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32 results

usbnet.c

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  • usbnet.c 49.04 KiB
    /*
     * USB Network driver infrastructure
     * Copyright (C) 2000-2005 by David Brownell
     * Copyright (C) 2003-2005 David Hollis <dhollis@davehollis.com>
     *
     * This program is free software; you can redistribute it and/or modify
     * it under the terms of the GNU General Public License as published by
     * the Free Software Foundation; either version 2 of the License, or
     * (at your option) any later version.
     *
     * This program is distributed in the hope that it will be useful,
     * but WITHOUT ANY WARRANTY; without even the implied warranty of
     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     * GNU General Public License for more details.
     *
     * You should have received a copy of the GNU General Public License
     * along with this program; if not, write to the Free Software
     * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
     */
    
    /*
     * This is a generic "USB networking" framework that works with several
     * kinds of full and high speed networking devices:  host-to-host cables,
     * smart usb peripherals, and actual Ethernet adapters.
     *
     * These devices usually differ in terms of control protocols (if they
     * even have one!) and sometimes they define new framing to wrap or batch
     * Ethernet packets.  Otherwise, they talk to USB pretty much the same,
     * so interface (un)binding, endpoint I/O queues, fault handling, and other
     * issues can usefully be addressed by this framework.
     */
    
    // #define	DEBUG			// error path messages, extra info
    // #define	VERBOSE			// more; success messages
    
    #include <linux/module.h>
    #include <linux/init.h>
    #include <linux/netdevice.h>
    #include <linux/etherdevice.h>
    #include <linux/ctype.h>
    #include <linux/ethtool.h>
    #include <linux/workqueue.h>
    #include <linux/mii.h>
    #include <linux/usb.h>
    #include <linux/usb/usbnet.h>
    #include <linux/slab.h>
    #include <linux/kernel.h>
    #include <linux/pm_runtime.h>
    
    #define DRIVER_VERSION		"22-Aug-2005"
    
    
    /*-------------------------------------------------------------------------*/
    
    /*
     * Nineteen USB 1.1 max size bulk transactions per frame (ms), max.
     * Several dozen bytes of IPv4 data can fit in two such transactions.
     * One maximum size Ethernet packet takes twenty four of them.
     * For high speed, each frame comfortably fits almost 36 max size
     * Ethernet packets (so queues should be bigger).
     *
     * REVISIT qlens should be members of 'struct usbnet'; the goal is to
     * let the USB host controller be busy for 5msec or more before an irq
     * is required, under load.  Jumbograms change the equation.
     */
    #define RX_MAX_QUEUE_MEMORY (60 * 1518)
    #define	RX_QLEN(dev) (((dev)->udev->speed == USB_SPEED_HIGH) ? \
    			(RX_MAX_QUEUE_MEMORY/(dev)->rx_urb_size) : 4)
    #define	TX_QLEN(dev) (((dev)->udev->speed == USB_SPEED_HIGH) ? \
    			(RX_MAX_QUEUE_MEMORY/(dev)->hard_mtu) : 4)
    
    // reawaken network queue this soon after stopping; else watchdog barks
    #define TX_TIMEOUT_JIFFIES	(5*HZ)
    
    // throttle rx/tx briefly after some faults, so khubd might disconnect()
    // us (it polls at HZ/4 usually) before we report too many false errors.
    #define THROTTLE_JIFFIES	(HZ/8)
    
    // between wakeups
    #define UNLINK_TIMEOUT_MS	3
    
    /*-------------------------------------------------------------------------*/
    
    // randomly generated ethernet address
    static u8	node_id [ETH_ALEN];
    
    static const char driver_name [] = "usbnet";
    
    /* use ethtool to change the level for any given device */
    static int msg_level = -1;
    module_param (msg_level, int, 0);
    MODULE_PARM_DESC (msg_level, "Override default message level");
    
    /*-------------------------------------------------------------------------*/
    
    /* handles CDC Ethernet and many other network "bulk data" interfaces */
    int usbnet_get_endpoints(struct usbnet *dev, struct usb_interface *intf)
    {
    	int				tmp;
    	struct usb_host_interface	*alt = NULL;
    	struct usb_host_endpoint	*in = NULL, *out = NULL;
    	struct usb_host_endpoint	*status = NULL;
    
    	for (tmp = 0; tmp < intf->num_altsetting; tmp++) {
    		unsigned	ep;
    
    		in = out = status = NULL;
    		alt = intf->altsetting + tmp;
    
    		/* take the first altsetting with in-bulk + out-bulk;
    		 * remember any status endpoint, just in case;
    		 * ignore other endpoints and altsettings.
    		 */
    		for (ep = 0; ep < alt->desc.bNumEndpoints; ep++) {
    			struct usb_host_endpoint	*e;
    			int				intr = 0;
    
    			e = alt->endpoint + ep;
    			switch (e->desc.bmAttributes) {
    			case USB_ENDPOINT_XFER_INT:
    				if (!usb_endpoint_dir_in(&e->desc))
    					continue;
    				intr = 1;
    				/* FALLTHROUGH */
    			case USB_ENDPOINT_XFER_BULK:
    				break;
    			default:
    				continue;
    			}
    			if (usb_endpoint_dir_in(&e->desc)) {
    				if (!intr && !in)
    					in = e;
    				else if (intr && !status)
    					status = e;
    			} else {
    				if (!out)
    					out = e;
    			}
    		}
    		if (in && out)
    			break;
    	}
    	if (!alt || !in || !out)
    		return -EINVAL;
    
    	if (alt->desc.bAlternateSetting != 0 ||
    	    !(dev->driver_info->flags & FLAG_NO_SETINT)) {
    		tmp = usb_set_interface (dev->udev, alt->desc.bInterfaceNumber,
    				alt->desc.bAlternateSetting);
    		if (tmp < 0)
    			return tmp;
    	}
    
    	dev->in = usb_rcvbulkpipe (dev->udev,
    			in->desc.bEndpointAddress & USB_ENDPOINT_NUMBER_MASK);
    	dev->out = usb_sndbulkpipe (dev->udev,
    			out->desc.bEndpointAddress & USB_ENDPOINT_NUMBER_MASK);
    	dev->status = status;
    	return 0;
    }
    EXPORT_SYMBOL_GPL(usbnet_get_endpoints);
    
    int usbnet_get_ethernet_addr(struct usbnet *dev, int iMACAddress)
    {
    	int 		tmp, i;
    	unsigned char	buf [13];
    
    	tmp = usb_string(dev->udev, iMACAddress, buf, sizeof buf);
    	if (tmp != 12) {
    		dev_dbg(&dev->udev->dev,
    			"bad MAC string %d fetch, %d\n", iMACAddress, tmp);
    		if (tmp >= 0)
    			tmp = -EINVAL;
    		return tmp;
    	}
    	for (i = tmp = 0; i < 6; i++, tmp += 2)
    		dev->net->dev_addr [i] =
    			(hex_to_bin(buf[tmp]) << 4) + hex_to_bin(buf[tmp + 1]);
    	return 0;
    }
    EXPORT_SYMBOL_GPL(usbnet_get_ethernet_addr);
    
    static void intr_complete (struct urb *urb)
    {
    	struct usbnet	*dev = urb->context;
    	int		status = urb->status;
    
    	switch (status) {
    	/* success */
    	case 0:
    		dev->driver_info->status(dev, urb);
    		break;
    
    	/* software-driven interface shutdown */
    	case -ENOENT:		/* urb killed */
    	case -ESHUTDOWN:	/* hardware gone */
    		netif_dbg(dev, ifdown, dev->net,
    			  "intr shutdown, code %d\n", status);
    		return;
    
    	/* NOTE:  not throttling like RX/TX, since this endpoint
    	 * already polls infrequently
    	 */
    	default:
    		netdev_dbg(dev->net, "intr status %d\n", status);
    		break;
    	}
    
    	if (!netif_running (dev->net))
    		return;
    
    	status = usb_submit_urb (urb, GFP_ATOMIC);
    	if (status != 0)
    		netif_err(dev, timer, dev->net,
    			  "intr resubmit --> %d\n", status);
    }
    
    static int init_status (struct usbnet *dev, struct usb_interface *intf)
    {
    	char		*buf = NULL;
    	unsigned	pipe = 0;
    	unsigned	maxp;
    	unsigned	period;
    
    	if (!dev->driver_info->status)
    		return 0;
    
    	pipe = usb_rcvintpipe (dev->udev,
    			dev->status->desc.bEndpointAddress
    				& USB_ENDPOINT_NUMBER_MASK);
    	maxp = usb_maxpacket (dev->udev, pipe, 0);
    
