/*
 * 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>

#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 altsetttings.
                 */
                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);

static u8 nibble(unsigned char c)
{
        if (likely(isdigit(c)))
                return c - '0';
        c = toupper(c);
        if (likely(isxdigit(c)))
                return 10 + c - 'A';
        return 0;
}

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] =
                        (nibble(buf [tmp]) << 4) + nibble(buf [tmp + 1]);
        return 0;
}
EXPORT_SYMBOL_GPL(usbnet_get_ethernet_addr);

static void intr_complete (struct urb *urb);

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_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;

        if (netif_msg_rx_status (dev))
                devdbg (dev, "< rx, len %zu, type 0x%x",
                        skb->len + sizeof (struct ethhdr), skb->protocol);
        memset (skb->cb, 0, sizeof (struct skb_data));
        status = netif_rx (skb);
        if (status != NET_RX_SUCCESS && netif_msg_rx_err (dev))
                devdbg (dev, "netif_rx status %d", 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);

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

/* some LK 2.4 HCDs oopsed if we freed or resubmitted urbs from
 * completion callbacks.  2.5 should have fixed those bugs...
 */

static void defer_bh(struct usbnet *dev, struct sk_buff *skb, struct sk_buff_head *list)
{
        unsigned long           flags;

        spin_lock_irqsave(&list->lock, flags);
        __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);
}

/* 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))
                deverr (dev, "kevent %d may have been dropped", work);
        else
                devdbg (dev, "kevent %d scheduled", work);
}
EXPORT_SYMBOL_GPL(usbnet_defer_kevent);

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

static void rx_complete (struct urb *urb);

static void 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;

        if ((skb = alloc_skb (size + NET_IP_ALIGN, flags)) == NULL) {
                if (netif_msg_rx_err (dev))
                        devdbg (dev, "no rx skb");
                usbnet_defer_kevent (dev, EVENT_RX_MEMORY);
                usb_free_urb (urb);
                return;
        }
        skb_reserve (skb, NET_IP_ALIGN);

        entry = (struct skb_data *) skb->cb;
        entry->urb = urb;
        entry->dev = dev;
        entry->state = rx_start;
        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)) {
                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:
                        if (netif_msg_ifdown (dev))
                                devdbg (dev, "device gone");
                        netif_device_detach (dev->net);
                        break;
                default:
                        if (netif_msg_rx_err (dev))
                                devdbg (dev, "rx submit, %d", retval);
                        tasklet_schedule (&dev->bh);
                        break;
                case 0:
                        __skb_queue_tail (&dev->rxq, skb);
                }
        } else {
                if (netif_msg_ifdown (dev))
                        devdbg (dev, "rx: stopped");
                retval = -ENOLINK;
        }
        spin_unlock_irqrestore (&dev->rxq.lock, lockflags);
        if (retval) {
                dev_kfree_skb_any (skb);
                usb_free_urb (urb);
        }
}


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

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))
                goto error;
        // else network stack removes extra byte if we forced a short packet

        if (skb->len)
                usbnet_skb_return (dev, skb);
        else {
                if (netif_msg_rx_err (dev))
                        devdbg (dev, "drop");
error:
                dev->net->stats.rx_errors++;
                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;

        skb_put (skb, urb->actual_length);
        entry->state = rx_done;
        entry->urb = NULL;

        switch (urb_status) {
        /* success */
        case 0:
                if (skb->len < dev->net->hard_header_len) {
                        entry->state = rx_cleanup;
                        dev->net->stats.rx_errors++;
                        dev->net->stats.rx_length_errors++;
                        if (netif_msg_rx_err (dev))
                                devdbg (dev, "rx length %d", 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 */
                if (netif_msg_ifdown (dev))
                        devdbg (dev, "rx shutdown, code %d", 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);
                        if (netif_msg_link (dev))
                                devdbg (dev, "rx throttle %d", urb_status);
                }
block:
                entry->state = rx_cleanup;
                entry->urb = urb;
                urb = NULL;
                break;

