usb ethernet gadget: split out network core

Abstract the peripheral side Ethernet-over-USB link layer code from
the all-in-one Ethernet gadget driver into a component that can be
called by various functions, so the various flavors can be split
apart and selectively reused.

A notable difference from the approach taken with the serial link
layer code (beyond talking to NET not TTY) is that because of the
initialization requirements, this only supports one network link.
(And one set of Ethernet link addresses.)

That is, each configuration may have only one instance of a network
function.  This doesn't change behavior; the current code has that
same restriction.  If you want multiple logical links, that can
easily be done using network layer tools.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 967 insertions, 0 deletions

diff --git a/drivers/usb/gadget/u_ether.c b/drivers/usb/gadget/u_ether.c
new file mode 100644
index 000000000000..5458f43a8668
--- /dev/null
+++ b/drivers/usb/gadget/u_ether.c
@@ -0,0 +1,967 @@
+/*
+ * u_ether.c -- Ethernet-over-USB link layer utilities for Gadget stack
+ *
+ * Copyright (C) 2003-2005,2008 David Brownell
+ * Copyright (C) 2003-2004 Robert Schwebel, Benedikt Spranger
+ * Copyright (C) 2008 Nokia Corporation
+ *
+ * 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
+ */
+
+/* #define VERBOSE_DEBUG */
+
+#include <linux/kernel.h>
+#include <linux/utsname.h>
+#include <linux/device.h>
+#include <linux/ctype.h>
+#include <linux/etherdevice.h>
+#include <linux/ethtool.h>
+
+#include "u_ether.h"
+
+
+/*
+ * This component encapsulates the Ethernet link glue needed to provide
+ * one (!) network link through the USB gadget stack, normally "usb0".
+ *
+ * The control and data models are handled by the function driver which
+ * connects to this code; such as CDC Ethernet, "CDC Subset", or RNDIS.
+ * That includes all descriptor and endpoint management.
+ *
+ * Link level addressing is handled by this component using module
+ * parameters; if no such parameters are provided, random link level
+ * addresses are used.  Each end of the link uses one address.  The
+ * host end address is exported in various ways, and is often recorded
+ * in configuration databases.
+ *
+ * The driver which assembles each configuration using such a link is
+ * responsible for ensuring that each configuration includes at most one
+ * instance of is network link.  (The network layer provides ways for
+ * this single "physical" link to be used by multiple virtual links.)
+ */
+
+#define DRIVER_VERSION	"29-May-2008"
+
+struct eth_dev {
+	/* lock is held while accessing port_usb
+	 * or updating its backlink port_usb->ioport
+	 */
+	spinlock_t		lock;
+	struct gether		*port_usb;
+
+	struct net_device	*net;
+	struct usb_gadget	*gadget;
+
+	spinlock_t		req_lock;	/* guard {rx,tx}_reqs */
+	struct list_head	tx_reqs, rx_reqs;
+	atomic_t		tx_qlen;
+
+	unsigned		header_len;
+	struct sk_buff		*(*wrap)(struct sk_buff *skb);
+	int			(*unwrap)(struct sk_buff *skb);
+
+	struct work_struct	work;
+
+	unsigned long		todo;
+#define	WORK_RX_MEMORY		0
+
+	bool			zlp;
+	u8			host_mac[ETH_ALEN];
+};
+
+/*-------------------------------------------------------------------------*/
+
+#define RX_EXTRA	20	/* bytes guarding against rx overflows */
+
+#define DEFAULT_QLEN	2	/* double buffering by default */
+
+
+#ifdef CONFIG_USB_GADGET_DUALSPEED
+
+static unsigned qmult = 5;
+module_param(qmult, uint, S_IRUGO|S_IWUSR);
+MODULE_PARM_DESC(qmult, "queue length multiplier at high speed");
+
+#else	/* full speed (low speed doesn't do bulk) */
+#define qmult		1
+#endif
+
+/* for dual-speed hardware, use deeper queues at highspeed */
+static inline int qlen(struct usb_gadget *gadget)
+{
+	if (gadget_is_dualspeed(gadget) && gadget->speed == USB_SPEED_HIGH)
+		return qmult * DEFAULT_QLEN;
+	else
+		return DEFAULT_QLEN;
+}
+
+/*-------------------------------------------------------------------------*/
+
+/* REVISIT there must be a better way than having two sets
+ * of debug calls ...
