text: /*
   * message.c - synchronous message handling
   */
  
  #include <linux/pci.h>	/* for scatterlist macros */
  #include <linux/usb.h>
  #include <linux/module.h>
  #include <linux/slab.h>
  #include <linux/mm.h>
  #include <linux/timer.h>
  #include <linux/ctype.h>
  #include <linux/nls.h>
  #include <linux/device.h>
  #include <linux/scatterlist.h>
  #include <linux/usb/quirks.h>
  #include <linux/usb/hcd.h>	/* for usbcore internals */
  #include <asm/byteorder.h>
  
  #include "usb.h"
  
  static void cancel_async_set_config(struct usb_device *udev);
  
  struct api_context {
  	struct completion	done;
  	int			status;
  };
  
  static void usb_api_blocking_completion(struct urb *urb)
  {
  	struct api_context *ctx = urb->context;
  
  	ctx->status = urb->status;
  	complete(&ctx->done);
  }
  
  
  /*
   * Starts urb and waits for completion or timeout. Note that this call
   * is NOT interruptible. Many device driver i/o requests should be
   * interruptible and therefore these drivers should implement their
   * own interruptible routines.
   */
  static int usb_start_wait_urb(struct urb *urb, int timeout, int *actual_length)
  {
  	struct api_context ctx;
  	unsigned long expire;
  	int retval;
  
  	init_completion(&ctx.done);
  	urb->context = &ctx;
  	urb->actual_length = 0;
  	retval = usb_submit_urb(urb, GFP_NOIO);
  	if (unlikely(retval))
  		goto out;
  
  	expire = timeout ? msecs_to_jiffies(timeout) : MAX_SCHEDULE_TIMEOUT;
  	if (!wait_for_completion_timeout(&ctx.done, expire)) {
  		usb_kill_urb(urb);
  		retval = (ctx.status == -ENOENT ? -ETIMEDOUT : ctx.status);
  
  		dev_dbg(&urb->dev->dev,
  			"%s timed out on ep%d%s len=%u/%u\n",
  			current->comm,
  			usb_endpoint_num(&urb->ep->desc),
  			usb_urb_dir_in(urb) ? "in" : "out",
  			urb->actual_length,
  			urb->transfer_buffer_length);
  	} else
  		retval = ctx.status;
  out:
  	if (actual_length)
  		*actual_length = urb->actual_length;
  
  	usb_free_urb(urb);
  	return retval;
  }
  
  /*-------------------------------------------------------------------*/
  /* returns status (negative) or length (positive) */
  static int usb_internal_control_msg(struct usb_device *usb_dev,
  				    unsigned int pipe,
  				    struct usb_ctrlrequest *cmd,
  				    void *data, int len, int timeout)
  {
  	struct urb *urb;
  	int retv;
  	int length;
  
  	urb = usb_alloc_urb(0, GFP_NOIO);
  	if (!urb)
  		return -ENOMEM;
  
  	usb_fill_control_urb(urb, usb_dev, pipe, (unsigned char *)cmd, data,
  			     len, usb_api_blocking_completion, NULL);
  
  	retv = usb_start_wait_urb(urb, timeout, &length);
  	if (retv < 0)
  		return retv;
  	else
  		return length;
  }
  
  /**
   * usb_control_msg - Builds a control urb, sends it off and waits for completion
   * @dev: pointer to the usb device to send the message to
   * @pipe: endpoint "pipe" to send the message to
   * @request: USB message request value
   * @requesttype: USB message request type value
   * @value: USB message value
   * @index: USB message index value
   * @data: pointer to the data to send
   * @size: length in bytes of the data to send
   * @timeout: time in msecs to wait for the message to complete before timing
   *	out (if 0 the wait is forever)
   *
   * Context: !in_interrupt ()
   *
   * This function sends a simple control message to a specified endpoint and
   * waits for the message to complete, or timeout.
   *
   * Don't use this function from within an interrupt context, like a bottom half
   * handler.  If you need an asynchronous message, or need to send a message
   * from within interrupt context, use usb_submit_urb().
   * If a thread in your driver uses this call, make sure your disconnect()
   * method can wait for it to complete.  Since you don't have a handle on the
   * URB used, you can't cancel the request.
   *
   * Return: If successful, the number of bytes transferred. Otherwise, a negative
   * error number.
   */
  int usb_control_msg(struct usb_device *dev, unsigned int pipe, __u8 request,
  		    __u8 requesttype, __u16 value, __u16 index, void *data,
  		    __u16 size, int timeout)
  {
  	struct usb_ctrlrequest *dr;
  	int ret;
  
  	dr = kmalloc(sizeof(struct usb_ctrlrequest), GFP_NOIO);
  	if (!dr)
  		return -ENOMEM;
  
  	dr->bRequestType = requesttype;
  	dr->bRequest = request;
  	dr->wValue = cpu_to_le16(value);
  	dr->wIndex = cpu_to_le16(index);
  	dr->wLength = cpu_to_le16(size);
  
  	ret = usb_internal_control_msg(dev, pipe, dr, data, size, timeout);
  
  	kfree(dr);
  
  	return ret;
  }
  EXPORT_SYMBOL_GPL(usb_control_msg);
  
  /**
   * usb_interrupt_msg - Builds an interrupt urb, sends it off and waits for completion
   * @usb_dev: pointer to the usb device to send the message to
   * @pipe: endpoint "pipe" to send the message to
   * @data: pointer to the data to send
   * @len: length in bytes of the data to send
   * @actual_length: pointer to a location to put the actual length transferred
   *	in bytes
   * @timeout: time in msecs to wait for the message to complete before
   *	timing out (if 0 the wait is forever)
   *
   * Context: !in_interrupt ()
   *
   * This function sends a simple interrupt message to a specified endpoint and
   * waits for the message to complete, or timeout.
   *
   * Don't use this function from within an interrupt context, like a bottom half
   * handler.  If you need an asynchronous message, or need to send a message
   * from within interrupt context, use usb_submit_urb() If a thread in your
   * driver uses this call, make sure your disconnect() method can wait for it to
   * complete.  Since you don't have a handle on the URB used, you can't cancel
   * the request.
   *
   * Return:
   * If successful, 0. Otherwise a negative error number. The number of actual
   * bytes transferred will be stored in the @actual_length parameter.
   */
  int usb_interrupt_msg(struct usb_device *usb_dev, unsigned int pipe,
  		      void *data, int len, int *actual_length, int timeout)
  {
  	return usb_bulk_msg(usb_dev, pipe, data, len, actual_length, timeout);
  }
  EXPORT_SYMBOL_GPL(usb_interrupt_msg);
  
  /**
   * usb_bulk_msg - Builds a bulk urb, sends it off and waits for completion
   * @usb_dev: pointer to the usb device to send the message to
   * @pipe: endpoint "pipe" to send the message to
   * @data: pointer to the data to send
   * @len: length in bytes of the data to send
   * @actual_length: pointer to a location to put the actual length transferred
   *	in bytes
   * @timeout: time in msecs to wait for the message to complete before
   *	timing out (if 0 the wait is forever)
   *
   * Context: !in_interrupt ()
   *
   * This function sends a simple bulk message to a specified endpoint
   * and waits for the message to complete, or timeout.
   *
   * Don't use this function from within an interrupt context, like a bottom half
   * handler.  If you need an asynchronous message, or need to send a message
   * from within interrupt context, use usb_submit_urb() If a thread in your
   * driver uses this call, make sure your disconnect() method can wait for it to
   * complete.  Since you don't have a handle on the URB used, you can't cancel
   * the request.
   *
   * Because there is no usb_interrupt_msg() and no USBDEVFS_INTERRUPT ioctl,
   * users are forced to abuse this routine by using it to submit URBs for
   * interrupt endpoints.  We will take the liberty of creating an interrupt URB
   * (with the default interval) if the target is an interrupt endpoint.
   *
   * Return:
   * If successful, 0. Otherwise a negative error number. The number of actual
   * bytes transferred will be stored in the @actual_length parameter.
   *
   */
  int usb_bulk_msg(struct usb_device *usb_dev, unsigned int pipe,
  		 void *data, int len, int *actual_length, int timeout)
  {
  	struct urb *urb;
  	struct usb_host_endpoint *ep;
  
  	ep = usb_pipe_endpoint(usb_dev, pipe);
  	if (!ep || len < 0)
  		return -EINVAL;
  
  	urb = usb_alloc_urb(0, GFP_KERNEL);
  	if (!urb)
  		return -ENOMEM;
  
  	if ((ep->desc.bmAttributes & USB_ENDPOINT_XFERTYPE_MASK) ==
  			USB_ENDPOINT_XFER_INT) {
  		pipe = (pipe & ~(3 << 30)) | (PIPE_INTERRUPT << 30);
  		usb_fill_int_urb(urb, usb_dev, pipe, data, len,
  				usb_api_blocking_completion, NULL,
  				ep->desc.bInterval);
  	} else
  		usb_fill_bulk_urb(urb, usb_dev, pipe, data, len,
  				usb_api_blocking_completion, NULL);
  
  	return usb_start_wait_urb(urb, timeout, actual_length);
  }
  EXPORT_SYMBOL_GPL(usb_bulk_msg);
  
  /*-------------------------------------------------------------------*/
  
  static void sg_clean(struct usb_sg_request *io)
  {
  	if (io->urbs) {
  		while (io->entries--)
  			usb_free_urb(io->urbs[io->entries]);
  		kfree(io->urbs);
  		io->urbs = NULL;
  	}
  	io->dev = NULL;
  }
  
  static void sg_complete(struct urb *urb)
  {
  	struct usb_sg_request *io = urb->context;
  	int status = urb->status;
  
  	spin_lock(&io->lock);
  