        /* data overrun ... flush fifo? */
        case -EOVERFLOW:
                dev->net->stats.rx_over_errors++;
                // FALLTHROUGH

        default:
                entry->state = rx_cleanup;
                dev->net->stats.rx_errors++;
                if (netif_msg_rx_err (dev))
                        devdbg (dev, "rx status %d", urb_status);
                break;
        }

        defer_bh(dev, skb, &dev->rxq);

        if (urb) {
                if (netif_running (dev->net)
                                && !test_bit (EVENT_RX_HALT, &dev->flags)) {
                        rx_submit (dev, urb, GFP_ATOMIC);
                        return;
                }
                usb_free_urb (urb);
        }
        if (netif_msg_rx_err (dev))
                devdbg (dev, "no read resubmitted");
}

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 */
                if (netif_msg_ifdown (dev))
                        devdbg (dev, "intr shutdown, code %d", status);
                return;

        /* NOTE:  not throttling like RX/TX, since this endpoint
         * already polls infrequently
         */
        default:
                devdbg (dev, "intr status %d", status);
                break;
        }

        if (!netif_running (dev->net))
                return;

        memset(urb->transfer_buffer, 0, urb->transfer_buffer_length);
        status = usb_submit_urb (urb, GFP_ATOMIC);
        if (status != 0 && netif_msg_timer (dev))
                deverr(dev, "intr resubmit --> %d", status);
}

/*-------------------------------------------------------------------------*/
void usbnet_pause_rx(struct usbnet *dev)
{
        set_bit(EVENT_RX_PAUSED, &dev->flags);

        if (netif_msg_rx_status(dev))
                devdbg(dev, "paused rx queue enabled");
}
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);

        if (netif_msg_rx_status(dev))
                devdbg(dev, "paused rx queue disabled, %d skbs requeued", 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, *skbnext;
        int                     count = 0;

        spin_lock_irqsave (&q->lock, flags);
        skb_queue_walk_safe(q, skb, skbnext) {
                struct skb_data         *entry;
                struct urb              *urb;
                int                     retval;

                entry = (struct skb_data *) skb->cb;
                urb = entry->urb;

                // during some PM-driven resume scenarios,
                // these (async) unlinks complete immediately
                retval = usb_unlink_urb (urb);
                if (retval != -EINPROGRESS && retval != 0)
                        devdbg (dev, "unlink urb err, %d", retval);
                else
                        count++;
        }
        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

int usbnet_stop (struct net_device *net)
{
        struct usbnet           *dev = netdev_priv(net);
        struct driver_info      *info = dev->driver_info;
        int                     temp;
        int                     retval;
        DECLARE_WAIT_QUEUE_HEAD_ONSTACK (unlink_wakeup);
        DECLARE_WAITQUEUE (wait, current);

        netif_stop_queue (net);

        if (netif_msg_ifdown (dev))
                devinfo (dev, "stop stats: rx/tx %ld/%ld, errs %ld/%ld",
                        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_msg_ifdown(dev))
                        devinfo(dev,
                                "stop fail (%d) usbnet usb-%s-%s, %s",
                                retval,
                                dev->udev->bus->bus_name, dev->udev->devpath,
                                info->description);
        }

        if (!(info->flags & FLAG_AVOID_UNLINK_URBS)) {
                /* ensure there are no more active urbs */
                add_wait_queue(&unlink_wakeup, &wait);
                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)) {
                        msleep(UNLINK_TIMEOUT_MS);
                        if (netif_msg_ifdown(dev))
                                devdbg(dev, "waited for %d urb completions",
                                        temp);
                }
                dev->wait = NULL;
                remove_wait_queue(&unlink_wakeup, &wait);
        }

        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);
        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) {
                if (netif_msg_ifup (dev))
                        devinfo (dev,
                                "resumption fail (%d) usbnet usb-%s-%s, %s",
                                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) {
                if (netif_msg_ifup (dev))
                        devinfo (dev,
                                "open reset fail (%d) usbnet usb-%s-%s, %s",
                                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) {
                if (netif_msg_ifup (dev))
                        devdbg (dev, "can't open; %d", retval);
                goto done;
        }

