drivers/usb/core/driver.c

/*
 * drivers/usb/driver.c - most of the driver model stuff for usb
 *
 * (C) Copyright 2005 Greg Kroah-Hartman <gregkh@suse.de>
 *
 * based on drivers/usb/usb.c which had the following copyrights:
 *	(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
 * matching, probing, releasing, suspending and resuming for
 * real drivers.
 *
 */

#include <linux/device.h>
#include <linux/usb.h>
#include <linux/usb/quirks.h>
#include <linux/workqueue.h>
#include "hcd.h"
#include "usb.h"


#ifdef CONFIG_HOTPLUG

/*
 * Adds a new dynamic USBdevice ID to this driver,
 * and cause the driver to probe for all devices again.
 */
ssize_t usb_store_new_id(struct usb_dynids *dynids,
			 struct device_driver *driver,
			 const char *buf, size_t count)
{
	struct usb_dynid *dynid;
	u32 idVendor = 0;
	u32 idProduct = 0;
	int fields = 0;
	int retval = 0;

	fields = sscanf(buf, "%x %x", &idVendor, &idProduct);
	if (fields < 2)
		return -EINVAL;

	dynid = kzalloc(sizeof(*dynid), GFP_KERNEL);
	if (!dynid)
		return -ENOMEM;

	INIT_LIST_HEAD(&dynid->node);
	dynid->id.idVendor = idVendor;
	dynid->id.idProduct = idProduct;
	dynid->id.match_flags = USB_DEVICE_ID_MATCH_DEVICE;

	spin_lock(&dynids->lock);
	list_add_tail(&dynid->node, &dynids->list);
	spin_unlock(&dynids->lock);

	if (get_driver(driver)) {
		retval = driver_attach(driver);
		put_driver(driver);
	}

	if (retval)
		return retval;
	return count;
}
EXPORT_SYMBOL_GPL(usb_store_new_id);

static ssize_t store_new_id(struct device_driver *driver,
			    const char *buf, size_t count)
{
	struct usb_driver *usb_drv = to_usb_driver(driver);

	return usb_store_new_id(&usb_drv->dynids, driver, buf, count);
}
static DRIVER_ATTR(new_id, S_IWUSR, NULL, store_new_id);

static int usb_create_newid_file(struct usb_driver *usb_drv)
{
	int error = 0;

	if (usb_drv->no_dynamic_id)
		goto exit;

	if (usb_drv->probe != NULL)
		error = sysfs_create_file(&usb_drv->drvwrap.driver.kobj,
					  &driver_attr_new_id.attr);
exit:
	return error;
}

static void usb_remove_newid_file(struct usb_driver *usb_drv)
{
	if (usb_drv->no_dynamic_id)
		return;

	if (usb_drv->probe != NULL)
		sysfs_remove_file(&usb_drv->drvwrap.driver.kobj,
				  &driver_attr_new_id.attr);
}

static void usb_free_dynids(struct usb_driver *usb_drv)
{
	struct usb_dynid *dynid, *n;

	spin_lock(&usb_drv->dynids.lock);
	list_for_each_entry_safe(dynid, n, &usb_drv->dynids.list, node) {
		list_del(&dynid->node);
		kfree(dynid);
	}
	spin_unlock(&usb_drv->dynids.lock);
}
#else
static inline int usb_create_newid_file(struct usb_driver *usb_drv)
{
	return 0;
}

static void usb_remove_newid_file(struct usb_driver *usb_drv)
{
}

static inline void usb_free_dynids(struct usb_driver *usb_drv)
{
}
#endif

static const struct usb_device_id *usb_match_dynamic_id(struct usb_interface *intf,
							struct usb_driver *drv)
{
	struct usb_dynid *dynid;

	spin_lock(&drv->dynids.lock);
	list_for_each_entry(dynid, &drv->dynids.list, node) {
		if (usb_match_one_id(intf, &dynid->id)) {
			spin_unlock(&drv->dynids.lock);
			return &dynid->id;
		}
	}
	spin_unlock(&drv->dynids.lock);
	return NULL;
}


/* called from driver core with dev locked */
static int usb_probe_device(struct device *dev)
{
	struct usb_device_driver *udriver = to_usb_device_driver(dev->driver);
	struct usb_device *udev;
	int error = -ENODEV;

	dev_dbg(dev, "%s\n", __FUNCTION__);

	if (!is_usb_device(dev))	/* Sanity check */
		return error;

	udev = to_usb_device(dev);

	/* TODO: Add real matching code */

	/* The device should always appear to be in use
	 * unless the driver suports autosuspend.
	 */
	udev->pm_usage_cnt = !(udriver->supports_autosuspend);

	error = udriver->probe(udev);
	return error;
}

/* called from driver core with dev locked */
static int usb_unbind_device(struct device *dev)
{
	struct usb_device_driver *udriver = to_usb_device_driver(dev->driver);

	udriver->disconnect(to_usb_device(dev));
	return 0;
}


/* called from driver core with dev locked */
static int usb_probe_interface(struct device *dev)
{
	struct usb_driver *driver = to_usb_driver(dev->driver);
	struct usb_interface *intf;
	struct usb_device *udev;
	const struct usb_device_id *id;
	int error = -ENODEV;

	dev_dbg(dev, "%s\n", __FUNCTION__);

	if (is_usb_device(dev))		/* Sanity check */
		return error;

	intf = to_usb_interface(dev);
	udev = interface_to_usbdev(intf);

	id = usb_match_id(intf, driver->id_table);
	if (!id)
		id = usb_match_dynamic_id(intf, driver);
	if (id) {
		dev_dbg(dev, "%s - got id\n", __FUNCTION__);

		error = usb_autoresume_device(udev);
		if (error)
			return error;

		/* Interface "power state" doesn't correspond to any hardware
		 * state whatsoever.  We use it to record when it's bound to
		 * a driver that may start I/0:  it's not frozen/quiesced.
		 */
		mark_active(intf);
		intf->condition = USB_INTERFACE_BINDING;

		/* The interface should always appear to be in use
		 * unless the driver suports autosuspend.
		 */
		intf->pm_usage_cnt = !(driver->supports_autosuspend);

		error = driver->probe(intf, id);
		if (error) {
			mark_quiesced(intf);
			intf->needs_remote_wakeup = 0;
			intf->condition = USB_INTERFACE_UNBOUND;
		} else
			intf->condition = USB_INTERFACE_BOUND;

		usb_autosuspend_device(udev);
	}

	return error;
}

/* called from driver core with dev locked */
static int usb_unbind_interface(struct device *dev)
{
	struct usb_driver *driver = to_usb_driver(dev->driver);
	struct usb_interface *intf = to_usb_interface(dev);
	struct usb_device *udev;
	int error;

	intf->condition = USB_INTERFACE_UNBINDING;

