text: /*
   * drivers/usb/core/usb.c
   *
   * (C) Copyright Linus Torvalds 1999
   * (C) Copyright Johannes Erdfelt 1999-2001
   * (C) Copyright Andreas Gal 1999
   * (C) Copyright Gregory P. Smith 1999
   * (C) Copyright Deti Fliegl 1999 (new USB architecture)
   * (C) Copyright Randy Dunlap 2000
   * (C) Copyright David Brownell 2000-2004
   * (C) Copyright Yggdrasil Computing, Inc. 2000
   *     (usb_device_id matching changes by Adam J. Richter)
   * (C) Copyright Greg Kroah-Hartman 2002-2003
   *
   * NOTE! This is not actually a driver at all, rather this is
   * just a collection of helper routines that implement the
   * generic USB things that the real drivers can use..
   *
   * Think of this as a "USB library" rather than anything else.
   * It should be considered a slave, with no callbacks. Callbacks
   * are evil.
   */
  
  #include <linux/module.h>
  #include <linux/moduleparam.h>
  #include <linux/string.h>
  #include <linux/bitops.h>
  #include <linux/slab.h>
  #include <linux/interrupt.h>  /* for in_interrupt() */
  #include <linux/kmod.h>
  #include <linux/init.h>
  #include <linux/spinlock.h>
  #include <linux/errno.h>
  #include <linux/usb.h>
  #include <linux/usb/hcd.h>
  #include <linux/mutex.h>
  #include <linux/workqueue.h>
  #include <linux/debugfs.h>
  
  #include <asm/io.h>
  #include <linux/scatterlist.h>
  #include <linux/mm.h>
  #include <linux/dma-mapping.h>
  
  #include "usb.h"
  
  
  const char *usbcore_name = "usbcore";
  
  static bool nousb;	/* Disable USB when built into kernel image */
  
  #ifdef	CONFIG_USB_SUSPEND
  static int usb_autosuspend_delay = 2;		/* Default delay value,
  						 * in seconds */
  module_param_named(autosuspend, usb_autosuspend_delay, int, 0644);
  MODULE_PARM_DESC(autosuspend, "default autosuspend delay");
  
  #else
  #define usb_autosuspend_delay		0
  #endif
  
  
  /**
   * usb_find_alt_setting() - Given a configuration, find the alternate setting
   * for the given interface.
   * @config: the configuration to search (not necessarily the current config).
   * @iface_num: interface number to search in
   * @alt_num: alternate interface setting number to search for.
   *
   * Search the configuration's interface cache for the given alt setting.
   */
  struct usb_host_interface *usb_find_alt_setting(
  		struct usb_host_config *config,
  		unsigned int iface_num,
  		unsigned int alt_num)
  {
  	struct usb_interface_cache *intf_cache = NULL;
  	int i;
  
  	for (i = 0; i < config->desc.bNumInterfaces; i++) {
  		if (config->intf_cache[i]->altsetting[0].desc.bInterfaceNumber
  				== iface_num) {
  			intf_cache = config->intf_cache[i];
  			break;
  		}
  	}
  	if (!intf_cache)
  		return NULL;
  	for (i = 0; i < intf_cache->num_altsetting; i++)
  		if (intf_cache->altsetting[i].desc.bAlternateSetting == alt_num)
  			return &intf_cache->altsetting[i];
  
  	printk(KERN_DEBUG "Did not find alt setting %u for intf %u, "
  			"config %u\n", alt_num, iface_num,
  			config->desc.bConfigurationValue);
  	return NULL;
  }
  EXPORT_SYMBOL_GPL(usb_find_alt_setting);
  
  /**
   * usb_ifnum_to_if - get the interface object with a given interface number
   * @dev: the device whose current configuration is considered
   * @ifnum: the desired interface
   *
   * This walks the device descriptor for the currently active configuration
   * and returns a pointer to the interface with that particular interface
   * number, or null.
   *
   * Note that configuration descriptors are not required to assign interface
   * numbers sequentially, so that it would be incorrect to assume that
   * the first interface in that descriptor corresponds to interface zero.
   * This routine helps device drivers avoid such mistakes.
   * However, you should make sure that you do the right thing with any
   * alternate settings available for this interfaces.
   *
   * Don't call this function unless you are bound to one of the interfaces
   * on this device or you have locked the device!
   */
  struct usb_interface *usb_ifnum_to_if(const struct usb_device *dev,
  				      unsigned ifnum)
  {
  	struct usb_host_config *config = dev->actconfig;
  	int i;
  
  	if (!config)
  		return NULL;
  	for (i = 0; i < config->desc.bNumInterfaces; i++)
  		if (config->interface[i]->altsetting[0]
  				.desc.bInterfaceNumber == ifnum)
  			return config->interface[i];
  
  	return NULL;
  }
  EXPORT_SYMBOL_GPL(usb_ifnum_to_if);
  
