cdc-wdm.c

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/*
 * cdc-wdm.c
 *
 * This driver supports USB CDC WCM Device Management.
 *
 * Copyright (c) 2007-2009 Oliver Neukum
 *
 * Some code taken from cdc-acm.c
 *
 * Released under the GPLv2.
 *
 * Many thanks to Carl Nordbeck
 */
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/uaccess.h>
#include <linux/bitops.h>
#include <linux/poll.h>
#include <linux/usb.h>
#include <linux/usb/cdc.h>
#include <asm/byteorder.h>
#include <asm/unaligned.h>
#include <linux/usb/cdc-wdm.h>

/*
 * Version Information
 */
#define DRIVER_VERSION "v0.03"
#define DRIVER_AUTHOR "Oliver Neukum"
#define DRIVER_DESC "USB Abstract Control Model driver for USB WCM Device Management"

static const struct usb_device_id wdm_ids[] = {
    {
        .match_flags = USB_DEVICE_ID_MATCH_INT_CLASS |
                 USB_DEVICE_ID_MATCH_INT_SUBCLASS,
        .bInterfaceClass = USB_CLASS_COMM,
        .bInterfaceSubClass = USB_CDC_SUBCLASS_DMM
    },
    { }
};

MODULE_DEVICE_TABLE (usb, wdm_ids);

#define WDM_MINOR_BASE  176


#define WDM_IN_USE      1
#define WDM_DISCONNECTING   2
#define WDM_RESULT      3
#define WDM_READ        4
#define WDM_INT_STALL       5
#define WDM_POLL_RUNNING    6
#define WDM_RESPONDING      7
#define WDM_SUSPENDING      8
#define WDM_RESETTING       9

#define WDM_MAX         16

/* CDC-WMC r1.1 requires wMaxCommand to be "at least 256 decimal (0x100)" */
#define WDM_DEFAULT_BUFSIZE 256

static DEFINE_MUTEX(wdm_mutex);
static DEFINE_SPINLOCK(wdm_device_list_lock);
static LIST_HEAD(wdm_device_list);

/* --- method tables --- */

struct wdm_device {
    u8          *inbuf; /* buffer for response */
    u8          *outbuf; /* buffer for command */
    u8          *sbuf; /* buffer for status */
    u8          *ubuf; /* buffer for copy to user space */

    struct urb      *command;
    struct urb      *response;
    struct urb      *validity;
    struct usb_interface    *intf;
    struct usb_ctrlrequest  *orq;
    struct usb_ctrlrequest  *irq;
    spinlock_t      iuspin;

    unsigned long       flags;
    u16         bufsize;
    u16         wMaxCommand;
    u16         wMaxPacketSize;
    __le16          inum;
    int         reslength;
    int         length;
    int         read;
    int         count;
    dma_addr_t      shandle;
    dma_addr_t      ihandle;
    struct mutex        wlock;
    struct mutex        rlock;
    wait_queue_head_t   wait;
    struct work_struct  rxwork;
    int         werr;
    int         rerr;

    struct list_head    device_list;
    int         (*manage_power)(struct usb_interface *, int);
};

static struct usb_driver wdm_driver;

/* return intfdata if we own the interface, else look up intf in the list */
static struct wdm_device *wdm_find_device(struct usb_interface *intf)
{
    struct wdm_device *desc;

    spin_lock(&wdm_device_list_lock);
    list_for_each_entry(desc, &wdm_device_list, device_list)
        if (desc->intf == intf)
            goto found;
    desc = NULL;
found:
    spin_unlock(&wdm_device_list_lock);

    return desc;
}

static struct wdm_device *wdm_find_device_by_minor(int minor)
{
    struct wdm_device *desc;

    spin_lock(&wdm_device_list_lock);
    list_for_each_entry(desc, &wdm_device_list, device_list)
        if (desc->intf->minor == minor)
            goto found;
    desc = NULL;
found:
    spin_unlock(&wdm_device_list_lock);

