net1080.c

讲述linux的初始化过程

		// netif_device_detach (&dev->net);
		// FALLTHROUGH
			
	    // software-driven interface shutdown
	    case -ECONNRESET:
		entry->state = rx_cleanup;
		usb_free_urb (urb);
		urb = 0;
		dbg ("%s ... shutdown rx (%d)", dev->net.name, urb_status);
		break;

	    // data overrun ... flush fifo?
	    case -EOVERFLOW:
		dev->stats.rx_over_errors++;
		// FALLTHROUGH
	    
	    default:
		entry->state = rx_cleanup;
		dev->stats.rx_errors++;
		err ("%s rx: status %d", dev->net.name, urb_status);
		break;
	}
	defer_bh (dev, skb);

	if (urb) {
		if (!netif_queue_stopped (&dev->net)) {
			rx_submit (dev, urb, GFP_ATOMIC);
			return;
		} else
			usb_free_urb (urb);
	}
#ifdef	VERBOSE
	dbg ("no read resubmitted");
#endif	VERBOSE
}

/*-------------------------------------------------------------------------*/

// unlink pending rx/tx; completion handlers do all other cleanup

static int unlink_urbs (struct sk_buff_head *q)
{
	unsigned long		flags;
	struct sk_buff		*skb;
	struct skb_data		*entry;
	int			retval;
	int			count = 0;

	spin_lock_irqsave (&q->lock, flags);
	for (skb = q->next; skb != (struct sk_buff *) q; skb = skb->next) {
		entry = (struct skb_data *) skb->cb;
		entry->urb->transfer_flags |= USB_ASYNC_UNLINK;
		retval = usb_unlink_urb (entry->urb);
		if (retval < 0)
			dbg ("unlink urb err, %d", retval);
		else
			count++;
	}
	spin_unlock_irqrestore (&q->lock, flags);
	return count;
}


/*-------------------------------------------------------------------------*/

// precondition: never called in_interrupt

static int net1080_stop (struct net_device *net)
{
	struct net1080		*dev = (struct net1080 *) net->priv;
	int			temp;
	DECLARE_WAIT_QUEUE_HEAD (unlink_wakeup); 
	DECLARE_WAITQUEUE (wait, current);

	mutex_lock (&dev->mutex);
	
	dbg ("%s stop stats: rx/tx %ld/%ld, errs %ld/%ld", net->name,
		dev->stats.rx_packets, dev->stats.tx_packets, 
		dev->stats.rx_errors, dev->stats.tx_errors
		);

	netif_stop_queue(net);

	// ensure there are no more active urbs
	add_wait_queue (&unlink_wakeup, &wait);
	dev->wait = &unlink_wakeup;
	temp = unlink_urbs (&dev->txq) + unlink_urbs (&dev->rxq);

	// maybe wait for deletions to finish.
	if (temp) {
		current->state = TASK_UNINTERRUPTIBLE;
		schedule ();
		dbg ("waited for %d urb completions", temp);
	}
	dev->wait = 0;
	current->state = TASK_RUNNING;
	remove_wait_queue (&unlink_wakeup, &wait); 

	mutex_unlock (&dev->mutex);
	MOD_DEC_USE_COUNT;
	return 0;
}

/*-------------------------------------------------------------------------*/

// posts a read, and enables write queing

// precondition: never called in_interrupt

static int net1080_open (struct net_device *net)
{
	struct net1080		*dev = (struct net1080 *) net->priv;
	int			retval;
	u16			status;
	int			i;

	MOD_INC_USE_COUNT;
	mutex_lock (&dev->mutex);

	// insist peer be connected -- is this the best place?
	if ((retval = register_read (dev, REG_STATUS, &status)) != 0) {
		dbg ("%s open: status read failed - %d", net->name, retval);
		goto done;
	}
	if ((status & STATUS_CONN_OTHER) != STATUS_CONN_OTHER)  {
		retval = -ENOLINK;
		dbg ("%s open: peer not connected", net->name);
		goto done;
	}

	MOD_INC_USE_COUNT;
	netif_start_queue (net);
	for (i = 0; i < RX_QLEN; i++)
		rx_submit (dev, usb_alloc_urb (0), GFP_KERNEL);

	dbg ("%s open: started queueing (rx %d, tx %d)",
		net->name, RX_QLEN, TX_QLEN);
done:
	mutex_unlock (&dev->mutex);
	MOD_DEC_USE_COUNT;
	return retval;
}