    	/* avoid 1 msec chatter:  min 8 msec poll rate */
    	period = max ((int) dev->status->desc.bInterval,
    		(dev->udev->speed == USB_SPEED_HIGH) ? 7 : 3);
    
    	buf = kmalloc (maxp, GFP_KERNEL);
    	if (buf) {
    		dev->interrupt = usb_alloc_urb (0, GFP_KERNEL);
    		if (!dev->interrupt) {
    			kfree (buf);
    			return -ENOMEM;
    		} else {
    			usb_fill_int_urb(dev->interrupt, dev->udev, pipe,
    				buf, maxp, intr_complete, dev, period);
    			dev->interrupt->transfer_flags |= URB_FREE_BUFFER;
    			dev_dbg(&intf->dev,
    				"status ep%din, %d bytes period %d\n",
    				usb_pipeendpoint(pipe), maxp, period);
    		}
    	}
    	return 0;
    }
    
    /* Passes this packet up the stack, updating its accounting.
     * Some link protocols batch packets, so their rx_fixup paths
     * can return clones as well as just modify the original skb.
     */
    void usbnet_skb_return (struct usbnet *dev, struct sk_buff *skb)
    {
    	int	status;
    
    	if (test_bit(EVENT_RX_PAUSED, &dev->flags)) {
    		skb_queue_tail(&dev->rxq_pause, skb);
    		return;
    	}
    
    	skb->protocol = eth_type_trans (skb, dev->net);
    	dev->net->stats.rx_packets++;
    	dev->net->stats.rx_bytes += skb->len;
    
    	netif_dbg(dev, rx_status, dev->net, "< rx, len %zu, type 0x%x\n",
    		  skb->len + sizeof (struct ethhdr), skb->protocol);
    	memset (skb->cb, 0, sizeof (struct skb_data));
    
    	if (skb_defer_rx_timestamp(skb))
    		return;
    
    	status = netif_rx (skb);
    	if (status != NET_RX_SUCCESS)
    		netif_dbg(dev, rx_err, dev->net,
    			  "netif_rx status %d\n", status);
    }
    EXPORT_SYMBOL_GPL(usbnet_skb_return);
    
    
    /*-------------------------------------------------------------------------
     *
     * Network Device Driver (peer link to "Host Device", from USB host)
     *
     *-------------------------------------------------------------------------*/
    
    int usbnet_change_mtu (struct net_device *net, int new_mtu)
    {
    	struct usbnet	*dev = netdev_priv(net);
    	int		ll_mtu = new_mtu + net->hard_header_len;
    	int		old_hard_mtu = dev->hard_mtu;
    	int		old_rx_urb_size = dev->rx_urb_size;
    
    	if (new_mtu <= 0)
    		return -EINVAL;
    	// no second zero-length packet read wanted after mtu-sized packets
    	if ((ll_mtu % dev->maxpacket) == 0)
    		return -EDOM;
    	net->mtu = new_mtu;
    
    	dev->hard_mtu = net->mtu + net->hard_header_len;
    	if (dev->rx_urb_size == old_hard_mtu) {
    		dev->rx_urb_size = dev->hard_mtu;
    		if (dev->rx_urb_size > old_rx_urb_size)
    			usbnet_unlink_rx_urbs(dev);
    	}
    
    	return 0;
    }
    EXPORT_SYMBOL_GPL(usbnet_change_mtu);
    
    /* The caller must hold list->lock */
    static void __usbnet_queue_skb(struct sk_buff_head *list,
    			struct sk_buff *newsk, enum skb_state state)
    {
    	struct skb_data *entry = (struct skb_data *) newsk->cb;
    
    	__skb_queue_tail(list, newsk);
    	entry->state = state;
    }
    
    /*-------------------------------------------------------------------------*/
    
    /* some LK 2.4 HCDs oopsed if we freed or resubmitted urbs from
     * completion callbacks.  2.5 should have fixed those bugs...
     */
    
    static enum skb_state defer_bh(struct usbnet *dev, struct sk_buff *skb,
    		struct sk_buff_head *list, enum skb_state state)
    {
    	unsigned long		flags;
    	enum skb_state 		old_state;
    	struct skb_data *entry = (struct skb_data *) skb->cb;
    
    	spin_lock_irqsave(&list->lock, flags);
    	old_state = entry->state;
    	entry->state = state;
    	__skb_unlink(skb, list);
    	spin_unlock(&list->lock);
    	spin_lock(&dev->done.lock);
    	__skb_queue_tail(&dev->done, skb);
    	if (dev->done.qlen == 1)
    		tasklet_schedule(&dev->bh);
    	spin_unlock_irqrestore(&dev->done.lock, flags);
    	return old_state;
    }
    
    /* some work can't be done in tasklets, so we use keventd
     *
     * NOTE:  annoying asymmetry:  if it's active, schedule_work() fails,
     * but tasklet_schedule() doesn't.  hope the failure is rare.
     */
    void usbnet_defer_kevent (struct usbnet *dev, int work)
    {
    	set_bit (work, &dev->flags);
    	if (!schedule_work (&dev->kevent)) {
    		if (net_ratelimit())
    			netdev_err(dev->net, "kevent %d may have been dropped\n", work);
    	} else {
    		netdev_dbg(dev->net, "kevent %d scheduled\n", work);
    	}
    }
    EXPORT_SYMBOL_GPL(usbnet_defer_kevent);
    
    /*-------------------------------------------------------------------------*/
    
    static void rx_complete (struct urb *urb);
    
    static int rx_submit (struct usbnet *dev, struct urb *urb, gfp_t flags)
    {
    	struct sk_buff		*skb;
    	struct skb_data		*entry;
    	int			retval = 0;
    	unsigned long		lockflags;
    	size_t			size = dev->rx_urb_size;
    
    	/* prevent rx skb allocation when error ratio is high */
    	if (test_bit(EVENT_RX_KILL, &dev->flags)) {
    		usb_free_urb(urb);
    		return -ENOLINK;
    	}
    
    	skb = __netdev_alloc_skb_ip_align(dev->net, size, flags);
    	if (!skb) {
    		netif_dbg(dev, rx_err, dev->net, "no rx skb\n");
    		usbnet_defer_kevent (dev, EVENT_RX_MEMORY);
    		usb_free_urb (urb);
    		return -ENOMEM;
    	}
    
    	entry = (struct skb_data *) skb->cb;
    	entry->urb = urb;
    	entry->dev = dev;
    	entry->length = 0;
    
    	usb_fill_bulk_urb (urb, dev->udev, dev->in,
    		skb->data, size, rx_complete, skb);
    
    	spin_lock_irqsave (&dev->rxq.lock, lockflags);
    
    	if (netif_running (dev->net) &&
    	    netif_device_present (dev->net) &&
    	    !test_bit (EVENT_RX_HALT, &dev->flags) &&
    	    !test_bit (EVENT_DEV_ASLEEP, &dev->flags)) {
    		switch (retval = usb_submit_urb (urb, GFP_ATOMIC)) {
    		case -EPIPE:
    			usbnet_defer_kevent (dev, EVENT_RX_HALT);
    			break;
    		case -ENOMEM:
    			usbnet_defer_kevent (dev, EVENT_RX_MEMORY);
    			break;
    		case -ENODEV:
    			netif_dbg(dev, ifdown, dev->net, "device gone\n");
    			netif_device_detach (dev->net);
    			break;
    		case -EHOSTUNREACH:
    			retval = -ENOLINK;
    			break;
    		default:
    			netif_dbg(dev, rx_err, dev->net,
    				  "rx submit, %d\n", retval);
    			tasklet_schedule (&dev->bh);
    			break;
    		case 0:
    			__usbnet_queue_skb(&dev->rxq, skb, rx_start);
    		}
    	} else {
    		netif_dbg(dev, ifdown, dev->net, "rx: stopped\n");
    		retval = -ENOLINK;
    	}
    	spin_unlock_irqrestore (&dev->rxq.lock, lockflags);
    	if (retval) {
    		dev_kfree_skb_any (skb);
    		usb_free_urb (urb);
    	}
    	return retval;
    }
    