+ */
+
+#undef DBG
+#undef VDBG
+#undef ERROR
+#undef WARN
+#undef INFO
+
+#define xprintk(d, level, fmt, args...) \
+	printk(level "%s: " fmt , (d)->net->name , ## args)
+
+#ifdef DEBUG
+#undef DEBUG
+#define DBG(dev, fmt, args...) \
+	xprintk(dev , KERN_DEBUG , fmt , ## args)
+#else
+#define DBG(dev, fmt, args...) \
+	do { } while (0)
+#endif /* DEBUG */
+
+#ifdef VERBOSE_DEBUG
+#define VDBG	DBG
+#else
+#define VDBG(dev, fmt, args...) \
+	do { } while (0)
+#endif /* DEBUG */
+
+#define ERROR(dev, fmt, args...) \
+	xprintk(dev , KERN_ERR , fmt , ## args)
+#define WARN(dev, fmt, args...) \
+	xprintk(dev , KERN_WARNING , fmt , ## args)
+#define INFO(dev, fmt, args...) \
+	xprintk(dev , KERN_INFO , fmt , ## args)
+
+/*-------------------------------------------------------------------------*/
+
+/* NETWORK DRIVER HOOKUP (to the layer above this driver) */
+
+static int eth_change_mtu(struct net_device *net, int new_mtu)
+{
+	struct eth_dev	*dev = netdev_priv(net);
+	unsigned long	flags;
+	int		status = 0;
+
+	/* don't change MTU on "live" link (peer won't know) */
+	spin_lock_irqsave(&dev->lock, flags);
+	if (dev->port_usb)
+		status = -EBUSY;
+	else if (new_mtu <= ETH_HLEN || new_mtu > ETH_FRAME_LEN)
+		status = -ERANGE;
+	else
+		net->mtu = new_mtu;
+	spin_unlock_irqrestore(&dev->lock, flags);
+
+	return status;
+}
+
+static void eth_get_drvinfo(struct net_device *net, struct ethtool_drvinfo *p)
+{
+	struct eth_dev	*dev = netdev_priv(net);
+
+	strlcpy(p->driver, "g_ether", sizeof p->driver);
+	strlcpy(p->version, DRIVER_VERSION, sizeof p->version);
+	strlcpy(p->fw_version, dev->gadget->name, sizeof p->fw_version);
+	strlcpy(p->bus_info, dev_name(&dev->gadget->dev), sizeof p->bus_info);
+}
+
+static u32 eth_get_link(struct net_device *net)
+{
+	struct eth_dev	*dev = netdev_priv(net);
+	return dev->gadget->speed != USB_SPEED_UNKNOWN;
+}
+
+/* REVISIT can also support:
+ *   - WOL (by tracking suspends and issuing remote wakeup)
+ *   - msglevel (implies updated messaging)
+ *   - ... probably more ethtool ops
+ */
+
+static struct ethtool_ops ops = {
+	.get_drvinfo = eth_get_drvinfo,
+	.get_link = eth_get_link
+};
+
+static void defer_kevent(struct eth_dev *dev, int flag)
+{
+	if (test_and_set_bit(flag, &dev->todo))
+		return;
+	if (!schedule_work(&dev->work))
+		ERROR(dev, "kevent %d may have been dropped\n", flag);
+	else
+		DBG(dev, "kevent %d scheduled\n", flag);
+}
+
+static void rx_complete(struct usb_ep *ep, struct usb_request *req);
+
+static int
+rx_submit(struct eth_dev *dev, struct usb_request *req, gfp_t gfp_flags)
+{
+	struct sk_buff	*skb;
+	int		retval = -ENOMEM;
+	size_t		size = 0;
+	struct usb_ep	*out;
+	unsigned long	flags;
+
+	spin_lock_irqsave(&dev->lock, flags);
+	if (dev->port_usb)
+		out = dev->port_usb->out_ep;
+	else
+		out = NULL;
+	spin_unlock_irqrestore(&dev->lock, flags);
+
+	if (!out)
+		return -ENOTCONN;
+
+
+	/* Padding up to RX_EXTRA handles minor disagreements with host.