  /**
   * usb_altnum_to_altsetting - get the altsetting structure with a given alternate setting number.
   * @intf: the interface containing the altsetting in question
   * @altnum: the desired alternate setting number
   *
   * This searches the altsetting array of the specified interface for
   * an entry with the correct bAlternateSetting value and returns a pointer
   * to that entry, or null.
   *
   * Note that altsettings need not be stored sequentially by number, so
   * it would be incorrect to assume that the first altsetting entry in
   * the array corresponds to altsetting zero.  This routine helps device
   * drivers avoid such mistakes.
   *
   * Don't call this function unless you are bound to the intf interface
   * or you have locked the device!
   */
  struct usb_host_interface *usb_altnum_to_altsetting(
  					const struct usb_interface *intf,
  					unsigned int altnum)
  {
  	int i;
  
  	for (i = 0; i < intf->num_altsetting; i++) {
  		if (intf->altsetting[i].desc.bAlternateSetting == altnum)
  			return &intf->altsetting[i];
  	}
  	return NULL;
  }
  EXPORT_SYMBOL_GPL(usb_altnum_to_altsetting);
  
  struct find_interface_arg {
  	int minor;
  	struct device_driver *drv;
  };
  
  static int __find_interface(struct device *dev, void *data)
  {
  	struct find_interface_arg *arg = data;
  	struct usb_interface *intf;
  
  	if (!is_usb_interface(dev))
  		return 0;
  
  	if (dev->driver != arg->drv)
  		return 0;
  	intf = to_usb_interface(dev);
  	return intf->minor == arg->minor;
  }
  
  /**
   * usb_find_interface - find usb_interface pointer for driver and device
   * @drv: the driver whose current configuration is considered
   * @minor: the minor number of the desired device
   *
   * This walks the bus device list and returns a pointer to the interface
   * with the matching minor and driver.  Note, this only works for devices
   * that share the USB major number.
   */
  struct usb_interface *usb_find_interface(struct usb_driver *drv, int minor)
  {
  	struct find_interface_arg argb;
  	struct device *dev;
  
  	argb.minor = minor;
  	argb.drv = &drv->drvwrap.driver;
  
  	dev = bus_find_device(&usb_bus_type, NULL, &argb, __find_interface);
  
  	/* Drop reference count from bus_find_device */
  	put_device(dev);
  
  	return dev ? to_usb_interface(dev) : NULL;
  }
  EXPORT_SYMBOL_GPL(usb_find_interface);
  
  /**
   * usb_release_dev - free a usb device structure when all users of it are finished.
   * @dev: device that's been disconnected
   *
   * Will be called only by the device core when all users of this usb device are
   * done.
   */
  static void usb_release_dev(struct device *dev)
  {
  	struct usb_device *udev;
  	struct usb_hcd *hcd;
  
  	udev = to_usb_device(dev);
  	hcd = bus_to_hcd(udev->bus);
  
  	usb_destroy_configuration(udev);
  	usb_release_bos_descriptor(udev);
  	usb_put_hcd(hcd);
  	kfree(udev->product);
  	kfree(udev->manufacturer);
  	kfree(udev->serial);
  	kfree(udev);
  }
  
  #ifdef	CONFIG_HOTPLUG
  static int usb_dev_uevent(struct device *dev, struct kobj_uevent_env *env)
  {
  	struct usb_device *usb_dev;
  
  	usb_dev = to_usb_device(dev);
  
  	if (add_uevent_var(env, "BUSNUM=%03d", usb_dev->bus->busnum))
  		return -ENOMEM;
  
  	if (add_uevent_var(env, "DEVNUM=%03d", usb_dev->devnum))
  		return -ENOMEM;
  
  	return 0;
  }
  
  #else
  
  static int usb_dev_uevent(struct device *dev, struct kobj_uevent_env *env)
  {
  	return -ENODEV;
  }
  #endif	/* CONFIG_HOTPLUG */
  
  #ifdef	CONFIG_PM
  
  /* USB device Power-Management thunks.
   * There's no need to distinguish here between quiescing a USB device
   * and powering it down; the generic_suspend() routine takes care of
   * it by skipping the usb_port_suspend() call for a quiesce.  And for
   * USB interfaces there's no difference at all.
   */
  
  static int usb_dev_prepare(struct device *dev)
  {
  	return 0;		/* Implement eventually? */
  }
  
  static void usb_dev_complete(struct device *dev)
  {
  	/* Currently used only for rebinding interfaces */
  	usb_resume_complete(dev);
  }
  
  static int usb_dev_suspend(struct device *dev)
  {
  	return usb_suspend(dev, PMSG_SUSPEND);
  }
  