    return desc;
}

/* --- callbacks --- */
static void wdm_out_callback(struct urb *urb)
{
    struct wdm_device *desc;
    desc = urb->context;
    spin_lock(&desc->iuspin);
    desc->werr = urb->status;
    spin_unlock(&desc->iuspin);
    kfree(desc->outbuf);
    desc->outbuf = NULL;
    clear_bit(WDM_IN_USE, &desc->flags);
    wake_up(&desc->wait);
}

static void wdm_in_callback(struct urb *urb)
{
    struct wdm_device *desc = urb->context;
    int status = urb->status;

    spin_lock(&desc->iuspin);
    clear_bit(WDM_RESPONDING, &desc->flags);

    if (status) {
        switch (status) {
        case -ENOENT:
            dev_dbg(&desc->intf->dev,
                "nonzero urb status received: -ENOENT");
            goto skip_error;
        case -ECONNRESET:
            dev_dbg(&desc->intf->dev,
                "nonzero urb status received: -ECONNRESET");
            goto skip_error;
        case -ESHUTDOWN:
            dev_dbg(&desc->intf->dev,
                "nonzero urb status received: -ESHUTDOWN");
            goto skip_error;
        case -EPIPE:
            dev_err(&desc->intf->dev,
                "nonzero urb status received: -EPIPE\n");
            break;
        default:
            dev_err(&desc->intf->dev,
                "Unexpected error %d\n", status);
            break;
        }
    }

    desc->rerr = status;
    desc->reslength = urb->actual_length;
    memmove(desc->ubuf + desc->length, desc->inbuf, desc->reslength);
    desc->length += desc->reslength;
skip_error:
    wake_up(&desc->wait);

    set_bit(WDM_READ, &desc->flags);
    spin_unlock(&desc->iuspin);
}

static void wdm_int_callback(struct urb *urb)
{
    int rv = 0;
    int status = urb->status;
    struct wdm_device *desc;
    struct usb_cdc_notification *dr;

    desc = urb->context;
    dr = (struct usb_cdc_notification *)desc->sbuf;

    if (status) {
        switch (status) {
        case -ESHUTDOWN:
        case -ENOENT:
        case -ECONNRESET:
            return; /* unplug */
        case -EPIPE:
            set_bit(WDM_INT_STALL, &desc->flags);
            dev_err(&desc->intf->dev, "Stall on int endpoint\n");
            goto sw; /* halt is cleared in work */
        default:
            dev_err(&desc->intf->dev,
                "nonzero urb status received: %d\n", status);
            break;
        }
    }

    if (urb->actual_length < sizeof(struct usb_cdc_notification)) {
        dev_err(&desc->intf->dev, "wdm_int_callback - %d bytes\n",
            urb->actual_length);
        goto exit;
    }

    switch (dr->bNotificationType) {
    case USB_CDC_NOTIFY_RESPONSE_AVAILABLE:
        dev_dbg(&desc->intf->dev,
            "NOTIFY_RESPONSE_AVAILABLE received: index %d len %d",
            dr->wIndex, dr->wLength);
        break;

    case USB_CDC_NOTIFY_NETWORK_CONNECTION:

        dev_dbg(&desc->intf->dev,
            "NOTIFY_NETWORK_CONNECTION %s network",
            dr->wValue ? "connected to" : "disconnected from");
        goto exit;
    default:
        clear_bit(WDM_POLL_RUNNING, &desc->flags);
        dev_err(&desc->intf->dev,
            "unknown notification %d received: index %d len %d\n",
            dr->bNotificationType, dr->wIndex, dr->wLength);
        goto exit;
    }