	/* Autoresume for set_interface call below */
	udev = interface_to_usbdev(intf);
	error = usb_autoresume_device(udev);

	/* release all urbs for this interface */
	usb_disable_interface(interface_to_usbdev(intf), intf);

	driver->disconnect(intf);

	/* reset other interface state */
	usb_set_interface(interface_to_usbdev(intf),
			intf->altsetting[0].desc.bInterfaceNumber,
			0);
	usb_set_intfdata(intf, NULL);

	intf->condition = USB_INTERFACE_UNBOUND;
	mark_quiesced(intf);
	intf->needs_remote_wakeup = 0;

	if (!error)
		usb_autosuspend_device(udev);

	return 0;
}

/**
 * usb_driver_claim_interface - bind a driver to an interface
 * @driver: the driver to be bound
 * @iface: the interface to which it will be bound; must be in the
 *	usb device's active configuration
 * @priv: driver data associated with that interface
 *
 * This is used by usb device drivers that need to claim more than one
 * interface on a device when probing (audio and acm are current examples).
 * No device driver should directly modify internal usb_interface or
 * usb_device structure members.
 *
 * Few drivers should need to use this routine, since the most natural
 * way to bind to an interface is to return the private data from
 * the driver's probe() method.
 *
 * Callers must own the device lock, so driver probe() entries don't need
 * extra locking, but other call contexts may need to explicitly claim that
 * lock.
 */
int usb_driver_claim_interface(struct usb_driver *driver,
				struct usb_interface *iface, void* priv)
{
	struct device *dev = &iface->dev;
	struct usb_device *udev = interface_to_usbdev(iface);
	int retval = 0;

	if (dev->driver)
		return -EBUSY;

	dev->driver = &driver->drvwrap.driver;
	usb_set_intfdata(iface, priv);

	usb_pm_lock(udev);
	iface->condition = USB_INTERFACE_BOUND;
	mark_active(iface);
	iface->pm_usage_cnt = !(driver->supports_autosuspend);
	usb_pm_unlock(udev);

	/* if interface was already added, bind now; else let
	 * the future device_add() bind it, bypassing probe()
	 */
	if (device_is_registered(dev))
		retval = device_bind_driver(dev);

	return retval;
}
EXPORT_SYMBOL(usb_driver_claim_interface);

/**
 * usb_driver_release_interface - unbind a driver from an interface
 * @driver: the driver to be unbound
 * @iface: the interface from which it will be unbound
 *
 * This can be used by drivers to release an interface without waiting
 * for their disconnect() methods to be called.  In typical cases this
 * also causes the driver disconnect() method to be called.
 *
 * This call is synchronous, and may not be used in an interrupt context.
 * Callers must own the device lock, so driver disconnect() entries don't
 * need extra locking, but other call contexts may need to explicitly claim
 * that lock.
 */
void usb_driver_release_interface(struct usb_driver *driver,
					struct usb_interface *iface)
{
	struct device *dev = &iface->dev;
	struct usb_device *udev = interface_to_usbdev(iface);

	/* this should never happen, don't release something that's not ours */
	if (!dev->driver || dev->driver != &driver->drvwrap.driver)
		return;

	/* don't release from within disconnect() */
	if (iface->condition != USB_INTERFACE_BOUND)
		return;

	/* don't release if the interface hasn't been added yet */
	if (device_is_registered(dev)) {
		iface->condition = USB_INTERFACE_UNBINDING;
		device_release_driver(dev);
	}

	dev->driver = NULL;
	usb_set_intfdata(iface, NULL);

	usb_pm_lock(udev);
	iface->condition = USB_INTERFACE_UNBOUND;
	mark_quiesced(iface);
	iface->needs_remote_wakeup = 0;
	usb_pm_unlock(udev);
}
EXPORT_SYMBOL(usb_driver_release_interface);

/* returns 0 if no match, 1 if match */
int usb_match_device(struct usb_device *dev, const struct usb_device_id *id)
{
	if ((id->match_flags & USB_DEVICE_ID_MATCH_VENDOR) &&
	    id->idVendor != le16_to_cpu(dev->descriptor.idVendor))
		return 0;

	if ((id->match_flags & USB_DEVICE_ID_MATCH_PRODUCT) &&
	    id->idProduct != le16_to_cpu(dev->descriptor.idProduct))
		return 0;

	/* No need to test id->bcdDevice_lo != 0, since 0 is never
	   greater than any unsigned number. */
	if ((id->match_flags & USB_DEVICE_ID_MATCH_DEV_LO) &&
	    (id->bcdDevice_lo > le16_to_cpu(dev->descriptor.bcdDevice)))
		return 0;

	if ((id->match_flags & USB_DEVICE_ID_MATCH_DEV_HI) &&
	    (id->bcdDevice_hi < le16_to_cpu(dev->descriptor.bcdDevice)))
		return 0;

	if ((id->match_flags & USB_DEVICE_ID_MATCH_DEV_CLASS) &&
	    (id->bDeviceClass != dev->descriptor.bDeviceClass))
		return 0;

	if ((id->match_flags & USB_DEVICE_ID_MATCH_DEV_SUBCLASS) &&
	    (id->bDeviceSubClass!= dev->descriptor.bDeviceSubClass))
		return 0;

	if ((id->match_flags & USB_DEVICE_ID_MATCH_DEV_PROTOCOL) &&
	    (id->bDeviceProtocol != dev->descriptor.bDeviceProtocol))
		return 0;

	return 1;
}

/* returns 0 if no match, 1 if match */
int usb_match_one_id(struct usb_interface *interface,
		     const struct usb_device_id *id)
{
	struct usb_host_interface *intf;
	struct usb_device *dev;

	/* proc_connectinfo in devio.c may call us with id == NULL. */
	if (id == NULL)
		return 0;

	intf = interface->cur_altsetting;
	dev = interface_to_usbdev(interface);

	if (!usb_match_device(dev, id))
		return 0;