    
    /*-------------------------------------------------------------------------*/
    
    static inline void rx_process (struct usbnet *dev, struct sk_buff *skb)
    {
    	if (dev->driver_info->rx_fixup &&
    	    !dev->driver_info->rx_fixup (dev, skb)) {
    		/* With RX_ASSEMBLE, rx_fixup() must update counters */
    		if (!(dev->driver_info->flags & FLAG_RX_ASSEMBLE))
    			dev->net->stats.rx_errors++;
    		goto done;
    	}
    	// else network stack removes extra byte if we forced a short packet
    
    	if (skb->len) {
    		/* all data was already cloned from skb inside the driver */
    		if (dev->driver_info->flags & FLAG_MULTI_PACKET)
    			dev_kfree_skb_any(skb);
    		else
    			usbnet_skb_return(dev, skb);
    		return;
    	}
    
    	netif_dbg(dev, rx_err, dev->net, "drop\n");
    	dev->net->stats.rx_errors++;
    done:
    	skb_queue_tail(&dev->done, skb);
    }
    
    /*-------------------------------------------------------------------------*/
    
    static void rx_complete (struct urb *urb)
    {
    	struct sk_buff		*skb = (struct sk_buff *) urb->context;
    	struct skb_data		*entry = (struct skb_data *) skb->cb;
    	struct usbnet		*dev = entry->dev;
    	int			urb_status = urb->status;
    	enum skb_state		state;
    
    	skb_put (skb, urb->actual_length);
    	state = rx_done;
    	entry->urb = NULL;
    
    	switch (urb_status) {
    	/* success */
    	case 0:
    		if (skb->len < dev->net->hard_header_len) {
    			state = rx_cleanup;
    			dev->net->stats.rx_errors++;
    			dev->net->stats.rx_length_errors++;
    			netif_dbg(dev, rx_err, dev->net,
    				  "rx length %d\n", skb->len);
    		}
    		break;
    
    	/* stalls need manual reset. this is rare ... except that
    	 * when going through USB 2.0 TTs, unplug appears this way.
    	 * we avoid the highspeed version of the ETIMEDOUT/EILSEQ
    	 * storm, recovering as needed.
    	 */
    	case -EPIPE:
    		dev->net->stats.rx_errors++;
    		usbnet_defer_kevent (dev, EVENT_RX_HALT);
    		// FALLTHROUGH
    
    	/* software-driven interface shutdown */
    	case -ECONNRESET:		/* async unlink */
    	case -ESHUTDOWN:		/* hardware gone */
    		netif_dbg(dev, ifdown, dev->net,
    			  "rx shutdown, code %d\n", urb_status);
    		goto block;
    
    	/* we get controller i/o faults during khubd disconnect() delays.
    	 * throttle down resubmits, to avoid log floods; just temporarily,
    	 * so we still recover when the fault isn't a khubd delay.
    	 */
    	case -EPROTO:
    	case -ETIME:
    	case -EILSEQ:
    		dev->net->stats.rx_errors++;
    		if (!timer_pending (&dev->delay)) {
    			mod_timer (&dev->delay, jiffies + THROTTLE_JIFFIES);
    			netif_dbg(dev, link, dev->net,
    				  "rx throttle %d\n", urb_status);
    		}
    block:
    		state = rx_cleanup;
    		entry->urb = urb;
    		urb = NULL;
    		break;
    
    	/* data overrun ... flush fifo? */
    	case -EOVERFLOW:
    		dev->net->stats.rx_over_errors++;
    		// FALLTHROUGH
    
    	default:
    		state = rx_cleanup;
    		dev->net->stats.rx_errors++;
    		netif_dbg(dev, rx_err, dev->net, "rx status %d\n", urb_status);
    		break;
    	}
    
    	/* stop rx if packet error rate is high */
    	if (++dev->pkt_cnt > 30) {
    		dev->pkt_cnt = 0;
    		dev->pkt_err = 0;
    	} else {
    		if (state == rx_cleanup)
    			dev->pkt_err++;
    		if (dev->pkt_err > 20)
    			set_bit(EVENT_RX_KILL, &dev->flags);
    	}
    
    	state = defer_bh(dev, skb, &dev->rxq, state);
    
    	if (urb) {
    		if (netif_running (dev->net) &&
    		    !test_bit (EVENT_RX_HALT, &dev->flags) &&
    		    state != unlink_start) {
    			rx_submit (dev, urb, GFP_ATOMIC);
    			usb_mark_last_busy(dev->udev);
    			return;
    		}
    		usb_free_urb (urb);
    	}
    	netif_dbg(dev, rx_err, dev->net, "no read resubmitted\n");
    }
    
    /*-------------------------------------------------------------------------*/
    void usbnet_pause_rx(struct usbnet *dev)
    {
    	set_bit(EVENT_RX_PAUSED, &dev->flags);
    
    	netif_dbg(dev, rx_status, dev->net, "paused rx queue enabled\n");
    }
    EXPORT_SYMBOL_GPL(usbnet_pause_rx);
    
    void usbnet_resume_rx(struct usbnet *dev)
    {
    	struct sk_buff *skb;
    	int num = 0;
    
    	clear_bit(EVENT_RX_PAUSED, &dev->flags);
    
    	while ((skb = skb_dequeue(&dev->rxq_pause)) != NULL) {
    		usbnet_skb_return(dev, skb);
    		num++;
    	}
    
    	tasklet_schedule(&dev->bh);
    
    	netif_dbg(dev, rx_status, dev->net,
    		  "paused rx queue disabled, %d skbs requeued\n", num);
    }
    EXPORT_SYMBOL_GPL(usbnet_resume_rx);
    
    void usbnet_purge_paused_rxq(struct usbnet *dev)
    {
    	skb_queue_purge(&dev->rxq_pause);
    }
    EXPORT_SYMBOL_GPL(usbnet_purge_paused_rxq);
    
    /*-------------------------------------------------------------------------*/
    
    // unlink pending rx/tx; completion handlers do all other cleanup
    
    static int unlink_urbs (struct usbnet *dev, struct sk_buff_head *q)
    {
    	unsigned long		flags;
    	struct sk_buff		*skb;
    	int			count = 0;
    
    	spin_lock_irqsave (&q->lock, flags);
    	while (!skb_queue_empty(q)) {
    		struct skb_data		*entry;
    		struct urb		*urb;
    		int			retval;
    
    		skb_queue_walk(q, skb) {
    			entry = (struct skb_data *) skb->cb;
    			if (entry->state != unlink_start)
    				goto found;
    		}
    		break;
    found:
    		entry->state = unlink_start;
    		urb = entry->urb;
    
    		/*
    		 * Get reference count of the URB to avoid it to be
    		 * freed during usb_unlink_urb, which may trigger
    		 * use-after-free problem inside usb_unlink_urb since
    		 * usb_unlink_urb is always racing with .complete
    		 * handler(include defer_bh).
    		 */
    		usb_get_urb(urb);
    		spin_unlock_irqrestore(&q->lock, flags);
    		// during some PM-driven resume scenarios,
    		// these (async) unlinks complete immediately
    		retval = usb_unlink_urb (urb);
    		if (retval != -EINPROGRESS && retval != 0)
    			netdev_dbg(dev->net, "unlink urb err, %d\n", retval);
    		else
    			count++;
    		usb_put_urb(urb);
    		spin_lock_irqsave(&q->lock, flags);
    	}
    	spin_unlock_irqrestore (&q->lock, flags);
    	return count;
    }
    
    // Flush all pending rx urbs
    // minidrivers may need to do this when the MTU changes
    
    void usbnet_unlink_rx_urbs(struct usbnet *dev)
    {
    	if (netif_running(dev->net)) {
    		(void) unlink_urbs (dev, &dev->rxq);
    		tasklet_schedule(&dev->bh);
    	}
    }
    EXPORT_SYMBOL_GPL(usbnet_unlink_rx_urbs);
    
    /*-------------------------------------------------------------------------*/
    
    // precondition: never called in_interrupt
    static void usbnet_terminate_urbs(struct usbnet *dev)
    {
    	DECLARE_WAIT_QUEUE_HEAD_ONSTACK(unlink_wakeup);
    	DECLARE_WAITQUEUE(wait, current);
    	int temp;
    
    	/* ensure there are no more active urbs */
    	add_wait_queue(&unlink_wakeup, &wait);
    	set_current_state(TASK_UNINTERRUPTIBLE);
    	dev->wait = &unlink_wakeup;
    	temp = unlink_urbs(dev, &dev->txq) +
    		unlink_urbs(dev, &dev->rxq);
    