/*-------------------------------------------------------------------------*/

static void tx_complete (struct urb *urb)
{
	struct sk_buff		*skb = (struct sk_buff *) urb->context;
	struct skb_data		*entry = (struct skb_data *) skb->cb;
	struct net1080		*dev = entry->dev;

	urb->dev = 0;
	entry->state = tx_done;
	defer_bh (dev, skb);
	netif_wake_queue (&dev->net);
}

/*-------------------------------------------------------------------------*/

static struct sk_buff *fixup_skb (struct sk_buff *skb)
{
	int			padlen;
	struct sk_buff		*skb2;

	padlen = ((skb->len + sizeof (struct nc_header)
			+ sizeof (struct nc_trailer)) & 0x01) ? 0 : 1;
	if (!skb_cloned (skb)) {
		int	headroom = skb_headroom (skb);
		int	tailroom = skb_tailroom (skb);

		if ((padlen + sizeof (struct nc_trailer)) <= tailroom
			    && sizeof (struct nc_header) <= headroom)
			return skb;

		if ((sizeof (struct nc_header) + padlen
					+ sizeof (struct nc_trailer)) <
				(headroom + tailroom)) {
			skb->data = memmove (skb->head
						+ sizeof (struct nc_header),
					    skb->data, skb->len);
			skb->tail = skb->data + skb->len;
			return skb;
		}
	}
	skb2 = skb_copy_expand (skb,
				sizeof (struct nc_header),
				sizeof (struct nc_trailer) + padlen,
				in_interrupt () ? GFP_ATOMIC : GFP_KERNEL);
	dev_kfree_skb_any (skb);
	return skb2;
}

/*-------------------------------------------------------------------------*/

static int net1080_start_xmit (struct sk_buff *skb, struct net_device *net)
{
	struct net1080		*dev = (struct net1080 *) net->priv;
	int			length = skb->len;
	int			retval = 0;
	struct urb		*urb = 0;
	struct skb_data		*entry;
	struct nc_header	*header;
	struct nc_trailer	*trailer;
	unsigned long		flags;

	if ((skb = fixup_skb (skb)) == 0) {
		dbg ("can't fixup skb");
		goto drop;
	}
	if ((urb = usb_alloc_urb (0)) == 0) {
		dbg ("no urb");
		goto drop;
	}

	entry = (struct skb_data *) skb->cb;
	entry->urb = urb;
	entry->dev = dev;
	entry->state = tx_start;
	entry->length = length;

	header = (struct nc_header *) skb_push (skb, sizeof *header);
	header->hdr_len = cpu_to_le16 (sizeof (*header));
	header->packet_len = cpu_to_le16 (length);
	if (!((skb->len + sizeof *trailer) & 0x01))
		*skb_put (skb, 1) = NC_PAD_BYTE;
	trailer = (struct nc_trailer *) skb_put (skb, sizeof *trailer);

	FILL_BULK_URB (urb, dev->udev,
			usb_sndbulkpipe (dev->udev, 1),
			skb->data, skb->len, tx_complete, skb);
	urb->transfer_flags |= USB_QUEUE_BULK;
	// FIXME urb->timeout = ...;

	spin_lock_irqsave (&dev->txq.lock, flags);
	if (!netif_queue_stopped (&dev->net)) {
		header->packet_id = cpu_to_le16 (dev->packet_id++);
		put_unaligned (header->packet_id, &trailer->packet_id);

		netif_stop_queue (net);
		if ((retval = usb_submit_urb (urb)) != 0) {
			netif_start_queue (net);
			dbg ("%s tx: submit urb err %d", net->name, retval);
		} else {
			net->trans_start = jiffies;
			__skb_queue_tail (&dev->txq, skb);
			if (dev->txq.qlen < TX_QLEN)
				netif_start_queue (net);
		}
	} else
		retval = -ENOLINK;
	spin_unlock_irqrestore (&dev->txq.lock, flags);

	if (retval) {
		dbg ("drop");
drop:
		dev->stats.tx_dropped++;
		dev_kfree_skb_any (skb);
		usb_free_urb (urb);
#ifdef	VERBOSE
	} else {
		dbg ("%s: tx %p len %d", net->name, skb, length);
#endif
	}
	return retval;
}