        /* start any status interrupt transfer */
        if (dev->interrupt) {
                retval = usb_submit_urb (dev->interrupt, GFP_KERNEL);
                if (retval < 0) {
                        if (netif_msg_ifup (dev))
                                deverr (dev, "intr submit %d", retval);
                        goto done;
                }
        }

        netif_start_queue (net);
        if (netif_msg_ifup (dev)) {
                char    *framing;

                if (dev->driver_info->flags & FLAG_FRAMING_NC)
                        framing = "NetChip";
                else if (dev->driver_info->flags & FLAG_FRAMING_GL)
                        framing = "GeneSys";
                else if (dev->driver_info->flags & FLAG_FRAMING_Z)
                        framing = "Zaurus";
                else if (dev->driver_info->flags & FLAG_FRAMING_RN)
                        framing = "RNDIS";
                else if (dev->driver_info->flags & FLAG_FRAMING_AX)
                        framing = "ASIX";
                else
                        framing = "simple";

                devinfo (dev, "open: enable queueing "
                                "(rx %d, tx %d) mtu %d %s framing",
                        (int)RX_QLEN (dev), (int)TX_QLEN (dev), dev->net->mtu,
                        framing);
        }

        // delay posting reads until we're fully open
        tasklet_schedule (&dev->bh);
        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);

        strncpy (info->driver, dev->driver_name, sizeof info->driver);
        strncpy (info->version, DRIVER_VERSION, sizeof info->version);
        strncpy (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,
};

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

/* 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_clear_halt (dev->udev, dev->out);
                if (status < 0
                                && status != -EPIPE
                                && status != -ESHUTDOWN) {
                        if (netif_msg_tx_err (dev))
                                deverr (dev, "can't clear tx halt, status %d",
                                        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_clear_halt (dev->udev, dev->in);
                if (status < 0
                                && status != -EPIPE
                                && status != -ESHUTDOWN) {
                        if (netif_msg_rx_err (dev))
                                deverr (dev, "can't clear rx halt, status %d",
                                        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;

                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);
                        rx_submit (dev, urb, GFP_KERNEL);
                        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);
                if(info->link_reset && (retval = info->link_reset(dev)) < 0) {
                        devinfo(dev, "link reset failed (%d) usbnet usb-%s-%s, %s",
                                retval,
                                dev->udev->bus->bus_name, dev->udev->devpath,
                                info->description);
                }
        }

        if (dev->flags)
                devdbg (dev, "kevent done, flags = 0x%lx",
                        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) {
                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:
                        if (!timer_pending (&dev->delay)) {
                                mod_timer (&dev->delay,
                                        jiffies + THROTTLE_JIFFIES);
                                if (netif_msg_link (dev))
                                        devdbg (dev, "tx throttle %d",
                                                        urb->status);
                        }
                        netif_stop_queue (dev->net);
                        break;
                default:
                        if (netif_msg_tx_err (dev))
                                devdbg (dev, "tx err %d", entry->urb->status);
                        break;
                }
        }

        urb->dev = NULL;
        entry->state = tx_done;
        defer_bh(dev, skb, &dev->txq);
}

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

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;

        // 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) {
                        if (netif_msg_tx_err (dev))
                                devdbg (dev, "can't tx_fixup skb");
                        goto drop;
                }
        }
        length = skb->len;

        if (!(urb = usb_alloc_urb (0, GFP_ATOMIC))) {
                if (netif_msg_tx_err (dev))
                        devdbg (dev, "no urb");
                goto drop;
        }

        entry = (struct skb_data *) skb->cb;
        entry->urb = urb;
        entry->dev = dev;
        entry->state = tx_start;
        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.
         */
        if (!(info->flags & FLAG_SEND_ZLP) && (length % dev->maxpacket) == 0) {
                urb->transfer_buffer_length++;
                if (skb_tailroom(skb)) {
                        skb->data[skb->len] = 0;
                        __skb_put(skb, 1);
                }
        }