+	 * Normally we use the USB "terminate on short read" convention;
+	 * so allow up to (N*maxpacket), since that memory is normally
+	 * already allocated.  Some hardware doesn't deal well with short
+	 * reads (e.g. DMA must be N*maxpacket), so for now don't trim a
+	 * byte off the end (to force hardware errors on overflow).
+	 *
+	 * RNDIS uses internal framing, and explicitly allows senders to
+	 * pad to end-of-packet.  That's potentially nice for speed, but
+	 * means receivers can't recover lost synch on their own (because
+	 * new packets don't only start after a short RX).
+	 */
+	size += sizeof(struct ethhdr) + dev->net->mtu + RX_EXTRA;
+	size += dev->port_usb->header_len;
+	size += out->maxpacket - 1;
+	size -= size % out->maxpacket;
+
+	skb = alloc_skb(size + NET_IP_ALIGN, gfp_flags);
+	if (skb == NULL) {
+		DBG(dev, "no rx skb\n");
+		goto enomem;
+	}
+
+	/* Some platforms perform better when IP packets are aligned,
+	 * but on at least one, checksumming fails otherwise.  Note:
+	 * RNDIS headers involve variable numbers of LE32 values.
+	 */
+	skb_reserve(skb, NET_IP_ALIGN);
+
+	req->buf = skb->data;
+	req->length = size;
+	req->complete = rx_complete;
+	req->context = skb;
+
+	retval = usb_ep_queue(out, req, gfp_flags);
+	if (retval == -ENOMEM)
+enomem:
+		defer_kevent(dev, WORK_RX_MEMORY);
+	if (retval) {
+		DBG(dev, "rx submit --> %d\n", retval);
+		if (skb)
+			dev_kfree_skb_any(skb);
+		spin_lock_irqsave(&dev->req_lock, flags);
+		list_add(&req->list, &dev->rx_reqs);
+		spin_unlock_irqrestore(&dev->req_lock, flags);
+	}
+	return retval;
+}
+
+static void rx_complete(struct usb_ep *ep, struct usb_request *req)
+{
+	struct sk_buff	*skb = req->context;
+	struct eth_dev	*dev = ep->driver_data;
+	int		status = req->status;
+
+	switch (status) {
+
+	/* normal completion */
+	case 0:
+		skb_put(skb, req->actual);
+		if (dev->unwrap)
+			status = dev->unwrap(skb);
+		if (status < 0
+				|| ETH_HLEN > skb->len
+				|| skb->len > ETH_FRAME_LEN) {
+			dev->net->stats.rx_errors++;
+			dev->net->stats.rx_length_errors++;
+			DBG(dev, "rx length %d\n", skb->len);
+			break;
+		}
+
+		skb->protocol = eth_type_trans(skb, dev->net);
+		dev->net->stats.rx_packets++;
+		dev->net->stats.rx_bytes += skb->len;
+
+		/* no buffer copies needed, unless hardware can't
+		 * use skb buffers.