  static int usb_dev_resume(struct device *dev)
  {
  	return usb_resume(dev, PMSG_RESUME);
  }
  
  static int usb_dev_freeze(struct device *dev)
  {
  	return usb_suspend(dev, PMSG_FREEZE);
  }
  
  static int usb_dev_thaw(struct device *dev)
  {
  	return usb_resume(dev, PMSG_THAW);
  }
  
  static int usb_dev_poweroff(struct device *dev)
  {
  	return usb_suspend(dev, PMSG_HIBERNATE);
  }
  
  static int usb_dev_restore(struct device *dev)
  {
  	return usb_resume(dev, PMSG_RESTORE);
  }
  
  static const struct dev_pm_ops usb_device_pm_ops = {
  	.prepare =	usb_dev_prepare,
  	.complete =	usb_dev_complete,
  	.suspend =	usb_dev_suspend,
  	.resume =	usb_dev_resume,
  	.freeze =	usb_dev_freeze,
  	.thaw =		usb_dev_thaw,
  	.poweroff =	usb_dev_poweroff,
  	.restore =	usb_dev_restore,
  #ifdef CONFIG_USB_SUSPEND
  	.runtime_suspend =	usb_runtime_suspend,
  	.runtime_resume =	usb_runtime_resume,
  	.runtime_idle =		usb_runtime_idle,
  #endif
  };
  
  #endif	/* CONFIG_PM */
  
  
  static char *usb_devnode(struct device *dev, umode_t *mode)
  {
  	struct usb_device *usb_dev;
  
  	usb_dev = to_usb_device(dev);
  	return kasprintf(GFP_KERNEL, "bus/usb/%03d/%03d",
  			 usb_dev->bus->busnum, usb_dev->devnum);
  }
  
  struct device_type usb_device_type = {
  	.name =		"usb_device",
  	.release =	usb_release_dev,
  	.uevent =	usb_dev_uevent,
  	.devnode = 	usb_devnode,
  #ifdef CONFIG_PM
  	.pm =		&usb_device_pm_ops,
  #endif
  };
  
  
  /* Returns 1 if @usb_bus is WUSB, 0 otherwise */
  static unsigned usb_bus_is_wusb(struct usb_bus *bus)
  {
  	struct usb_hcd *hcd = container_of(bus, struct usb_hcd, self);
  	return hcd->wireless;
  }
  
  
  /**
   * usb_alloc_dev - usb device constructor (usbcore-internal)
   * @parent: hub to which device is connected; null to allocate a root hub
   * @bus: bus used to access the device
   * @port1: one-based index of port; ignored for root hubs
   * Context: !in_interrupt()
   *
   * Only hub drivers (including virtual root hub drivers for host
   * controllers) should ever call this.
   *
   * This call may not be used in a non-sleeping context.
   */
  struct usb_device *usb_alloc_dev(struct usb_device *parent,
  				 struct usb_bus *bus, unsigned port1)
  {
  	struct usb_device *dev;
  	struct usb_hcd *usb_hcd = container_of(bus, struct usb_hcd, self);
  	unsigned root_hub = 0;
  
  	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
  	if (!dev)
  		return NULL;
  
  	if (!usb_get_hcd(bus_to_hcd(bus))) {
  		kfree(dev);
  		return NULL;
  	}
  	/* Root hubs aren't true devices, so don't allocate HCD resources */
  	if (usb_hcd->driver->alloc_dev && parent &&
  		!usb_hcd->driver->alloc_dev(usb_hcd, dev)) {
  		usb_put_hcd(bus_to_hcd(bus));
  		kfree(dev);
  		return NULL;
  	}
  
  	device_initialize(&dev->dev);
  	dev->dev.bus = &usb_bus_type;
  	dev->dev.type = &usb_device_type;
  	dev->dev.groups = usb_device_groups;
  	dev->dev.dma_mask = bus->controller->dma_mask;
  	set_dev_node(&dev->dev, dev_to_node(bus->controller));
  	dev->state = USB_STATE_ATTACHED;
  	dev->lpm_disable_count = 1;
  	atomic_set(&dev->urbnum, 0);
  
  	INIT_LIST_HEAD(&dev->ep0.urb_list);
  	dev->ep0.desc.bLength = USB_DT_ENDPOINT_SIZE;
  	dev->ep0.desc.bDescriptorType = USB_DT_ENDPOINT;
  	/* ep0 maxpacket comes later, from device descriptor */
  	usb_enable_endpoint(dev, &dev->ep0, false);
  	dev->can_submit = 1;
  