  	/* In 2.5 we require hcds' endpoint queues not to progress after fault
  	 * reports, until the completion callback (this!) returns.  That lets
  	 * device driver code (like this routine) unlink queued urbs first,
  	 * if it needs to, since the HC won't work on them at all.  So it's
  	 * not possible for page N+1 to overwrite page N, and so on.
  	 *
  	 * That's only for "hard" faults; "soft" faults (unlinks) sometimes
  	 * complete before the HCD can get requests away from hardware,
  	 * though never during cleanup after a hard fault.
  	 */
  	if (io->status
  			&& (io->status != -ECONNRESET
  				|| status != -ECONNRESET)
  			&& urb->actual_length) {
  		dev_err(io->dev->bus->controller,
  			"dev %s ep%d%s scatterlist error %d/%d\n",
  			io->dev->devpath,
  			usb_endpoint_num(&urb->ep->desc),
  			usb_urb_dir_in(urb) ? "in" : "out",
  			status, io->status);
  		/* BUG (); */
  	}
  
  	if (io->status == 0 && status && status != -ECONNRESET) {
  		int i, found, retval;
  
  		io->status = status;
  
  		/* the previous urbs, and this one, completed already.
  		 * unlink pending urbs so they won't rx/tx bad data.
  		 * careful: unlink can sometimes be synchronous...
  		 */
  		spin_unlock(&io->lock);
  		for (i = 0, found = 0; i < io->entries; i++) {
  			if (!io->urbs[i] || !io->urbs[i]->dev)
  				continue;
  			if (found) {
  				retval = usb_unlink_urb(io->urbs[i]);
  				if (retval != -EINPROGRESS &&
  				    retval != -ENODEV &&
  				    retval != -EBUSY &&
  				    retval != -EIDRM)
  					dev_err(&io->dev->dev,
  						"%s, unlink --> %d\n",
  						__func__, retval);
  			} else if (urb == io->urbs[i])
  				found = 1;
  		}
  		spin_lock(&io->lock);
  	}
  
  	/* on the last completion, signal usb_sg_wait() */
  	io->bytes += urb->actual_length;
  	io->count--;
  	if (!io->count)
  		complete(&io->complete);
  
  	spin_unlock(&io->lock);
  }
  
  
  /**
   * usb_sg_init - initializes scatterlist-based bulk/interrupt I/O request
   * @io: request block being initialized.  until usb_sg_wait() returns,
   *	treat this as a pointer to an opaque block of memory,
   * @dev: the usb device that will send or receive the data
   * @pipe: endpoint "pipe" used to transfer the data
   * @period: polling rate for interrupt endpoints, in frames or
   * 	(for high speed endpoints) microframes; ignored for bulk
   * @sg: scatterlist entries
   * @nents: how many entries in the scatterlist
   * @length: how many bytes to send from the scatterlist, or zero to
   * 	send every byte identified in the list.
   * @mem_flags: SLAB_* flags affecting memory allocations in this call
   *
   * This initializes a scatter/gather request, allocating resources such as
   * I/O mappings and urb memory (except maybe memory used by USB controller
   * drivers).
   *
   * The request must be issued using usb_sg_wait(), which waits for the I/O to
   * complete (or to be canceled) and then cleans up all resources allocated by
   * usb_sg_init().
   *
   * The request may be canceled with usb_sg_cancel(), either before or after
   * usb_sg_wait() is called.
   *
   * Return: Zero for success, else a negative errno value.
   */
  int usb_sg_init(struct usb_sg_request *io, struct usb_device *dev,
  		unsigned pipe, unsigned	period, struct scatterlist *sg,
  		int nents, size_t length, gfp_t mem_flags)
  {
  	int i;
  	int urb_flags;
  	int use_sg;
  
  	if (!io || !dev || !sg
  			|| usb_pipecontrol(pipe)
  			|| usb_pipeisoc(pipe)
  			|| nents <= 0)
  		return -EINVAL;
  
  	spin_lock_init(&io->lock);
  	io->dev = dev;
  	io->pipe = pipe;
  
  	if (dev->bus->sg_tablesize > 0) {
  		use_sg = true;
  		io->entries = 1;
  	} else {
  		use_sg = false;
  		io->entries = nents;
  	}
  
  	/* initialize all the urbs we'll use */
  	io->urbs = kmalloc(io->entries * sizeof(*io->urbs), mem_flags);
  	if (!io->urbs)
  		goto nomem;
  
  	urb_flags = URB_NO_INTERRUPT;
  	if (usb_pipein(pipe))
  		urb_flags |= URB_SHORT_NOT_OK;
  
  	for_each_sg(sg, sg, io->entries, i) {
  		struct urb *urb;
  		unsigned len;
  
  		urb = usb_alloc_urb(0, mem_flags);
  		if (!urb) {
  			io->entries = i;
  			goto nomem;
  		}
  		io->urbs[i] = urb;
  
  		urb->dev = NULL;
  		urb->pipe = pipe;
  		urb->interval = period;
  		urb->transfer_flags = urb_flags;
  		urb->complete = sg_complete;
  		urb->context = io;
  		urb->sg = sg;
  
  		if (use_sg) {
  			/* There is no single transfer buffer */
  			urb->transfer_buffer = NULL;
  			urb->num_sgs = nents;
  
  			/* A length of zero means transfer the whole sg list */
  			len = length;
  			if (len == 0) {
  				struct scatterlist	*sg2;
  				int			j;
  
  				for_each_sg(sg, sg2, nents, j)
  					len += sg2->length;
  			}
  		} else {
  			/*
  			 * Some systems can't use DMA; they use PIO instead.
  			 * For their sakes, transfer_buffer is set whenever
  			 * possible.
  			 */
  			if (!PageHighMem(sg_page(sg)))
  				urb->transfer_buffer = sg_virt(sg);
  			else
  				urb->transfer_buffer = NULL;
  
  			len = sg->length;
  			if (length) {
  				len = min_t(size_t, len, length);
  				length -= len;
  				if (length == 0)
  					io->entries = i + 1;
  			}
  		}
  		urb->transfer_buffer_length = len;
  	}
  	io->urbs[--i]->transfer_flags &= ~URB_NO_INTERRUPT;
  
  	/* transaction state */
  	io->count = io->entries;
  	io->status = 0;
  	io->bytes = 0;
  	init_completion(&io->complete);
  	return 0;
  
  nomem:
  	sg_clean(io);
  	return -ENOMEM;
  }
  EXPORT_SYMBOL_GPL(usb_sg_init);
  
  /**
   * usb_sg_wait - synchronously execute scatter/gather request
   * @io: request block handle, as initialized with usb_sg_init().
   * 	some fields become accessible when this call returns.
   * Context: !in_interrupt ()
   *
   * This function blocks until the specified I/O operation completes.  It
   * leverages the grouping of the related I/O requests to get good transfer
   * rates, by queueing the requests.  At higher speeds, such queuing can
   * significantly improve USB throughput.
   *
   * There are three kinds of completion for this function.
   * (1) success, where io->status is zero.  The number of io->bytes
   *     transferred is as requested.
   * (2) error, where io->status is a negative errno value.  The number
   *     of io->bytes transferred before the error is usually less
   *     than requested, and can be nonzero.
   * (3) cancellation, a type of error with status -ECONNRESET that
   *     is initiated by usb_sg_cancel().
   *
   * When this function returns, all memory allocated through usb_sg_init() or
   * this call will have been freed.  The request block parameter may still be
   * passed to usb_sg_cancel(), or it may be freed.  It could also be
   * reinitialized and then reused.
   *
   * Data Transfer Rates:
   *
   * Bulk transfers are valid for full or high speed endpoints.
   * The best full speed data rate is 19 packets of 64 bytes each
   * per frame, or 1216 bytes per millisecond.
   * The best high speed data rate is 13 packets of 512 bytes each
   * per microframe, or 52 KBytes per millisecond.
   *
   * The reason to use interrupt transfers through this API would most likely
   * be to reserve high speed bandwidth, where up to 24 KBytes per millisecond
   * could be transferred.  That capability is less useful for low or full
   * speed interrupt endpoints, which allow at most one packet per millisecond,
   * of at most 8 or 64 bytes (respectively).
   *
   * It is not necessary to call this function to reserve bandwidth for devices
   * under an xHCI host controller, as the bandwidth is reserved when the
   * configuration or interface alt setting is selected.
   */
  void usb_sg_wait(struct usb_sg_request *io)
  {
  	int i;
  	int entries = io->entries;
  
  	/* queue the urbs.  */
  	spin_lock_irq(&io->lock);
  	i = 0;
  	while (i < entries && !io->status) {
  		int retval;
  
  		io->urbs[i]->dev = io->dev;
  		retval = usb_submit_urb(io->urbs[i], GFP_ATOMIC);
  
  		/* after we submit, let completions or cancellations fire;
  		 * we handshake using io->status.
  		 */
  		spin_unlock_irq(&io->lock);
  		switch (retval) {
  			/* maybe we retrying will recover */
  		case -ENXIO:	/* hc didn't queue this one */
  		case -EAGAIN:
  		case -ENOMEM:
  			retval = 0;
  			yield();
  			break;
  
  			/* no error? continue immediately.
  			 *
  			 * NOTE: to work better with UHCI (4K I/O buffer may
  			 * need 3K of TDs) it may be good to limit how many
  			 * URBs are queued at once; N milliseconds?
  			 */
  		case 0:
  			++i;
  			cpu_relax();
  			break;
  
  			/* fail any uncompleted urbs */
  		default:
  			io->urbs[i]->status = retval;
  			dev_dbg(&io->dev->dev, "%s, submit --> %d\n",
  				__func__, retval);
  			usb_sg_cancel(io);
  		}
  		spin_lock_irq(&io->lock);
  		if (retval && (io->status == 0 || io->status == -ECONNRESET))
  			io->status = retval;
  	}
  	io->count -= entries - i;
  	if (io->count == 0)
  		complete(&io->complete);
  	spin_unlock_irq(&io->lock);
  
