netdev - Re: [PATCH net] tulip: Properly check dma mapping result

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Date:	Thu, 13 Jun 2013 15:26:14 -0700
From:	Grant Grundler <grantgrundler@...il.com>
To:	Neil Horman <nhorman@...driver.com>
Cc:	"open list:TULIP NETWORK DRI..." <netdev@...r.kernel.org>,
	Grant Grundler <grundler@...isc-linux.org>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH net] tulip: Properly check dma mapping result

On Thu, Jun 13, 2013 at 12:31 PM, Neil Horman <nhorman@...driver.com> wrote:
> Tulip throws an error when dma debugging is enabled, as it doesn't properly
> check dma mapping results with dma_mapping_error() durring tx ring refills.
>
> Easy fix, just add it in, and drop the frame if the mapping is bad
>
> Signed-off-by: Neil Horman <nhorman@...driver.com>
> CC: Grant Grundler <grundler@...isc-linux.org>

LGTM. thanks!

Reviewed-by: Grant Grundler <grundler@...isc-linux.org>

FYA: the original DMA mapping interface that was introduce in 2.4 did
not return errors. It would panic the system. The reasoning at the
time was (I'm paraphrasing): "Driver writers won't check the erorr or
handle it correctly so don't make it more complicated.

cheers,
grant

> CC: "David S. Miller" <davem@...emloft.net>
> ---
>  drivers/net/ethernet/dec/tulip/interrupt.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/net/ethernet/dec/tulip/interrupt.c b/drivers/net/ethernet/dec/tulip/interrupt.c
> index 28a5e42..92306b3 100644
> --- a/drivers/net/ethernet/dec/tulip/interrupt.c
> +++ b/drivers/net/ethernet/dec/tulip/interrupt.c
> @@ -76,6 +76,12 @@ int tulip_refill_rx(struct net_device *dev)
>
>                         mapping = pci_map_single(tp->pdev, skb->data, PKT_BUF_SZ,
>                                                  PCI_DMA_FROMDEVICE);
> +                       if (dma_mapping_error(&tp->pdev->dev, mapping)) {
> +                               dev_kfree_skb(skb);
> +                               tp->rx_buffers[entry].skb = NULL;
> +                               break;
> +                       }
> +
>                         tp->rx_buffers[entry].mapping = mapping;
>
>                         tp->rx_ring[entry].buffer1 = cpu_to_le32(mapping);
> --
> 1.8.1.4
>
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