	/* The interface class, subclass, and protocol should never be
	 * checked for a match if the device class is Vendor Specific,
	 * unless the match record specifies the Vendor ID. */
	if (dev->descriptor.bDeviceClass == USB_CLASS_VENDOR_SPEC &&
			!(id->match_flags & USB_DEVICE_ID_MATCH_VENDOR) &&
			(id->match_flags & (USB_DEVICE_ID_MATCH_INT_CLASS |
				USB_DEVICE_ID_MATCH_INT_SUBCLASS |
				USB_DEVICE_ID_MATCH_INT_PROTOCOL)))
		return 0;

	if ((id->match_flags & USB_DEVICE_ID_MATCH_INT_CLASS) &&
	    (id->bInterfaceClass != intf->desc.bInterfaceClass))
		return 0;

	if ((id->match_flags & USB_DEVICE_ID_MATCH_INT_SUBCLASS) &&
	    (id->bInterfaceSubClass != intf->desc.bInterfaceSubClass))
		return 0;

	if ((id->match_flags & USB_DEVICE_ID_MATCH_INT_PROTOCOL) &&
	    (id->bInterfaceProtocol != intf->desc.bInterfaceProtocol))
		return 0;

	return 1;
}
EXPORT_SYMBOL_GPL(usb_match_one_id);

/**
 * usb_match_id - find first usb_device_id matching device or interface
 * @interface: the interface of interest
 * @id: array of usb_device_id structures, terminated by zero entry
 *
 * usb_match_id searches an array of usb_device_id's and returns
 * the first one matching the device or interface, or null.
 * This is used when binding (or rebinding) a driver to an interface.
 * Most USB device drivers will use this indirectly, through the usb core,
 * but some layered driver frameworks use it directly.
 * These device tables are exported with MODULE_DEVICE_TABLE, through
 * modutils, to support the driver loading functionality of USB hotplugging.
 *
 * What Matches:
 *
 * The "match_flags" element in a usb_device_id controls which
 * members are used.  If the corresponding bit is set, the
 * value in the device_id must match its corresponding member
 * in the device or interface descriptor, or else the device_id
 * does not match.
 *
 * "driver_info" is normally used only by device drivers,
 * but you can create a wildcard "matches anything" usb_device_id
 * as a driver's "modules.usbmap" entry if you provide an id with
 * only a nonzero "driver_info" field.  If you do this, the USB device
 * driver's probe() routine should use additional intelligence to
 * decide whether to bind to the specified interface.
 *
 * What Makes Good usb_device_id Tables:
 *
 * The match algorithm is very simple, so that intelligence in
 * driver selection must come from smart driver id records.
 * Unless you have good reasons to use another selection policy,
 * provide match elements only in related groups, and order match
 * specifiers from specific to general.  Use the macros provided
 * for that purpose if you can.
 *
 * The most specific match specifiers use device descriptor
 * data.  These are commonly used with product-specific matches;
 * the USB_DEVICE macro lets you provide vendor and product IDs,
 * and you can also match against ranges of product revisions.
 * These are widely used for devices with application or vendor
 * specific bDeviceClass values.
 *
 * Matches based on device class/subclass/protocol specifications
 * are slightly more general; use the USB_DEVICE_INFO macro, or
 * its siblings.  These are used with single-function devices
 * where bDeviceClass doesn't specify that each interface has
 * its own class.
 *
 * Matches based on interface class/subclass/protocol are the
 * most general; they let drivers bind to any interface on a
 * multiple-function device.  Use the USB_INTERFACE_INFO
 * macro, or its siblings, to match class-per-interface style
 * devices (as recorded in bInterfaceClass).
 *
 * Note that an entry created by USB_INTERFACE_INFO won't match
 * any interface if the device class is set to Vendor-Specific.
 * This is deliberate; according to the USB spec the meanings of
 * the interface class/subclass/protocol for these devices are also
 * vendor-specific, and hence matching against a standard product
 * class wouldn't work anyway.  If you really want to use an
 * interface-based match for such a device, create a match record
 * that also specifies the vendor ID.  (Unforunately there isn't a
 * standard macro for creating records like this.)
 *
 * Within those groups, remember that not all combinations are
 * meaningful.  For example, don't give a product version range
 * without vendor and product IDs; or specify a protocol without
 * its associated class and subclass.
 */
const struct usb_device_id *usb_match_id(struct usb_interface *interface,
					 const struct usb_device_id *id)
{
	/* proc_connectinfo in devio.c may call us with id == NULL. */
	if (id == NULL)
		return NULL;

	/* It is important to check that id->driver_info is nonzero,
	   since an entry that is all zeroes except for a nonzero
	   id->driver_info is the way to create an entry that
	   indicates that the driver want to examine every
	   device and interface. */
	for (; id->idVendor || id->bDeviceClass || id->bInterfaceClass ||
	       id->driver_info; id++) {
		if (usb_match_one_id(interface, id))
			return id;
	}

	return NULL;
}
EXPORT_SYMBOL_GPL_FUTURE(usb_match_id);

static int usb_device_match(struct device *dev, struct device_driver *drv)
{
	/* devices and interfaces are handled separately */
	if (is_usb_device(dev)) {

		/* interface drivers never match devices */
		if (!is_usb_device_driver(drv))
			return 0;

		/* TODO: Add real matching code */
		return 1;

	} else {
		struct usb_interface *intf;
		struct usb_driver *usb_drv;
		const struct usb_device_id *id;

		/* device drivers never match interfaces */
		if (is_usb_device_driver(drv))
			return 0;

		intf = to_usb_interface(dev);
		usb_drv = to_usb_driver(drv);

		id = usb_match_id(intf, usb_drv->id_table);
		if (id)
			return 1;

		id = usb_match_dynamic_id(intf, usb_drv);
		if (id)
			return 1;
	}

	return 0;
}

#ifdef	CONFIG_HOTPLUG
static int usb_uevent(struct device *dev, struct kobj_uevent_env *env)
{
	struct usb_device *usb_dev;

	if (!dev)
		return -ENODEV;

	/* driver is often null here; dev_dbg() would oops */
	pr_debug ("usb %s: uevent\n", dev->bus_id);

	if (is_usb_device(dev))
		usb_dev = to_usb_device(dev);
	else {
		struct usb_interface *intf = to_usb_interface(dev);
		usb_dev = interface_to_usbdev(intf);
	}

	if (usb_dev->devnum < 0) {
		pr_debug ("usb %s: already deleted?\n", dev->bus_id);
		return -ENODEV;
	}
	if (!usb_dev->bus) {
		pr_debug ("usb %s: bus removed?\n", dev->bus_id);
		return -ENODEV;
	}