  	/* OK, yes, this could be packaged as non-blocking.
  	 * So could the submit loop above ... but it's easier to
  	 * solve neither problem than to solve both!
  	 */
  	wait_for_completion(&io->complete);
  
  	sg_clean(io);
  }
  EXPORT_SYMBOL_GPL(usb_sg_wait);
  
  /**
   * usb_sg_cancel - stop scatter/gather i/o issued by usb_sg_wait()
   * @io: request block, initialized with usb_sg_init()
   *
   * This stops a request after it has been started by usb_sg_wait().
   * It can also prevents one initialized by usb_sg_init() from starting,
   * so that call just frees resources allocated to the request.
   */
  void usb_sg_cancel(struct usb_sg_request *io)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(&io->lock, flags);
  
  	/* shut everything down, if it didn't already */
  	if (!io->status) {
  		int i;
  
  		io->status = -ECONNRESET;
  		spin_unlock(&io->lock);
  		for (i = 0; i < io->entries; i++) {
  			int retval;
  
  			if (!io->urbs[i]->dev)
  				continue;
  			retval = usb_unlink_urb(io->urbs[i]);
  			if (retval != -EINPROGRESS
  					&& retval != -ENODEV
  					&& retval != -EBUSY
  					&& retval != -EIDRM)
  				dev_warn(&io->dev->dev, "%s, unlink --> %d\n",
  					__func__, retval);
  		}
  		spin_lock(&io->lock);
  	}
  	spin_unlock_irqrestore(&io->lock, flags);
  }
  EXPORT_SYMBOL_GPL(usb_sg_cancel);
  
  /*-------------------------------------------------------------------*/
  
  /**
   * usb_get_descriptor - issues a generic GET_DESCRIPTOR request
   * @dev: the device whose descriptor is being retrieved
   * @type: the descriptor type (USB_DT_*)
   * @index: the number of the descriptor
   * @buf: where to put the descriptor
   * @size: how big is "buf"?
   * Context: !in_interrupt ()
   *
   * Gets a USB descriptor.  Convenience functions exist to simplify
   * getting some types of descriptors.  Use
   * usb_get_string() or usb_string() for USB_DT_STRING.
   * Device (USB_DT_DEVICE) and configuration descriptors (USB_DT_CONFIG)
   * are part of the device structure.
   * In addition to a number of USB-standard descriptors, some
   * devices also use class-specific or vendor-specific descriptors.
   *
   * This call is synchronous, and may not be used in an interrupt context.
   *
   * Return: The number of bytes received on success, or else the status code
   * returned by the underlying usb_control_msg() call.
   */
  int usb_get_descriptor(struct usb_device *dev, unsigned char type,
  		       unsigned char index, void *buf, int size)
  {
  	int i;
  	int result;
  
  	memset(buf, 0, size);	/* Make sure we parse really received data */
  
  	for (i = 0; i < 3; ++i) {
  		/* retry on length 0 or error; some devices are flakey */
  		result = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
  				USB_REQ_GET_DESCRIPTOR, USB_DIR_IN,
  				(type << 8) + index, 0, buf, size,
  				USB_CTRL_GET_TIMEOUT);
  		if (result <= 0 && result != -ETIMEDOUT)
  			continue;
  		if (result > 1 && ((u8 *)buf)[1] != type) {
  			result = -ENODATA;
  			continue;
  		}
  		break;
  	}
  	return result;
  }
  EXPORT_SYMBOL_GPL(usb_get_descriptor);
  
  /**
   * usb_get_string - gets a string descriptor
   * @dev: the device whose string descriptor is being retrieved
   * @langid: code for language chosen (from string descriptor zero)
   * @index: the number of the descriptor
   * @buf: where to put the string
   * @size: how big is "buf"?
   * Context: !in_interrupt ()
   *
   * Retrieves a string, encoded using UTF-16LE (Unicode, 16 bits per character,
   * in little-endian byte order).
   * The usb_string() function will often be a convenient way to turn
   * these strings into kernel-printable form.
   *
   * Strings may be referenced in device, configuration, interface, or other
   * descriptors, and could also be used in vendor-specific ways.
   *
   * This call is synchronous, and may not be used in an interrupt context.
   *
   * Return: The number of bytes received on success, or else the status code
   * returned by the underlying usb_control_msg() call.
   */
  static int usb_get_string(struct usb_device *dev, unsigned short langid,
  			  unsigned char index, void *buf, int size)
  {
  	int i;
  	int result;
  
  	for (i = 0; i < 3; ++i) {
  		/* retry on length 0 or stall; some devices are flakey */
  		result = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
  			USB_REQ_GET_DESCRIPTOR, USB_DIR_IN,
  			(USB_DT_STRING << 8) + index, langid, buf, size,
  			USB_CTRL_GET_TIMEOUT);
  		if (result == 0 || result == -EPIPE)
  			continue;
  		if (result > 1 && ((u8 *) buf)[1] != USB_DT_STRING) {
  			result = -ENODATA;
  			continue;
  		}
  		break;
  	}
  	return result;
  }
  
  static void usb_try_string_workarounds(unsigned char *buf, int *length)
  {
  	int newlength, oldlength = *length;
  
  	for (newlength = 2; newlength + 1 < oldlength; newlength += 2)
  		if (!isprint(buf[newlength]) || buf[newlength + 1])
  			break;
  
  	if (newlength > 2) {
  		buf[0] = newlength;
  		*length = newlength;
  	}
  }
  
  static int usb_string_sub(struct usb_device *dev, unsigned int langid,
  			  unsigned int index, unsigned char *buf)
  {
  	int rc;
  
  	/* Try to read the string descriptor by asking for the maximum
  	 * possible number of bytes */
  	if (dev->quirks & USB_QUIRK_STRING_FETCH_255)
  		rc = -EIO;
  	else
  		rc = usb_get_string(dev, langid, index, buf, 255);
  
  	/* If that failed try to read the descriptor length, then
  	 * ask for just that many bytes */
  	if (rc < 2) {
  		rc = usb_get_string(dev, langid, index, buf, 2);
  		if (rc == 2)
  			rc = usb_get_string(dev, langid, index, buf, buf[0]);
  	}
  
  	if (rc >= 2) {
  		if (!buf[0] && !buf[1])
  			usb_try_string_workarounds(buf, &rc);
  
  		/* There might be extra junk at the end of the descriptor */
  		if (buf[0] < rc)
  			rc = buf[0];
  
  		rc = rc - (rc & 1); /* force a multiple of two */
  	}
  
  	if (rc < 2)
  		rc = (rc < 0 ? rc : -EINVAL);
  
  	return rc;
  }
  
  static int usb_get_langid(struct usb_device *dev, unsigned char *tbuf)
  {
  	int err;
  
  	if (dev->have_langid)
  		return 0;
  
  	if (dev->string_langid < 0)
  		return -EPIPE;
  
  	err = usb_string_sub(dev, 0, 0, tbuf);
  
  	/* If the string was reported but is malformed, default to english
  	 * (0x0409) */
  	if (err == -ENODATA || (err > 0 && err < 4)) {
  		dev->string_langid = 0x0409;
  		dev->have_langid = 1;
  		dev_err(&dev->dev,
  			"language id specifier not provided by device, defaulting to English\n");
  		return 0;
  	}
  
  	/* In case of all other errors, we assume the device is not able to
  	 * deal with strings at all. Set string_langid to -1 in order to
  	 * prevent any string to be retrieved from the device */
  	if (err < 0) {
  		dev_err(&dev->dev, "string descriptor 0 read error: %d\n",
  					err);
  		dev->string_langid = -1;
  		return -EPIPE;
  	}
  
  	/* always use the first langid listed */
  	dev->string_langid = tbuf[2] | (tbuf[3] << 8);
  	dev->have_langid = 1;
  	dev_dbg(&dev->dev, "default language 0x%04x\n",
  				dev->string_langid);
  	return 0;
  }
  
  /**
   * usb_string - returns UTF-8 version of a string descriptor
   * @dev: the device whose string descriptor is being retrieved
   * @index: the number of the descriptor
   * @buf: where to put the string
   * @size: how big is "buf"?
   * Context: !in_interrupt ()
   *
   * This converts the UTF-16LE encoded strings returned by devices, from
   * usb_get_string_descriptor(), to null-terminated UTF-8 encoded ones
   * that are more usable in most kernel contexts.  Note that this function
   * chooses strings in the first language supported by the device.
   *
   * This call is synchronous, and may not be used in an interrupt context.
   *
   * Return: length of the string (>= 0) or usb_control_msg status (< 0).
   */
  int usb_string(struct usb_device *dev, int index, char *buf, size_t size)
  {
  	unsigned char *tbuf;
  	int err;
  
  	if (dev->state == USB_STATE_SUSPENDED)
  		return -EHOSTUNREACH;
  	if (size <= 0 || !buf || !index)
  		return -EINVAL;
  	buf[0] = 0;
  	tbuf = kmalloc(256, GFP_NOIO);
  	if (!tbuf)
  		return -ENOMEM;
  
  	err = usb_get_langid(dev, tbuf);
  	if (err < 0)
  		goto errout;
  
  	err = usb_string_sub(dev, dev->string_langid, index, tbuf);
  	if (err < 0)
  		goto errout;
  
  	size--;		/* leave room for trailing NULL char in output buffer */
  	err = utf16s_to_utf8s((wchar_t *) &tbuf[2], (err - 2) / 2,
  			UTF16_LITTLE_ENDIAN, buf, size);
  	buf[err] = 0;
  
  	if (tbuf[1] != USB_DT_STRING)
  		dev_dbg(&dev->dev,
  			"wrong descriptor type %02x for string %d (\"%s\")\n",
  			tbuf[1], index, buf);
  
   errout:
  	kfree(tbuf);
  	return err;
  }
  EXPORT_SYMBOL_GPL(usb_string);
  
  /* one UTF-8-encoded 16-bit character has at most three bytes */
  #define MAX_USB_STRING_SIZE (127 * 3 + 1)
  