  	/* Save readable and stable topology id, distinguishing devices
  	 * by location for diagnostics, tools, driver model, etc.  The
  	 * string is a path along hub ports, from the root.  Each device's
  	 * dev->devpath will be stable until USB is re-cabled, and hubs
  	 * are often labeled with these port numbers.  The name isn't
  	 * as stable:  bus->busnum changes easily from modprobe order,
  	 * cardbus or pci hotplugging, and so on.
  	 */
  	if (unlikely(!parent)) {
  		dev->devpath[0] = '0';
  		dev->route = 0;
  
  		dev->dev.parent = bus->controller;
  		dev_set_name(&dev->dev, "usb%d", bus->busnum);
  		root_hub = 1;
  	} else {
  		/* match any labeling on the hubs; it's one-based */
  		if (parent->devpath[0] == '0') {
  			snprintf(dev->devpath, sizeof dev->devpath,
  				"%d", port1);
  			/* Root ports are not counted in route string */
  			dev->route = 0;
  		} else {
  			snprintf(dev->devpath, sizeof dev->devpath,
  				"%s.%d", parent->devpath, port1);
  			/* Route string assumes hubs have less than 16 ports */
  			if (port1 < 15)
  				dev->route = parent->route +
  					(port1 << ((parent->level - 1)*4));
  			else
  				dev->route = parent->route +
  					(15 << ((parent->level - 1)*4));
  		}
  
  		dev->dev.parent = &parent->dev;
  		dev_set_name(&dev->dev, "%d-%s", bus->busnum, dev->devpath);
  
  		/* hub driver sets up TT records */
  	}
  
  	dev->portnum = port1;
  	dev->bus = bus;
  	dev->parent = parent;
  	INIT_LIST_HEAD(&dev->filelist);
  
  #ifdef	CONFIG_PM
  	pm_runtime_set_autosuspend_delay(&dev->dev,
  			usb_autosuspend_delay * 1000);
  	dev->connect_time = jiffies;
  	dev->active_duration = -jiffies;
  #endif
  	if (root_hub)	/* Root hub always ok [and always wired] */
  		dev->authorized = 1;
  	else {
  		dev->authorized = usb_hcd->authorized_default;
  		dev->wusb = usb_bus_is_wusb(bus)? 1 : 0;
  	}
  	return dev;
  }
  
  /**
   * usb_get_dev - increments the reference count of the usb device structure
   * @dev: the device being referenced
   *
   * Each live reference to a device should be refcounted.
   *
   * Drivers for USB interfaces should normally record such references in
   * their probe() methods, when they bind to an interface, and release
   * them by calling usb_put_dev(), in their disconnect() methods.
   *
   * A pointer to the device with the incremented reference counter is returned.
   */
  struct usb_device *usb_get_dev(struct usb_device *dev)
  {
  	if (dev)
  		get_device(&dev->dev);
  	return dev;
  }
  EXPORT_SYMBOL_GPL(usb_get_dev);
  
  /**
   * usb_put_dev - release a use of the usb device structure
   * @dev: device that's been disconnected
   *
   * Must be called when a user of a device is finished with it.  When the last
   * user of the device calls this function, the memory of the device is freed.
   */
  void usb_put_dev(struct usb_device *dev)
  {
  	if (dev)
  		put_device(&dev->dev);
  }
  EXPORT_SYMBOL_GPL(usb_put_dev);
  
  /**
   * usb_get_intf - increments the reference count of the usb interface structure
   * @intf: the interface being referenced
   *
   * Each live reference to a interface must be refcounted.
   *
   * Drivers for USB interfaces should normally record such references in
   * their probe() methods, when they bind to an interface, and release
   * them by calling usb_put_intf(), in their disconnect() methods.
   *
   * A pointer to the interface with the incremented reference counter is
   * returned.
   */
  struct usb_interface *usb_get_intf(struct usb_interface *intf)
  {
  	if (intf)
  		get_device(&intf->dev);
  	return intf;
  }
  EXPORT_SYMBOL_GPL(usb_get_intf);
  
  /**
   * usb_put_intf - release a use of the usb interface structure
   * @intf: interface that's been decremented
   *
   * Must be called when a user of an interface is finished with it.  When the
   * last user of the interface calls this function, the memory of the interface
   * is freed.
   */
  void usb_put_intf(struct usb_interface *intf)
  {
  	if (intf)
  		put_device(&intf->dev);
  }
  EXPORT_SYMBOL_GPL(usb_put_intf);
  
  /*			USB device locking
   *
   * USB devices and interfaces are locked using the semaphore in their
   * embedded struct device.  The hub driver guarantees that whenever a
   * device is connected or disconnected, drivers are called with the
   * USB device locked as well as their particular interface.
   *
   * Complications arise when several devices are to be locked at the same
   * time.  Only hub-aware drivers that are part of usbcore ever have to
   * do this; nobody else needs to worry about it.  The rule for locking
   * is simple:
   *
   *	When locking both a device and its parent, always lock the
   *	the parent first.
   */
  
