text: /*
   * 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/ioctl.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_OVERFLOW		10
  
  #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;
  	int                     resp_count;
  
  	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;
  	int length = urb->actual_length;
  
  	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;
  	if (length + desc->length > desc->wMaxCommand) {
  		/* The buffer would overflow */
  		set_bit(WDM_OVERFLOW, &desc->flags);
  	} else {
  		/* we may already be in overflow */
  		if (!test_bit(WDM_OVERFLOW, &desc->flags)) {
  			memmove(desc->ubuf + desc->length, desc->inbuf, length);
  			desc->length += length;
  			desc->reslength = length;
  		}
  	}
  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 responding;
  	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",
  			le16_to_cpu(dr->wIndex), le16_to_cpu(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;
  	case USB_CDC_NOTIFY_SPEED_CHANGE:
  		dev_dbg(&desc->intf->dev, "SPEED_CHANGE received (len %u)",
  			urb->actual_length);
  		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,
  			le16_to_cpu(dr->wIndex),
  			le16_to_cpu(dr->wLength));
  		goto exit;
  	}
  
  	spin_lock(&desc->iuspin);
  	responding = test_and_set_bit(WDM_RESPONDING, &desc->flags);
  	if (!desc->resp_count++ && !responding
  		&& !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; /* already converted */
  	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",
  			le16_to_cpu(req->wIndex));
  	}
  out:
  	usb_autopm_put_interface(desc->intf);
  outnp:
  	mutex_unlock(&desc->wlock);
  outnl:
  	return rv < 0 ? rv : count;
  }
  
  /*
   * clear WDM_READ flag and possibly submit the read urb if resp_count
   * is non-zero.
   *
   * Called with desc->iuspin locked
   */
  static int clear_wdm_read_flag(struct wdm_device *desc)
  {
  	int rv = 0;
  
  	clear_bit(WDM_READ, &desc->flags);
  
  	/* submit read urb only if the device is waiting for it */
  	if (!desc->resp_count || !--desc->resp_count)
  		goto out;
  
  	set_bit(WDM_RESPONDING, &desc->flags);
  	spin_unlock_irq(&desc->iuspin);
  	rv = usb_submit_urb(desc->response, GFP_KERNEL);
  	spin_lock_irq(&desc->iuspin);
  	if (rv) {
  		dev_err(&desc->intf->dev,
  			"usb_submit_urb failed with result %d\n", rv);
  
  		/* make sure the next notification trigger a submit */
  		clear_bit(WDM_RESPONDING, &desc->flags);
  		desc->resp_count = 0;
  	}
  out:
  	return rv;
  }
  
  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;
  		}
  		if (test_bit(WDM_OVERFLOW, &desc->flags)) {
  			clear_bit(WDM_OVERFLOW, &desc->flags);
  			rv = -ENOBUFS;
  			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__);
  			rv = clear_wdm_read_flag(desc);
  			spin_unlock_irq(&desc->iuspin);
  			if (rv < 0)
  				goto err;
  			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_wdm_read_flag(desc);
  	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);
  			spin_lock_irq(&desc->iuspin);
  			desc->resp_count = 0;
  			spin_unlock_irq(&desc->iuspin);
  			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 long wdm_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
  {
  	struct wdm_device *desc = file->private_data;
  	int rv = 0;
  
  	switch (cmd) {
  	case IOCTL_WDM_MAX_COMMAND:
  		if (copy_to_user((void __user *)arg, &desc->wMaxCommand, sizeof(desc->wMaxCommand)))
  			rv = -EFAULT;
  		break;
  	default:
  		rv = -ENOTTY;
  	}
  	return rv;
  }
  
  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,
  	.unlocked_ioctl = wdm_ioctl,
  	.compat_ioctl = wdm_ioctl,
  	.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 = 0;
  	int responding;
  
  	spin_lock_irqsave(&desc->iuspin, flags);
  	if (test_bit(WDM_DISCONNECTING, &desc->flags)) {
  		spin_unlock_irqrestore(&desc->iuspin, flags);
  	} else {
  		responding = test_and_set_bit(WDM_RESPONDING, &desc->flags);
  		spin_unlock_irqrestore(&desc->iuspin, flags);
  		if (!responding)
  			rv = usb_submit_urb(desc->response, GFP_KERNEL);
  		if (rv < 0 && rv != -EPERM) {
  			spin_lock_irqsave(&desc->iuspin, flags);
  			clear_bit(WDM_RESPONDING, &desc->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; /* already converted */
  	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);
  
  	intf->needs_remote_wakeup = on;
  	if (!rv)
  		usb_autopm_put_interface(intf);
  	return 0;
  }
  
  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;
  }
  
  /**
   * usb_cdc_wdm_register - register a WDM subdriver
   * @intf: usb interface the subdriver will associate with
   * @ep: interrupt endpoint to monitor for notifications
   * @bufsize: maximum message size to support for read/write
   *
   * Create WDM usb class character device and associate it with intf
   * without binding, allowing another driver to manage the interface.
   *
   * The subdriver will manage the given interrupt endpoint exclusively
   * and will issue control requests referring to the given intf. It
   * will otherwise avoid interferring, and in particular not do
   * usb_set_intfdata/usb_get_intfdata on intf.
   *
   * The return value is a pointer to the subdriver's struct usb_driver.
   * The registering driver is responsible for calling this subdriver's
   * disconnect, suspend, resume, pre_reset and post_reset methods from
   * its own.
   */
  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_OVERFLOW, &desc->flags);
  	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");
  