    	/* maybe wait for deletions to finish. */
    	while (!skb_queue_empty(&dev->rxq)
    		&& !skb_queue_empty(&dev->txq)
    		&& !skb_queue_empty(&dev->done)) {
    			schedule_timeout(msecs_to_jiffies(UNLINK_TIMEOUT_MS));
    			set_current_state(TASK_UNINTERRUPTIBLE);
    			netif_dbg(dev, ifdown, dev->net,
    				  "waited for %d urb completions\n", temp);
    	}
    	set_current_state(TASK_RUNNING);
    	dev->wait = NULL;
    	remove_wait_queue(&unlink_wakeup, &wait);
    }
    
    int usbnet_stop (struct net_device *net)
    {
    	struct usbnet		*dev = netdev_priv(net);
    	struct driver_info	*info = dev->driver_info;
    	int			retval;
    
    	clear_bit(EVENT_DEV_OPEN, &dev->flags);
    	netif_stop_queue (net);
    
    	netif_info(dev, ifdown, dev->net,
    		   "stop stats: rx/tx %lu/%lu, errs %lu/%lu\n",
    		   net->stats.rx_packets, net->stats.tx_packets,
    		   net->stats.rx_errors, net->stats.tx_errors);
    
    	/* allow minidriver to stop correctly (wireless devices to turn off
    	 * radio etc) */
    	if (info->stop) {
    		retval = info->stop(dev);
    		if (retval < 0)
    			netif_info(dev, ifdown, dev->net,
    				   "stop fail (%d) usbnet usb-%s-%s, %s\n",
    				   retval,
    				   dev->udev->bus->bus_name, dev->udev->devpath,
    				   info->description);
    	}
    
    	if (!(info->flags & FLAG_AVOID_UNLINK_URBS))
    		usbnet_terminate_urbs(dev);
    
    	usb_kill_urb(dev->interrupt);
    
    	usbnet_purge_paused_rxq(dev);
    
    	/* deferred work (task, timer, softirq) must also stop.
    	 * can't flush_scheduled_work() until we drop rtnl (later),
    	 * else workers could deadlock; so make workers a NOP.
    	 */
    	dev->flags = 0;
    	del_timer_sync (&dev->delay);
    	tasklet_kill (&dev->bh);
    	if (info->manage_power &&
    	    !test_and_clear_bit(EVENT_NO_RUNTIME_PM, &dev->flags))
    		info->manage_power(dev, 0);
    	else
    		usb_autopm_put_interface(dev->intf);
    
    	return 0;
    }
    EXPORT_SYMBOL_GPL(usbnet_stop);
    
    /*-------------------------------------------------------------------------*/
    
    // posts reads, and enables write queuing
    
    // precondition: never called in_interrupt
    
    int usbnet_open (struct net_device *net)
    {
    	struct usbnet		*dev = netdev_priv(net);
    	int			retval;
    	struct driver_info	*info = dev->driver_info;
    
    	if ((retval = usb_autopm_get_interface(dev->intf)) < 0) {
    		netif_info(dev, ifup, dev->net,
    			   "resumption fail (%d) usbnet usb-%s-%s, %s\n",
    			   retval,
    			   dev->udev->bus->bus_name,
    			   dev->udev->devpath,
    			   info->description);
    		goto done_nopm;
    	}
    
    	// put into "known safe" state
    	if (info->reset && (retval = info->reset (dev)) < 0) {
    		netif_info(dev, ifup, dev->net,
    			   "open reset fail (%d) usbnet usb-%s-%s, %s\n",
    			   retval,
    			   dev->udev->bus->bus_name,
    			   dev->udev->devpath,
    			   info->description);
    		goto done;
    	}
    
    	// insist peer be connected
    	if (info->check_connect && (retval = info->check_connect (dev)) < 0) {
    		netif_dbg(dev, ifup, dev->net, "can't open; %d\n", retval);
    		goto done;
    	}
    
    	/* start any status interrupt transfer */
    	if (dev->interrupt) {
    		retval = usb_submit_urb (dev->interrupt, GFP_KERNEL);
    		if (retval < 0) {
    			netif_err(dev, ifup, dev->net,
    				  "intr submit %d\n", retval);
    			goto done;
    		}
    	}
    
    	set_bit(EVENT_DEV_OPEN, &dev->flags);
    	netif_start_queue (net);
    	netif_info(dev, ifup, dev->net,
    		   "open: enable queueing (rx %d, tx %d) mtu %d %s framing\n",
    		   (int)RX_QLEN(dev), (int)TX_QLEN(dev),
    		   dev->net->mtu,
    		   (dev->driver_info->flags & FLAG_FRAMING_NC) ? "NetChip" :
    		   (dev->driver_info->flags & FLAG_FRAMING_GL) ? "GeneSys" :
    		   (dev->driver_info->flags & FLAG_FRAMING_Z) ? "Zaurus" :
    		   (dev->driver_info->flags & FLAG_FRAMING_RN) ? "RNDIS" :
    		   (dev->driver_info->flags & FLAG_FRAMING_AX) ? "ASIX" :
    		   "simple");
    
    	/* reset rx error state */
    	dev->pkt_cnt = 0;
    	dev->pkt_err = 0;
    	clear_bit(EVENT_RX_KILL, &dev->flags);
    
    	// delay posting reads until we're fully open
    	tasklet_schedule (&dev->bh);
    	if (info->manage_power) {
    		retval = info->manage_power(dev, 1);
    		if (retval < 0) {
    			retval = 0;
    			set_bit(EVENT_NO_RUNTIME_PM, &dev->flags);
    		} else {
    			usb_autopm_put_interface(dev->intf);
    		}
    	}
    	return retval;
    done:
    	usb_autopm_put_interface(dev->intf);
    done_nopm:
    	return retval;
    }
    EXPORT_SYMBOL_GPL(usbnet_open);
    
    /*-------------------------------------------------------------------------*/
    
    /* ethtool methods; minidrivers may need to add some more, but
     * they'll probably want to use this base set.
     */
    
    int usbnet_get_settings (struct net_device *net, struct ethtool_cmd *cmd)
    {
    	struct usbnet *dev = netdev_priv(net);
    
    	if (!dev->mii.mdio_read)
    		return -EOPNOTSUPP;
    
    	return mii_ethtool_gset(&dev->mii, cmd);
    }
    EXPORT_SYMBOL_GPL(usbnet_get_settings);
    
    int usbnet_set_settings (struct net_device *net, struct ethtool_cmd *cmd)
    {
    	struct usbnet *dev = netdev_priv(net);
    	int retval;
    
    	if (!dev->mii.mdio_write)
    		return -EOPNOTSUPP;
    
    	retval = mii_ethtool_sset(&dev->mii, cmd);
    
    	/* link speed/duplex might have changed */
    	if (dev->driver_info->link_reset)
    		dev->driver_info->link_reset(dev);
    
    	return retval;
    
    }
    EXPORT_SYMBOL_GPL(usbnet_set_settings);
    
    u32 usbnet_get_link (struct net_device *net)
    {
    	struct usbnet *dev = netdev_priv(net);
    
    	/* If a check_connect is defined, return its result */
    	if (dev->driver_info->check_connect)
    		return dev->driver_info->check_connect (dev) == 0;
    
    	/* if the device has mii operations, use those */
    	if (dev->mii.mdio_read)
    		return mii_link_ok(&dev->mii);
    
    	/* Otherwise, dtrt for drivers calling netif_carrier_{on,off} */
    	return ethtool_op_get_link(net);
    }
    EXPORT_SYMBOL_GPL(usbnet_get_link);
    
    int usbnet_nway_reset(struct net_device *net)
    {
    	struct usbnet *dev = netdev_priv(net);
    
    	if (!dev->mii.mdio_write)
    		return -EOPNOTSUPP;
    
    	return mii_nway_restart(&dev->mii);
    }
    EXPORT_SYMBOL_GPL(usbnet_nway_reset);
    
    void usbnet_get_drvinfo (struct net_device *net, struct ethtool_drvinfo *info)
    {
    	struct usbnet *dev = netdev_priv(net);
    
    	strlcpy (info->driver, dev->driver_name, sizeof info->driver);
    	strlcpy (info->version, DRIVER_VERSION, sizeof info->version);
    	strlcpy (info->fw_version, dev->driver_info->description,
    		sizeof info->fw_version);
    	usb_make_path (dev->udev, info->bus_info, sizeof info->bus_info);
    }
    EXPORT_SYMBOL_GPL(usbnet_get_drvinfo);
    
    u32 usbnet_get_msglevel (struct net_device *net)
    {
    	struct usbnet *dev = netdev_priv(net);
    
    	return dev->msg_enable;
    }
    EXPORT_SYMBOL_GPL(usbnet_get_msglevel);
    
    void usbnet_set_msglevel (struct net_device *net, u32 level)
    {
    	struct usbnet *dev = netdev_priv(net);
    
    	dev->msg_enable = level;
    }
    EXPORT_SYMBOL_GPL(usbnet_set_msglevel);
    