  /**
   * usb_lock_device_for_reset - cautiously acquire the lock for a usb device structure
   * @udev: device that's being locked
   * @iface: interface bound to the driver making the request (optional)
   *
   * Attempts to acquire the device lock, but fails if the device is
   * NOTATTACHED or SUSPENDED, or if iface is specified and the interface
   * is neither BINDING nor BOUND.  Rather than sleeping to wait for the
   * lock, the routine polls repeatedly.  This is to prevent deadlock with
   * disconnect; in some drivers (such as usb-storage) the disconnect()
   * or suspend() method will block waiting for a device reset to complete.
   *
   * Returns a negative error code for failure, otherwise 0.
   */
  int usb_lock_device_for_reset(struct usb_device *udev,
  			      const struct usb_interface *iface)
  {
  	unsigned long jiffies_expire = jiffies + HZ;
  
  	if (udev->state == USB_STATE_NOTATTACHED)
  		return -ENODEV;
  	if (udev->state == USB_STATE_SUSPENDED)
  		return -EHOSTUNREACH;
  	if (iface && (iface->condition == USB_INTERFACE_UNBINDING ||
  			iface->condition == USB_INTERFACE_UNBOUND))
  		return -EINTR;
  
  	while (!usb_trylock_device(udev)) {
  
  		/* If we can't acquire the lock after waiting one second,
  		 * we're probably deadlocked */
  		if (time_after(jiffies, jiffies_expire))
  			return -EBUSY;
  
  		msleep(15);
  		if (udev->state == USB_STATE_NOTATTACHED)
  			return -ENODEV;
  		if (udev->state == USB_STATE_SUSPENDED)
  			return -EHOSTUNREACH;
  		if (iface && (iface->condition == USB_INTERFACE_UNBINDING ||
  				iface->condition == USB_INTERFACE_UNBOUND))
  			return -EINTR;
  	}
  	return 0;
  }
  EXPORT_SYMBOL_GPL(usb_lock_device_for_reset);
  
  /**
   * usb_get_current_frame_number - return current bus frame number
   * @dev: the device whose bus is being queried
   *
   * Returns the current frame number for the USB host controller
   * used with the given USB device.  This can be used when scheduling
   * isochronous requests.
   *
   * Note that different kinds of host controller have different
   * "scheduling horizons".  While one type might support scheduling only
   * 32 frames into the future, others could support scheduling up to
   * 1024 frames into the future.
   */
  int usb_get_current_frame_number(struct usb_device *dev)
  {
  	return usb_hcd_get_frame_number(dev);
  }
  EXPORT_SYMBOL_GPL(usb_get_current_frame_number);
  
  /*-------------------------------------------------------------------*/
  /*
   * __usb_get_extra_descriptor() finds a descriptor of specific type in the
   * extra field of the interface and endpoint descriptor structs.
   */
  
  int __usb_get_extra_descriptor(char *buffer, unsigned size,
  			       unsigned char type, void **ptr)
  {
  	struct usb_descriptor_header *header;
  
  	while (size >= sizeof(struct usb_descriptor_header)) {
  		header = (struct usb_descriptor_header *)buffer;
  
  		if (header->bLength < 2) {
  			printk(KERN_ERR
  				"%s: bogus descriptor, type %d length %d\n",
  				usbcore_name,
  				header->bDescriptorType,
  				header->bLength);
  			return -1;
  		}
  
  		if (header->bDescriptorType == type) {
  			*ptr = header;
  			return 0;
  		}
  
  		buffer += header->bLength;
  		size -= header->bLength;
  	}
  	return -1;
  }
  EXPORT_SYMBOL_GPL(__usb_get_extra_descriptor);
  
  /**
   * usb_alloc_coherent - allocate dma-consistent buffer for URB_NO_xxx_DMA_MAP
   * @dev: device the buffer will be used with
   * @size: requested buffer size
   * @mem_flags: affect whether allocation may block
   * @dma: used to return DMA address of buffer
   *
   * Return value is either null (indicating no buffer could be allocated), or
   * the cpu-space pointer to a buffer that may be used to perform DMA to the
   * specified device.  Such cpu-space buffers are returned along with the DMA
   * address (through the pointer provided).
   *
   * These buffers are used with URB_NO_xxx_DMA_MAP set in urb->transfer_flags
   * to avoid behaviors like using "DMA bounce buffers", or thrashing IOMMU
   * hardware during URB completion/resubmit.  The implementation varies between
   * platforms, depending on details of how DMA will work to this device.
   * Using these buffers also eliminates cacheline sharing problems on
   * architectures where CPU caches are not DMA-coherent.  On systems without
   * bus-snooping caches, these buffers are uncached.
   *
   * When the buffer is no longer used, free it with usb_free_coherent().
   */
  void *usb_alloc_coherent(struct usb_device *dev, size_t size, gfp_t mem_flags,
  			 dma_addr_t *dma)
  {
  	if (!dev || !dev->bus)
  		return NULL;
  	return hcd_buffer_alloc(dev->bus, size, mem_flags, dma);
  }
  EXPORT_SYMBOL_GPL(usb_alloc_coherent);
  