        spin_lock_irqsave (&dev->txq.lock, flags);

        switch ((retval = usb_submit_urb (urb, GFP_ATOMIC))) {
        case -EPIPE:
                netif_stop_queue (net);
                usbnet_defer_kevent (dev, EVENT_TX_HALT);
                break;
        default:
                if (netif_msg_tx_err (dev))
                        devdbg (dev, "tx: submit urb err %d", retval);
                break;
        case 0:
                net->trans_start = jiffies;
                __skb_queue_tail (&dev->txq, skb);
                if (dev->txq.qlen >= TX_QLEN (dev))
                        netif_stop_queue (net);
        }
        spin_unlock_irqrestore (&dev->txq.lock, flags);

        if (retval) {
                if (netif_msg_tx_err (dev))
                        devdbg (dev, "drop, code %d", retval);
drop:
                dev->net->stats.tx_dropped++;
                if (skb)
                        dev_kfree_skb_any (skb);
                usb_free_urb (urb);
        } else if (netif_msg_tx_queued (dev)) {
                devdbg (dev, "> tx, len %d, type 0x%x",
                        length, skb->protocol);
        }
        return NETDEV_TX_OK;
}
EXPORT_SYMBOL_GPL(usbnet_start_xmit);

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

// 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:
                        devdbg (dev, "bogus skb state %d", 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_running (dev->net)
                        && netif_device_present (dev->net)
                        && !timer_pending (&dev->delay)
                        && !test_bit (EVENT_RX_HALT, &dev->flags)) {
                int     temp = dev->rxq.qlen;
                int     qlen = RX_QLEN (dev);

                if (temp < qlen) {
                        struct urb      *urb;
                        int             i;

                        // don't refill the queue all at once
                        for (i = 0; i < 10 && dev->rxq.qlen < qlen; i++) {
                                urb = usb_alloc_urb (0, GFP_ATOMIC);
                                if (urb != NULL)
                                        rx_submit (dev, urb, GFP_ATOMIC);
                        }
                        if (temp != dev->rxq.qlen && netif_msg_link (dev))
                                devdbg (dev, "rxqlen %d --> %d",
                                                temp, dev->rxq.qlen);
                        if (dev->rxq.qlen < qlen)
                                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);

        if (netif_msg_probe (dev))
                devinfo (dev, "unregister '%s' usb-%s-%s, %s",
                        intf->dev.driver->name,
                        xdev->bus->bus_name, xdev->devpath,
                        dev->driver_info->description);

        net = dev->net;
        unregister_netdev (net);

        /* we don't hold rtnl here ... */
        flush_scheduled_work ();

        if (dev->driver_info->unbind)
                dev->driver_info->unbind (dev, intf);

        free_netdev(net);
        usb_put_dev (xdev);
}
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

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;

        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;

        usb_get_dev (xdev);

        status = -ENOMEM;

        // set up our own records
        net = alloc_etherdev(sizeof(*dev));
        if (!net) {
                dbg ("can't kmalloc dev");
                goto out;
        }

        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);
        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
                                && (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");

                /* 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);

        SET_NETDEV_DEV(net, &udev->dev);
        status = register_netdev (net);
        if (status)
                goto out3;
        if (netif_msg_probe (dev))
                devinfo (dev, "register '%s' at usb-%s-%s, %s, %pM",
                        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);

        // start as if the link is up
        netif_device_attach (net);

        return 0;

out3:
        if (info->unbind)
                info->unbind (dev, udev);
out1:
        free_netdev(net);
out:
        usb_put_dev(xdev);
        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++) {
                /*
                 * accelerate emptying of the rx and queues, to avoid
                 * having everything error out.
                 */
                netif_device_detach (dev->net);
                (void) unlink_urbs (dev, &dev->rxq);
                (void) unlink_urbs (dev, &dev->txq);
                /*
                 * 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);

        if (!--dev->suspend_count)
                tasklet_schedule (&dev->bh);

        return 0;
}
EXPORT_SYMBOL_GPL(usbnet_resume);


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

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

        random_ether_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");