    /* drivers may override default ethtool_ops in their bind() routine */
    static const struct ethtool_ops usbnet_ethtool_ops = {
    	.get_settings		= usbnet_get_settings,
    	.set_settings		= usbnet_set_settings,
    	.get_link		= usbnet_get_link,
    	.nway_reset		= usbnet_nway_reset,
    	.get_drvinfo		= usbnet_get_drvinfo,
    	.get_msglevel		= usbnet_get_msglevel,
    	.set_msglevel		= usbnet_set_msglevel,
    	.get_ts_info		= ethtool_op_get_ts_info,
    };
    
    /*-------------------------------------------------------------------------*/
    
    /* work that cannot be done in interrupt context uses keventd.
     *
     * NOTE:  with 2.5 we could do more of this using completion callbacks,
     * especially now that control transfers can be queued.
     */
    static void
    kevent (struct work_struct *work)
    {
    	struct usbnet		*dev =
    		container_of(work, struct usbnet, kevent);
    	int			status;
    
    	/* usb_clear_halt() needs a thread context */
    	if (test_bit (EVENT_TX_HALT, &dev->flags)) {
    		unlink_urbs (dev, &dev->txq);
    		status = usb_autopm_get_interface(dev->intf);
    		if (status < 0)
    			goto fail_pipe;
    		status = usb_clear_halt (dev->udev, dev->out);
    		usb_autopm_put_interface(dev->intf);
    		if (status < 0 &&
    		    status != -EPIPE &&
    		    status != -ESHUTDOWN) {
    			if (netif_msg_tx_err (dev))
    fail_pipe:
    				netdev_err(dev->net, "can't clear tx halt, status %d\n",
    					   status);
    		} else {
    			clear_bit (EVENT_TX_HALT, &dev->flags);
    			if (status != -ESHUTDOWN)
    				netif_wake_queue (dev->net);
    		}
    	}
    	if (test_bit (EVENT_RX_HALT, &dev->flags)) {
    		unlink_urbs (dev, &dev->rxq);
    		status = usb_autopm_get_interface(dev->intf);
    		if (status < 0)
    			goto fail_halt;
    		status = usb_clear_halt (dev->udev, dev->in);
    		usb_autopm_put_interface(dev->intf);
    		if (status < 0 &&
    		    status != -EPIPE &&
    		    status != -ESHUTDOWN) {
    			if (netif_msg_rx_err (dev))
    fail_halt:
    				netdev_err(dev->net, "can't clear rx halt, status %d\n",
    					   status);
    		} else {
    			clear_bit (EVENT_RX_HALT, &dev->flags);
    			tasklet_schedule (&dev->bh);
    		}
    	}
    
    	/* tasklet could resubmit itself forever if memory is tight */
    	if (test_bit (EVENT_RX_MEMORY, &dev->flags)) {
    		struct urb	*urb = NULL;
    		int resched = 1;
    
    		if (netif_running (dev->net))
    			urb = usb_alloc_urb (0, GFP_KERNEL);
    		else
    			clear_bit (EVENT_RX_MEMORY, &dev->flags);
    		if (urb != NULL) {
    			clear_bit (EVENT_RX_MEMORY, &dev->flags);
    			status = usb_autopm_get_interface(dev->intf);
    			if (status < 0) {
    				usb_free_urb(urb);
    				goto fail_lowmem;
    			}
    			if (rx_submit (dev, urb, GFP_KERNEL) == -ENOLINK)
    				resched = 0;
    			usb_autopm_put_interface(dev->intf);
    fail_lowmem:
    			if (resched)
    				tasklet_schedule (&dev->bh);
    		}
    	}
    
    	if (test_bit (EVENT_LINK_RESET, &dev->flags)) {
    		struct driver_info	*info = dev->driver_info;
    		int			retval = 0;
    
    		clear_bit (EVENT_LINK_RESET, &dev->flags);
    		status = usb_autopm_get_interface(dev->intf);
    		if (status < 0)
    			goto skip_reset;
    		if(info->link_reset && (retval = info->link_reset(dev)) < 0) {
    			usb_autopm_put_interface(dev->intf);
    skip_reset:
    			netdev_info(dev->net, "link reset failed (%d) usbnet usb-%s-%s, %s\n",
    				    retval,
    				    dev->udev->bus->bus_name,
    				    dev->udev->devpath,
    				    info->description);
    		} else {
    			usb_autopm_put_interface(dev->intf);
    		}
    	}
    
    	if (dev->flags)
    		netdev_dbg(dev->net, "kevent done, flags = 0x%lx\n", dev->flags);
    }
    
    /*-------------------------------------------------------------------------*/
    
    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 usbnet		*dev = entry->dev;
    
    	if (urb->status == 0) {
    		if (!(dev->driver_info->flags & FLAG_MULTI_PACKET))
    			dev->net->stats.tx_packets++;
    		dev->net->stats.tx_bytes += entry->length;
    	} else {
    		dev->net->stats.tx_errors++;
    
    		switch (urb->status) {
    		case -EPIPE:
    			usbnet_defer_kevent (dev, EVENT_TX_HALT);
    			break;
    
    		/* software-driven interface shutdown */
    		case -ECONNRESET:		// async unlink
    		case -ESHUTDOWN:		// hardware gone
    			break;
    
    		// like rx, tx gets controller i/o faults during khubd delays
    		// and so it uses the same throttling mechanism.
    		case -EPROTO:
    		case -ETIME:
    		case -EILSEQ:
    			usb_mark_last_busy(dev->udev);
    			if (!timer_pending (&dev->delay)) {
    				mod_timer (&dev->delay,
    					jiffies + THROTTLE_JIFFIES);
    				netif_dbg(dev, link, dev->net,
    					  "tx throttle %d\n", urb->status);
    			}
    			netif_stop_queue (dev->net);
    			break;
    		default:
    			netif_dbg(dev, tx_err, dev->net,
    				  "tx err %d\n", entry->urb->status);
    			break;
    		}
    	}
    
    	usb_autopm_put_interface_async(dev->intf);
    	(void) defer_bh(dev, skb, &dev->txq, tx_done);
    }
    
    /*-------------------------------------------------------------------------*/
    
    void usbnet_tx_timeout (struct net_device *net)
    {
    	struct usbnet		*dev = netdev_priv(net);
    
    	unlink_urbs (dev, &dev->txq);
    	tasklet_schedule (&dev->bh);
    
    	// FIXME: device recovery -- reset?
    }
    EXPORT_SYMBOL_GPL(usbnet_tx_timeout);
    
    /*-------------------------------------------------------------------------*/
    
    netdev_tx_t usbnet_start_xmit (struct sk_buff *skb,
    				     struct net_device *net)
    {
    	struct usbnet		*dev = netdev_priv(net);
    	int			length;
    	struct urb		*urb = NULL;
    	struct skb_data		*entry;
    	struct driver_info	*info = dev->driver_info;
    	unsigned long		flags;
    	int retval;
    
    	if (skb)
    		skb_tx_timestamp(skb);
    
    	// some devices want funky USB-level framing, for
    	// win32 driver (usually) and/or hardware quirks
    	if (info->tx_fixup) {
    		skb = info->tx_fixup (dev, skb, GFP_ATOMIC);
    		if (!skb) {
    			/* packet collected; minidriver waiting for more */
    			if (info->flags & FLAG_MULTI_PACKET)
    				goto not_drop;
    			netif_dbg(dev, tx_err, dev->net, "can't tx_fixup skb\n");
    			goto drop;
    		}
    	}
    	length = skb->len;
    
    	if (!(urb = usb_alloc_urb (0, GFP_ATOMIC))) {
    		netif_dbg(dev, tx_err, dev->net, "no urb\n");
    		goto drop;
    	}
    
    	entry = (struct skb_data *) skb->cb;
    	entry->urb = urb;
    	entry->dev = dev;
    	entry->length = length;
    
    	usb_fill_bulk_urb (urb, dev->udev, dev->out,
    			skb->data, skb->len, tx_complete, skb);
    