    spin_lock(&desc->iuspin);
    clear_bit(WDM_READ, &desc->flags);
    set_bit(WDM_RESPONDING, &desc->flags);
    if (!test_bit(WDM_DISCONNECTING, &desc->flags)
        && !test_bit(WDM_SUSPENDING, &desc->flags)) {
        rv = usb_submit_urb(desc->response, GFP_ATOMIC);
        dev_dbg(&desc->intf->dev, "%s: usb_submit_urb %d",
            __func__, rv);
    }
    spin_unlock(&desc->iuspin);
    if (rv < 0) {
        clear_bit(WDM_RESPONDING, &desc->flags);
        if (rv == -EPERM)
            return;
        if (rv == -ENOMEM) {
sw:
            rv = schedule_work(&desc->rxwork);
            if (rv)
                dev_err(&desc->intf->dev,
                    "Cannot schedule work\n");
        }
    }
exit:
    rv = usb_submit_urb(urb, GFP_ATOMIC);
    if (rv)
        dev_err(&desc->intf->dev,
            "%s - usb_submit_urb failed with result %d\n",
            __func__, rv);

}

static void kill_urbs(struct wdm_device *desc)
{
    /* the order here is essential */
    usb_kill_urb(desc->command);
    usb_kill_urb(desc->validity);
    usb_kill_urb(desc->response);
}

static void free_urbs(struct wdm_device *desc)
{
    usb_free_urb(desc->validity);
    usb_free_urb(desc->response);
    usb_free_urb(desc->command);
}

static void cleanup(struct wdm_device *desc)
{
    kfree(desc->sbuf);
    kfree(desc->inbuf);
    kfree(desc->orq);
    kfree(desc->irq);
    kfree(desc->ubuf);
    free_urbs(desc);
    kfree(desc);
}

static ssize_t wdm_write
(struct file *file, const char __user *buffer, size_t count, loff_t *ppos)
{
    u8 *buf;
    int rv = -EMSGSIZE, r, we;
    struct wdm_device *desc = file->private_data;
    struct usb_ctrlrequest *req;

    if (count > desc->wMaxCommand)
        count = desc->wMaxCommand;

    spin_lock_irq(&desc->iuspin);
    we = desc->werr;
    desc->werr = 0;
    spin_unlock_irq(&desc->iuspin);
    if (we < 0)
        return -EIO;

    buf = kmalloc(count, GFP_KERNEL);
    if (!buf) {
        rv = -ENOMEM;
        goto outnl;
    }

    r = copy_from_user(buf, buffer, count);
    if (r > 0) {
        kfree(buf);
        rv = -EFAULT;
        goto outnl;
    }

    /* concurrent writes and disconnect */
    r = mutex_lock_interruptible(&desc->wlock);
    rv = -ERESTARTSYS;
    if (r) {
        kfree(buf);
        goto outnl;
    }

    if (test_bit(WDM_DISCONNECTING, &desc->flags)) {
        kfree(buf);
        rv = -ENODEV;
        goto outnp;
    }

    r = usb_autopm_get_interface(desc->intf);
    if (r < 0) {
        kfree(buf);
        rv = usb_translate_errors(r);
        goto outnp;
    }

    if (!(file->f_flags & O_NONBLOCK))
        r = wait_event_interruptible(desc->wait, !test_bit(WDM_IN_USE,
                                &desc->flags));
    else
        if (test_bit(WDM_IN_USE, &desc->flags))
            r = -EAGAIN;

    if (test_bit(WDM_RESETTING, &desc->flags))
        r = -EIO;

    if (r < 0) {
        kfree(buf);
        rv = r;
        goto out;
    }

    req = desc->orq;
    usb_fill_control_urb(
        desc->command,
        interface_to_usbdev(desc->intf),
        /* using common endpoint 0 */
        usb_sndctrlpipe(interface_to_usbdev(desc->intf), 0),
        (unsigned char *)req,
        buf,
        count,
        wdm_out_callback,
        desc
    );

    req->bRequestType = (USB_DIR_OUT | USB_TYPE_CLASS |
                 USB_RECIP_INTERFACE);
    req->bRequest = USB_CDC_SEND_ENCAPSULATED_COMMAND;
    req->wValue = 0;
    req->wIndex = desc->inum;
    req->wLength = cpu_to_le16(count);
    set_bit(WDM_IN_USE, &desc->flags);
    desc->outbuf = buf;

