linux-kernel - Re: [PATCH v5] net: ethernet: add driver for Aurora VLSI NB8800 Ethernet controller

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Date:	Tue, 10 Nov 2015 18:05:15 +0000
From:	Måns Rullgård <mans@...sr.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	slash.tmp@...e.fr
Subject: Re: [PATCH v5] net: ethernet: add driver for Aurora VLSI NB8800 Ethernet controller

Eric Dumazet <eric.dumazet@...il.com> writes:

> On Tue, 2015-11-10 at 16:14 +0000, Mans Rullgard wrote:
>> This adds a driver for the Aurora VLSI NB8800 Ethernet controller.
>> It is an almost complete rewrite of a driver originally found in
>> a Sigma Designs 2.6.22 tree.
>
> ...
>
>> +
>> +static void nb8800_receive(struct net_device *dev, int i, int len)
>> +{
>> +	struct nb8800_priv *priv = netdev_priv(dev);
>> +	struct nb8800_rx_desc *rxd = &priv->rx_descs[i];
>> +	struct page *page = priv->rx_bufs[i].page;
>> +	int offset = priv->rx_bufs[i].offset;
>> +	void *data = page_address(page) + offset;
>> +	dma_addr_t dma = rxd->desc.s_addr;
>> +	struct sk_buff *skb;
>> +	int size;
>> +	int err;
>> +
>> +	size = len <= RX_COPYBREAK ? len : RX_COPYHDR;
>> +
>> +	skb = napi_alloc_skb(&priv->napi, size);
>> +	if (!skb) {
>> +		netdev_err(dev, "rx skb allocation failed\n");
>> +		dev->stats.rx_dropped++;
>> +		return;
>> +	}
>> +
>> +	if (len <= RX_COPYBREAK) {
>> +		dma_sync_single_for_cpu(&dev->dev, dma, len, DMA_FROM_DEVICE);
>> +		memcpy(skb_put(skb, len), data, len);
>> +		dma_sync_single_for_device(&dev->dev, dma, len,
>> +					   DMA_FROM_DEVICE);
>> +	} else {
>> +		err = nb8800_alloc_rx(dev, i, true);
>> +		if (err) {
>> +			netdev_err(dev, "rx buffer allocation failed\n");
>> +			dev->stats.rx_dropped++;
>> +			return;
>> +		}
>> +
>> +		dma_unmap_page(&dev->dev, dma, RX_BUF_SIZE, DMA_FROM_DEVICE);
>> +		memcpy(skb_put(skb, RX_COPYHDR), data, RX_COPYHDR);
>> +		skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags, page,
>> +				offset + RX_COPYHDR, len - RX_COPYHDR,
>> +				RX_BUF_SIZE);
>> +	}
>> +
>> +	skb->protocol = eth_type_trans(skb, dev);
>> +	netif_receive_skb(skb);
>> +}
>> +
>
> Any reason you do not use napi_gro_receive(&priv->napi, skb) instead of
> netif_receive_skb() ?

Because I haven't been following the netdev list closely for the last
five years, and no documentation I read mentioned this function.  I can
certainly change it.

-- 
Måns Rullgård
mans@...sr.com
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