    	/* don't assume the hardware handles USB_ZERO_PACKET
    	 * NOTE:  strictly conforming cdc-ether devices should expect
    	 * the ZLP here, but ignore the one-byte packet.
    	 * NOTE2: CDC NCM specification is different from CDC ECM when
    	 * handling ZLP/short packets, so cdc_ncm driver will make short
    	 * packet itself if needed.
    	 */
    	if (length % dev->maxpacket == 0) {
    		if (!(info->flags & FLAG_SEND_ZLP)) {
    			if (!(info->flags & FLAG_MULTI_PACKET)) {
    				urb->transfer_buffer_length++;
    				if (skb_tailroom(skb)) {
    					skb->data[skb->len] = 0;
    					__skb_put(skb, 1);
    				}
    			}
    		} else
    			urb->transfer_flags |= URB_ZERO_PACKET;
    	}
    
    	spin_lock_irqsave(&dev->txq.lock, flags);
    	retval = usb_autopm_get_interface_async(dev->intf);
    	if (retval < 0) {
    		spin_unlock_irqrestore(&dev->txq.lock, flags);
    		goto drop;
    	}
    
    #ifdef CONFIG_PM
    	/* if this triggers the device is still a sleep */
    	if (test_bit(EVENT_DEV_ASLEEP, &dev->flags)) {
    		/* transmission will be done in resume */
    		usb_anchor_urb(urb, &dev->deferred);
    		/* no use to process more packets */
    		netif_stop_queue(net);
    		usb_put_urb(urb);
    		spin_unlock_irqrestore(&dev->txq.lock, flags);
    		netdev_dbg(dev->net, "Delaying transmission for resumption\n");
    		goto deferred;
    	}
    #endif
    
    	switch ((retval = usb_submit_urb (urb, GFP_ATOMIC))) {
    	case -EPIPE:
    		netif_stop_queue (net);
    		usbnet_defer_kevent (dev, EVENT_TX_HALT);
    		usb_autopm_put_interface_async(dev->intf);
    		break;
    	default:
    		usb_autopm_put_interface_async(dev->intf);
    		netif_dbg(dev, tx_err, dev->net,
    			  "tx: submit urb err %d\n", retval);
    		break;
    	case 0:
    		net->trans_start = jiffies;
    		__usbnet_queue_skb(&dev->txq, skb, tx_start);
    		if (dev->txq.qlen >= TX_QLEN (dev))
    			netif_stop_queue (net);
    	}
    	spin_unlock_irqrestore (&dev->txq.lock, flags);
    
    	if (retval) {
    		netif_dbg(dev, tx_err, dev->net, "drop, code %d\n", retval);
    drop:
    		dev->net->stats.tx_dropped++;
    not_drop:
    		if (skb)
    			dev_kfree_skb_any (skb);
    		usb_free_urb (urb);
    	} else
    		netif_dbg(dev, tx_queued, dev->net,
    			  "> tx, len %d, type 0x%x\n", length, skb->protocol);
    #ifdef CONFIG_PM
    deferred:
    #endif
    	return NETDEV_TX_OK;
    }
    EXPORT_SYMBOL_GPL(usbnet_start_xmit);
    
    static int rx_alloc_submit(struct usbnet *dev, gfp_t flags)
    {
    	struct urb	*urb;
    	int		i;
    	int		ret = 0;
    
    	/* don't refill the queue all at once */
    	for (i = 0; i < 10 && dev->rxq.qlen < RX_QLEN(dev); i++) {
    		urb = usb_alloc_urb(0, flags);
    		if (urb != NULL) {
    			ret = rx_submit(dev, urb, flags);
    			if (ret)
    				goto err;
    		} else {
    			ret = -ENOMEM;
    			goto err;
    		}
    	}
    err:
    	return ret;
    }
    
    /*-------------------------------------------------------------------------*/
    
    // tasklet (work deferred from completions, in_irq) or timer
    
    static void usbnet_bh (unsigned long param)
    {
    	struct usbnet		*dev = (struct usbnet *) 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:
    			entry->state = rx_cleanup;
    			rx_process (dev, skb);
    			continue;
    		case tx_done:
    		case rx_cleanup:
    			usb_free_urb (entry->urb);
    			dev_kfree_skb (skb);
    			continue;
    		default:
    			netdev_dbg(dev->net, "bogus skb state %d\n", entry->state);
    		}
    	}
    
    	/* restart RX again after disabling due to high error rate */
    	clear_bit(EVENT_RX_KILL, &dev->flags);
    
    	// 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_running (dev->net) &&
    		   netif_device_present (dev->net) &&
    		   !timer_pending (&dev->delay) &&
    		   !test_bit (EVENT_RX_HALT, &dev->flags)) {
    		int	temp = dev->rxq.qlen;
    
    		if (temp < RX_QLEN(dev)) {
    			if (rx_alloc_submit(dev, GFP_ATOMIC) == -ENOLINK)
    				return;
    			if (temp != dev->rxq.qlen)
    				netif_dbg(dev, link, dev->net,
    					  "rxqlen %d --> %d\n",
    					  temp, dev->rxq.qlen);
    			if (dev->rxq.qlen < RX_QLEN(dev))
    				tasklet_schedule (&dev->bh);
    		}
    		if (dev->txq.qlen < TX_QLEN (dev))
    			netif_wake_queue (dev->net);
    	}
    }
    
    
    /*-------------------------------------------------------------------------
     *
     * USB Device Driver support
     *
     *-------------------------------------------------------------------------*/
    
    // precondition: never called in_interrupt
    
    void usbnet_disconnect (struct usb_interface *intf)
    {
    	struct usbnet		*dev;
    	struct usb_device	*xdev;
    	struct net_device	*net;
    
    	dev = usb_get_intfdata(intf);
    	usb_set_intfdata(intf, NULL);
    	if (!dev)
    		return;
    
    	xdev = interface_to_usbdev (intf);
    
    	netif_info(dev, probe, dev->net, "unregister '%s' usb-%s-%s, %s\n",
    		   intf->dev.driver->name,
    		   xdev->bus->bus_name, xdev->devpath,
    		   dev->driver_info->description);
    
    	net = dev->net;
    	unregister_netdev (net);
    
    	cancel_work_sync(&dev->kevent);
    
    	usb_scuttle_anchored_urbs(&dev->deferred);
    
    	if (dev->driver_info->unbind)
    		dev->driver_info->unbind (dev, intf);
    
    	usb_kill_urb(dev->interrupt);
    	usb_free_urb(dev->interrupt);
    
    	free_netdev(net);
    }
    EXPORT_SYMBOL_GPL(usbnet_disconnect);
    
    static const struct net_device_ops usbnet_netdev_ops = {
    	.ndo_open		= usbnet_open,
    	.ndo_stop		= usbnet_stop,
    	.ndo_start_xmit		= usbnet_start_xmit,
    	.ndo_tx_timeout		= usbnet_tx_timeout,
    	.ndo_change_mtu		= usbnet_change_mtu,
    	.ndo_set_mac_address 	= eth_mac_addr,
    	.ndo_validate_addr	= eth_validate_addr,
    };
    
    /*-------------------------------------------------------------------------*/
    
    // precondition: never called in_interrupt
    
    static struct device_type wlan_type = {
    	.name	= "wlan",
    };
    
    static struct device_type wwan_type = {
    	.name	= "wwan",
    };
    
    int
    usbnet_probe (struct usb_interface *udev, const struct usb_device_id *prod)
    {
    	struct usbnet			*dev;
    	struct net_device		*net;
    	struct usb_host_interface	*interface;
    	struct driver_info		*info;
    	struct usb_device		*xdev;
    	int				status;
    	const char			*name;
    	struct usb_driver 	*driver = to_usb_driver(udev->dev.driver);
    
    	/* usbnet already took usb runtime pm, so have to enable the feature
    	 * for usb interface, otherwise usb_autopm_get_interface may return
    	 * failure if USB_SUSPEND(RUNTIME_PM) is enabled.
    	 */
    	if (!driver->supports_autosuspend) {
    		driver->supports_autosuspend = 1;
    		pm_runtime_enable(&udev->dev);
    	}
    
    	name = udev->dev.driver->name;
    	info = (struct driver_info *) prod->driver_info;
    	if (!info) {
    		dev_dbg (&udev->dev, "blacklisted by %s\n", name);
    		return -ENODEV;
    	}
    	xdev = interface_to_usbdev (udev);
    	interface = udev->cur_altsetting;
    
    	status = -ENOMEM;
    
    	// set up our own records
    	net = alloc_etherdev(sizeof(*dev));
    	if (!net)
    		goto out;
    
