text: /*
   * f_printer.c - USB printer function driver
   *
   * Copied from drivers/usb/gadget/legacy/printer.c,
   * which was:
   *
   * printer.c -- Printer gadget driver
   *
   * Copyright (C) 2003-2005 David Brownell
   * Copyright (C) 2006 Craig W. Nadler
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   */
  
  #include <linux/module.h>
  #include <linux/kernel.h>
  #include <linux/delay.h>
  #include <linux/ioport.h>
  #include <linux/sched.h>
  #include <linux/slab.h>
  #include <linux/mutex.h>
  #include <linux/errno.h>
  #include <linux/init.h>
  #include <linux/idr.h>
  #include <linux/timer.h>
  #include <linux/list.h>
  #include <linux/interrupt.h>
  #include <linux/device.h>
  #include <linux/moduleparam.h>
  #include <linux/fs.h>
  #include <linux/poll.h>
  #include <linux/types.h>
  #include <linux/ctype.h>
  #include <linux/cdev.h>
  
  #include <asm/byteorder.h>
  #include <linux/io.h>
  #include <linux/irq.h>
  #include <linux/uaccess.h>
  #include <asm/unaligned.h>
  
  #include <linux/usb/ch9.h>
  #include <linux/usb/composite.h>
  #include <linux/usb/gadget.h>
  #include <linux/usb/g_printer.h>
  
  #include "u_printer.h"
  
  #define PNP_STRING_LEN		1024
  #define PRINTER_MINORS		4
  #define GET_DEVICE_ID		0
  #define GET_PORT_STATUS		1
  #define SOFT_RESET		2
  
  static int major, minors;
  static struct class *usb_gadget_class;
  static DEFINE_IDA(printer_ida);
  static DEFINE_MUTEX(printer_ida_lock); /* protects access do printer_ida */
  
  /*-------------------------------------------------------------------------*/
  
  struct printer_dev {
  	spinlock_t		lock;		/* lock this structure */
  	/* lock buffer lists during read/write calls */
  	struct mutex		lock_printer_io;
  	struct usb_gadget	*gadget;
  	s8			interface;
  	struct usb_ep		*in_ep, *out_ep;
  
  	struct list_head	rx_reqs;	/* List of free RX structs */
  	struct list_head	rx_reqs_active;	/* List of Active RX xfers */
  	struct list_head	rx_buffers;	/* List of completed xfers */
  	/* wait until there is data to be read. */
  	wait_queue_head_t	rx_wait;
  	struct list_head	tx_reqs;	/* List of free TX structs */
  	struct list_head	tx_reqs_active; /* List of Active TX xfers */
  	/* Wait until there are write buffers available to use. */
  	wait_queue_head_t	tx_wait;
  	/* Wait until all write buffers have been sent. */
  	wait_queue_head_t	tx_flush_wait;
  	struct usb_request	*current_rx_req;
  	size_t			current_rx_bytes;
  	u8			*current_rx_buf;
  	u8			printer_status;
  	u8			reset_printer;
  	int			minor;
  	struct cdev		printer_cdev;
  	u8			printer_cdev_open;
  	wait_queue_head_t	wait;
  	unsigned		q_len;
  	char			*pnp_string;	/* We don't own memory! */
  	struct usb_function	function;
  };
  
  static inline struct printer_dev *func_to_printer(struct usb_function *f)
  {
  	return container_of(f, struct printer_dev, function);
  }
  
  /*-------------------------------------------------------------------------*/
  
  /*
   * DESCRIPTORS ... most are static, but strings and (full) configuration
   * descriptors are built on demand.
   */
  
  /* holds our biggest descriptor */
  #define USB_DESC_BUFSIZE		256
  #define USB_BUFSIZE			8192
  
  static struct usb_interface_descriptor intf_desc = {
  	.bLength =		sizeof(intf_desc),
  	.bDescriptorType =	USB_DT_INTERFACE,
  	.bNumEndpoints =	2,
  	.bInterfaceClass =	USB_CLASS_PRINTER,
  	.bInterfaceSubClass =	1,	/* Printer Sub-Class */
  	.bInterfaceProtocol =	2,	/* Bi-Directional */
  	.iInterface =		0
  };
  
  static struct usb_endpoint_descriptor fs_ep_in_desc = {
  	.bLength =		USB_DT_ENDPOINT_SIZE,
  	.bDescriptorType =	USB_DT_ENDPOINT,
  	.bEndpointAddress =	USB_DIR_IN,
  	.bmAttributes =		USB_ENDPOINT_XFER_BULK
  };
  