  /**
   * usb_free_coherent - free memory allocated with usb_alloc_coherent()
   * @dev: device the buffer was used with
   * @size: requested buffer size
   * @addr: CPU address of buffer
   * @dma: DMA address of buffer
   *
   * This reclaims an I/O buffer, letting it be reused.  The memory must have
   * been allocated using usb_alloc_coherent(), and the parameters must match
   * those provided in that allocation request.
   */
  void usb_free_coherent(struct usb_device *dev, size_t size, void *addr,
  		       dma_addr_t dma)
  {
  	if (!dev || !dev->bus)
  		return;
  	if (!addr)
  		return;
  	hcd_buffer_free(dev->bus, size, addr, dma);
  }
  EXPORT_SYMBOL_GPL(usb_free_coherent);
  
  /**
   * usb_buffer_map - create DMA mapping(s) for an urb
   * @urb: urb whose transfer_buffer/setup_packet will be mapped
   *
   * Return value is either null (indicating no buffer could be mapped), or
   * the parameter.  URB_NO_TRANSFER_DMA_MAP is
   * added to urb->transfer_flags if the operation succeeds.  If the device
   * is connected to this system through a non-DMA controller, this operation
   * always succeeds.
   *
   * This call would normally be used for an urb which is reused, perhaps
   * as the target of a large periodic transfer, with usb_buffer_dmasync()
   * calls to synchronize memory and dma state.
   *
   * Reverse the effect of this call with usb_buffer_unmap().
   */
  #if 0
  struct urb *usb_buffer_map(struct urb *urb)
  {
  	struct usb_bus		*bus;
  	struct device		*controller;
  
  	if (!urb
  			|| !urb->dev
  			|| !(bus = urb->dev->bus)
  			|| !(controller = bus->controller))
  		return NULL;
  
  	if (controller->dma_mask) {
  		urb->transfer_dma = dma_map_single(controller,
  			urb->transfer_buffer, urb->transfer_buffer_length,
  			usb_pipein(urb->pipe)
  				? DMA_FROM_DEVICE : DMA_TO_DEVICE);
  	/* FIXME generic api broken like pci, can't report errors */
  	/* if (urb->transfer_dma == DMA_ADDR_INVALID) return 0; */
  	} else
  		urb->transfer_dma = ~0;
  	urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
  	return urb;
  }
  EXPORT_SYMBOL_GPL(usb_buffer_map);
  #endif  /*  0  */
  
  /* XXX DISABLED, no users currently.  If you wish to re-enable this
   * XXX please determine whether the sync is to transfer ownership of
   * XXX the buffer from device to cpu or vice verse, and thusly use the
   * XXX appropriate _for_{cpu,device}() method.  -DaveM
   */
  #if 0
  
  /**
   * usb_buffer_dmasync - synchronize DMA and CPU view of buffer(s)
   * @urb: urb whose transfer_buffer/setup_packet will be synchronized
   */
  void usb_buffer_dmasync(struct urb *urb)
  {
  	struct usb_bus		*bus;
  	struct device		*controller;
  
  	if (!urb
  			|| !(urb->transfer_flags & URB_NO_TRANSFER_DMA_MAP)
  			|| !urb->dev
  			|| !(bus = urb->dev->bus)
  			|| !(controller = bus->controller))
  		return;
  
  	if (controller->dma_mask) {
  		dma_sync_single_for_cpu(controller,
  			urb->transfer_dma, urb->transfer_buffer_length,
  			usb_pipein(urb->pipe)
  				? DMA_FROM_DEVICE : DMA_TO_DEVICE);
  		if (usb_pipecontrol(urb->pipe))
  			dma_sync_single_for_cpu(controller,
  					urb->setup_dma,
  					sizeof(struct usb_ctrlrequest),
  					DMA_TO_DEVICE);
  	}
  }
  EXPORT_SYMBOL_GPL(usb_buffer_dmasync);
  #endif
  
  /**
   * usb_buffer_unmap - free DMA mapping(s) for an urb
   * @urb: urb whose transfer_buffer will be unmapped
   *
   * Reverses the effect of usb_buffer_map().
   */
  #if 0
  void usb_buffer_unmap(struct urb *urb)
  {
  	struct usb_bus		*bus;
  	struct device		*controller;
  
  	if (!urb
  			|| !(urb->transfer_flags & URB_NO_TRANSFER_DMA_MAP)
  			|| !urb->dev
  			|| !(bus = urb->dev->bus)
  			|| !(controller = bus->controller))
  		return;
  
  	if (controller->dma_mask) {
  		dma_unmap_single(controller,
  			urb->transfer_dma, urb->transfer_buffer_length,
  			usb_pipein(urb->pipe)
  				? DMA_FROM_DEVICE : DMA_TO_DEVICE);
  	}
  	urb->transfer_flags &= ~URB_NO_TRANSFER_DMA_MAP;
  }
  EXPORT_SYMBOL_GPL(usb_buffer_unmap);
  #endif  /*  0  */
  