    rv = usb_submit_urb(desc->command, GFP_KERNEL);
    if (rv < 0) {
        kfree(buf);
        desc->outbuf = NULL;
        clear_bit(WDM_IN_USE, &desc->flags);
        dev_err(&desc->intf->dev, "Tx URB error: %d\n", rv);
        rv = usb_translate_errors(rv);
    } else {
        dev_dbg(&desc->intf->dev, "Tx URB has been submitted index=%d",
            req->wIndex);
    }
out:
    usb_autopm_put_interface(desc->intf);
outnp:
    mutex_unlock(&desc->wlock);
outnl:
    return rv < 0 ? rv : count;
}

static ssize_t wdm_read
(struct file *file, char __user *buffer, size_t count, loff_t *ppos)
{
    int rv, cntr;
    int i = 0;
    struct wdm_device *desc = file->private_data;


    rv = mutex_lock_interruptible(&desc->rlock); /*concurrent reads */
    if (rv < 0)
        return -ERESTARTSYS;

    cntr = ACCESS_ONCE(desc->length);
    if (cntr == 0) {
        desc->read = 0;
retry:
        if (test_bit(WDM_DISCONNECTING, &desc->flags)) {
            rv = -ENODEV;
            goto err;
        }
        i++;
        if (file->f_flags & O_NONBLOCK) {
            if (!test_bit(WDM_READ, &desc->flags)) {
                rv = cntr ? cntr : -EAGAIN;
                goto err;
            }
            rv = 0;
        } else {
            rv = wait_event_interruptible(desc->wait,
                test_bit(WDM_READ, &desc->flags));
        }

        /* may have happened while we slept */
        if (test_bit(WDM_DISCONNECTING, &desc->flags)) {
            rv = -ENODEV;
            goto err;
        }
        if (test_bit(WDM_RESETTING, &desc->flags)) {
            rv = -EIO;
            goto err;
        }
        usb_mark_last_busy(interface_to_usbdev(desc->intf));
        if (rv < 0) {
            rv = -ERESTARTSYS;
            goto err;
        }

        spin_lock_irq(&desc->iuspin);

        if (desc->rerr) { /* read completed, error happened */
            desc->rerr = 0;
            spin_unlock_irq(&desc->iuspin);
            rv = -EIO;
            goto err;
        }
        /*
         * recheck whether we've lost the race
         * against the completion handler
         */
        if (!test_bit(WDM_READ, &desc->flags)) { /* lost race */
            spin_unlock_irq(&desc->iuspin);
            goto retry;
        }
        if (!desc->reslength) { /* zero length read */
            dev_dbg(&desc->intf->dev, "%s: zero length - clearing WDM_READ\n", __func__);
            clear_bit(WDM_READ, &desc->flags);
            spin_unlock_irq(&desc->iuspin);
            goto retry;
        }
        cntr = desc->length;
        spin_unlock_irq(&desc->iuspin);
    }

    if (cntr > count)
        cntr = count;
    rv = copy_to_user(buffer, desc->ubuf, cntr);
    if (rv > 0) {
        rv = -EFAULT;
        goto err;
    }

    spin_lock_irq(&desc->iuspin);

    for (i = 0; i < desc->length - cntr; i++)
        desc->ubuf[i] = desc->ubuf[i + cntr];

    desc->length -= cntr;
    /* in case we had outstanding data */
    if (!desc->length)
        clear_bit(WDM_READ, &desc->flags);

    spin_unlock_irq(&desc->iuspin);

    rv = cntr;

err:
    mutex_unlock(&desc->rlock);
    return rv;
}

static int wdm_flush(struct file *file, fl_owner_t id)
{
    struct wdm_device *desc = file->private_data;

    wait_event(desc->wait, !test_bit(WDM_IN_USE, &desc->flags));