+		 */
+		status = netif_rx(skb);
+		skb = NULL;
+		break;
+
+	/* software-driven interface shutdown */
+	case -ECONNRESET:		/* unlink */
+	case -ESHUTDOWN:		/* disconnect etc */
+		VDBG(dev, "rx shutdown, code %d\n", status);
+		goto quiesce;
+
+	/* for hardware automagic (such as pxa) */
+	case -ECONNABORTED:		/* endpoint reset */
+		DBG(dev, "rx %s reset\n", ep->name);
+		defer_kevent(dev, WORK_RX_MEMORY);
+quiesce:
+		dev_kfree_skb_any(skb);
+		goto clean;
+
+	/* data overrun */
+	case -EOVERFLOW:
+		dev->net->stats.rx_over_errors++;
+		/* FALLTHROUGH */
+
+	default:
+		dev->net->stats.rx_errors++;
+		DBG(dev, "rx status %d\n", status);
+		break;
+	}
+
+	if (skb)
+		dev_kfree_skb_any(skb);
+	if (!netif_running(dev->net)) {
+clean:
+		spin_lock(&dev->req_lock);
+		list_add(&req->list, &dev->rx_reqs);
+		spin_unlock(&dev->req_lock);
+		req = NULL;
+	}
+	if (req)
+		rx_submit(dev, req, GFP_ATOMIC);
+}
+
+static int prealloc(struct list_head *list, struct usb_ep *ep, unsigned n)
+{
+	unsigned		i;
+	struct usb_request	*req;
+
+	if (!n)
+		return -ENOMEM;
+
+	/* queue/recycle up to N requests */
+	i = n;
+	list_for_each_entry(req, list, list) {
+		if (i-- == 0)
+			goto extra;
+	}
+	while (i--) {
+		req = usb_ep_alloc_request(ep, GFP_ATOMIC);
+		if (!req)
+			return list_empty(list) ? -ENOMEM : 0;
+		list_add(&req->list, list);
+	}
+	return 0;
+
+extra:
+	/* free extras */
+	for (;;) {
+		struct list_head	*next;
+
+		next = req->list.next;
+		list_del(&req->list);
+		usb_ep_free_request(ep, req);
+
+		if (next == list)
+			break;
+
+		req = container_of(next, struct usb_request, list);
+	}
+	return 0;
+}
+
+static int alloc_requests(struct eth_dev *dev, struct gether *link, unsigned n)
+{
+	int	status;
+
+	spin_lock(&dev->req_lock);
+	status = prealloc(&dev->tx_reqs, link->in_ep, n);
+	if (status < 0)
+		goto fail;
+	status = prealloc(&dev->rx_reqs, link->out_ep, n);
+	if (status < 0)
+		goto fail;
+	goto done;
+fail:
+	DBG(dev, "can't alloc requests\n");
+done:
+	spin_unlock(&dev->req_lock);
+	return status;
+}
+
+static void rx_fill(struct eth_dev *dev, gfp_t gfp_flags)
+{
+	struct usb_request	*req;
+	unsigned long		flags;
+
+	/* fill unused rxq slots with some skb */
+	spin_lock_irqsave(&dev->req_lock, flags);
+	while (!list_empty(&dev->rx_reqs)) {
+		req = container_of(dev->rx_reqs.next,
+				struct usb_request, list);
+		list_del_init(&req->list);
+		spin_unlock_irqrestore(&dev->req_lock, flags);
+
+		if (rx_submit(dev, req, gfp_flags) < 0) {
+			defer_kevent(dev, WORK_RX_MEMORY);
+			return;
+		}
+
+		spin_lock_irqsave(&dev->req_lock, flags);
+	}
+	spin_unlock_irqrestore(&dev->req_lock, flags);
+}
+
+static void eth_work(struct work_struct *work)
+{
+	struct eth_dev	*dev = container_of(work, struct eth_dev, work);
+
+	if (test_and_clear_bit(WORK_RX_MEMORY, &dev->todo)) {
+		if (netif_running(dev->net))
+			rx_fill(dev, GFP_KERNEL);
+	}
+
+	if (dev->todo)
+		DBG(dev, "work done, flags = 0x%lx\n", dev->todo);
+}
+
+static void tx_complete(struct usb_ep *ep, struct usb_request *req)
+{