  /**
   * usb_cache_string - read a string descriptor and cache it for later use
   * @udev: the device whose string descriptor is being read
   * @index: the descriptor index
   *
   * Return: A pointer to a kmalloc'ed buffer containing the descriptor string,
   * or %NULL if the index is 0 or the string could not be read.
   */
  char *usb_cache_string(struct usb_device *udev, int index)
  {
  	char *buf;
  	char *smallbuf = NULL;
  	int len;
  
  	if (index <= 0)
  		return NULL;
  
  	buf = kmalloc(MAX_USB_STRING_SIZE, GFP_NOIO);
  	if (buf) {
  		len = usb_string(udev, index, buf, MAX_USB_STRING_SIZE);
  		if (len > 0) {
  			smallbuf = kmalloc(++len, GFP_NOIO);
  			if (!smallbuf)
  				return buf;
  			memcpy(smallbuf, buf, len);
  		}
  		kfree(buf);
  	}
  	return smallbuf;
  }
  
  /*
   * usb_get_device_descriptor - (re)reads the device descriptor (usbcore)
   * @dev: the device whose device descriptor is being updated
   * @size: how much of the descriptor to read
   * Context: !in_interrupt ()
   *
   * Updates the copy of the device descriptor stored in the device structure,
   * which dedicates space for this purpose.
   *
   * Not exported, only for use by the core.  If drivers really want to read
   * the device descriptor directly, they can call usb_get_descriptor() with
   * type = USB_DT_DEVICE and index = 0.
   *
   * This call is synchronous, and may not be used in an interrupt context.
   *
   * Return: The number of bytes received on success, or else the status code
   * returned by the underlying usb_control_msg() call.
   */
  int usb_get_device_descriptor(struct usb_device *dev, unsigned int size)
  {
  	struct usb_device_descriptor *desc;
  	int ret;
  
  	if (size > sizeof(*desc))
  		return -EINVAL;
  	desc = kmalloc(sizeof(*desc), GFP_NOIO);
  	if (!desc)
  		return -ENOMEM;
  
  	ret = usb_get_descriptor(dev, USB_DT_DEVICE, 0, desc, size);
  	if (ret >= 0)
  		memcpy(&dev->descriptor, desc, size);
  	kfree(desc);
  	return ret;
  }
  
  /**
   * usb_get_status - issues a GET_STATUS call
   * @dev: the device whose status is being checked
   * @type: USB_RECIP_*; for device, interface, or endpoint
   * @target: zero (for device), else interface or endpoint number
   * @data: pointer to two bytes of bitmap data
   * Context: !in_interrupt ()
   *
   * Returns device, interface, or endpoint status.  Normally only of
   * interest to see if the device is self powered, or has enabled the
   * remote wakeup facility; or whether a bulk or interrupt endpoint
   * is halted ("stalled").
   *
   * Bits in these status bitmaps are set using the SET_FEATURE request,
   * and cleared using the CLEAR_FEATURE request.  The usb_clear_halt()
   * function should be used to clear halt ("stall") status.
   *
   * This call is synchronous, and may not be used in an interrupt context.
   *
   * Returns 0 and the status value in *@data (in host byte order) on success,
   * or else the status code from the underlying usb_control_msg() call.
   */
  int usb_get_status(struct usb_device *dev, int type, int target, void *data)
  {
  	int ret;
  	__le16 *status = kmalloc(sizeof(*status), GFP_KERNEL);
  
  	if (!status)
  		return -ENOMEM;
  
  	ret = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
  		USB_REQ_GET_STATUS, USB_DIR_IN | type, 0, target, status,
  		sizeof(*status), USB_CTRL_GET_TIMEOUT);
  
  	if (ret == 2) {
  		*(u16 *) data = le16_to_cpu(*status);
  		ret = 0;
  	} else if (ret >= 0) {
  		ret = -EIO;
  	}
  	kfree(status);
  	return ret;
  }
  EXPORT_SYMBOL_GPL(usb_get_status);
  
  /**
   * usb_clear_halt - tells device to clear endpoint halt/stall condition
   * @dev: device whose endpoint is halted
   * @pipe: endpoint "pipe" being cleared
   * Context: !in_interrupt ()
   *
   * This is used to clear halt conditions for bulk and interrupt endpoints,
   * as reported by URB completion status.  Endpoints that are halted are
   * sometimes referred to as being "stalled".  Such endpoints are unable
   * to transmit or receive data until the halt status is cleared.  Any URBs
   * queued for such an endpoint should normally be unlinked by the driver
   * before clearing the halt condition, as described in sections 5.7.5
   * and 5.8.5 of the USB 2.0 spec.
   *
   * Note that control and isochronous endpoints don't halt, although control
   * endpoints report "protocol stall" (for unsupported requests) using the
   * same status code used to report a true stall.
   *
   * This call is synchronous, and may not be used in an interrupt context.
   *
   * Return: Zero on success, or else the status code returned by the
   * underlying usb_control_msg() call.
   */
  int usb_clear_halt(struct usb_device *dev, int pipe)
  {
  	int result;
  	int endp = usb_pipeendpoint(pipe);
  
  	if (usb_pipein(pipe))
  		endp |= USB_DIR_IN;
  
  	/* we don't care if it wasn't halted first. in fact some devices
  	 * (like some ibmcam model 1 units) seem to expect hosts to make
  	 * this request for iso endpoints, which can't halt!
  	 */
  	result = usb_control_msg(dev, usb_sndctrlpipe(dev, 0),
  		USB_REQ_CLEAR_FEATURE, USB_RECIP_ENDPOINT,
  		USB_ENDPOINT_HALT, endp, NULL, 0,
  		USB_CTRL_SET_TIMEOUT);
  
  	/* don't un-halt or force to DATA0 except on success */
  	if (result < 0)
  		return result;
  
  	/* NOTE:  seems like Microsoft and Apple don't bother verifying
  	 * the clear "took", so some devices could lock up if you check...
  	 * such as the Hagiwara FlashGate DUAL.  So we won't bother.
  	 *
  	 * NOTE:  make sure the logic here doesn't diverge much from
  	 * the copy in usb-storage, for as long as we need two copies.
  	 */
  
  	usb_reset_endpoint(dev, endp);
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(usb_clear_halt);
  
  static int create_intf_ep_devs(struct usb_interface *intf)
  {
  	struct usb_device *udev = interface_to_usbdev(intf);
  	struct usb_host_interface *alt = intf->cur_altsetting;
  	int i;
  
  	if (intf->ep_devs_created || intf->unregistering)
  		return 0;
  
  	for (i = 0; i < alt->desc.bNumEndpoints; ++i)
  		(void) usb_create_ep_devs(&intf->dev, &alt->endpoint[i], udev);
  	intf->ep_devs_created = 1;
  	return 0;
  }
  
  static void remove_intf_ep_devs(struct usb_interface *intf)
  {
  	struct usb_host_interface *alt = intf->cur_altsetting;
  	int i;
  
  	if (!intf->ep_devs_created)
  		return;
  
  	for (i = 0; i < alt->desc.bNumEndpoints; ++i)
  		usb_remove_ep_devs(&alt->endpoint[i]);
  	intf->ep_devs_created = 0;
  }
  
  /**
   * usb_disable_endpoint -- Disable an endpoint by address
   * @dev: the device whose endpoint is being disabled
   * @epaddr: the endpoint's address.  Endpoint number for output,
   *	endpoint number + USB_DIR_IN for input
   * @reset_hardware: flag to erase any endpoint state stored in the
   *	controller hardware
   *
   * Disables the endpoint for URB submission and nukes all pending URBs.
   * If @reset_hardware is set then also deallocates hcd/hardware state
   * for the endpoint.
   */
  void usb_disable_endpoint(struct usb_device *dev, unsigned int epaddr,
  		bool reset_hardware)
  {
  	unsigned int epnum = epaddr & USB_ENDPOINT_NUMBER_MASK;
  	struct usb_host_endpoint *ep;
  
  	if (!dev)
  		return;
  
  	if (usb_endpoint_out(epaddr)) {
  		ep = dev->ep_out[epnum];
  		if (reset_hardware)
  			dev->ep_out[epnum] = NULL;
  	} else {
  		ep = dev->ep_in[epnum];
  		if (reset_hardware)
  			dev->ep_in[epnum] = NULL;
  	}
  	if (ep) {
  		ep->enabled = 0;
  		usb_hcd_flush_endpoint(dev, ep);
  		if (reset_hardware)
  			usb_hcd_disable_endpoint(dev, ep);
  	}
  }
  
  /**
   * usb_reset_endpoint - Reset an endpoint's state.
   * @dev: the device whose endpoint is to be reset
   * @epaddr: the endpoint's address.  Endpoint number for output,
   *	endpoint number + USB_DIR_IN for input
   *
   * Resets any host-side endpoint state such as the toggle bit,
   * sequence number or current window.
   */
  void usb_reset_endpoint(struct usb_device *dev, unsigned int epaddr)
  {
  	unsigned int epnum = epaddr & USB_ENDPOINT_NUMBER_MASK;
  	struct usb_host_endpoint *ep;
  
  	if (usb_endpoint_out(epaddr))
  		ep = dev->ep_out[epnum];
  	else
  		ep = dev->ep_in[epnum];
  	if (ep)
  		usb_hcd_reset_endpoint(dev, ep);
  }
  EXPORT_SYMBOL_GPL(usb_reset_endpoint);
  
  
  /**
   * usb_disable_interface -- Disable all endpoints for an interface
   * @dev: the device whose interface is being disabled
   * @intf: pointer to the interface descriptor
   * @reset_hardware: flag to erase any endpoint state stored in the
   *	controller hardware
   *
   * Disables all the endpoints for the interface's current altsetting.
   */
  void usb_disable_interface(struct usb_device *dev, struct usb_interface *intf,
  		bool reset_hardware)
  {
  	struct usb_host_interface *alt = intf->cur_altsetting;
  	int i;
  
  	for (i = 0; i < alt->desc.bNumEndpoints; ++i) {
  		usb_disable_endpoint(dev,
  				alt->endpoint[i].desc.bEndpointAddress,
  				reset_hardware);
  	}
  }
  
