On Thu, Jan 12, 2017 at 10:21:02AM -0500, David Miller wrote: > From: Simon Horman <horms+rene...@verge.net.au> > Date: Thu, 12 Jan 2017 14:53:37 +0100 > > > diff --git a/drivers/net/ethernet/renesas/ravb_main.c > > b/drivers/net/ethernet/renesas/ravb_main.c > > index 92d7692c840d..3b4d2504285e 100644 > > --- a/drivers/net/ethernet/renesas/ravb_main.c > > +++ b/drivers/net/ethernet/renesas/ravb_main.c > > @@ -1508,6 +1508,8 @@ static netdev_tx_t ravb_start_xmit(struct sk_buff > > *skb, struct net_device *ndev) > > buffer = PTR_ALIGN(priv->tx_align[q], DPTR_ALIGN) + > > entry / NUM_TX_DESC * DPTR_ALIGN; > > len = PTR_ALIGN(skb->data, DPTR_ALIGN) - skb->data; > > + if (len == 0) > > + len = skb->len > 4 ? 4 : skb->len; > > memcpy(buffer, skb->data, len); > > dma_addr = dma_map_single(ndev->dev.parent, buffer, len, DMA_TO_DEVICE); > > if (dma_mapping_error(ndev->dev.parent, dma_addr)) > > Assume len ends up being skb->len, then the second DMA mapping will be > made of zero length. > > This code needs a bit of TLC.
Thanks, I realised that after sending this patch. What I now see is that a few lines further up there is: if (skb_put_padto(skb, ETH_ZLEN)) goto drop; where ETH_ZLEN is 60. So I don't think we need to worry about skb->len being less than 60 and this patch can be simplified to: if (len == 0) len = 4;