+	struct sk_buff	*skb = req->context;
+	struct eth_dev	*dev = ep->driver_data;
+
+	switch (req->status) {
+	default:
+		dev->net->stats.tx_errors++;
+		VDBG(dev, "tx err %d\n", req->status);
+		/* FALLTHROUGH */
+	case -ECONNRESET:		/* unlink */
+	case -ESHUTDOWN:		/* disconnect etc */
+		break;
+	case 0:
+		dev->net->stats.tx_bytes += skb->len;
+	}
+	dev->net->stats.tx_packets++;
+
+	spin_lock(&dev->req_lock);
+	list_add(&req->list, &dev->tx_reqs);
+	spin_unlock(&dev->req_lock);
+	dev_kfree_skb_any(skb);
+
+	atomic_dec(&dev->tx_qlen);
+	if (netif_carrier_ok(dev->net))
+		netif_wake_queue(dev->net);
+}
+
+static inline int is_promisc(u16 cdc_filter)
+{
+	return cdc_filter & USB_CDC_PACKET_TYPE_PROMISCUOUS;
+}
+
+static int eth_start_xmit(struct sk_buff *skb, struct net_device *net)
+{
+	struct eth_dev		*dev = netdev_priv(net);
+	int			length = skb->len;
+	int			retval;
+	struct usb_request	*req = NULL;
+	unsigned long		flags;
+	struct usb_ep		*in;
+	u16			cdc_filter;
+
+	spin_lock_irqsave(&dev->lock, flags);
+	if (dev->port_usb) {
+		in = dev->port_usb->in_ep;
+		cdc_filter = dev->port_usb->cdc_filter;
+	} else {
+		in = NULL;
+		cdc_filter = 0;
+	}
+	spin_unlock_irqrestore(&dev->lock, flags);
+
+	if (!in) {
+		dev_kfree_skb_any(skb);
+		return 0;
+	}
+
+	/* apply outgoing CDC or RNDIS filters */
+	if (!is_promisc(cdc_filter)) {
+		u8		*dest = skb->data;
+
+		if (is_multicast_ether_addr(dest)) {
+			u16	type;
+
+			/* ignores USB_CDC_PACKET_TYPE_MULTICAST and host
+			 * SET_ETHERNET_MULTICAST_FILTERS requests
+			 */
+			if (is_broadcast_ether_addr(dest))
+				type = USB_CDC_PACKET_TYPE_BROADCAST;
+			else
+				type = USB_CDC_PACKET_TYPE_ALL_MULTICAST;
+			if (!(cdc_filter & type)) {
+				dev_kfree_skb_any(skb);
+				return 0;
+			}
+		}
+		/* ignores USB_CDC_PACKET_TYPE_DIRECTED */
+	}
+
+	spin_lock_irqsave(&dev->req_lock, flags);
+	/*
+	 * this freelist can be empty if an interrupt triggered disconnect()
+	 * and reconfigured the gadget (shutting down this queue) after the
+	 * network stack decided to xmit but before we got the spinlock.
+	 */
+	if (list_empty(&dev->tx_reqs)) {
+		spin_unlock_irqrestore(&dev->req_lock, flags);
+		return 1;
+	}
+
+	req = container_of(dev->tx_reqs.next, struct usb_request, list);
+	list_del(&req->list);
+
+	/* temporarily stop TX queue when the freelist empties */
+	if (list_empty(&dev->tx_reqs))
+		netif_stop_queue(net);
+	spin_unlock_irqrestore(&dev->req_lock, flags);
+
+	/* no buffer copies needed, unless the network stack did it
+	 * or the hardware can't use skb buffers.
+	 * or there's not enough space for extra headers we need
+	 */
+	if (dev->wrap) {
+		struct sk_buff	*skb_new;
+
+		skb_new = dev->wrap(skb);
+		if (!skb_new)
+			goto drop;
+
+		dev_kfree_skb_any(skb);
+		skb = skb_new;
+		length = skb->len;
+	}
+	req->buf = skb->data;
+	req->context = skb;
+	req->complete = tx_complete;
+
+	/* use zlp framing on tx for strict CDC-Ether conformance,
+	 * though any robust network rx path ignores extra padding.
+	 * and some hardware doesn't like to write zlps.