  static struct usb_endpoint_descriptor fs_ep_out_desc = {
  	.bLength =		USB_DT_ENDPOINT_SIZE,
  	.bDescriptorType =	USB_DT_ENDPOINT,
  	.bEndpointAddress =	USB_DIR_OUT,
  	.bmAttributes =		USB_ENDPOINT_XFER_BULK
  };
  
  static struct usb_descriptor_header *fs_printer_function[] = {
  	(struct usb_descriptor_header *) &intf_desc,
  	(struct usb_descriptor_header *) &fs_ep_in_desc,
  	(struct usb_descriptor_header *) &fs_ep_out_desc,
  	NULL
  };
  
  /*
   * usb 2.0 devices need to expose both high speed and full speed
   * descriptors, unless they only run at full speed.
   */
  
  static struct usb_endpoint_descriptor hs_ep_in_desc = {
  	.bLength =		USB_DT_ENDPOINT_SIZE,
  	.bDescriptorType =	USB_DT_ENDPOINT,
  	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
  	.wMaxPacketSize =	cpu_to_le16(512)
  };
  
  static struct usb_endpoint_descriptor hs_ep_out_desc = {
  	.bLength =		USB_DT_ENDPOINT_SIZE,
  	.bDescriptorType =	USB_DT_ENDPOINT,
  	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
  	.wMaxPacketSize =	cpu_to_le16(512)
  };
  
  static struct usb_qualifier_descriptor dev_qualifier = {
  	.bLength =		sizeof(dev_qualifier),
  	.bDescriptorType =	USB_DT_DEVICE_QUALIFIER,
  	.bcdUSB =		cpu_to_le16(0x0200),
  	.bDeviceClass =		USB_CLASS_PRINTER,
  	.bNumConfigurations =	1
  };
  
  static struct usb_descriptor_header *hs_printer_function[] = {
  	(struct usb_descriptor_header *) &intf_desc,
  	(struct usb_descriptor_header *) &hs_ep_in_desc,
  	(struct usb_descriptor_header *) &hs_ep_out_desc,
  	NULL
  };
  
  /*
   * Added endpoint descriptors for 3.0 devices
   */
  
  static struct usb_endpoint_descriptor ss_ep_in_desc = {
  	.bLength =              USB_DT_ENDPOINT_SIZE,
  	.bDescriptorType =      USB_DT_ENDPOINT,
  	.bmAttributes =         USB_ENDPOINT_XFER_BULK,
  	.wMaxPacketSize =       cpu_to_le16(1024),
  };
  
  static struct usb_ss_ep_comp_descriptor ss_ep_in_comp_desc = {
  	.bLength =              sizeof(ss_ep_in_comp_desc),
  	.bDescriptorType =      USB_DT_SS_ENDPOINT_COMP,
  };
  
  static struct usb_endpoint_descriptor ss_ep_out_desc = {
  	.bLength =              USB_DT_ENDPOINT_SIZE,
  	.bDescriptorType =      USB_DT_ENDPOINT,
  	.bmAttributes =         USB_ENDPOINT_XFER_BULK,
  	.wMaxPacketSize =       cpu_to_le16(1024),
  };
  
  static struct usb_ss_ep_comp_descriptor ss_ep_out_comp_desc = {
  	.bLength =              sizeof(ss_ep_out_comp_desc),
  	.bDescriptorType =      USB_DT_SS_ENDPOINT_COMP,
  };
  
  static struct usb_descriptor_header *ss_printer_function[] = {
  	(struct usb_descriptor_header *) &intf_desc,
  	(struct usb_descriptor_header *) &ss_ep_in_desc,
  	(struct usb_descriptor_header *) &ss_ep_in_comp_desc,
  	(struct usb_descriptor_header *) &ss_ep_out_desc,
  	(struct usb_descriptor_header *) &ss_ep_out_comp_desc,
  	NULL
  };
  
  /* maxpacket and other transfer characteristics vary by speed. */
  static inline struct usb_endpoint_descriptor *ep_desc(struct usb_gadget *gadget,
  					struct usb_endpoint_descriptor *fs,
  					struct usb_endpoint_descriptor *hs,
  					struct usb_endpoint_descriptor *ss)
  {
  	switch (gadget->speed) {
  	case USB_SPEED_SUPER:
  		return ss;
  	case USB_SPEED_HIGH:
  		return hs;
  	default:
  		return fs;
  	}
  }
  