    /* cannot dereference desc->intf if WDM_DISCONNECTING */
    if (desc->werr < 0 && !test_bit(WDM_DISCONNECTING, &desc->flags))
        dev_err(&desc->intf->dev, "Error in flush path: %d\n",
            desc->werr);

    return usb_translate_errors(desc->werr);
}

static unsigned int wdm_poll(struct file *file, struct poll_table_struct *wait)
{
    struct wdm_device *desc = file->private_data;
    unsigned long flags;
    unsigned int mask = 0;

    spin_lock_irqsave(&desc->iuspin, flags);
    if (test_bit(WDM_DISCONNECTING, &desc->flags)) {
        mask = POLLHUP | POLLERR;
        spin_unlock_irqrestore(&desc->iuspin, flags);
        goto desc_out;
    }
    if (test_bit(WDM_READ, &desc->flags))
        mask = POLLIN | POLLRDNORM;
    if (desc->rerr || desc->werr)
        mask |= POLLERR;
    if (!test_bit(WDM_IN_USE, &desc->flags))
        mask |= POLLOUT | POLLWRNORM;
    spin_unlock_irqrestore(&desc->iuspin, flags);

    poll_wait(file, &desc->wait, wait);

desc_out:
    return mask;
}

static int wdm_open(struct inode *inode, struct file *file)
{
    int minor = iminor(inode);
    int rv = -ENODEV;
    struct usb_interface *intf;
    struct wdm_device *desc;

    mutex_lock(&wdm_mutex);
    desc = wdm_find_device_by_minor(minor);
    if (!desc)
        goto out;

    intf = desc->intf;
    if (test_bit(WDM_DISCONNECTING, &desc->flags))
        goto out;
    file->private_data = desc;

    rv = usb_autopm_get_interface(desc->intf);
    if (rv < 0) {
        dev_err(&desc->intf->dev, "Error autopm - %d\n", rv);
        goto out;
    }

    /* using write lock to protect desc->count */
    mutex_lock(&desc->wlock);
    if (!desc->count++) {
        desc->werr = 0;
        desc->rerr = 0;
        rv = usb_submit_urb(desc->validity, GFP_KERNEL);
        if (rv < 0) {
            desc->count--;
            dev_err(&desc->intf->dev,
                "Error submitting int urb - %d\n", rv);
            rv = usb_translate_errors(rv);
        }
    } else {
        rv = 0;
    }
    mutex_unlock(&desc->wlock);
    if (desc->count == 1)
        desc->manage_power(intf, 1);
    usb_autopm_put_interface(desc->intf);
out:
    mutex_unlock(&wdm_mutex);
    return rv;
}

static int wdm_release(struct inode *inode, struct file *file)
{
    struct wdm_device *desc = file->private_data;

    mutex_lock(&wdm_mutex);

    /* using write lock to protect desc->count */
    mutex_lock(&desc->wlock);
    desc->count--;
    mutex_unlock(&desc->wlock);

    if (!desc->count) {
        if (!test_bit(WDM_DISCONNECTING, &desc->flags)) {
            dev_dbg(&desc->intf->dev, "wdm_release: cleanup");
            kill_urbs(desc);
            desc->manage_power(desc->intf, 0);
        } else {
            /* must avoid dev_printk here as desc->intf is invalid */
            pr_debug(KBUILD_MODNAME " %s: device gone - cleaning up\n", __func__);
            cleanup(desc);
        }
    }
    mutex_unlock(&wdm_mutex);
    return 0;
}

static const struct file_operations wdm_fops = {
    .owner =    THIS_MODULE,
    .read =     wdm_read,
    .write =    wdm_write,
    .open =     wdm_open,
    .flush =    wdm_flush,
    .release =  wdm_release,
    .poll =     wdm_poll,
    .llseek =   noop_llseek,
};

static struct usb_class_driver wdm_class = {
    .name =     "cdc-wdm%d",
    .fops =     &wdm_fops,
    .minor_base =   WDM_MINOR_BASE,
};