  #if 0
  /**
   * usb_buffer_map_sg - create scatterlist DMA mapping(s) for an endpoint
   * @dev: device to which the scatterlist will be mapped
   * @is_in: mapping transfer direction
   * @sg: the scatterlist to map
   * @nents: the number of entries in the scatterlist
   *
   * Return value is either < 0 (indicating no buffers could be mapped), or
   * the number of DMA mapping array entries in the scatterlist.
   *
   * The caller is responsible for placing the resulting DMA addresses from
   * the scatterlist into URB transfer buffer pointers, and for setting the
   * URB_NO_TRANSFER_DMA_MAP transfer flag in each of those URBs.
   *
   * Top I/O rates come from queuing URBs, instead of waiting for each one
   * to complete before starting the next I/O.   This is particularly easy
   * to do with scatterlists.  Just allocate and submit one URB for each DMA
   * mapping entry returned, stopping on the first error or when all succeed.
   * Better yet, use the usb_sg_*() calls, which do that (and more) for you.
   *
   * This call would normally be used when translating scatterlist requests,
   * rather than usb_buffer_map(), since on some hardware (with IOMMUs) it
   * may be able to coalesce mappings for improved I/O efficiency.
   *
   * Reverse the effect of this call with usb_buffer_unmap_sg().
   */
  int usb_buffer_map_sg(const struct usb_device *dev, int is_in,
  		      struct scatterlist *sg, int nents)
  {
  	struct usb_bus		*bus;
  	struct device		*controller;
  
  	if (!dev
  			|| !(bus = dev->bus)
  			|| !(controller = bus->controller)
  			|| !controller->dma_mask)
  		return -EINVAL;
  
  	/* FIXME generic api broken like pci, can't report errors */
  	return dma_map_sg(controller, sg, nents,
  			is_in ? DMA_FROM_DEVICE : DMA_TO_DEVICE) ? : -ENOMEM;
  }
  EXPORT_SYMBOL_GPL(usb_buffer_map_sg);
  #endif
  
  /* XXX DISABLED, no users currently.  If you wish to re-enable this
   * XXX please determine whether the sync is to transfer ownership of
   * XXX the buffer from device to cpu or vice verse, and thusly use the
   * XXX appropriate _for_{cpu,device}() method.  -DaveM
   */
  #if 0
  
  /**
   * usb_buffer_dmasync_sg - synchronize DMA and CPU view of scatterlist buffer(s)
   * @dev: device to which the scatterlist will be mapped
   * @is_in: mapping transfer direction
   * @sg: the scatterlist to synchronize
   * @n_hw_ents: the positive return value from usb_buffer_map_sg
   *
   * Use this when you are re-using a scatterlist's data buffers for
   * another USB request.
   */
  void usb_buffer_dmasync_sg(const struct usb_device *dev, int is_in,
  			   struct scatterlist *sg, int n_hw_ents)
  {
  	struct usb_bus		*bus;
  	struct device		*controller;
  
  	if (!dev
  			|| !(bus = dev->bus)
  			|| !(controller = bus->controller)
  			|| !controller->dma_mask)
  		return;
  
  	dma_sync_sg_for_cpu(controller, sg, n_hw_ents,
  			    is_in ? DMA_FROM_DEVICE : DMA_TO_DEVICE);
  }
  EXPORT_SYMBOL_GPL(usb_buffer_dmasync_sg);
  #endif
  
  #if 0
  /**
   * usb_buffer_unmap_sg - free DMA mapping(s) for a scatterlist
   * @dev: device to which the scatterlist will be mapped
   * @is_in: mapping transfer direction
   * @sg: the scatterlist to unmap
   * @n_hw_ents: the positive return value from usb_buffer_map_sg
   *
   * Reverses the effect of usb_buffer_map_sg().
   */
  void usb_buffer_unmap_sg(const struct usb_device *dev, int is_in,
  			 struct scatterlist *sg, int n_hw_ents)
  {
  	struct usb_bus		*bus;
  	struct device		*controller;
  
  	if (!dev
  			|| !(bus = dev->bus)
  			|| !(controller = bus->controller)
  			|| !controller->dma_mask)
  		return;
  
  	dma_unmap_sg(controller, sg, n_hw_ents,
  			is_in ? DMA_FROM_DEVICE : DMA_TO_DEVICE);
  }
  EXPORT_SYMBOL_GPL(usb_buffer_unmap_sg);
  #endif
  
