Re: [PATCH v2] net: add Faraday FTMAC100 10/100 Ethernet driver

Le lundi 17 janvier 2011 à 18:58 +0000, Ben Hutchings a écrit :

On Mon, 2011-01-17 at 18:29 +0100, Eric Dumazet wrote:

quoted

Le lundi 17 janvier 2011 à 17:21 +0800, Po-Yu Chuang a écrit :

quoted

+static int ftmac100_rx_packet(struct ftmac100 *priv, int *processed)
+{
+	struct net_device *netdev = priv->netdev;
+	struct ftmac100_rxdes *rxdes;
+	struct sk_buff *skb;
+	int length;
+	int copied = 0;
+	int done = 0;
+
+	rxdes = ftmac100_rx_locate_first_segment(priv);
+	if (!rxdes)
+		return 0;
+
+	length = ftmac100_rxdes_frame_length(rxdes);
+
+	netdev->stats.rx_packets++;
+	netdev->stats.rx_bytes += length;
+
+	if (unlikely(ftmac100_rx_packet_error(priv, rxdes))) {
+		ftmac100_rx_drop_packet(priv);
+		return 1;
+	}
+
+	/* start processing */
+	skb = netdev_alloc_skb_ip_align(netdev, length);
+	if (unlikely(!skb)) {
+		if (net_ratelimit())
+			netdev_err(netdev, "rx skb alloc failed\n");
+
+		ftmac100_rx_drop_packet(priv);
+		return 1;
+	}
+

Please dont increase rx_packets/rx_bytes before the
netdev_alloc_skb_ip_align().

In case of mem allocation failure, it would be better not pretending we
handled a packet.

drivers/net/r8169.c for example does the rx_packets/rx_bytes only if
packet is delivered to upper stack.

That's news to me.  I specifically advised Po-Yu Chuang to increment
these earlier because my understanding is that all packets/bytes should
be counted.  And drivers which use hardware MAC stats will generally do
that, so I really don't think it makes sense to make other drivers
different deliberately.

I see, but when one frame is dropped because of RX ring buffer
under/overflow we dont account for the lost packet/bytes.

Thats probably not very important, but would be good if all drivers
behave the same.