+	 */
+	req->zero = 1;
+	if (!dev->zlp && (length % in->maxpacket) == 0)
+		length++;
+
+	req->length = length;
+
+	/* throttle highspeed IRQ rate back slightly */
+	if (gadget_is_dualspeed(dev->gadget))
+		req->no_interrupt = (dev->gadget->speed == USB_SPEED_HIGH)
+			? ((atomic_read(&dev->tx_qlen) % qmult) != 0)
+			: 0;
+
+	retval = usb_ep_queue(in, req, GFP_ATOMIC);
+	switch (retval) {
+	default:
+		DBG(dev, "tx queue err %d\n", retval);
+		break;
+	case 0:
+		net->trans_start = jiffies;
+		atomic_inc(&dev->tx_qlen);
+	}
+
+	if (retval) {
+drop:
+		dev->net->stats.tx_dropped++;
+		dev_kfree_skb_any(skb);
+		spin_lock_irqsave(&dev->req_lock, flags);
+		if (list_empty(&dev->tx_reqs))
+			netif_start_queue(net);
+		list_add(&req->list, &dev->tx_reqs);
+		spin_unlock_irqrestore(&dev->req_lock, flags);
+	}
+	return 0;
+}
+
+/*-------------------------------------------------------------------------*/
+
+static void eth_start(struct eth_dev *dev, gfp_t gfp_flags)
+{
+	DBG(dev, "%s\n", __func__);
+
+	/* fill the rx queue */
+	rx_fill(dev, gfp_flags);
+
+	/* and open the tx floodgates */
+	atomic_set(&dev->tx_qlen, 0);
+	netif_wake_queue(dev->net);
+}
+
+static int eth_open(struct net_device *net)
+{
+	struct eth_dev	*dev = netdev_priv(net);
+	struct gether	*link;
+
+	DBG(dev, "%s\n", __func__);
+	if (netif_carrier_ok(dev->net))
+		eth_start(dev, GFP_KERNEL);
+
+	spin_lock_irq(&dev->lock);
+	link = dev->port_usb;
+	if (link && link->open)
+		link->open(link);
+	spin_unlock_irq(&dev->lock);
+
+	return 0;
+}
+
+static int eth_stop(struct net_device *net)
+{
+	struct eth_dev	*dev = netdev_priv(net);
+	unsigned long	flags;
+
+	VDBG(dev, "%s\n", __func__);
+	netif_stop_queue(net);
+
+	DBG(dev, "stop stats: rx/tx %ld/%ld, errs %ld/%ld\n",
+		dev->net->stats.rx_packets, dev->net->stats.tx_packets,
+		dev->net->stats.rx_errors, dev->net->stats.tx_errors
+		);
+
+	/* ensure there are no more active requests */
+	spin_lock_irqsave(&dev->lock, flags);
+	if (dev->port_usb) {
+		struct gether	*link = dev->port_usb;
+
+		if (link->close)
+			link->close(link);
+
+		/* NOTE:  we have no abort-queue primitive we could use
+		 * to cancel all pending I/O.  Instead, we disable then
+		 * reenable the endpoints ... this idiom may leave toggle
+		 * wrong, but that's a self-correcting error.
+		 *
+		 * REVISIT:  we *COULD* just let the transfers complete at
+		 * their own pace; the network stack can handle old packets.
+		 * For the moment we leave this here, since it works.
+		 */
+		usb_ep_disable(link->in_ep);
+		usb_ep_disable(link->out_ep);
+		if (netif_carrier_ok(net)) {
+			DBG(dev, "host still using in/out endpoints\n");
+			usb_ep_enable(link->in_ep, link->in);
+			usb_ep_enable(link->out_ep, link->out);
+		}
+	}
+	spin_unlock_irqrestore(&dev->lock, flags);
+
+	return 0;
+}
+
+/*-------------------------------------------------------------------------*/
+
+/* initial value, changed by "ifconfig usb0 hw ether xx:xx:xx:xx:xx:xx" */
+static char *dev_addr;
+module_param(dev_addr, charp, S_IRUGO);
+MODULE_PARM_DESC(dev_addr, "Device Ethernet Address");
+
+/* this address is invisible to ifconfig */
+static char *host_addr;
+module_param(host_addr, charp, S_IRUGO);
+MODULE_PARM_DESC(host_addr, "Host Ethernet Address");
+
+
+static u8 __init nibble(unsigned char c)
+{
+	if (isdigit(c))
+		return c - '0';
+	c = toupper(c);
+	if (isxdigit(c))
+		return 10 + c - 'A';
+	return 0;
+}
+
+static int __init get_ether_addr(const char *str, u8 *dev_addr)
+{
+	if (str) {
+		unsigned	i;
+
+		for (i = 0; i < 6; i++) {
+			unsigned char num;
+
+			if ((*str == '.') || (*str == ':'))
+				str++;
+			num = nibble(*str++) << 4;
+			num |= (nibble(*str++));
+			dev_addr [i] = num;
+		}
+		if (is_valid_ether_addr(dev_addr))
+			return 0;
+	}
+	random_ether_addr(dev_addr);
+	return 1;
+}
+
+static struct eth_dev *the_dev;
+
+
+/**
+ * gether_setup - initialize one ethernet-over-usb link
+ * @g: gadget to associated with these links
+ * @ethaddr: NULL, or a buffer in which the ethernet address of the
+ *	host side of the link is recorded
+ * Context: may sleep
+ *
+ * This sets up the single network link that may be exported by a
+ * gadget driver using this framework.  The link layer addresses are
+ * set up using module parameters.