/* --- error handling --- */
static void wdm_rxwork(struct work_struct *work)
{
    struct wdm_device *desc = container_of(work, struct wdm_device, rxwork);
    unsigned long flags;
    int rv;

    spin_lock_irqsave(&desc->iuspin, flags);
    if (test_bit(WDM_DISCONNECTING, &desc->flags)) {
        spin_unlock_irqrestore(&desc->iuspin, flags);
    } else {
        spin_unlock_irqrestore(&desc->iuspin, flags);
        rv = usb_submit_urb(desc->response, GFP_KERNEL);
        if (rv < 0 && rv != -EPERM) {
            spin_lock_irqsave(&desc->iuspin, flags);
            if (!test_bit(WDM_DISCONNECTING, &desc->flags))
                schedule_work(&desc->rxwork);
            spin_unlock_irqrestore(&desc->iuspin, flags);
        }
    }
}

/* --- hotplug --- */

static int wdm_create(struct usb_interface *intf, struct usb_endpoint_descriptor *ep,
        u16 bufsize, int (*manage_power)(struct usb_interface *, int))
{
    int rv = -ENOMEM;
    struct wdm_device *desc;

    desc = kzalloc(sizeof(struct wdm_device), GFP_KERNEL);
    if (!desc)
        goto out;
    INIT_LIST_HEAD(&desc->device_list);
    mutex_init(&desc->rlock);
    mutex_init(&desc->wlock);
    spin_lock_init(&desc->iuspin);
    init_waitqueue_head(&desc->wait);
    desc->wMaxCommand = bufsize;
    /* this will be expanded and needed in hardware endianness */
    desc->inum = cpu_to_le16((u16)intf->cur_altsetting->desc.bInterfaceNumber);
    desc->intf = intf;
    INIT_WORK(&desc->rxwork, wdm_rxwork);

    rv = -EINVAL;
    if (!usb_endpoint_is_int_in(ep))
        goto err;

    desc->wMaxPacketSize = usb_endpoint_maxp(ep);

    desc->orq = kmalloc(sizeof(struct usb_ctrlrequest), GFP_KERNEL);
    if (!desc->orq)
        goto err;
    desc->irq = kmalloc(sizeof(struct usb_ctrlrequest), GFP_KERNEL);
    if (!desc->irq)
        goto err;

    desc->validity = usb_alloc_urb(0, GFP_KERNEL);
    if (!desc->validity)
        goto err;

    desc->response = usb_alloc_urb(0, GFP_KERNEL);
    if (!desc->response)
        goto err;

    desc->command = usb_alloc_urb(0, GFP_KERNEL);
    if (!desc->command)
        goto err;

    desc->ubuf = kmalloc(desc->wMaxCommand, GFP_KERNEL);
    if (!desc->ubuf)
        goto err;

    desc->sbuf = kmalloc(desc->wMaxPacketSize, GFP_KERNEL);
    if (!desc->sbuf)
        goto err;

    desc->inbuf = kmalloc(desc->wMaxCommand, GFP_KERNEL);
    if (!desc->inbuf)
        goto err;

    usb_fill_int_urb(
        desc->validity,
        interface_to_usbdev(intf),
        usb_rcvintpipe(interface_to_usbdev(intf), ep->bEndpointAddress),
        desc->sbuf,
        desc->wMaxPacketSize,
        wdm_int_callback,
        desc,
        ep->bInterval
    );

    desc->irq->bRequestType = (USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE);
    desc->irq->bRequest = USB_CDC_GET_ENCAPSULATED_RESPONSE;
    desc->irq->wValue = 0;
    desc->irq->wIndex = desc->inum;
    desc->irq->wLength = cpu_to_le16(desc->wMaxCommand);

    usb_fill_control_urb(
        desc->response,
        interface_to_usbdev(intf),
        /* using common endpoint 0 */
        usb_rcvctrlpipe(interface_to_usbdev(desc->intf), 0),
        (unsigned char *)desc->irq,
        desc->inbuf,
        desc->wMaxCommand,
        wdm_in_callback,
        desc
    );

    desc->manage_power = manage_power;

    spin_lock(&wdm_device_list_lock);
    list_add(&desc->device_list, &wdm_device_list);
    spin_unlock(&wdm_device_list_lock);

