linux-kernel - Re: [RFC PATCH v4 linux-next] et131x: Promote staging et131x driver to drivers/net

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Message-Id: <20130128.231057.57111832691623178.davem@davemloft.net>
Date:	Mon, 28 Jan 2013 23:10:57 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	mark.einon@...il.com
Cc:	gregkh@...uxfoundation.org, sfr@...b.auug.org.au,
	netdev@...r.kernel.org, devel@...verdev.osuosl.org,
	linux-kernel@...r.kernel.org, dan.carpenter@...cle.com
Subject: Re: [RFC PATCH v4 linux-next] et131x: Promote staging et131x
 driver to drivers/net

From: Mark Einon <mark.einon@...il.com>
Date: Wed, 23 Jan 2013 16:24:38 +0000

> +endif # NET_VENDOR_AGERE
> +

Trailing empty line, delete it.

> @@ -0,0 +1,6 @@
> +#
> +# Makefile for the Agere ET-131x ethernet driver
> +#
> +
> +obj-$(CONFIG_ET131X) += et131x.o
> +

Likewise, get rid of this trailing empty line.

> +	/* Spinlocks */
> +	spinlock_t lock;
> +
> +	spinlock_t tcb_send_qlock;
> +	spinlock_t tcb_ready_qlock;
> +	spinlock_t send_hw_lock;
> +
> +	spinlock_t rcv_lock;
> +	spinlock_t rcv_pend_lock;
> +	spinlock_t fbr_lock;
> +
> +	spinlock_t phy_lock;

Do you really need _8_ spinlocks in an ethernet driver?  To me that's
way over the top and excessive.

The most recent driver I've written, for the 10Gbit Sun NIU parts,
has only one spinlock.

> +	/* Determine if this is a multicast packet coming in */

What in the world are you doing in this huge code block?

Such much complexity, multicast list iteration, etc. just to get some
statistics correct?  This stuff is going to run on every multicast
packet receive.

No other driver does crap like this, get rid of this stuff.

> +	skb->dev = adapter->netdev;
> +	skb->protocol = eth_type_trans(skb, adapter->netdev);

eth_type_trans() sets skb->dev, you don't need to duplicate that.

> +	netif_rx_ni(skb);

Why isn't this driver supporting NAPI?  If you're going to put this
much time into a driver, use the best interfaces for event processing
rather than something that might have been appropriate in a new driver
two decades ago.

> +static int et131x_tx(struct sk_buff *skb, struct net_device *netdev)
> +{
> +	int status = 0;
> +	struct et131x_adapter *adapter = netdev_priv(netdev);
> +
> +	/* stop the queue if it's getting full */
> +	if (adapter->tx_ring.used >= NUM_TCB - 1 &&
> +	    !netif_queue_stopped(netdev))
> +		netif_stop_queue(netdev);
> +
> +	/* Save the timestamp for the TX timeout watchdog */
> +	netdev->trans_start = jiffies;
> +
> +	/* Call the device-specific data Tx routine */
> +	status = et131x_send_packets(skb, netdev);
> +
> +	/* Check status and manage the netif queue if necessary */
> +	if (status != 0) {
> +		if (status == -ENOMEM)
> +			status = NETDEV_TX_BUSY;
> +		else
> +			status = NETDEV_TX_OK;
> +	}
> +	return status;
> +}

Returning NETDEV_TX_BUSY is an error, no driver should ever return
that status under normal circumstances.  Some drivers return it
when internal consistency checks fail, but that indicates a driver
bug rather than a normal condition.

Memory allocation erorrs do not denote NETDEV_TX_BUSY, simply drop
the packet silently with kfree_skb() and return NETDEV_TX_OK.

That's about enough for me, this driver still needs a lot of work
and is far from being ready to move out of staging.
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