  /*-------------------------------------------------------------------------*/
  
  static struct usb_request *
  printer_req_alloc(struct usb_ep *ep, unsigned len, gfp_t gfp_flags)
  {
  	struct usb_request	*req;
  
  	req = usb_ep_alloc_request(ep, gfp_flags);
  
  	if (req != NULL) {
  		req->length = len;
  		req->buf = kmalloc(len, gfp_flags);
  		if (req->buf == NULL) {
  			usb_ep_free_request(ep, req);
  			return NULL;
  		}
  	}
  
  	return req;
  }
  
  static void
  printer_req_free(struct usb_ep *ep, struct usb_request *req)
  {
  	if (ep != NULL && req != NULL) {
  		kfree(req->buf);
  		usb_ep_free_request(ep, req);
  	}
  }
  
  /*-------------------------------------------------------------------------*/
  
  static void rx_complete(struct usb_ep *ep, struct usb_request *req)
  {
  	struct printer_dev	*dev = ep->driver_data;
  	int			status = req->status;
  	unsigned long		flags;
  
  	spin_lock_irqsave(&dev->lock, flags);
  
  	list_del_init(&req->list);	/* Remode from Active List */
  
  	switch (status) {
  
  	/* normal completion */
  	case 0:
  		if (req->actual > 0) {
  			list_add_tail(&req->list, &dev->rx_buffers);
  			DBG(dev, "G_Printer : rx length %d\n", req->actual);
  		} else {
  			list_add(&req->list, &dev->rx_reqs);
  		}
  		break;
  
  	/* software-driven interface shutdown */
  	case -ECONNRESET:		/* unlink */
  	case -ESHUTDOWN:		/* disconnect etc */
  		VDBG(dev, "rx shutdown, code %d\n", status);
  		list_add(&req->list, &dev->rx_reqs);
  		break;
  
  	/* for hardware automagic (such as pxa) */
  	case -ECONNABORTED:		/* endpoint reset */
  		DBG(dev, "rx %s reset\n", ep->name);
  		list_add(&req->list, &dev->rx_reqs);
  		break;
  
  	/* data overrun */
  	case -EOVERFLOW:
  		/* FALLTHROUGH */
  
  	default:
  		DBG(dev, "rx status %d\n", status);
  		list_add(&req->list, &dev->rx_reqs);
  		break;
  	}
  
  	wake_up_interruptible(&dev->rx_wait);
  	spin_unlock_irqrestore(&dev->lock, flags);
  }
  
  static void tx_complete(struct usb_ep *ep, struct usb_request *req)
  {
  	struct printer_dev	*dev = ep->driver_data;
  
  	switch (req->status) {
  	default:
  		VDBG(dev, "tx err %d\n", req->status);
  		/* FALLTHROUGH */
  	case -ECONNRESET:		/* unlink */
  	case -ESHUTDOWN:		/* disconnect etc */
  		break;
  	case 0:
  		break;
  	}
  
  	spin_lock(&dev->lock);
  	/* Take the request struct off the active list and put it on the
  	 * free list.
  	 */
  	list_del_init(&req->list);
  	list_add(&req->list, &dev->tx_reqs);
  	wake_up_interruptible(&dev->tx_wait);
  	if (likely(list_empty(&dev->tx_reqs_active)))
  		wake_up_interruptible(&dev->tx_flush_wait);
  
  	spin_unlock(&dev->lock);
  }
  
  /*-------------------------------------------------------------------------*/
  
  static int
  printer_open(struct inode *inode, struct file *fd)
  {
  	struct printer_dev	*dev;
  	unsigned long		flags;
  	int			ret = -EBUSY;
  
  	dev = container_of(inode->i_cdev, struct printer_dev, printer_cdev);
  
  	spin_lock_irqsave(&dev->lock, flags);
  
  	if (!dev->printer_cdev_open) {
  		dev->printer_cdev_open = 1;
  		fd->private_data = dev;
  		ret = 0;
  		/* Change the printer status to show that it's on-line. */
  		dev->printer_status |= PRINTER_SELECTED;
  	}
  
  	spin_unlock_irqrestore(&dev->lock, flags);
  
  	DBG(dev, "printer_open returned %x\n", ret);
  	return ret;
  }
  
  static int
  printer_close(struct inode *inode, struct file *fd)
  {
  	struct printer_dev	*dev = fd->private_data;
  	unsigned long		flags;
  
  	spin_lock_irqsave(&dev->lock, flags);
  	dev->printer_cdev_open = 0;
  	fd->private_data = NULL;
  	/* Change printer status to show that the printer is off-line. */
  	dev->printer_status &= ~PRINTER_SELECTED;
  	spin_unlock_irqrestore(&dev->lock, flags);
  
