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SubjectRe: [PATCH ref0] net: add Faraday FTMAC100 10/100 Ethernet driver
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Le jeudi 24 février 2011 à 18:39 +0100, Eric Dumazet a écrit :
> Le jeudi 24 février 2011 à 17:29 +0800, Po-Yu Chuang a écrit :
> > From: Po-Yu Chuang <ratbert@faraday-tech.com>
> >
>
>
> > +
> > +static bool ftmac100_rx_packet(struct ftmac100 *priv, int *processed)
> > +{
> > + struct net_device *netdev = priv->netdev;
> > + struct ftmac100_rxdes *rxdes;
> > + struct sk_buff *skb;
> > + struct page *page;
> > + dma_addr_t map;
> > + int length;
> > +
> > + rxdes = ftmac100_rx_locate_first_segment(priv);
> > + if (!rxdes)
> > + return false;
> > +
> > + if (unlikely(ftmac100_rx_packet_error(priv, rxdes))) {
> > + ftmac100_rx_drop_packet(priv);
> > + return true;
> > + }
> > +
> > + /*
> > + * It is impossible to get multi-segment packets
> > + * because we always provide big enough receive buffers.
> > + */
> > + if (unlikely(!ftmac100_rxdes_last_segment(rxdes)))
> > + BUG();
> > +
> > + /* start processing */
> > + skb = netdev_alloc_skb_ip_align(netdev, ETH_HLEN);
>
> Oh I see... You should allocate a bigger head (say... 128 bytes)
>
> And copy in it up to 128 bytes of first part... this to avoid upper
> stack to reallocate skb head (because IP/TCP processing need to get
> their headers in skb head)

Take a look at drivers/net/niu.c :

#define RX_SKB_ALLOC_SIZE 128 + NET_IP_ALIGN

static int niu_process_rx_pkt(...)
{
...
skb = netdev_alloc_skb(np->dev, RX_SKB_ALLOC_SIZE);
...
while (1) {
...
niu_rx_skb_append(skb, page, off, append_size);
}
}



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