#ifdef	CONFIG_USB_DEVICEFS
	/* If this is available, userspace programs can directly read
	 * all the device descriptors we don't tell them about.  Or
	 * act as usermode drivers.
	 */
	if (add_uevent_var(env, "DEVICE=/proc/bus/usb/%03d/%03d",
			   usb_dev->bus->busnum, usb_dev->devnum))
		return -ENOMEM;
#endif

	/* per-device configurations are common */
	if (add_uevent_var(env, "PRODUCT=%x/%x/%x",
			   le16_to_cpu(usb_dev->descriptor.idVendor),
			   le16_to_cpu(usb_dev->descriptor.idProduct),
			   le16_to_cpu(usb_dev->descriptor.bcdDevice)))
		return -ENOMEM;

	/* class-based driver binding models */
	if (add_uevent_var(env, "TYPE=%d/%d/%d",
			   usb_dev->descriptor.bDeviceClass,
			   usb_dev->descriptor.bDeviceSubClass,
			   usb_dev->descriptor.bDeviceProtocol))
		return -ENOMEM;

	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_uevent(struct device *dev, struct kobj_uevent_env *env)
{
	return -ENODEV;
}
#endif	/* CONFIG_HOTPLUG */

/**
 * usb_register_device_driver - register a USB device (not interface) driver
 * @new_udriver: USB operations for the device driver
 * @owner: module owner of this driver.
 *
 * Registers a USB device driver with the USB core.  The list of
 * unattached devices will be rescanned whenever a new driver is
 * added, allowing the new driver to attach to any recognized devices.
 * Returns a negative error code on failure and 0 on success.
 */
int usb_register_device_driver(struct usb_device_driver *new_udriver,
		struct module *owner)
{
	int retval = 0;

	if (usb_disabled())
		return -ENODEV;

	new_udriver->drvwrap.for_devices = 1;
	new_udriver->drvwrap.driver.name = (char *) new_udriver->name;
	new_udriver->drvwrap.driver.bus = &usb_bus_type;
	new_udriver->drvwrap.driver.probe = usb_probe_device;
	new_udriver->drvwrap.driver.remove = usb_unbind_device;
	new_udriver->drvwrap.driver.owner = owner;

	retval = driver_register(&new_udriver->drvwrap.driver);

	if (!retval) {
		pr_info("%s: registered new device driver %s\n",
			usbcore_name, new_udriver->name);
		usbfs_update_special();
	} else {
		printk(KERN_ERR "%s: error %d registering device "
			"	driver %s\n",
			usbcore_name, retval, new_udriver->name);
	}

	return retval;
}
EXPORT_SYMBOL_GPL(usb_register_device_driver);

/**
 * usb_deregister_device_driver - unregister a USB device (not interface) driver
 * @udriver: USB operations of the device driver to unregister
 * Context: must be able to sleep
 *
 * Unlinks the specified driver from the internal USB driver list.
 */
void usb_deregister_device_driver(struct usb_device_driver *udriver)
{
	pr_info("%s: deregistering device driver %s\n",
			usbcore_name, udriver->name);

	driver_unregister(&udriver->drvwrap.driver);
	usbfs_update_special();
}
EXPORT_SYMBOL_GPL(usb_deregister_device_driver);

/**
 * usb_register_driver - register a USB interface driver
 * @new_driver: USB operations for the interface driver
 * @owner: module owner of this driver.
 * @mod_name: module name string
 *
 * Registers a USB interface driver with the USB core.  The list of
 * unattached interfaces will be rescanned whenever a new driver is
 * added, allowing the new driver to attach to any recognized interfaces.
 * Returns a negative error code on failure and 0 on success.
 *
 * NOTE: if you want your driver to use the USB major number, you must call
 * usb_register_dev() to enable that functionality.  This function no longer
 * takes care of that.
 */
int usb_register_driver(struct usb_driver *new_driver, struct module *owner,
			const char *mod_name)
{
	int retval = 0;

	if (usb_disabled())
		return -ENODEV;

	new_driver->drvwrap.for_devices = 0;
	new_driver->drvwrap.driver.name = (char *) new_driver->name;
	new_driver->drvwrap.driver.bus = &usb_bus_type;
	new_driver->drvwrap.driver.probe = usb_probe_interface;
	new_driver->drvwrap.driver.remove = usb_unbind_interface;
	new_driver->drvwrap.driver.owner = owner;
	new_driver->drvwrap.driver.mod_name = mod_name;
	spin_lock_init(&new_driver->dynids.lock);
	INIT_LIST_HEAD(&new_driver->dynids.list);

	retval = driver_register(&new_driver->drvwrap.driver);

	if (!retval) {
		pr_info("%s: registered new interface driver %s\n",
			usbcore_name, new_driver->name);
		usbfs_update_special();
		usb_create_newid_file(new_driver);
	} else {
		printk(KERN_ERR "%s: error %d registering interface "
			"	driver %s\n",
			usbcore_name, retval, new_driver->name);
	}

	return retval;
}
EXPORT_SYMBOL_GPL_FUTURE(usb_register_driver);

/**
 * usb_deregister - unregister a USB interface driver
 * @driver: USB operations of the interface driver to unregister
 * Context: must be able to sleep
 *
 * Unlinks the specified driver from the internal USB driver list.
 *
 * NOTE: If you called usb_register_dev(), you still need to call
 * usb_deregister_dev() to clean up your driver's allocated minor numbers,
 * this * call will no longer do it for you.
 */
void usb_deregister(struct usb_driver *driver)
{
	pr_info("%s: deregistering interface driver %s\n",
			usbcore_name, driver->name);

	usb_remove_newid_file(driver);
	usb_free_dynids(driver);
	driver_unregister(&driver->drvwrap.driver);

	usbfs_update_special();
}
EXPORT_SYMBOL_GPL_FUTURE(usb_deregister);

#ifdef CONFIG_PM

/* Caller has locked udev's pm_mutex */
static int usb_suspend_device(struct usb_device *udev, pm_message_t msg)
{
	struct usb_device_driver	*udriver;
	int				status = 0;

	if (udev->state == USB_STATE_NOTATTACHED ||
			udev->state == USB_STATE_SUSPENDED)
		goto done;

	/* For devices that don't have a driver, we do a generic suspend. */
	if (udev->dev.driver)
		udriver = to_usb_device_driver(udev->dev.driver);
	else {
		udev->do_remote_wakeup = 0;
		udriver = &usb_generic_driver;
	}
	status = udriver->suspend(udev, msg);

 done:
	dev_vdbg(&udev->dev, "%s: status %d\n", __FUNCTION__, status);
	if (status == 0)
		udev->dev.power.power_state.event = msg.event;
	return status;
}