  /**
   * usb_disable_device - Disable all the endpoints for a USB device
   * @dev: the device whose endpoints are being disabled
   * @skip_ep0: 0 to disable endpoint 0, 1 to skip it.
   *
   * Disables all the device's endpoints, potentially including endpoint 0.
   * Deallocates hcd/hardware state for the endpoints (nuking all or most
   * pending urbs) and usbcore state for the interfaces, so that usbcore
   * must usb_set_configuration() before any interfaces could be used.
   */
  void usb_disable_device(struct usb_device *dev, int skip_ep0)
  {
  	int i;
  	struct usb_hcd *hcd = bus_to_hcd(dev->bus);
  
  	/* getting rid of interfaces will disconnect
  	 * any drivers bound to them (a key side effect)
  	 */
  	if (dev->actconfig) {
  		/*
  		 * FIXME: In order to avoid self-deadlock involving the
  		 * bandwidth_mutex, we have to mark all the interfaces
  		 * before unregistering any of them.
  		 */
  		for (i = 0; i < dev->actconfig->desc.bNumInterfaces; i++)
  			dev->actconfig->interface[i]->unregistering = 1;
  
  		for (i = 0; i < dev->actconfig->desc.bNumInterfaces; i++) {
  			struct usb_interface	*interface;
  
  			/* remove this interface if it has been registered */
  			interface = dev->actconfig->interface[i];
  			if (!device_is_registered(&interface->dev))
  				continue;
  			dev_dbg(&dev->dev, "unregistering interface %s\n",
  				dev_name(&interface->dev));
  			remove_intf_ep_devs(interface);
  			device_del(&interface->dev);
  		}
  
  		/* Now that the interfaces are unbound, nobody should
  		 * try to access them.
  		 */
  		for (i = 0; i < dev->actconfig->desc.bNumInterfaces; i++) {
  			put_device(&dev->actconfig->interface[i]->dev);
  			dev->actconfig->interface[i] = NULL;
  		}
  
  		if (dev->usb2_hw_lpm_enabled == 1)
  			usb_set_usb2_hardware_lpm(dev, 0);
  		usb_unlocked_disable_lpm(dev);
  		usb_disable_ltm(dev);
  
  		dev->actconfig = NULL;
  		if (dev->state == USB_STATE_CONFIGURED)
  			usb_set_device_state(dev, USB_STATE_ADDRESS);
  	}
  
  	dev_dbg(&dev->dev, "%s nuking %s URBs\n", __func__,
  		skip_ep0 ? "non-ep0" : "all");
  	if (hcd->driver->check_bandwidth) {
  		/* First pass: Cancel URBs, leave endpoint pointers intact. */
  		for (i = skip_ep0; i < 16; ++i) {
  			usb_disable_endpoint(dev, i, false);
  			usb_disable_endpoint(dev, i + USB_DIR_IN, false);
  		}
  		/* Remove endpoints from the host controller internal state */
  		mutex_lock(hcd->bandwidth_mutex);
  		usb_hcd_alloc_bandwidth(dev, NULL, NULL, NULL);
  		mutex_unlock(hcd->bandwidth_mutex);
  		/* Second pass: remove endpoint pointers */
  	}
  	for (i = skip_ep0; i < 16; ++i) {
  		usb_disable_endpoint(dev, i, true);
  		usb_disable_endpoint(dev, i + USB_DIR_IN, true);
  	}
  }
  
  /**
   * usb_enable_endpoint - Enable an endpoint for USB communications
   * @dev: the device whose interface is being enabled
   * @ep: the endpoint
   * @reset_ep: flag to reset the endpoint state
   *
   * Resets the endpoint state if asked, and sets dev->ep_{in,out} pointers.
   * For control endpoints, both the input and output sides are handled.
   */
  void usb_enable_endpoint(struct usb_device *dev, struct usb_host_endpoint *ep,
  		bool reset_ep)
  {
  	int epnum = usb_endpoint_num(&ep->desc);
  	int is_out = usb_endpoint_dir_out(&ep->desc);
  	int is_control = usb_endpoint_xfer_control(&ep->desc);
  
  	if (reset_ep)
  		usb_hcd_reset_endpoint(dev, ep);
  	if (is_out || is_control)
  		dev->ep_out[epnum] = ep;
  	if (!is_out || is_control)
  		dev->ep_in[epnum] = ep;
  	ep->enabled = 1;
  }
  
  /**
   * usb_enable_interface - Enable all the endpoints for an interface
   * @dev: the device whose interface is being enabled
   * @intf: pointer to the interface descriptor
   * @reset_eps: flag to reset the endpoints' state
   *
   * Enables all the endpoints for the interface's current altsetting.
   */
  void usb_enable_interface(struct usb_device *dev,
  		struct usb_interface *intf, bool reset_eps)
  {
  	struct usb_host_interface *alt = intf->cur_altsetting;
  	int i;
  
  	for (i = 0; i < alt->desc.bNumEndpoints; ++i)
  		usb_enable_endpoint(dev, &alt->endpoint[i], reset_eps);
  }
  
  /**
   * usb_set_interface - Makes a particular alternate setting be current
   * @dev: the device whose interface is being updated
   * @interface: the interface being updated
   * @alternate: the setting being chosen.
   * Context: !in_interrupt ()
   *
   * This is used to enable data transfers on interfaces that may not
   * be enabled by default.  Not all devices support such configurability.
   * Only the driver bound to an interface may change its setting.
   *
   * Within any given configuration, each interface may have several
   * alternative settings.  These are often used to control levels of
   * bandwidth consumption.  For example, the default setting for a high
   * speed interrupt endpoint may not send more than 64 bytes per microframe,
   * while interrupt transfers of up to 3KBytes per microframe are legal.
   * Also, isochronous endpoints may never be part of an
   * interface's default setting.  To access such bandwidth, alternate
   * interface settings must be made current.
   *
   * Note that in the Linux USB subsystem, bandwidth associated with
   * an endpoint in a given alternate setting is not reserved until an URB
   * is submitted that needs that bandwidth.  Some other operating systems
   * allocate bandwidth early, when a configuration is chosen.
   *
   * This call is synchronous, and may not be used in an interrupt context.
   * Also, drivers must not change altsettings while urbs are scheduled for
   * endpoints in that interface; all such urbs must first be completed
   * (perhaps forced by unlinking).
   *
   * Return: Zero on success, or else the status code returned by the
   * underlying usb_control_msg() call.
   */
  int usb_set_interface(struct usb_device *dev, int interface, int alternate)
  {
  	struct usb_interface *iface;
  	struct usb_host_interface *alt;
  	struct usb_hcd *hcd = bus_to_hcd(dev->bus);
  	int i, ret, manual = 0;
  	unsigned int epaddr;
  	unsigned int pipe;
  
  	if (dev->state == USB_STATE_SUSPENDED)
  		return -EHOSTUNREACH;
  
  	iface = usb_ifnum_to_if(dev, interface);
  	if (!iface) {
  		dev_dbg(&dev->dev, "selecting invalid interface %d\n",
  			interface);
  		return -EINVAL;
  	}
  	if (iface->unregistering)
  		return -ENODEV;
  
  	alt = usb_altnum_to_altsetting(iface, alternate);
  	if (!alt) {
  		dev_warn(&dev->dev, "selecting invalid altsetting %d\n",
  			 alternate);
  		return -EINVAL;
  	}
  
  	/* Make sure we have enough bandwidth for this alternate interface.
  	 * Remove the current alt setting and add the new alt setting.
  	 */
  	mutex_lock(hcd->bandwidth_mutex);
  	/* Disable LPM, and re-enable it once the new alt setting is installed,
  	 * so that the xHCI driver can recalculate the U1/U2 timeouts.
  	 */
  	if (usb_disable_lpm(dev)) {
  		dev_err(&iface->dev, "%s Failed to disable LPM\n.", __func__);
  		mutex_unlock(hcd->bandwidth_mutex);
  		return -ENOMEM;
  	}
  	/* Changing alt-setting also frees any allocated streams */
  	for (i = 0; i < iface->cur_altsetting->desc.bNumEndpoints; i++)
  		iface->cur_altsetting->endpoint[i].streams = 0;
  
  	ret = usb_hcd_alloc_bandwidth(dev, NULL, iface->cur_altsetting, alt);
  	if (ret < 0) {
  		dev_info(&dev->dev, "Not enough bandwidth for altsetting %d\n",
  				alternate);
  		usb_enable_lpm(dev);
  		mutex_unlock(hcd->bandwidth_mutex);
  		return ret;
  	}
  
  	if (dev->quirks & USB_QUIRK_NO_SET_INTF)
  		ret = -EPIPE;
  	else
  		ret = usb_control_msg(dev, usb_sndctrlpipe(dev, 0),
  				   USB_REQ_SET_INTERFACE, USB_RECIP_INTERFACE,
  				   alternate, interface, NULL, 0, 5000);
  
  	/* 9.4.10 says devices don't need this and are free to STALL the
  	 * request if the interface only has one alternate setting.
  	 */
  	if (ret == -EPIPE && iface->num_altsetting == 1) {
  		dev_dbg(&dev->dev,
  			"manual set_interface for iface %d, alt %d\n",
  			interface, alternate);
  		manual = 1;
  	} else if (ret < 0) {
  		/* Re-instate the old alt setting */
  		usb_hcd_alloc_bandwidth(dev, NULL, alt, iface->cur_altsetting);
  		usb_enable_lpm(dev);
  		mutex_unlock(hcd->bandwidth_mutex);
  		return ret;
  	}
  	mutex_unlock(hcd->bandwidth_mutex);
  