    	/* netdev_printk() needs this so do it as early as possible */
    	SET_NETDEV_DEV(net, &udev->dev);
    
    	dev = netdev_priv(net);
    	dev->udev = xdev;
    	dev->intf = udev;
    	dev->driver_info = info;
    	dev->driver_name = name;
    	dev->msg_enable = netif_msg_init (msg_level, NETIF_MSG_DRV
    				| NETIF_MSG_PROBE | NETIF_MSG_LINK);
    	skb_queue_head_init (&dev->rxq);
    	skb_queue_head_init (&dev->txq);
    	skb_queue_head_init (&dev->done);
    	skb_queue_head_init(&dev->rxq_pause);
    	dev->bh.func = usbnet_bh;
    	dev->bh.data = (unsigned long) dev;
    	INIT_WORK (&dev->kevent, kevent);
    	init_usb_anchor(&dev->deferred);
    	dev->delay.function = usbnet_bh;
    	dev->delay.data = (unsigned long) dev;
    	init_timer (&dev->delay);
    	mutex_init (&dev->phy_mutex);
    
    	dev->net = net;
    	strcpy (net->name, "usb%d");
    	memcpy (net->dev_addr, node_id, sizeof node_id);
    
    	/* rx and tx sides can use different message sizes;
    	 * bind() should set rx_urb_size in that case.
    	 */
    	dev->hard_mtu = net->mtu + net->hard_header_len;
    #if 0
    // dma_supported() is deeply broken on almost all architectures
    	// possible with some EHCI controllers
    	if (dma_supported (&udev->dev, DMA_BIT_MASK(64)))
    		net->features |= NETIF_F_HIGHDMA;
    #endif
    
    	net->netdev_ops = &usbnet_netdev_ops;
    	net->watchdog_timeo = TX_TIMEOUT_JIFFIES;
    	net->ethtool_ops = &usbnet_ethtool_ops;
    
    	// allow device-specific bind/init procedures
    	// NOTE net->name still not usable ...
    	if (info->bind) {
    		status = info->bind (dev, udev);
    		if (status < 0)
    			goto out1;
    
    		// heuristic:  "usb%d" for links we know are two-host,
    		// else "eth%d" when there's reasonable doubt.  userspace
    		// can rename the link if it knows better.
    		if ((dev->driver_info->flags & FLAG_ETHER) != 0 &&
    		    ((dev->driver_info->flags & FLAG_POINTTOPOINT) == 0 ||
    		     (net->dev_addr [0] & 0x02) == 0))
    			strcpy (net->name, "eth%d");
    		/* WLAN devices should always be named "wlan%d" */
    		if ((dev->driver_info->flags & FLAG_WLAN) != 0)
    			strcpy(net->name, "wlan%d");
    		/* WWAN devices should always be named "wwan%d" */
    		if ((dev->driver_info->flags & FLAG_WWAN) != 0)
    			strcpy(net->name, "wwan%d");
    
    		/* devices that cannot do ARP */
    		if ((dev->driver_info->flags & FLAG_NOARP) != 0)
    			net->flags |= IFF_NOARP;
    
    		/* maybe the remote can't receive an Ethernet MTU */
    		if (net->mtu > (dev->hard_mtu - net->hard_header_len))
    			net->mtu = dev->hard_mtu - net->hard_header_len;
    	} else if (!info->in || !info->out)
    		status = usbnet_get_endpoints (dev, udev);
    	else {
    		dev->in = usb_rcvbulkpipe (xdev, info->in);
    		dev->out = usb_sndbulkpipe (xdev, info->out);
    		if (!(info->flags & FLAG_NO_SETINT))
    			status = usb_set_interface (xdev,
    				interface->desc.bInterfaceNumber,
    				interface->desc.bAlternateSetting);
    		else
    			status = 0;
    
    	}
    	if (status >= 0 && dev->status)
    		status = init_status (dev, udev);
    	if (status < 0)
    		goto out3;
    
    	if (!dev->rx_urb_size)
    		dev->rx_urb_size = dev->hard_mtu;
    	dev->maxpacket = usb_maxpacket (dev->udev, dev->out, 1);
    
    	if ((dev->driver_info->flags & FLAG_WLAN) != 0)
    		SET_NETDEV_DEVTYPE(net, &wlan_type);
    	if ((dev->driver_info->flags & FLAG_WWAN) != 0)
    		SET_NETDEV_DEVTYPE(net, &wwan_type);
    
    	status = register_netdev (net);
    	if (status)
    		goto out4;
    	netif_info(dev, probe, dev->net,
    		   "register '%s' at usb-%s-%s, %s, %pM\n",
    		   udev->dev.driver->name,
    		   xdev->bus->bus_name, xdev->devpath,
    		   dev->driver_info->description,
    		   net->dev_addr);
    
    	// ok, it's ready to go.
    	usb_set_intfdata (udev, dev);
    
    	netif_device_attach (net);
    
    	if (dev->driver_info->flags & FLAG_LINK_INTR)
    		netif_carrier_off(net);
    
    	return 0;
    
    out4:
    	usb_free_urb(dev->interrupt);
    out3:
    	if (info->unbind)
    		info->unbind (dev, udev);
    out1:
    	free_netdev(net);
    out:
    	return status;
    }
    EXPORT_SYMBOL_GPL(usbnet_probe);
    
    /*-------------------------------------------------------------------------*/
    
    /*
     * suspend the whole driver as soon as the first interface is suspended
     * resume only when the last interface is resumed
     */
    
    int usbnet_suspend (struct usb_interface *intf, pm_message_t message)
    {
    	struct usbnet		*dev = usb_get_intfdata(intf);
    
    	if (!dev->suspend_count++) {
    		spin_lock_irq(&dev->txq.lock);
    		/* don't autosuspend while transmitting */
    		if (dev->txq.qlen && PMSG_IS_AUTO(message)) {
    			dev->suspend_count--;
    			spin_unlock_irq(&dev->txq.lock);
    			return -EBUSY;
    		} else {
    			set_bit(EVENT_DEV_ASLEEP, &dev->flags);
    			spin_unlock_irq(&dev->txq.lock);
    		}
    		/*
    		 * accelerate emptying of the rx and queues, to avoid
    		 * having everything error out.
    		 */
    		netif_device_detach (dev->net);
    		usbnet_terminate_urbs(dev);
    		usb_kill_urb(dev->interrupt);
    
    		/*
    		 * reattach so runtime management can use and
    		 * wake the device
    		 */
    		netif_device_attach (dev->net);
    	}
    	return 0;
    }
    EXPORT_SYMBOL_GPL(usbnet_suspend);
    
    int usbnet_resume (struct usb_interface *intf)
    {
    	struct usbnet		*dev = usb_get_intfdata(intf);
    	struct sk_buff          *skb;
    	struct urb              *res;
    	int                     retval;
    
    	if (!--dev->suspend_count) {
    		/* resume interrupt URBs */
    		if (dev->interrupt && test_bit(EVENT_DEV_OPEN, &dev->flags))
    			usb_submit_urb(dev->interrupt, GFP_NOIO);
    
    		spin_lock_irq(&dev->txq.lock);
    		while ((res = usb_get_from_anchor(&dev->deferred))) {
    
    			skb = (struct sk_buff *)res->context;
    			retval = usb_submit_urb(res, GFP_ATOMIC);
    			if (retval < 0) {
    				dev_kfree_skb_any(skb);
    				usb_free_urb(res);
    				usb_autopm_put_interface_async(dev->intf);
    			} else {
    				dev->net->trans_start = jiffies;
    				__skb_queue_tail(&dev->txq, skb);
    			}
    		}
    
    		smp_mb();
    		clear_bit(EVENT_DEV_ASLEEP, &dev->flags);
    		spin_unlock_irq(&dev->txq.lock);
    
    		if (test_bit(EVENT_DEV_OPEN, &dev->flags)) {
    			/* handle remote wakeup ASAP */
    			if (!dev->wait &&
    				netif_device_present(dev->net) &&
    				!timer_pending(&dev->delay) &&
    				!test_bit(EVENT_RX_HALT, &dev->flags))
    					rx_alloc_submit(dev, GFP_NOIO);
    
    			if (!(dev->txq.qlen >= TX_QLEN(dev)))
    				netif_tx_wake_all_queues(dev->net);
    			tasklet_schedule (&dev->bh);
    		}
    	}
    
    	if (test_and_clear_bit(EVENT_DEVICE_REPORT_IDLE, &dev->flags))
    		usb_autopm_get_interface_no_resume(intf);
    
    	return 0;
    }
    EXPORT_SYMBOL_GPL(usbnet_resume);
    