/* Caller has locked udev's pm_mutex */
static int usb_resume_device(struct usb_device *udev)
{
	struct usb_device_driver	*udriver;
	int				status = 0;

	if (udev->state == USB_STATE_NOTATTACHED)
		goto done;
	if (udev->state != USB_STATE_SUSPENDED && !udev->reset_resume)
		goto done;

	/* Can't resume it if it doesn't have a driver. */
	if (udev->dev.driver == NULL) {
		status = -ENOTCONN;
		goto done;
	}

	if (udev->quirks & USB_QUIRK_RESET_RESUME)
		udev->reset_resume = 1;

	udriver = to_usb_device_driver(udev->dev.driver);
	status = udriver->resume(udev);

 done:
	dev_vdbg(&udev->dev, "%s: status %d\n", __FUNCTION__, status);
	if (status == 0) {
		udev->autoresume_disabled = 0;
		udev->dev.power.power_state.event = PM_EVENT_ON;
	}
	return status;
}

/* Caller has locked intf's usb_device's pm mutex */
static int usb_suspend_interface(struct usb_interface *intf, pm_message_t msg)
{
	struct usb_driver	*driver;
	int			status = 0;

	/* with no hardware, USB interfaces only use FREEZE and ON states */
	if (interface_to_usbdev(intf)->state == USB_STATE_NOTATTACHED ||
			!is_active(intf))
		goto done;

	if (intf->condition == USB_INTERFACE_UNBOUND)	/* This can't happen */
		goto done;
	driver = to_usb_driver(intf->dev.driver);

	if (driver->suspend && driver->resume) {
		status = driver->suspend(intf, msg);
		if (status == 0)
			mark_quiesced(intf);
		else if (!interface_to_usbdev(intf)->auto_pm)
			dev_err(&intf->dev, "%s error %d\n",
					"suspend", status);
	} else {
		// FIXME else if there's no suspend method, disconnect...
		// Not possible if auto_pm is set...
		dev_warn(&intf->dev, "no suspend for driver %s?\n",
				driver->name);
		mark_quiesced(intf);
	}

 done:
	dev_vdbg(&intf->dev, "%s: status %d\n", __FUNCTION__, status);
	return status;
}

/* Caller has locked intf's usb_device's pm_mutex */
static int usb_resume_interface(struct usb_interface *intf, int reset_resume)
{
	struct usb_driver	*driver;
	int			status = 0;

	if (interface_to_usbdev(intf)->state == USB_STATE_NOTATTACHED ||
			is_active(intf))
		goto done;

	/* Don't let autoresume interfere with unbinding */
	if (intf->condition == USB_INTERFACE_UNBINDING)
		goto done;

	/* Can't resume it if it doesn't have a driver. */
	if (intf->condition == USB_INTERFACE_UNBOUND) {
		status = -ENOTCONN;
		goto done;
	}
	driver = to_usb_driver(intf->dev.driver);

	if (reset_resume) {
		if (driver->reset_resume) {
			status = driver->reset_resume(intf);
			if (status)
				dev_err(&intf->dev, "%s error %d\n",
						"reset_resume", status);
		} else {
			// status = -EOPNOTSUPP;
			dev_warn(&intf->dev, "no %s for driver %s?\n",
					"reset_resume", driver->name);
		}
	} else {
		if (driver->resume) {
			status = driver->resume(intf);
			if (status)
				dev_err(&intf->dev, "%s error %d\n",
						"resume", status);
		} else {
			// status = -EOPNOTSUPP;
			dev_warn(&intf->dev, "no %s for driver %s?\n",
					"resume", driver->name);
		}
	}

done:
	dev_vdbg(&intf->dev, "%s: status %d\n", __FUNCTION__, status);
	if (status == 0)
		mark_active(intf);

	/* FIXME: Unbind the driver and reprobe if the resume failed
	 * (not possible if auto_pm is set) */
	return status;
}

#ifdef	CONFIG_USB_SUSPEND

/* Internal routine to check whether we may autosuspend a device. */
static int autosuspend_check(struct usb_device *udev)
{
	int			i;
	struct usb_interface	*intf;
	unsigned long		suspend_time;

	/* For autosuspend, fail fast if anything is in use or autosuspend
	 * is disabled.  Also fail if any interfaces require remote wakeup
	 * but it isn't available.
	 */
	udev->do_remote_wakeup = device_may_wakeup(&udev->dev);
	if (udev->pm_usage_cnt > 0)
		return -EBUSY;
	if (udev->autosuspend_delay < 0 || udev->autosuspend_disabled)
		return -EPERM;

	suspend_time = udev->last_busy + udev->autosuspend_delay;
	if (udev->actconfig) {
		for (i = 0; i < udev->actconfig->desc.bNumInterfaces; i++) {
			intf = udev->actconfig->interface[i];
			if (!is_active(intf))
				continue;
			if (intf->pm_usage_cnt > 0)
				return -EBUSY;
			if (intf->needs_remote_wakeup &&
					!udev->do_remote_wakeup) {
				dev_dbg(&udev->dev, "remote wakeup needed "
						"for autosuspend\n");
				return -EOPNOTSUPP;
			}

			/* Don't allow autosuspend if the device will need
			 * a reset-resume and any of its interface drivers
			 * doesn't include support.
			 */
			if (udev->quirks & USB_QUIRK_RESET_RESUME) {
				struct usb_driver *driver;

				driver = to_usb_driver(intf->dev.driver);
				if (!driver->reset_resume)
					return -EOPNOTSUPP;
			}
		}
	}

	/* If everything is okay but the device hasn't been idle for long
	 * enough, queue a delayed autosuspend request.
	 */
	if (time_after(suspend_time, jiffies)) {
		if (!timer_pending(&udev->autosuspend.timer)) {

			/* The value of jiffies may change between the
			 * time_after() comparison above and the subtraction
			 * below.  That's okay; the system behaves sanely
			 * when a timer is registered for the present moment
			 * or for the past.
			 */
			queue_delayed_work(ksuspend_usb_wq, &udev->autosuspend,
				round_jiffies_relative(suspend_time - jiffies));
			}
		return -EAGAIN;
	}
	return 0;
}