  	/* FIXME drivers shouldn't need to replicate/bugfix the logic here
  	 * when they implement async or easily-killable versions of this or
  	 * other "should-be-internal" functions (like clear_halt).
  	 * should hcd+usbcore postprocess control requests?
  	 */
  
  	/* prevent submissions using previous endpoint settings */
  	if (iface->cur_altsetting != alt) {
  		remove_intf_ep_devs(iface);
  		usb_remove_sysfs_intf_files(iface);
  	}
  	usb_disable_interface(dev, iface, true);
  
  	iface->cur_altsetting = alt;
  
  	/* Now that the interface is installed, re-enable LPM. */
  	usb_unlocked_enable_lpm(dev);
  
  	/* If the interface only has one altsetting and the device didn't
  	 * accept the request, we attempt to carry out the equivalent action
  	 * by manually clearing the HALT feature for each endpoint in the
  	 * new altsetting.
  	 */
  	if (manual) {
  		for (i = 0; i < alt->desc.bNumEndpoints; i++) {
  			epaddr = alt->endpoint[i].desc.bEndpointAddress;
  			pipe = __create_pipe(dev,
  					USB_ENDPOINT_NUMBER_MASK & epaddr) |
  					(usb_endpoint_out(epaddr) ?
  					USB_DIR_OUT : USB_DIR_IN);
  
  			usb_clear_halt(dev, pipe);
  		}
  	}
  
  	/* 9.1.1.5: reset toggles for all endpoints in the new altsetting
  	 *
  	 * Note:
  	 * Despite EP0 is always present in all interfaces/AS, the list of
  	 * endpoints from the descriptor does not contain EP0. Due to its
  	 * omnipresence one might expect EP0 being considered "affected" by
  	 * any SetInterface request and hence assume toggles need to be reset.
  	 * However, EP0 toggles are re-synced for every individual transfer
  	 * during the SETUP stage - hence EP0 toggles are "don't care" here.
  	 * (Likewise, EP0 never "halts" on well designed devices.)
  	 */
  	usb_enable_interface(dev, iface, true);
  	if (device_is_registered(&iface->dev)) {
  		usb_create_sysfs_intf_files(iface);
  		create_intf_ep_devs(iface);
  	}
  	return 0;
  }
  EXPORT_SYMBOL_GPL(usb_set_interface);
  
  /**
   * usb_reset_configuration - lightweight device reset
   * @dev: the device whose configuration is being reset
   *
   * This issues a standard SET_CONFIGURATION request to the device using
   * the current configuration.  The effect is to reset most USB-related
   * state in the device, including interface altsettings (reset to zero),
   * endpoint halts (cleared), and endpoint state (only for bulk and interrupt
   * endpoints).  Other usbcore state is unchanged, including bindings of
   * usb device drivers to interfaces.
   *
   * Because this affects multiple interfaces, avoid using this with composite
   * (multi-interface) devices.  Instead, the driver for each interface may
   * use usb_set_interface() on the interfaces it claims.  Be careful though;
   * some devices don't support the SET_INTERFACE request, and others won't
   * reset all the interface state (notably endpoint state).  Resetting the whole
   * configuration would affect other drivers' interfaces.
   *
   * The caller must own the device lock.
   *
   * Return: Zero on success, else a negative error code.
   */
  int usb_reset_configuration(struct usb_device *dev)
  {
  	int			i, retval;
  	struct usb_host_config	*config;
  	struct usb_hcd *hcd = bus_to_hcd(dev->bus);
  
  	if (dev->state == USB_STATE_SUSPENDED)
  		return -EHOSTUNREACH;
  
  	/* caller must have locked the device and must own
  	 * the usb bus readlock (so driver bindings are stable);
  	 * calls during probe() are fine
  	 */
  
  	for (i = 1; i < 16; ++i) {
  		usb_disable_endpoint(dev, i, true);
  		usb_disable_endpoint(dev, i + USB_DIR_IN, true);
  	}
  
  	config = dev->actconfig;
  	retval = 0;
  	mutex_lock(hcd->bandwidth_mutex);
  	/* Disable LPM, and re-enable it once the configuration is reset, so
  	 * that the xHCI driver can recalculate the U1/U2 timeouts.
  	 */
  	if (usb_disable_lpm(dev)) {
  		dev_err(&dev->dev, "%s Failed to disable LPM\n.", __func__);
  		mutex_unlock(hcd->bandwidth_mutex);
  		return -ENOMEM;
  	}
  	/* Make sure we have enough bandwidth for each alternate setting 0 */
  	for (i = 0; i < config->desc.bNumInterfaces; i++) {
  		struct usb_interface *intf = config->interface[i];
  		struct usb_host_interface *alt;
  
  		alt = usb_altnum_to_altsetting(intf, 0);
  		if (!alt)
  			alt = &intf->altsetting[0];
  		if (alt != intf->cur_altsetting)
  			retval = usb_hcd_alloc_bandwidth(dev, NULL,
  					intf->cur_altsetting, alt);
  		if (retval < 0)
  			break;
  	}
  	/* If not, reinstate the old alternate settings */
  	if (retval < 0) {
  reset_old_alts:
  		for (i--; i >= 0; i--) {
  			struct usb_interface *intf = config->interface[i];
  			struct usb_host_interface *alt;
  
  			alt = usb_altnum_to_altsetting(intf, 0);
  			if (!alt)
  				alt = &intf->altsetting[0];
  			if (alt != intf->cur_altsetting)
  				usb_hcd_alloc_bandwidth(dev, NULL,
  						alt, intf->cur_altsetting);
  		}
  		usb_enable_lpm(dev);
  		mutex_unlock(hcd->bandwidth_mutex);
  		return retval;
  	}
  	retval = usb_control_msg(dev, usb_sndctrlpipe(dev, 0),
  			USB_REQ_SET_CONFIGURATION, 0,
  			config->desc.bConfigurationValue, 0,
  			NULL, 0, USB_CTRL_SET_TIMEOUT);
  	if (retval < 0)
  		goto reset_old_alts;
  	mutex_unlock(hcd->bandwidth_mutex);
  
  	/* re-init hc/hcd interface/endpoint state */
  	for (i = 0; i < config->desc.bNumInterfaces; i++) {
  		struct usb_interface *intf = config->interface[i];
  		struct usb_host_interface *alt;
  
  		alt = usb_altnum_to_altsetting(intf, 0);
  
  		/* No altsetting 0?  We'll assume the first altsetting.
  		 * We could use a GetInterface call, but if a device is
  		 * so non-compliant that it doesn't have altsetting 0
  		 * then I wouldn't trust its reply anyway.
  		 */
  		if (!alt)
  			alt = &intf->altsetting[0];
  
  		if (alt != intf->cur_altsetting) {
  			remove_intf_ep_devs(intf);
  			usb_remove_sysfs_intf_files(intf);
  		}
  		intf->cur_altsetting = alt;
  		usb_enable_interface(dev, intf, true);
  		if (device_is_registered(&intf->dev)) {
  			usb_create_sysfs_intf_files(intf);
  			create_intf_ep_devs(intf);
  		}
  	}
  	/* Now that the interfaces are installed, re-enable LPM. */
  	usb_unlocked_enable_lpm(dev);
  	return 0;
  }
  EXPORT_SYMBOL_GPL(usb_reset_configuration);
  
  static void usb_release_interface(struct device *dev)
  {
  	struct usb_interface *intf = to_usb_interface(dev);
  	struct usb_interface_cache *intfc =
  			altsetting_to_usb_interface_cache(intf->altsetting);
  
  	kref_put(&intfc->ref, usb_release_interface_cache);
  	usb_put_dev(interface_to_usbdev(intf));
  	kfree(intf);
  }
  
  /*
   * usb_deauthorize_interface - deauthorize an USB interface
   *
   * @intf: USB interface structure
   */
  void usb_deauthorize_interface(struct usb_interface *intf)
  {
  	struct device *dev = &intf->dev;
  
  	device_lock(dev->parent);
  
  	if (intf->authorized) {
  		device_lock(dev);
  		intf->authorized = 0;
  		device_unlock(dev);
  
  		usb_forced_unbind_intf(intf);
  	}
  
  	device_unlock(dev->parent);
  }
  
  /*
   * usb_authorize_interface - authorize an USB interface
   *
   * @intf: USB interface structure
   */
  void usb_authorize_interface(struct usb_interface *intf)
  {
  	struct device *dev = &intf->dev;
  
  	if (!intf->authorized) {
  		device_lock(dev);
  		intf->authorized = 1; /* authorize interface */
  		device_unlock(dev);
  	}
  }
  
  static int usb_if_uevent(struct device *dev, struct kobj_uevent_env *env)
  {
  	struct usb_device *usb_dev;
  	struct usb_interface *intf;
  	struct usb_host_interface *alt;
  
  	intf = to_usb_interface(dev);
  	usb_dev = interface_to_usbdev(intf);
  	alt = intf->cur_altsetting;
  
  	if (add_uevent_var(env, "INTERFACE=%d/%d/%d",
  		   alt->desc.bInterfaceClass,
  		   alt->desc.bInterfaceSubClass,
  		   alt->desc.bInterfaceProtocol))
  		return -ENOMEM;
  
  	if (add_uevent_var(env,
  		   "MODALIAS=usb:"
  		   "v%04Xp%04Xd%04Xdc%02Xdsc%02Xdp%02Xic%02Xisc%02Xip%02Xin%02X",
  		   le16_to_cpu(usb_dev->descriptor.idVendor),
  		   le16_to_cpu(usb_dev->descriptor.idProduct),
  		   le16_to_cpu(usb_dev->descriptor.bcdDevice),
  		   usb_dev->descriptor.bDeviceClass,
  		   usb_dev->descriptor.bDeviceSubClass,
  		   usb_dev->descriptor.bDeviceProtocol,
  		   alt->desc.bInterfaceClass,
  		   alt->desc.bInterfaceSubClass,
  		   alt->desc.bInterfaceProtocol,
  		   alt->desc.bInterfaceNumber))
  		return -ENOMEM;
  