/*-------------------------------------------------------------------------*/

static void rx_process (struct net1080 *dev, struct sk_buff *skb)
{
	struct nc_header	*header;
	struct nc_trailer	*trailer;

	header = (struct nc_header *) skb->data;
	le16_to_cpus (&header->hdr_len);
	le16_to_cpus (&header->packet_len);
	if (header->packet_len > MAX_PACKET) {
		dev->stats.rx_frame_errors++;
		dbg ("packet too big, %d", header->packet_len);
		goto error;
	} else if (header->hdr_len < NC_MIN_HEADER) {
		dev->stats.rx_frame_errors++;
		dbg ("header too short, %d", header->hdr_len);
		goto error;
	} else if (header->hdr_len > header->packet_len) {
		dev->stats.rx_frame_errors++;
		dbg ("header too big, %d packet %d", header->hdr_len, header->packet_len);
		goto error;
	} else if (header->hdr_len != sizeof *header) {
		// out of band data for us?
		dbg ("header OOB, %d bytes", header->hdr_len - NC_MIN_HEADER);
		// switch (vendor/product ids) { ... }
	}
	skb_pull (skb, header->hdr_len);

	trailer = (struct nc_trailer *)
		(skb->data + skb->len - sizeof *trailer);
	skb_trim (skb, skb->len - sizeof *trailer);

	if ((header->packet_len & 0x01) == 0) {
		if (skb->data [header->packet_len] != NC_PAD_BYTE) {
			dev->stats.rx_frame_errors++;
			dbg ("bad pad");
			goto error;
		}
		skb_trim (skb, skb->len - 1);
	}
	if (skb->len != header->packet_len) {
		dev->stats.rx_length_errors++;
		dbg ("bad packet len %d (expected %d)",
			skb->len, header->packet_len);
		goto error;
	}
	if (header->packet_id != get_unaligned (&trailer->packet_id)) {
		dev->stats.rx_fifo_errors++;
		dbg ("(2+ dropped) rx packet_id mismatch 0x%x 0x%x",
			header->packet_id, trailer->packet_id);
		goto error;
	}

	if (skb->len) {
		skb->dev = &dev->net;
		skb->protocol = eth_type_trans (skb, &dev->net);
		dev->stats.rx_packets++;
		dev->stats.rx_bytes += skb->len;

#ifdef	VERBOSE
		dbg ("%s: rx %p len %d, type 0x%x, id 0x%x",
			dev->net.name, skb, skb->len, skb->protocol,
			le16_to_cpu (header->packet_id));
#endif
		netif_rx (skb);
	} else {
		dbg ("drop");
error:
		dev->stats.rx_errors++;
		dev_kfree_skb (skb);
	}
}

/*-------------------------------------------------------------------------*/

// tasklet

// We can have a state machine in this tasklet monitor the link state,
// using async control messaging and calling attach/detach routines.

// But then some listener ought to respond to the changes; do those
// network attach/detach notifications get to userland somehow, such
// as by calling "ifup usb0" and "ifdown usb0"?

static void net1080_bh (unsigned long param)
{
	struct net1080		*dev = (struct net1080 *) param;
	struct sk_buff		*skb;
	struct skb_data		*entry;

	while ((skb = skb_dequeue (&dev->done))) {
		entry = (struct skb_data *) skb->cb;
		switch (entry->state) {
		    case rx_done:
			rx_process (dev, skb);
			continue;
		    case tx_done:
			if (entry->urb->status) {
				// can this statistic become more specific?
				dev->stats.tx_errors++;
				dbg ("%s tx: err %d", dev->net.name,
					entry->urb->status);
			} else {
				dev->stats.tx_packets++;
				dev->stats.tx_bytes += entry->length;
			}
			// FALLTHROUGH:
		    case rx_cleanup:
			usb_free_urb (entry->urb);
			dev_kfree_skb (skb);
			continue;
		    default:
			dbg ("%s: bogus skb state %d",
				dev->net.name, entry->state);
		}
	}

	// waiting for all pending urbs to complete?
	if (dev->wait) {
		if ((dev->txq.qlen + dev->rxq.qlen + dev->done.qlen) == 0) {
			wake_up (dev->wait);
		}

	// or are we maybe short a few urbs?
	} else if (!netif_queue_stopped (&dev->net)) {
		if (dev->rxq.qlen < TX_QLEN) {
			struct urb	*urb;
			int		i;
			for (i = 0; i < 3 && dev->rxq.qlen < TX_QLEN; i++) {
				if ((urb = usb_alloc_urb (0)) != 0)
					rx_submit (dev, urb, GFP_ATOMIC);
			}
			dbg ("%s: rxqlen now %d",
				dev->net.name, dev->rxq.qlen);
		}
	}
}