    /*
     * Either a subdriver implements manage_power, then it is assumed to always
     * be ready to be suspended or it reports the readiness to be suspended
     * explicitly
     */
    void usbnet_device_suggests_idle(struct usbnet *dev)
    {
    	if (!test_and_set_bit(EVENT_DEVICE_REPORT_IDLE, &dev->flags)) {
    		dev->intf->needs_remote_wakeup = 1;
    		usb_autopm_put_interface_async(dev->intf);
    	}
    }
    EXPORT_SYMBOL(usbnet_device_suggests_idle);
    
    /*
     * For devices that can do without special commands
     */
    int usbnet_manage_power(struct usbnet *dev, int on)
    {
    	dev->intf->needs_remote_wakeup = on;
    	return 0;
    }
    EXPORT_SYMBOL(usbnet_manage_power);
    
    /*-------------------------------------------------------------------------*/
    static int __usbnet_read_cmd(struct usbnet *dev, u8 cmd, u8 reqtype,
    			     u16 value, u16 index, void *data, u16 size)
    {
    	void *buf = NULL;
    	int err = -ENOMEM;
    
    	netdev_dbg(dev->net, "usbnet_read_cmd cmd=0x%02x reqtype=%02x"
    		   " value=0x%04x index=0x%04x size=%d\n",
    		   cmd, reqtype, value, index, size);
    
    	if (data) {
    		buf = kmalloc(size, GFP_KERNEL);
    		if (!buf)
    			goto out;
    	}
    
    	err = usb_control_msg(dev->udev, usb_rcvctrlpipe(dev->udev, 0),
    			      cmd, reqtype, value, index, buf, size,
    			      USB_CTRL_GET_TIMEOUT);
    	if (err > 0 && err <= size)
    		memcpy(data, buf, err);
    	kfree(buf);
    out:
    	return err;
    }
    
    static int __usbnet_write_cmd(struct usbnet *dev, u8 cmd, u8 reqtype,
    			      u16 value, u16 index, const void *data,
    			      u16 size)
    {
    	void *buf = NULL;
    	int err = -ENOMEM;
    
    	netdev_dbg(dev->net, "usbnet_write_cmd cmd=0x%02x reqtype=%02x"
    		   " value=0x%04x index=0x%04x size=%d\n",
    		   cmd, reqtype, value, index, size);
    
    	if (data) {
    		buf = kmemdup(data, size, GFP_KERNEL);
    		if (!buf)
    			goto out;
    	}
    
    	err = usb_control_msg(dev->udev, usb_sndctrlpipe(dev->udev, 0),
    			      cmd, reqtype, value, index, buf, size,
    			      USB_CTRL_SET_TIMEOUT);
    	kfree(buf);
    
    out:
    	return err;
    }
    
    /*
     * The function can't be called inside suspend/resume callback,
     * otherwise deadlock will be caused.
     */
    int usbnet_read_cmd(struct usbnet *dev, u8 cmd, u8 reqtype,
    		    u16 value, u16 index, void *data, u16 size)
    {
    	int ret;
    
    	if (usb_autopm_get_interface(dev->intf) < 0)
    		return -ENODEV;
    	ret = __usbnet_read_cmd(dev, cmd, reqtype, value, index,
    				data, size);
    	usb_autopm_put_interface(dev->intf);
    	return ret;
    }
    EXPORT_SYMBOL_GPL(usbnet_read_cmd);
    
    /*
     * The function can't be called inside suspend/resume callback,
     * otherwise deadlock will be caused.
     */
    int usbnet_write_cmd(struct usbnet *dev, u8 cmd, u8 reqtype,
    		     u16 value, u16 index, const void *data, u16 size)
    {
    	int ret;
    
    	if (usb_autopm_get_interface(dev->intf) < 0)
    		return -ENODEV;
    	ret = __usbnet_write_cmd(dev, cmd, reqtype, value, index,
    				 data, size);
    	usb_autopm_put_interface(dev->intf);
    	return ret;
    }
    EXPORT_SYMBOL_GPL(usbnet_write_cmd);
    
    /*
     * The function can be called inside suspend/resume callback safely
     * and should only be called by suspend/resume callback generally.
     */
    int usbnet_read_cmd_nopm(struct usbnet *dev, u8 cmd, u8 reqtype,
    			  u16 value, u16 index, void *data, u16 size)
    {
    	return __usbnet_read_cmd(dev, cmd, reqtype, value, index,
    				 data, size);
    }
    EXPORT_SYMBOL_GPL(usbnet_read_cmd_nopm);
    
    /*
     * The function can be called inside suspend/resume callback safely
     * and should only be called by suspend/resume callback generally.
     */
    int usbnet_write_cmd_nopm(struct usbnet *dev, u8 cmd, u8 reqtype,
    			  u16 value, u16 index, const void *data,
    			  u16 size)
    {
    	return __usbnet_write_cmd(dev, cmd, reqtype, value, index,
    				  data, size);
    }
    EXPORT_SYMBOL_GPL(usbnet_write_cmd_nopm);
    
    static void usbnet_async_cmd_cb(struct urb *urb)
    {
    	struct usb_ctrlrequest *req = (struct usb_ctrlrequest *)urb->context;
    	int status = urb->status;
    
    	if (status < 0)
    		dev_dbg(&urb->dev->dev, "%s failed with %d",
    			__func__, status);
    
    	kfree(req);
    	usb_free_urb(urb);
    }
    
    /*
     * The caller must make sure that device can't be put into suspend
     * state until the control URB completes.
     */
    int usbnet_write_cmd_async(struct usbnet *dev, u8 cmd, u8 reqtype,
    			   u16 value, u16 index, const void *data, u16 size)
    {
    	struct usb_ctrlrequest *req = NULL;
    	struct urb *urb;
    	int err = -ENOMEM;
    	void *buf = NULL;
    
    	netdev_dbg(dev->net, "usbnet_write_cmd cmd=0x%02x reqtype=%02x"
    		   " value=0x%04x index=0x%04x size=%d\n",
    		   cmd, reqtype, value, index, size);
    
    	urb = usb_alloc_urb(0, GFP_ATOMIC);
    	if (!urb) {
    		netdev_err(dev->net, "Error allocating URB in"
    			   " %s!\n", __func__);
    		goto fail;
    	}
    
    	if (data) {
    		buf = kmemdup(data, size, GFP_ATOMIC);
    		if (!buf) {
    			netdev_err(dev->net, "Error allocating buffer"
    				   " in %s!\n", __func__);
    			goto fail_free;
    		}
    	}
    
    	req = kmalloc(sizeof(struct usb_ctrlrequest), GFP_ATOMIC);
    	if (!req) {
    		netdev_err(dev->net, "Failed to allocate memory for %s\n",
    			   __func__);
    		goto fail_free_buf;
    	}
    
    	req->bRequestType = reqtype;
    	req->bRequest = cmd;
    	req->wValue = cpu_to_le16(value);
    	req->wIndex = cpu_to_le16(index);
    	req->wLength = cpu_to_le16(size);
    
    	usb_fill_control_urb(urb, dev->udev,
    			     usb_sndctrlpipe(dev->udev, 0),
    			     (void *)req, buf, size,
    			     usbnet_async_cmd_cb, req);
    	urb->transfer_flags |= URB_FREE_BUFFER;
    
    	err = usb_submit_urb(urb, GFP_ATOMIC);
    	if (err < 0) {
    		netdev_err(dev->net, "Error submitting the control"
    			   " message: status=%d\n", err);
    		goto fail_free;
    	}
    	return 0;
    
    fail_free_buf:
    	kfree(buf);
    fail_free:
    	kfree(req);
    	usb_free_urb(urb);
    fail:
    	return err;
    
    }
    EXPORT_SYMBOL_GPL(usbnet_write_cmd_async);
    /*-------------------------------------------------------------------------*/
    
    static int __init usbnet_init(void)
    {
    	/* Compiler should optimize this out. */
    	BUILD_BUG_ON(
    		FIELD_SIZEOF(struct sk_buff, cb) < sizeof(struct skb_data));
    
    	eth_random_addr(node_id);
    	return 0;
    }
    module_init(usbnet_init);
    
    static void __exit usbnet_exit(void)
    {
    }
    module_exit(usbnet_exit);
    
    MODULE_AUTHOR("David Brownell");
    MODULE_DESCRIPTION("USB network driver framework");
    MODULE_LICENSE("GPL");