  	return 0;
  }
  
  struct device_type usb_if_device_type = {
  	.name =		"usb_interface",
  	.release =	usb_release_interface,
  	.uevent =	usb_if_uevent,
  };
  
  static struct usb_interface_assoc_descriptor *find_iad(struct usb_device *dev,
  						struct usb_host_config *config,
  						u8 inum)
  {
  	struct usb_interface_assoc_descriptor *retval = NULL;
  	struct usb_interface_assoc_descriptor *intf_assoc;
  	int first_intf;
  	int last_intf;
  	int i;
  
  	for (i = 0; (i < USB_MAXIADS && config->intf_assoc[i]); i++) {
  		intf_assoc = config->intf_assoc[i];
  		if (intf_assoc->bInterfaceCount == 0)
  			continue;
  
  		first_intf = intf_assoc->bFirstInterface;
  		last_intf = first_intf + (intf_assoc->bInterfaceCount - 1);
  		if (inum >= first_intf && inum <= last_intf) {
  			if (!retval)
  				retval = intf_assoc;
  			else
  				dev_err(&dev->dev, "Interface #%d referenced"
  					" by multiple IADs\n", inum);
  		}
  	}
  
  	return retval;
  }
  
  
  /*
   * Internal function to queue a device reset
   * See usb_queue_reset_device() for more details
   */
  static void __usb_queue_reset_device(struct work_struct *ws)
  {
  	int rc;
  	struct usb_interface *iface =
  		container_of(ws, struct usb_interface, reset_ws);
  	struct usb_device *udev = interface_to_usbdev(iface);
  
  	rc = usb_lock_device_for_reset(udev, iface);
  	if (rc >= 0) {
  		usb_reset_device(udev);
  		usb_unlock_device(udev);
  	}
  	usb_put_intf(iface);	/* Undo _get_ in usb_queue_reset_device() */
  }
  
  
  /*
   * usb_set_configuration - Makes a particular device setting be current
   * @dev: the device whose configuration is being updated
   * @configuration: the configuration being chosen.
   * Context: !in_interrupt(), caller owns the device lock
   *
   * This is used to enable non-default device modes.  Not all devices
   * use this kind of configurability; many devices only have one
   * configuration.
   *
   * @configuration is the value of the configuration to be installed.
   * According to the USB spec (e.g. section 9.1.1.5), configuration values
   * must be non-zero; a value of zero indicates that the device in
   * unconfigured.  However some devices erroneously use 0 as one of their
   * configuration values.  To help manage such devices, this routine will
   * accept @configuration = -1 as indicating the device should be put in
   * an unconfigured state.
   *
   * USB device configurations may affect Linux interoperability,
   * power consumption and the functionality available.  For example,
   * the default configuration is limited to using 100mA of bus power,
   * so that when certain device functionality requires more power,
   * and the device is bus powered, that functionality should be in some
   * non-default device configuration.  Other device modes may also be
   * reflected as configuration options, such as whether two ISDN
   * channels are available independently; and choosing between open
   * standard device protocols (like CDC) or proprietary ones.
   *
   * Note that a non-authorized device (dev->authorized == 0) will only
   * be put in unconfigured mode.
   *
   * Note that USB has an additional level of device configurability,
   * associated with interfaces.  That configurability is accessed using
   * usb_set_interface().
   *
   * This call is synchronous. The calling context must be able to sleep,
   * must own the device lock, and must not hold the driver model's USB
   * bus mutex; usb interface driver probe() methods cannot use this routine.
   *
   * Returns zero on success, or else the status code returned by the
   * underlying call that failed.  On successful completion, each interface
   * in the original device configuration has been destroyed, and each one
   * in the new configuration has been probed by all relevant usb device
   * drivers currently known to the kernel.
   */
  int usb_set_configuration(struct usb_device *dev, int configuration)
  {
  	int i, ret;
  	struct usb_host_config *cp = NULL;
  	struct usb_interface **new_interfaces = NULL;
  	struct usb_hcd *hcd = bus_to_hcd(dev->bus);
  	int n, nintf;
  
  	if (dev->authorized == 0 || configuration == -1)
  		configuration = 0;
  	else {
  		for (i = 0; i < dev->descriptor.bNumConfigurations; i++) {
  			if (dev->config[i].desc.bConfigurationValue ==
  					configuration) {
  				cp = &dev->config[i];
  				break;
  			}
  		}
  	}
  	if ((!cp && configuration != 0))
  		return -EINVAL;
  
  	/* The USB spec says configuration 0 means unconfigured.
  	 * But if a device includes a configuration numbered 0,
  	 * we will accept it as a correctly configured state.
  	 * Use -1 if you really want to unconfigure the device.
  	 */
  	if (cp && configuration == 0)
  		dev_warn(&dev->dev, "config 0 descriptor??\n");
  
  	/* Allocate memory for new interfaces before doing anything else,
  	 * so that if we run out then nothing will have changed. */
  	n = nintf = 0;
  	if (cp) {
  		nintf = cp->desc.bNumInterfaces;
  		new_interfaces = kmalloc(nintf * sizeof(*new_interfaces),
  				GFP_NOIO);
  		if (!new_interfaces) {
  			dev_err(&dev->dev, "Out of memory\n");
  			return -ENOMEM;
  		}
  
  		for (; n < nintf; ++n) {
  			new_interfaces[n] = kzalloc(
  					sizeof(struct usb_interface),
  					GFP_NOIO);
  			if (!new_interfaces[n]) {
  				dev_err(&dev->dev, "Out of memory\n");
  				ret = -ENOMEM;
  free_interfaces:
  				while (--n >= 0)
  					kfree(new_interfaces[n]);
  				kfree(new_interfaces);
  				return ret;
  			}
  		}
  
  		i = dev->bus_mA - usb_get_max_power(dev, cp);
  		if (i < 0)
  			dev_warn(&dev->dev, "new config #%d exceeds power "
  					"limit by %dmA\n",
  					configuration, -i);
  	}
  
  	/* Wake up the device so we can send it the Set-Config request */
  	ret = usb_autoresume_device(dev);
  	if (ret)
  		goto free_interfaces;
  
  	/* if it's already configured, clear out old state first.
  	 * getting rid of old interfaces means unbinding their drivers.
  	 */
  	if (dev->state != USB_STATE_ADDRESS)
  		usb_disable_device(dev, 1);	/* Skip ep0 */
  
  	/* Get rid of pending async Set-Config requests for this device */
  	cancel_async_set_config(dev);
  
  	/* Make sure we have bandwidth (and available HCD resources) for this
  	 * configuration.  Remove endpoints from the schedule if we're dropping
  	 * this configuration to set configuration 0.  After this point, the
  	 * host controller will not allow submissions to dropped endpoints.  If
  	 * this call fails, the device state is unchanged.
  	 */
  	mutex_lock(hcd->bandwidth_mutex);
  	/* Disable LPM, and re-enable it once the new configuration is
  	 * installed, so that the xHCI driver can recalculate the U1/U2
  	 * timeouts.
  	 */
  	if (dev->actconfig && usb_disable_lpm(dev)) {
  		dev_err(&dev->dev, "%s Failed to disable LPM\n.", __func__);
  		mutex_unlock(hcd->bandwidth_mutex);
  		ret = -ENOMEM;
  		goto free_interfaces;
  	}
  	ret = usb_hcd_alloc_bandwidth(dev, cp, NULL, NULL);
  	if (ret < 0) {
  		if (dev->actconfig)
  			usb_enable_lpm(dev);
  		mutex_unlock(hcd->bandwidth_mutex);
  		usb_autosuspend_device(dev);
  		goto free_interfaces;
  	}
  
  	/*
  	 * Initialize the new interface structures and the
  	 * hc/hcd/usbcore interface/endpoint state.
  	 */
  	for (i = 0; i < nintf; ++i) {
  		struct usb_interface_cache *intfc;
  		struct usb_interface *intf;
  		struct usb_host_interface *alt;
  
  		cp->interface[i] = intf = new_interfaces[i];
  		intfc = cp->intf_cache[i];
  		intf->altsetting = intfc->altsetting;
  		intf->num_altsetting = intfc->num_altsetting;
  		intf->authorized = !!HCD_INTF_AUTHORIZED(hcd);
  		kref_get(&intfc->ref);
  
  		alt = usb_altnum_to_altsetting(intf, 0);
  
  		/* No altsetting 0?  We'll assume the first altsetting.
  		 * We could use a GetInterface call, but if a device is
  		 * so non-compliant that it doesn't have altsetting 0
  		 * then I wouldn't trust its reply anyway.
  		 */
  		if (!alt)
  			alt = &intf->altsetting[0];
  
  		intf->intf_assoc =
  			find_iad(dev, cp, alt->desc.bInterfaceNumber);
  		intf->cur_altsetting = alt;
  		usb_enable_interface(dev, intf, true);
  		intf->dev.parent = &dev->dev;
  		intf->dev.driver = NULL;
  		intf->dev.bus = &usb_bus_type;
  		intf->dev.type = &usb_if_device_type;
  		intf->dev.groups = usb_interface_groups;
  		intf->dev.dma_mask = dev->dev.dma_mask;
  		INIT_WORK(&intf->reset_ws, __usb_queue_reset_device);
  		intf->minor = -1;
  		device_initialize(&intf->dev);
  		pm_runtime_no_callbacks(&intf->dev);
  		dev_set_name(&intf->dev, "%d-%s:%d.%d",
  			dev->bus->busnum, dev->devpath,
  			configuration, alt->desc.bInterfaceNumber);
  		usb_get_dev(dev);
  	}
  	kfree(new_interfaces);
  
  	ret = usb_control_msg(dev, usb_sndctrlpipe(dev, 0),
  			      USB_REQ_SET_CONFIGURATION, 0, configuration, 0,
  			      NULL, 0, USB_CTRL_SET_TIMEOUT);
  	if (ret < 0 && cp) {
  		/*
  		 * All the old state is gone, so what else can we do?
  		 * The device is probably useless now anyway.
  		 */
  		usb_hcd_alloc_bandwidth(dev, NULL, NULL, NULL);
  		for (i = 0; i < nintf; ++i) {
  			usb_disable_interface(dev, cp->interface[i], true);
  			put_device(&cp->interface[i]->dev);
  			cp->interface[i] = NULL;
  		}
  		cp = NULL;
  	}
  
  	dev->actconfig = cp;
  	mutex_unlock(hcd->bandwidth_mutex);
  
  	if (!cp) {
  		usb_set_device_state(dev, USB_STATE_ADDRESS);
  