#else

static inline int autosuspend_check(struct usb_device *udev)
{
	return 0;
}

#endif	/* CONFIG_USB_SUSPEND */

/**
 * usb_suspend_both - suspend a USB device and its interfaces
 * @udev: the usb_device to suspend
 * @msg: Power Management message describing this state transition
 *
 * This is the central routine for suspending USB devices.  It calls the
 * suspend methods for all the interface drivers in @udev and then calls
 * the suspend method for @udev itself.  If an error occurs at any stage,
 * all the interfaces which were suspended are resumed so that they remain
 * in the same state as the device.
 *
 * If an autosuspend is in progress (@udev->auto_pm is set), the routine
 * checks first to make sure that neither the device itself or any of its
 * active interfaces is in use (pm_usage_cnt is greater than 0).  If they
 * are, the autosuspend fails.
 *
 * If the suspend succeeds, the routine recursively queues an autosuspend
 * request for @udev's parent device, thereby propagating the change up
 * the device tree.  If all of the parent's children are now suspended,
 * the parent will autosuspend in turn.
 *
 * The suspend method calls are subject to mutual exclusion under control
 * of @udev's pm_mutex.  Many of these calls are also under the protection
 * of @udev's device lock (including all requests originating outside the
 * USB subsystem), but autosuspend requests generated by a child device or
 * interface driver may not be.  Usbcore will insure that the method calls
 * do not arrive during bind, unbind, or reset operations.  However, drivers
 * must be prepared to handle suspend calls arriving at unpredictable times.
 * The only way to block such calls is to do an autoresume (preventing
 * autosuspends) while holding @udev's device lock (preventing outside
 * suspends).
 *
 * The caller must hold @udev->pm_mutex.
 *
 * This routine can run only in process context.
 */
static int usb_suspend_both(struct usb_device *udev, pm_message_t msg)
{
	int			status = 0;
	int			i = 0;
	struct usb_interface	*intf;
	struct usb_device	*parent = udev->parent;

	if (udev->state == USB_STATE_NOTATTACHED ||
			udev->state == USB_STATE_SUSPENDED)
		goto done;

	udev->do_remote_wakeup = device_may_wakeup(&udev->dev);

	if (udev->auto_pm) {
		status = autosuspend_check(udev);
		if (status < 0)
			goto done;
	}

	/* Suspend all the interfaces and then udev itself */
	if (udev->actconfig) {
		for (; i < udev->actconfig->desc.bNumInterfaces; i++) {
			intf = udev->actconfig->interface[i];
			status = usb_suspend_interface(intf, msg);
			if (status != 0)
				break;
		}
	}
	if (status == 0) {

		/* Non-root devices don't need to do anything for FREEZE
		 * or PRETHAW. */
		if (udev->parent && (msg.event == PM_EVENT_FREEZE ||
				msg.event == PM_EVENT_PRETHAW))
			goto done;
		status = usb_suspend_device(udev, msg);
	}

	/* If the suspend failed, resume interfaces that did get suspended */
	if (status != 0) {
		while (--i >= 0) {
			intf = udev->actconfig->interface[i];
			usb_resume_interface(intf, 0);
		}

		/* Try another autosuspend when the interfaces aren't busy */
		if (udev->auto_pm)
			autosuspend_check(udev);

	/* If the suspend succeeded, propagate it up the tree */
	} else {
		cancel_delayed_work(&udev->autosuspend);
		if (parent)
			usb_autosuspend_device(parent);
	}

 done:
	dev_vdbg(&udev->dev, "%s: status %d\n", __FUNCTION__, status);
	return status;
}

/**
 * usb_resume_both - resume a USB device and its interfaces
 * @udev: the usb_device to resume
 *
 * This is the central routine for resuming USB devices.  It calls the
 * the resume method for @udev and then calls the resume methods for all
 * the interface drivers in @udev.
 *
 * Before starting the resume, the routine calls itself recursively for
 * the parent device of @udev, thereby propagating the change up the device
 * tree and assuring that @udev will be able to resume.  If the parent is
 * unable to resume successfully, the routine fails.
 *
 * The resume method calls are subject to mutual exclusion under control
 * of @udev's pm_mutex.  Many of these calls are also under the protection
 * of @udev's device lock (including all requests originating outside the
 * USB subsystem), but autoresume requests generated by a child device or
 * interface driver may not be.  Usbcore will insure that the method calls
 * do not arrive during bind, unbind, or reset operations.  However, drivers
 * must be prepared to handle resume calls arriving at unpredictable times.
 * The only way to block such calls is to do an autoresume (preventing
 * other autoresumes) while holding @udev's device lock (preventing outside
 * resumes).
 *
 * The caller must hold @udev->pm_mutex.
 *
 * This routine can run only in process context.
 */
static int usb_resume_both(struct usb_device *udev)
{
	int			status = 0;
	int			i;
	struct usb_interface	*intf;
	struct usb_device	*parent = udev->parent;

	cancel_delayed_work(&udev->autosuspend);
	if (udev->state == USB_STATE_NOTATTACHED) {
		status = -ENODEV;
		goto done;
	}

	/* Propagate the resume up the tree, if necessary */
	if (udev->state == USB_STATE_SUSPENDED) {
		if (udev->auto_pm && udev->autoresume_disabled) {
			status = -EPERM;
			goto done;
		}
		if (parent) {
			status = usb_autoresume_device(parent);
			if (status == 0) {
				status = usb_resume_device(udev);
				if (status || udev->state ==
						USB_STATE_NOTATTACHED) {
					usb_autosuspend_device(parent);

					/* It's possible usb_resume_device()
					 * failed after the port was
					 * unsuspended, causing udev to be
					 * logically disconnected.  We don't
					 * want usb_disconnect() to autosuspend
					 * the parent again, so tell it that
					 * udev disconnected while still
					 * suspended. */
					if (udev->state ==
							USB_STATE_NOTATTACHED)
						udev->discon_suspended = 1;
				}
			}
		} else {

			/* We can't progagate beyond the USB subsystem,
			 * so if a root hub's controller is suspended
			 * then we're stuck. */
			status = usb_resume_device(udev);
 		}
	} else {

		/* Needed for setting udev->dev.power.power_state.event,
		 * for possible debugging message, and for reset_resume. */
		status = usb_resume_device(udev);
	}

	if (status == 0 && udev->actconfig) {
		for (i = 0; i < udev->actconfig->desc.bNumInterfaces; i++) {
			intf = udev->actconfig->interface[i];
			usb_resume_interface(intf, udev->reset_resume);
		}
	}

 done:
	dev_vdbg(&udev->dev, "%s: status %d\n", __FUNCTION__, status);
	udev->reset_resume = 0;
	return status;
}