+ *
+ * Returns negative errno, or zero on success
+ */
+int __init gether_setup(struct usb_gadget *g, u8 ethaddr[ETH_ALEN])
+{
+	struct eth_dev		*dev;
+	struct net_device	*net;
+	int			status;
+
+	if (the_dev)
+		return -EBUSY;
+
+	net = alloc_etherdev(sizeof *dev);
+	if (!net)
+		return -ENOMEM;
+
+	dev = netdev_priv(net);
+	spin_lock_init(&dev->lock);
+	spin_lock_init(&dev->req_lock);
+	INIT_WORK(&dev->work, eth_work);
+	INIT_LIST_HEAD(&dev->tx_reqs);
+	INIT_LIST_HEAD(&dev->rx_reqs);
+
+	/* network device setup */
+	dev->net = net;
+	strcpy(net->name, "usb%d");
+
+	if (get_ether_addr(dev_addr, net->dev_addr))
+		dev_warn(&g->dev,
+			"using random %s ethernet address\n", "self");
+	if (get_ether_addr(host_addr, dev->host_mac))
+		dev_warn(&g->dev,
+			"using random %s ethernet address\n", "host");
+
+	if (ethaddr)
+		memcpy(ethaddr, dev->host_mac, ETH_ALEN);
+
+	net->change_mtu = eth_change_mtu;
+	net->hard_start_xmit = eth_start_xmit;
+	net->open = eth_open;
+	net->stop = eth_stop;
+	/* watchdog_timeo, tx_timeout ... */
+	/* set_multicast_list */
+	SET_ETHTOOL_OPS(net, &ops);
+
+	/* two kinds of host-initiated state changes:
+	 *  - iff DATA transfer is active, carrier is "on"
+	 *  - tx queueing enabled if open *and* carrier is "on"
+	 */
+	netif_stop_queue(net);
+	netif_carrier_off(net);
+
+	dev->gadget = g;
+	SET_NETDEV_DEV(net, &g->dev);
+
+	status = register_netdev(net);
+	if (status < 0) {
+		dev_dbg(&g->dev, "register_netdev failed, %d\n", status);
+		free_netdev(net);
+	} else {
+		DECLARE_MAC_BUF(tmp);
+
+		INFO(dev, "MAC %s\n", print_mac(tmp, net->dev_addr));
+		INFO(dev, "HOST MAC %s\n", print_mac(tmp, dev->host_mac));
+
+		the_dev = dev;
+	}
+
+	return status;
+}
+
+/**
+ * gether_cleanup - remove Ethernet-over-USB device
+ * Context: may sleep
+ *
+ * This is called to free all resources allocated by @gether_setup().
+ */
+void gether_cleanup(void)
+{
+	if (!the_dev)
+		return;
+
+	unregister_netdev(the_dev->net);
+	free_netdev(the_dev->net);
+
+	/* assuming we used keventd, it must quiesce too */
+	flush_scheduled_work();
+
+	the_dev = NULL;
+}
+
+
+/**
+ * gether_connect - notify network layer that USB link is active
+ * @link: the USB link, set up with endpoints, descriptors matching
+ *	current device speed, and any framing wrapper(s) set up.
+ * Context: irqs blocked
+ *
+ * This is called to activate endpoints and let the network layer know
+ * the connection is active ("carrier detect").  It may cause the I/O
+ * queues to open and start letting network packets flow, but will in
+ * any case activate the endpoints so that they respond properly to the
+ * USB host.
+ *
+ * Verify net_device pointer returned using IS_ERR().  If it doesn't
+ * indicate some error code (negative errno), ep->driver_data values
+ * have been overwritten.
