PCI_DMA_FROMDEVICE);
+					       pci_unmap_len(re, data_size),
+					       PCI_DMA_FROMDEVICE);
  		re->skb->ip_summed = CHECKSUM_NONE;
  		skb_put(skb, length);
  	}
   

That not only compiled, but it cleared the error as well. Additionally, 
I used to see a bit of a delay receiving the login prompt when first 
connecting to the box by ssh. That delay is gone with this patch. I'd 
guess that the warning wasn't quite as innocuous as I thought.
Note: tested on 2.6.32.4.  I'll leave this up for a bit before 
attempting to move back to head.

Seems like an underlying bug in the DMA api. Maybe it just can't
handle operations on partial mapping.

Other drivers with same problem:
  bnx2, cassini, pcnet32, r8169, rrunner, skge, sungem, tg3, 

I didn't read the start of this thread and may misunderstand the issue,
but I comment anyway...:

Documentation/DMA-API.txt says the following about (pci_)dma_sync_single
and friends:  "All the parameters must be the same as those passed into
the single mapping API."
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=Documentation/DMA-API.txt;h=5aceb88b3f8b622c8c23ed288f37f42de705c904;hb=HEAD#l367

So, it might be considered an API bug --- but it is a documented one. :-)
-- 
Stefan Richter
-=====-==-=- ---= =-=-=
http://arcgraph.de/sr/