#ifdef CONFIG_USB_SUSPEND

/* Internal routine to adjust a device's usage counter and change
 * its autosuspend state.
 */
static int usb_autopm_do_device(struct usb_device *udev, int inc_usage_cnt)
{
	int	status = 0;

	usb_pm_lock(udev);
	udev->auto_pm = 1;
	udev->pm_usage_cnt += inc_usage_cnt;
	WARN_ON(udev->pm_usage_cnt < 0);
	if (inc_usage_cnt)
		udev->last_busy = jiffies;
	if (inc_usage_cnt >= 0 && udev->pm_usage_cnt > 0) {
		if (udev->state == USB_STATE_SUSPENDED)
			status = usb_resume_both(udev);
		if (status != 0)
			udev->pm_usage_cnt -= inc_usage_cnt;
		else if (inc_usage_cnt)
			udev->last_busy = jiffies;
	} else if (inc_usage_cnt <= 0 && udev->pm_usage_cnt <= 0) {
		status = usb_suspend_both(udev, PMSG_SUSPEND);
	}
	usb_pm_unlock(udev);
	return status;
}

/* usb_autosuspend_work - callback routine to autosuspend a USB device */
void usb_autosuspend_work(struct work_struct *work)
{
	struct usb_device *udev =
		container_of(work, struct usb_device, autosuspend.work);

	usb_autopm_do_device(udev, 0);
}

/**
 * usb_autosuspend_device - delayed autosuspend of a USB device and its interfaces
 * @udev: the usb_device to autosuspend
 *
 * This routine should be called when a core subsystem is finished using
 * @udev and wants to allow it to autosuspend.  Examples would be when
 * @udev's device file in usbfs is closed or after a configuration change.
 *
 * @udev's usage counter is decremented.  If it or any of the usage counters
 * for an active interface is greater than 0, no autosuspend request will be
 * queued.  (If an interface driver does not support autosuspend then its
 * usage counter is permanently positive.)  Furthermore, if an interface
 * driver requires remote-wakeup capability during autosuspend but remote
 * wakeup is disabled, the autosuspend will fail.
 *
 * Often the caller will hold @udev's device lock, but this is not
 * necessary.
 *
 * This routine can run only in process context.
 */
void usb_autosuspend_device(struct usb_device *udev)
{
	int	status;

	status = usb_autopm_do_device(udev, -1);
	dev_vdbg(&udev->dev, "%s: cnt %d\n",
			__FUNCTION__, udev->pm_usage_cnt);
}

/**
 * usb_try_autosuspend_device - attempt an autosuspend of a USB device and its interfaces
 * @udev: the usb_device to autosuspend
 *
 * This routine should be called when a core subsystem thinks @udev may
 * be ready to autosuspend.
 *
 * @udev's usage counter left unchanged.  If it or any of the usage counters
 * for an active interface is greater than 0, or autosuspend is not allowed
 * for any other reason, no autosuspend request will be queued.
 *
 * This routine can run only in process context.
 */
void usb_try_autosuspend_device(struct usb_device *udev)
{
	usb_autopm_do_device(udev, 0);
	dev_vdbg(&udev->dev, "%s: cnt %d\n",
			__FUNCTION__, udev->pm_usage_cnt);
}

/**
 * usb_autoresume_device - immediately autoresume a USB device and its interfaces
 * @udev: the usb_device to autoresume
 *
 * This routine should be called when a core subsystem wants to use @udev
 * and needs to guarantee that it is not suspended.  No autosuspend will
 * occur until usb_autosuspend_device is called.  (Note that this will not
 * prevent suspend events originating in the PM core.)  Examples would be
 * when @udev's device file in usbfs is opened or when a remote-wakeup
 * request is received.
 *
 * @udev's usage counter is incremented to prevent subsequent autosuspends.
 * However if the autoresume fails then the usage counter is re-decremented.
 *
 * Often the caller will hold @udev's device lock, but this is not
 * necessary (and attempting it might cause deadlock).
 *
 * This routine can run only in process context.
 */
int usb_autoresume_device(struct usb_device *udev)
{
	int	status;

	status = usb_autopm_do_device(udev, 1);
	dev_vdbg(&udev->dev, "%s: status %d cnt %d\n",
			__FUNCTION__, status, udev->pm_usage_cnt);
	return status;
}

/* Internal routine to adjust an interface's usage counter and change
 * its device's autosuspend state.
 */
static int usb_autopm_do_interface(struct usb_interface *intf,
		int inc_usage_cnt)
{
	struct usb_device	*udev = interface_to_usbdev(intf);
	int			status = 0;

	usb_pm_lock(udev);
	if (intf->condition == USB_INTERFACE_UNBOUND)
		status = -ENODEV;
	else {
		udev->auto_pm = 1;
		intf->pm_usage_cnt += inc_usage_cnt;
		udev->last_busy = jiffies;
		if (inc_usage_cnt >= 0 && intf->pm_usage_cnt > 0) {
			if (udev->state == USB_STATE_SUSPENDED)
				status = usb_resume_both(udev);
			if (status != 0)
				intf->pm_usage_cnt -= inc_usage_cnt;
			else
				udev->last_busy = jiffies;
		} else if (inc_usage_cnt <= 0 && intf->pm_usage_cnt <= 0) {
			status = usb_suspend_both(udev, PMSG_SUSPEND);
		}
	}
	usb_pm_unlock(udev);
	return status;
}

/**
 * usb_autopm_put_interface - decrement a USB interface's PM-usage counter
 * @intf: the usb_interface whose counter should be decremented
 *
 * This routine should be called by an interface driver when it is
 * finished using @intf and wants to allow it to autosuspend.  A typical
 * example would be a character-device driver when its device file is
 * closed.
 *
 * The routine decrements @intf's usage counter.  When the counter reaches
 * 0, a delayed autosuspend request for @intf's device is queued.  When
 * the delay expires, if @intf->pm_usage_cnt is still <= 0 along with all
 * the other usage counters for the sibling interfaces and @intf's
 * usb_device, the device and all its interfaces will be autosuspended.
 *
 * Note that @intf->pm_usage_cnt is owned by the interface driver.  The
 * core will not change its value other than the increment and decrement
 * in usb_autopm_get_interface and usb_autopm_put_interface.  The driver
 * may use this simple counter-oriented discipline or may set the value
 * any way it likes.
 *
 * If the driver has set @intf->needs_remote_wakeup then autosuspend will
 * take place only if the device's remote-wakeup facility is enabled.
 *
 * Suspend method calls queued by this routine can arrive at any time
 * while @intf is resumed and its usage counter is equal to 0.  They are
 * not protected by the usb_device's lock but only by its pm_mutex.
 * Drivers must provide their own synchronization.
 *
 * This routine can run only in process context.
 */
void usb_autopm_put_interface(struct usb_interface *intf)
{
	int	status;

	status = usb_autopm_do_interface(intf, -1);
	dev_vdbg(&intf->dev, "%s: status %d cnt %d\n",
			__FUNCTION__, status, intf->pm_usage_cnt);
}
EXPORT_SYMBOL_GPL(usb_autopm_put_interface);