+ */
+struct net_device *gether_connect(struct gether *link)
+{
+	struct eth_dev		*dev = the_dev;
+	int			result = 0;
+
+	if (!dev)
+		return ERR_PTR(-EINVAL);
+
+	link->in_ep->driver_data = dev;
+	result = usb_ep_enable(link->in_ep, link->in);
+	if (result != 0) {
+		DBG(dev, "enable %s --> %d\n",
+			link->in_ep->name, result);
+		goto fail0;
+	}
+
+	link->out_ep->driver_data = dev;
+	result = usb_ep_enable(link->out_ep, link->out);
+	if (result != 0) {
+		DBG(dev, "enable %s --> %d\n",
+			link->out_ep->name, result);
+		goto fail1;
+	}
+
+	if (result == 0)
+		result = alloc_requests(dev, link, qlen(dev->gadget));
+
+	if (result == 0) {
+		dev->zlp = link->is_zlp_ok;
+		DBG(dev, "qlen %d\n", qlen(dev->gadget));
+
+		dev->header_len = link->header_len;
+		dev->unwrap = link->unwrap;
+		dev->wrap = link->wrap;
+
+		spin_lock(&dev->lock);
+		dev->port_usb = link;
+		link->ioport = dev;
+		spin_unlock(&dev->lock);
+
+		netif_carrier_on(dev->net);
+		if (netif_running(dev->net))
+			eth_start(dev, GFP_ATOMIC);
+
+	/* on error, disable any endpoints  */
+	} else {
+		(void) usb_ep_disable(link->out_ep);
+fail1:
+		(void) usb_ep_disable(link->in_ep);
+	}
+fail0:
+	/* caller is responsible for cleanup on error */
+	if (result < 0)
+		return ERR_PTR(result);
+	return dev->net;
+}
+
+/**
+ * gether_disconnect - notify network layer that USB link is inactive
+ * @link: the USB link, on which gether_connect() was called
+ * Context: irqs blocked
+ *
+ * This is called to deactivate endpoints and let the network layer know
+ * the connection went inactive ("no carrier").
+ *
+ * On return, the state is as if gether_connect() had never been called.
+ * The endpoints are inactive, and accordingly without active USB I/O.
+ * Pointers to endpoint descriptors and endpoint private data are nulled.
+ */
+void gether_disconnect(struct gether *link)
+{
+	struct eth_dev		*dev = link->ioport;
+	struct usb_request	*req;
+
+	WARN_ON(!dev);
+	if (!dev)
+		return;
+
+	DBG(dev, "%s\n", __func__);
+
+	netif_stop_queue(dev->net);
+	netif_carrier_off(dev->net);
+
+	/* disable endpoints, forcing (synchronous) completion
+	 * of all pending i/o.  then free the request objects
+	 * and forget about the endpoints.
+	 */
+	usb_ep_disable(link->in_ep);
+	spin_lock(&dev->req_lock);
+	while (!list_empty(&dev->tx_reqs)) {
+		req = container_of(dev->tx_reqs.next,
+					struct usb_request, list);
+		list_del(&req->list);
+
+		spin_unlock(&dev->req_lock);
+		usb_ep_free_request(link->in_ep, req);
+		spin_lock(&dev->req_lock);
+	}
+	spin_unlock(&dev->req_lock);
+	link->in_ep->driver_data = NULL;
+	link->in = NULL;
+
+	usb_ep_disable(link->out_ep);
+	spin_lock(&dev->req_lock);
+	while (!list_empty(&dev->rx_reqs)) {
+		req = container_of(dev->rx_reqs.next,
+					struct usb_request, list);
+		list_del(&req->list);
+
+		spin_unlock(&dev->req_lock);
+		usb_ep_free_request(link->out_ep, req);
+		spin_lock(&dev->req_lock);
+	}
+	spin_unlock(&dev->req_lock);
+	link->out_ep->driver_data = NULL;
+	link->out = NULL;
+
+	/* finish forgetting about this USB link episode */
+	dev->header_len = 0;
+	dev->unwrap = NULL;
+	dev->wrap = NULL;
+
+	spin_lock(&dev->lock);
+	dev->port_usb = NULL;
+	link->ioport = NULL;
+	spin_unlock(&dev->lock);
+}