  		/* Leave LPM disabled while the device is unconfigured. */
  		usb_autosuspend_device(dev);
  		return ret;
  	}
  	usb_set_device_state(dev, USB_STATE_CONFIGURED);
  
  	if (cp->string == NULL &&
  			!(dev->quirks & USB_QUIRK_CONFIG_INTF_STRINGS))
  		cp->string = usb_cache_string(dev, cp->desc.iConfiguration);
  /* Uncomment this define to enable the HS Electrical Test support */
  #define DWC_HS_ELECT_TST 1
  #ifdef DWC_HS_ELECT_TST
  		/* Here we implement the HS Electrical Test support. The
  		 * tester uses a vendor ID of 0x1A0A to indicate we should
  		 * run a special test sequence. The product ID tells us
  		 * which sequence to run. We invoke the test sequence by
  		 * sending a non-standard SetFeature command to our root
  		 * hub port. Our dwc_otg_hcd_hub_control() routine will
  		 * recognize the command and perform the desired test
  		 * sequence.
  		 */
  		if (dev->descriptor.idVendor == 0x1A0A) {
  			/* HSOTG Electrical Test */
  			dev_warn(&dev->dev, "VID from HSOTG Electrical Test Fixture\n");
  
  			if (dev->bus && dev->bus->root_hub) {
  				struct usb_device *hdev = dev->bus->root_hub;
  				dev_warn(&dev->dev, "Got PID 0x%x\n", dev->descriptor.idProduct);
  
  				switch (dev->descriptor.idProduct) {
  				case 0x0101:	/* TEST_SE0_NAK */
  					dev_warn(&dev->dev, "TEST_SE0_NAK\n");
  					usb_control_msg(hdev, usb_sndctrlpipe(hdev, 0),
  							USB_REQ_SET_FEATURE, USB_RT_PORT,
  							USB_PORT_FEAT_TEST, 0x300, NULL, 0, HZ);
  					break;
  
  				case 0x0102:	/* TEST_J */
  					dev_warn(&dev->dev, "TEST_J\n");
  					usb_control_msg(hdev, usb_sndctrlpipe(hdev, 0),
  							USB_REQ_SET_FEATURE, USB_RT_PORT,
  							USB_PORT_FEAT_TEST, 0x100, NULL, 0, HZ);
  					break;
  
  				case 0x0103:	/* TEST_K */
  					dev_warn(&dev->dev, "TEST_K\n");
  					usb_control_msg(hdev, usb_sndctrlpipe(hdev, 0),
  							USB_REQ_SET_FEATURE, USB_RT_PORT,
  							USB_PORT_FEAT_TEST, 0x200, NULL, 0, HZ);
  					break;
  
  				case 0x0104:	/* TEST_PACKET */
  					dev_warn(&dev->dev, "TEST_PACKET\n");
  					usb_control_msg(hdev, usb_sndctrlpipe(hdev, 0),
  							USB_REQ_SET_FEATURE, USB_RT_PORT,
  							USB_PORT_FEAT_TEST, 0x400, NULL, 0, HZ);
  					break;
  
  				case 0x0105:	/* TEST_FORCE_ENABLE */
  					dev_warn(&dev->dev, "TEST_FORCE_ENABLE\n");
  					usb_control_msg(hdev, usb_sndctrlpipe(hdev, 0),
  							USB_REQ_SET_FEATURE, USB_RT_PORT,
  							USB_PORT_FEAT_TEST, 0x500, NULL, 0, HZ);
  					break;
  
  				case 0x0106:	/* HS_HOST_PORT_SUSPEND_RESUME */
  					dev_warn(&dev->dev, "HS_HOST_PORT_SUSPEND_RESUME\n");
  					usb_control_msg(hdev, usb_sndctrlpipe(hdev, 0),
  							USB_REQ_SET_FEATURE, USB_RT_PORT,
  							USB_PORT_FEAT_TEST, 0x600, NULL, 0, 40 * HZ);
  					break;
  
  				case 0x0107:	/* SINGLE_STEP_GET_DEVICE_DESCRIPTOR setup */
  					dev_warn(&dev->dev, "SINGLE_STEP_GET_DEVICE_DESCRIPTOR setup\n");
  					usb_control_msg(hdev, usb_sndctrlpipe(hdev, 0),
  							USB_REQ_SET_FEATURE, USB_RT_PORT,
  							USB_PORT_FEAT_TEST, 0x700, NULL, 0, 40 * HZ);
  					break;
  
  				case 0x0108:	/* SINGLE_STEP_GET_DEVICE_DESCRIPTOR execute */
  					dev_warn(&dev->dev, "SINGLE_STEP_GET_DEVICE_DESCRIPTOR execute\n");
  					usb_control_msg(hdev, usb_sndctrlpipe(hdev, 0),
  							USB_REQ_SET_FEATURE, USB_RT_PORT,
  							USB_PORT_FEAT_TEST, 0x800, NULL, 0, 40 * HZ);
  				}
  			}
  		}
  #endif /* DWC_HS_ELECT_TST */
  
  	/* Now that the interfaces are installed, re-enable LPM. */
  	usb_unlocked_enable_lpm(dev);
  	/* Enable LTM if it was turned off by usb_disable_device. */
  	usb_enable_ltm(dev);
  
  	/* Now that all the interfaces are set up, register them
  	 * to trigger binding of drivers to interfaces.  probe()
  	 * routines may install different altsettings and may
  	 * claim() any interfaces not yet bound.  Many class drivers
  	 * need that: CDC, audio, video, etc.
  	 */
  	for (i = 0; i < nintf; ++i) {
  		struct usb_interface *intf = cp->interface[i];
  
  		dev_dbg(&dev->dev,
  			"adding %s (config #%d, interface %d)\n",
  			dev_name(&intf->dev), configuration,
  			intf->cur_altsetting->desc.bInterfaceNumber);
  		device_enable_async_suspend(&intf->dev);
  		ret = device_add(&intf->dev);
  		if (ret != 0) {
  			dev_err(&dev->dev, "device_add(%s) --> %d\n",
  				dev_name(&intf->dev), ret);
  			continue;
  		}
  		create_intf_ep_devs(intf);
  	}
  
  	usb_autosuspend_device(dev);
  	return 0;
  }
  EXPORT_SYMBOL_GPL(usb_set_configuration);
  
  static LIST_HEAD(set_config_list);
  static DEFINE_SPINLOCK(set_config_lock);
  
  struct set_config_request {
  	struct usb_device	*udev;
  	int			config;
  	struct work_struct	work;
  	struct list_head	node;
  };
  
  /* Worker routine for usb_driver_set_configuration() */
  static void driver_set_config_work(struct work_struct *work)
  {
  	struct set_config_request *req =
  		container_of(work, struct set_config_request, work);
  	struct usb_device *udev = req->udev;
  
  	usb_lock_device(udev);
  	spin_lock(&set_config_lock);
  	list_del(&req->node);
  	spin_unlock(&set_config_lock);
  
  	if (req->config >= -1)		/* Is req still valid? */
  		usb_set_configuration(udev, req->config);
  	usb_unlock_device(udev);
  	usb_put_dev(udev);
  	kfree(req);
  }
  
  /* Cancel pending Set-Config requests for a device whose configuration
   * was just changed
   */
  static void cancel_async_set_config(struct usb_device *udev)
  {
  	struct set_config_request *req;
  
  	spin_lock(&set_config_lock);
  	list_for_each_entry(req, &set_config_list, node) {
  		if (req->udev == udev)
  			req->config = -999;	/* Mark as cancelled */
  	}
  	spin_unlock(&set_config_lock);
  }
  
  /**
   * usb_driver_set_configuration - Provide a way for drivers to change device configurations
   * @udev: the device whose configuration is being updated
   * @config: the configuration being chosen.
   * Context: In process context, must be able to sleep
   *
   * Device interface drivers are not allowed to change device configurations.
   * This is because changing configurations will destroy the interface the
   * driver is bound to and create new ones; it would be like a floppy-disk
   * driver telling the computer to replace the floppy-disk drive with a
   * tape drive!
   *
   * Still, in certain specialized circumstances the need may arise.  This
   * routine gets around the normal restrictions by using a work thread to
   * submit the change-config request.
   *
   * Return: 0 if the request was successfully queued, error code otherwise.
   * The caller has no way to know whether the queued request will eventually
   * succeed.
   */
  int usb_driver_set_configuration(struct usb_device *udev, int config)
  {
  	struct set_config_request *req;
  
  	req = kmalloc(sizeof(*req), GFP_KERNEL);
  	if (!req)
  		return -ENOMEM;
  	req->udev = udev;
  	req->config = config;
  	INIT_WORK(&req->work, driver_set_config_work);
  
  	spin_lock(&set_config_lock);
  	list_add(&req->node, &set_config_list);
  	spin_unlock(&set_config_lock);
  
  	usb_get_dev(udev);
  	schedule_work(&req->work);
  	return 0;
  }
  EXPORT_SYMBOL_GPL(usb_driver_set_configuration);
  