/*-------------------------------------------------------------------------
 *
 * USB Device Driver support
 *
 --------------------------------------------------------------------------*/
 
// precondition: never called in_interrupt

static void net1080_disconnect (struct usb_device *udev, void *ptr)
{
	struct net1080	*dev = (struct net1080 *) ptr;

	info ("%s: USB %d dev %d, %s, disconnected",
		dev->net.name,
		udev->bus->busnum, udev->devnum,
		(char *) dev->prod_info->driver_info);
	
	unregister_netdev (&dev->net);

	mutex_lock (&net1080_mutex);
	mutex_lock (&dev->mutex);
	list_del (&dev->dev_list);
	mutex_unlock (&net1080_mutex);

#ifdef DEBUG
	memset (dev, 0x55, sizeof *dev);
#endif
	kfree (dev);
	usb_dec_dev_use (udev);
}


/*-------------------------------------------------------------------------*/

// precondition: never called in_interrupt

static void *
net1080_probe (struct usb_device *udev, unsigned ifnum, const struct usb_device_id *prod)
{
	struct net1080		*dev;
	struct net_device 	*net;
	struct usb_interface_descriptor	*interface;
	int			retval;

	// sanity check; expect dedicated interface/devices for now.
	interface = &udev->actconfig->interface [ifnum].altsetting[0];
	if (udev->descriptor.bNumConfigurations != 1
			|| udev->config[0].bNumInterfaces != 1
			|| udev->config[0].bNumInterfaces != 1
			|| interface->bInterfaceClass != USB_CLASS_VENDOR_SPEC
			|| interface->bNumEndpoints != 5
			) {
		dbg ("Bogus config info");
		return 0;
	}

	// set up our own records
	if (!(dev = kmalloc (sizeof *dev, GFP_KERNEL))) {
		dbg ("can't kmalloc dev");
		return 0;
	}
	memset (dev, 0, sizeof *dev);

	init_MUTEX_LOCKED (&dev->mutex);
	usb_inc_dev_use (udev);
	dev->udev = udev;
	dev->prod_info = prod;
	INIT_LIST_HEAD (&dev->dev_list);
	skb_queue_head_init (&dev->rxq);
	skb_queue_head_init (&dev->txq);
	skb_queue_head_init (&dev->done);
	dev->bh.func = net1080_bh;
	dev->bh.data = (unsigned long) dev;

	// set up network interface records
	net = &dev->net;
	net->priv = dev;
	strcpy (net->name, "usb%d");
	memcpy (net->dev_addr, node_id, sizeof node_id);

	ether_setup (net);
	// net->flags |= IFF_POINTOPOINT;

	net->change_mtu = net1080_change_mtu;
	net->get_stats = net1080_get_stats;
	net->hard_start_xmit = net1080_start_xmit;
	net->open = net1080_open;
	net->stop = net1080_stop;

	register_netdev (&dev->net);

	// ... talk to the device
	// dump_registers (dev);

	if ((retval = net1080_reset (dev)) < 0) {
		err ("%s: init reset fail on USB %d dev %d - %d",
			dev->net.name, udev->bus->busnum, udev->devnum, retval);
		mutex_unlock (&dev->mutex);
		net1080_disconnect (udev, dev);
		return 0;
	}

	// ok, it's ready to go.
	mutex_lock (&net1080_mutex);
	list_add (&dev->dev_list, &net1080_list);
	mutex_unlock (&dev->mutex);

	// start as if the link is up
	netif_device_attach (&dev->net);

	mutex_unlock (&net1080_mutex);

	return dev;
}


/*-------------------------------------------------------------------------*/

static struct usb_driver net1080_driver = {
	name:		"net1080",
	id_table:	products,
	probe:		net1080_probe,
	disconnect:	net1080_disconnect,
};

/*-------------------------------------------------------------------------*/

static int __init net1080_init (void)
{
	// compiler should optimize this out
	if (sizeof (((struct sk_buff *)0)->cb) < sizeof (struct skb_data))
		BUG ();

 	if (usb_register (&net1080_driver) < 0)
 		return -1;

	get_random_bytes (node_id, sizeof node_id);
	node_id [0] &= 0x7f;

	return 0;
}
module_init (net1080_init);

static void __exit net1080_exit (void)
{
 	usb_deregister (&net1080_driver);
}
module_exit (net1080_exit);

MODULE_AUTHOR ("David Brownell <[e-mail]>");
MODULE_DESCRIPTION ("NetChip 1080 Driver (USB Host-to-Host Link)");