  /* To disable USB, kernel command line is 'nousb' not 'usbcore.nousb' */
  #ifdef MODULE
  module_param(nousb, bool, 0444);
  #else
  core_param(nousb, nousb, bool, 0444);
  #endif
  
  /*
   * for external read access to <nousb>
   */
  int usb_disabled(void)
  {
  	return nousb;
  }
  EXPORT_SYMBOL_GPL(usb_disabled);
  
  /*
   * Notifications of device and interface registration
   */
  static int usb_bus_notify(struct notifier_block *nb, unsigned long action,
  		void *data)
  {
  	struct device *dev = data;
  
  	switch (action) {
  	case BUS_NOTIFY_ADD_DEVICE:
  		if (dev->type == &usb_device_type)
  			(void) usb_create_sysfs_dev_files(to_usb_device(dev));
  		else if (dev->type == &usb_if_device_type)
  			usb_create_sysfs_intf_files(to_usb_interface(dev));
  		break;
  
  	case BUS_NOTIFY_DEL_DEVICE:
  		if (dev->type == &usb_device_type)
  			usb_remove_sysfs_dev_files(to_usb_device(dev));
  		else if (dev->type == &usb_if_device_type)
  			usb_remove_sysfs_intf_files(to_usb_interface(dev));
  		break;
  	}
  	return 0;
  }
  
  static struct notifier_block usb_bus_nb = {
  	.notifier_call = usb_bus_notify,
  };
  
  struct dentry *usb_debug_root;
  EXPORT_SYMBOL_GPL(usb_debug_root);
  
  static struct dentry *usb_debug_devices;
  
  static int usb_debugfs_init(void)
  {
  	usb_debug_root = debugfs_create_dir("usb", NULL);
  	if (!usb_debug_root)
  		return -ENOENT;
  
  	usb_debug_devices = debugfs_create_file("devices", 0444,
  						usb_debug_root, NULL,
  						&usbfs_devices_fops);
  	if (!usb_debug_devices) {
  		debugfs_remove(usb_debug_root);
  		usb_debug_root = NULL;
  		return -ENOENT;
  	}
  
  	return 0;
  }
  
  static void usb_debugfs_cleanup(void)
  {
  	debugfs_remove(usb_debug_devices);
  	debugfs_remove(usb_debug_root);
  }
  
  /*
   * Init
   */
  static int __init usb_init(void)
  {
  	int retval;
  	if (nousb) {
  		pr_info("%s: USB support disabled\n", usbcore_name);
  		return 0;
  	}
  
  	retval = usb_debugfs_init();
  	if (retval)
  		goto out;
  
  	usb_acpi_register();
  	retval = bus_register(&usb_bus_type);
  	if (retval)
  		goto bus_register_failed;
  	retval = bus_register_notifier(&usb_bus_type, &usb_bus_nb);
  	if (retval)
  		goto bus_notifier_failed;
  	retval = usb_major_init();
  	if (retval)
  		goto major_init_failed;
  	retval = usb_register(&usbfs_driver);
  	if (retval)
  		goto driver_register_failed;
  	retval = usb_devio_init();
  	if (retval)
  		goto usb_devio_init_failed;
  	retval = usb_hub_init();
  	if (retval)
  		goto hub_init_failed;
  	retval = usb_register_device_driver(&usb_generic_driver, THIS_MODULE);
  	if (!retval)
  		goto out;
  
  	usb_hub_cleanup();
  hub_init_failed:
  	usb_devio_cleanup();
  usb_devio_init_failed:
  	usb_deregister(&usbfs_driver);
  driver_register_failed:
  	usb_major_cleanup();
  major_init_failed:
  	bus_unregister_notifier(&usb_bus_type, &usb_bus_nb);
  bus_notifier_failed:
  	bus_unregister(&usb_bus_type);
  bus_register_failed:
  	usb_acpi_unregister();
  	usb_debugfs_cleanup();
  out:
  	return retval;
  }
  
  /*
   * Cleanup
   */
  static void __exit usb_exit(void)
  {
  	/* This will matter if shutdown/reboot does exitcalls. */
  	if (nousb)
  		return;
  
  	usb_deregister_device_driver(&usb_generic_driver);
  	usb_major_cleanup();
  	usb_deregister(&usbfs_driver);
  	usb_devio_cleanup();
  	usb_hub_cleanup();
  	bus_unregister_notifier(&usb_bus_type, &usb_bus_nb);
  	bus_unregister(&usb_bus_type);
  	usb_acpi_unregister();
  	usb_debugfs_cleanup();
  }
  
  subsys_initcall(usb_init);
  module_exit(usb_exit);
  MODULE_LICENSE("GPL");
  