    rv = usb_register_dev(intf, &wdm_class);
    if (rv < 0)
        goto err;
    else
        dev_info(&intf->dev, "%s: USB WDM device\n", dev_name(intf->usb_dev));
out:
    return rv;
err:
    spin_lock(&wdm_device_list_lock);
    list_del(&desc->device_list);
    spin_unlock(&wdm_device_list_lock);
    cleanup(desc);
    return rv;
}

static int wdm_manage_power(struct usb_interface *intf, int on)
{
    /* need autopm_get/put here to ensure the usbcore sees the new value */
    int rv = usb_autopm_get_interface(intf);
    if (rv < 0)
        goto err;

    intf->needs_remote_wakeup = on;
    usb_autopm_put_interface(intf);
err:
    return rv;
}

static int wdm_probe(struct usb_interface *intf, const struct usb_device_id *id)
{
    int rv = -EINVAL;
    struct usb_host_interface *iface;
    struct usb_endpoint_descriptor *ep;
    struct usb_cdc_dmm_desc *dmhd;
    u8 *buffer = intf->altsetting->extra;
    int buflen = intf->altsetting->extralen;
    u16 maxcom = WDM_DEFAULT_BUFSIZE;

    if (!buffer)
        goto err;
    while (buflen > 2) {
        if (buffer[1] != USB_DT_CS_INTERFACE) {
            dev_err(&intf->dev, "skipping garbage\n");
            goto next_desc;
        }

        switch (buffer[2]) {
        case USB_CDC_HEADER_TYPE:
            break;
        case USB_CDC_DMM_TYPE:
            dmhd = (struct usb_cdc_dmm_desc *)buffer;
            maxcom = le16_to_cpu(dmhd->wMaxCommand);
            dev_dbg(&intf->dev,
                "Finding maximum buffer length: %d", maxcom);
            break;
        default:
            dev_err(&intf->dev,
                "Ignoring extra header, type %d, length %d\n",
                buffer[2], buffer[0]);
            break;
        }
next_desc:
        buflen -= buffer[0];
        buffer += buffer[0];
    }

    iface = intf->cur_altsetting;
    if (iface->desc.bNumEndpoints != 1)
        goto err;
    ep = &iface->endpoint[0].desc;

    rv = wdm_create(intf, ep, maxcom, &wdm_manage_power);

err:
    return rv;
}

struct usb_driver *usb_cdc_wdm_register(struct usb_interface *intf,
                    struct usb_endpoint_descriptor *ep,
                    int bufsize,
                    int (*manage_power)(struct usb_interface *, int))
{
    int rv = -EINVAL;

    rv = wdm_create(intf, ep, bufsize, manage_power);
    if (rv < 0)
        goto err;

    return &wdm_driver;
err:
    return ERR_PTR(rv);
}
EXPORT_SYMBOL(usb_cdc_wdm_register);

static void wdm_disconnect(struct usb_interface *intf)
{
    struct wdm_device *desc;
    unsigned long flags;

    usb_deregister_dev(intf, &wdm_class);
    desc = wdm_find_device(intf);
    mutex_lock(&wdm_mutex);

    /* the spinlock makes sure no new urbs are generated in the callbacks */
    spin_lock_irqsave(&desc->iuspin, flags);
    set_bit(WDM_DISCONNECTING, &desc->flags);
    set_bit(WDM_READ, &desc->flags);
    /* to terminate pending flushes */
    clear_bit(WDM_IN_USE, &desc->flags);
    spin_unlock_irqrestore(&desc->iuspin, flags);
    wake_up_all(&desc->wait);
    mutex_lock(&desc->rlock);
    mutex_lock(&desc->wlock);
    kill_urbs(desc);
    cancel_work_sync(&desc->rxwork);
    mutex_unlock(&desc->wlock);
    mutex_unlock(&desc->rlock);

    /* the desc->intf pointer used as list key is now invalid */
    spin_lock(&wdm_device_list_lock);
    list_del(&desc->device_list);
    spin_unlock(&wdm_device_list_lock);

    if (!desc->count)
        cleanup(desc);
    else
        dev_dbg(&intf->dev, "%s: %d open files - postponing cleanup\n", __func__, desc->count);
    mutex_unlock(&wdm_mutex);
}