/**
 * usb_autopm_get_interface - increment a USB interface's PM-usage counter
 * @intf: the usb_interface whose counter should be incremented
 *
 * This routine should be called by an interface driver when it wants to
 * use @intf and needs to guarantee that it is not suspended.  In addition,
 * the routine prevents @intf from being autosuspended subsequently.  (Note
 * that this will not prevent suspend events originating in the PM core.)
 * This prevention will persist until usb_autopm_put_interface() is called
 * or @intf is unbound.  A typical example would be a character-device
 * driver when its device file is opened.
 *
 *
 * The routine increments @intf's usage counter.  (However if the
 * autoresume fails then the counter is re-decremented.)  So long as the
 * counter is greater than 0, autosuspend will not be allowed for @intf
 * or its usb_device.  When the driver is finished using @intf it should
 * call usb_autopm_put_interface() to decrement the usage counter and
 * queue a delayed autosuspend request (if the counter is <= 0).
 *
 *
 * Note that @intf->pm_usage_cnt is owned by the interface driver.  The
 * core will not change its value other than the increment and decrement
 * in usb_autopm_get_interface and usb_autopm_put_interface.  The driver
 * may use this simple counter-oriented discipline or may set the value
 * any way it likes.
 *
 * Resume method calls generated by this routine can arrive at any time
 * while @intf is suspended.  They are not protected by the usb_device's
 * lock but only by its pm_mutex.  Drivers must provide their own
 * synchronization.
 *
 * This routine can run only in process context.
 */
int usb_autopm_get_interface(struct usb_interface *intf)
{
	int	status;

	status = usb_autopm_do_interface(intf, 1);
	dev_vdbg(&intf->dev, "%s: status %d cnt %d\n",
			__FUNCTION__, status, intf->pm_usage_cnt);
	return status;
}
EXPORT_SYMBOL_GPL(usb_autopm_get_interface);

/**
 * usb_autopm_set_interface - set a USB interface's autosuspend state
 * @intf: the usb_interface whose state should be set
 *
 * This routine sets the autosuspend state of @intf's device according
 * to @intf's usage counter, which the caller must have set previously.
 * If the counter is <= 0, the device is autosuspended (if it isn't
 * already suspended and if nothing else prevents the autosuspend).  If
 * the counter is > 0, the device is autoresumed (if it isn't already
 * awake).
 */
int usb_autopm_set_interface(struct usb_interface *intf)
{
	int	status;

	status = usb_autopm_do_interface(intf, 0);
	dev_vdbg(&intf->dev, "%s: status %d cnt %d\n",
			__FUNCTION__, status, intf->pm_usage_cnt);
	return status;
}
EXPORT_SYMBOL_GPL(usb_autopm_set_interface);

#else

void usb_autosuspend_work(struct work_struct *work)
{}

#endif /* CONFIG_USB_SUSPEND */

/**
 * usb_external_suspend_device - external suspend of a USB device and its interfaces
 * @udev: the usb_device to suspend
 * @msg: Power Management message describing this state transition
 *
 * This routine handles external suspend requests: ones not generated
 * internally by a USB driver (autosuspend) but rather coming from the user
 * (via sysfs) or the PM core (system sleep).  The suspend will be carried
 * out regardless of @udev's usage counter or those of its interfaces,
 * and regardless of whether or not remote wakeup is enabled.  Of course,
 * interface drivers still have the option of failing the suspend (if
 * there are unsuspended children, for example).
 *
 * The caller must hold @udev's device lock.
 */
int usb_external_suspend_device(struct usb_device *udev, pm_message_t msg)
{
	int	status;

	usb_pm_lock(udev);
	udev->auto_pm = 0;
	status = usb_suspend_both(udev, msg);
	usb_pm_unlock(udev);
	return status;
}

/**
 * usb_external_resume_device - external resume of a USB device and its interfaces
 * @udev: the usb_device to resume
 *
 * This routine handles external resume requests: ones not generated
 * internally by a USB driver (autoresume) but rather coming from the user
 * (via sysfs), the PM core (system resume), or the device itself (remote
 * wakeup).  @udev's usage counter is unaffected.
 *
 * The caller must hold @udev's device lock.
 */
int usb_external_resume_device(struct usb_device *udev)
{
	int	status;

	usb_pm_lock(udev);
	udev->auto_pm = 0;
	status = usb_resume_both(udev);
	udev->last_busy = jiffies;
	usb_pm_unlock(udev);

	/* Now that the device is awake, we can start trying to autosuspend
	 * it again. */
	if (status == 0)
		usb_try_autosuspend_device(udev);
	return status;
}

static int usb_suspend(struct device *dev, pm_message_t message)
{
	if (!is_usb_device(dev))	/* Ignore PM for interfaces */
		return 0;
	return usb_external_suspend_device(to_usb_device(dev), message);
}

static int usb_resume(struct device *dev)
{
	struct usb_device	*udev;

	if (!is_usb_device(dev))	/* Ignore PM for interfaces */
		return 0;
	udev = to_usb_device(dev);

	/* If autoresume is disabled then we also want to prevent resume
	 * during system wakeup.  However, a "persistent-device" reset-resume
	 * after power loss counts as a wakeup event.  So allow a
	 * reset-resume to occur if remote wakeup is enabled. */
	if (udev->autoresume_disabled) {
		if (!(udev->reset_resume && udev->do_remote_wakeup))
			return -EPERM;
	}
	return usb_external_resume_device(udev);
}

#else

#define usb_suspend	NULL
#define usb_resume	NULL

#endif /* CONFIG_PM */

struct bus_type usb_bus_type = {
	.name =		"usb",
	.match =	usb_device_match,
	.uevent =	usb_uevent,
	.suspend =	usb_suspend,
	.resume =	usb_resume,
};