#ifdef CONFIG_PM
static int wdm_suspend(struct usb_interface *intf, pm_message_t message)
{
    struct wdm_device *desc = wdm_find_device(intf);
    int rv = 0;

    dev_dbg(&desc->intf->dev, "wdm%d_suspend\n", intf->minor);

    /* if this is an autosuspend the caller does the locking */
    if (!PMSG_IS_AUTO(message)) {
        mutex_lock(&desc->rlock);
        mutex_lock(&desc->wlock);
    }
    spin_lock_irq(&desc->iuspin);

    if (PMSG_IS_AUTO(message) &&
            (test_bit(WDM_IN_USE, &desc->flags)
            || test_bit(WDM_RESPONDING, &desc->flags))) {
        spin_unlock_irq(&desc->iuspin);
        rv = -EBUSY;
    } else {

        set_bit(WDM_SUSPENDING, &desc->flags);
        spin_unlock_irq(&desc->iuspin);
        /* callback submits work - order is essential */
        kill_urbs(desc);
        cancel_work_sync(&desc->rxwork);
    }
    if (!PMSG_IS_AUTO(message)) {
        mutex_unlock(&desc->wlock);
        mutex_unlock(&desc->rlock);
    }

    return rv;
}
#endif

static int recover_from_urb_loss(struct wdm_device *desc)
{
    int rv = 0;

    if (desc->count) {
        rv = usb_submit_urb(desc->validity, GFP_NOIO);
        if (rv < 0)
            dev_err(&desc->intf->dev,
                "Error resume submitting int urb - %d\n", rv);
    }
    return rv;
}

#ifdef CONFIG_PM
static int wdm_resume(struct usb_interface *intf)
{
    struct wdm_device *desc = wdm_find_device(intf);
    int rv;

    dev_dbg(&desc->intf->dev, "wdm%d_resume\n", intf->minor);

    clear_bit(WDM_SUSPENDING, &desc->flags);
    rv = recover_from_urb_loss(desc);

    return rv;
}
#endif

static int wdm_pre_reset(struct usb_interface *intf)
{
    struct wdm_device *desc = wdm_find_device(intf);

    /*
     * we notify everybody using poll of
     * an exceptional situation
     * must be done before recovery lest a spontaneous
     * message from the device is lost
     */
    spin_lock_irq(&desc->iuspin);
    set_bit(WDM_RESETTING, &desc->flags);   /* inform read/write */
    set_bit(WDM_READ, &desc->flags);    /* unblock read */
    clear_bit(WDM_IN_USE, &desc->flags);    /* unblock write */
    desc->rerr = -EINTR;
    spin_unlock_irq(&desc->iuspin);
    wake_up_all(&desc->wait);
    mutex_lock(&desc->rlock);
    mutex_lock(&desc->wlock);
    kill_urbs(desc);
    cancel_work_sync(&desc->rxwork);
    return 0;
}

static int wdm_post_reset(struct usb_interface *intf)
{
    struct wdm_device *desc = wdm_find_device(intf);
    int rv;

    clear_bit(WDM_RESETTING, &desc->flags);
    rv = recover_from_urb_loss(desc);
    mutex_unlock(&desc->wlock);
    mutex_unlock(&desc->rlock);
    return 0;
}

static struct usb_driver wdm_driver = {
    .name =     "cdc_wdm",
    .probe =    wdm_probe,
    .disconnect =   wdm_disconnect,
#ifdef CONFIG_PM
    .suspend =  wdm_suspend,
    .resume =   wdm_resume,
    .reset_resume = wdm_resume,
#endif
    .pre_reset =    wdm_pre_reset,
    .post_reset =   wdm_post_reset,
    .id_table = wdm_ids,
    .supports_autosuspend = 1,
    .disable_hub_initiated_lpm = 1,
};

module_usb_driver(wdm_driver);

MODULE_AUTHOR(DRIVER_AUTHOR);
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_LICENSE("GPL");