  	DBG(dev, "printer_close\n");
  
  	return 0;
  }
  
  /* This function must be called with interrupts turned off. */
  static void
  setup_rx_reqs(struct printer_dev *dev)
  {
  	struct usb_request              *req;
  
  	while (likely(!list_empty(&dev->rx_reqs))) {
  		int error;
  
  		req = container_of(dev->rx_reqs.next,
  				struct usb_request, list);
  		list_del_init(&req->list);
  
  		/* The USB Host sends us whatever amount of data it wants to
  		 * so we always set the length field to the full USB_BUFSIZE.
  		 * If the amount of data is more than the read() caller asked
  		 * for it will be stored in the request buffer until it is
  		 * asked for by read().
  		 */
  		req->length = USB_BUFSIZE;
  		req->complete = rx_complete;
  
  		/* here, we unlock, and only unlock, to avoid deadlock. */
  		spin_unlock(&dev->lock);
  		error = usb_ep_queue(dev->out_ep, req, GFP_ATOMIC);
  		spin_lock(&dev->lock);
  		if (error) {
  			DBG(dev, "rx submit --> %d\n", error);
  			list_add(&req->list, &dev->rx_reqs);
  			break;
  		}
  		/* if the req is empty, then add it into dev->rx_reqs_active. */
  		else if (list_empty(&req->list))
  			list_add(&req->list, &dev->rx_reqs_active);
  	}
  }
  
  static ssize_t
  printer_read(struct file *fd, char __user *buf, size_t len, loff_t *ptr)
  {
  	struct printer_dev		*dev = fd->private_data;
  	unsigned long			flags;
  	size_t				size;
  	size_t				bytes_copied;
  	struct usb_request		*req;
  	/* This is a pointer to the current USB rx request. */
  	struct usb_request		*current_rx_req;
  	/* This is the number of bytes in the current rx buffer. */
  	size_t				current_rx_bytes;
  	/* This is a pointer to the current rx buffer. */
  	u8				*current_rx_buf;
  
  	if (len == 0)
  		return -EINVAL;
  
  	DBG(dev, "printer_read trying to read %d bytes\n", (int)len);
  
  	mutex_lock(&dev->lock_printer_io);
  	spin_lock_irqsave(&dev->lock, flags);
  
  	/* We will use this flag later to check if a printer reset happened
  	 * after we turn interrupts back on.
  	 */
  	dev->reset_printer = 0;
  
  	setup_rx_reqs(dev);
  
  	bytes_copied = 0;
  	current_rx_req = dev->current_rx_req;
  	current_rx_bytes = dev->current_rx_bytes;
  	current_rx_buf = dev->current_rx_buf;
  	dev->current_rx_req = NULL;
  	dev->current_rx_bytes = 0;
  	dev->current_rx_buf = NULL;
  
  	/* Check if there is any data in the read buffers. Please note that
  	 * current_rx_bytes is the number of bytes in the current rx buffer.
  	 * If it is zero then check if there are any other rx_buffers that
  	 * are on the completed list. We are only out of data if all rx
  	 * buffers are empty.
  	 */
  	if ((current_rx_bytes == 0) &&
  			(likely(list_empty(&dev->rx_buffers)))) {
  		/* Turn interrupts back on before sleeping. */
  		spin_unlock_irqrestore(&dev->lock, flags);
  
  		/*
  		 * If no data is available check if this is a NON-Blocking
  		 * call or not.
  		 */
  		if (fd->f_flags & (O_NONBLOCK|O_NDELAY)) {
  			mutex_unlock(&dev->lock_printer_io);
  			return -EAGAIN;
  		}
  
  		/* Sleep until data is available */
  		wait_event_interruptible(dev->rx_wait,
  				(likely(!list_empty(&dev->rx_buffers))));
  		spin_lock_irqsave(&dev->lock, flags);
  	}
  
  	/* We have data to return then copy it to the caller's buffer.*/
  	while ((current_rx_bytes || likely(!list_empty(&dev->rx_buffers)))
  			&& len) {
  		if (current_rx_bytes == 0) {
  			req = container_of(dev->rx_buffers.next,
  					struct usb_request, list);
  			list_del_init(&req->list);
  
  			if (req->actual && req->buf) {
  				current_rx_req = req;
  				current_rx_bytes = req->actual;
  				current_rx_buf = req->buf;
  			} else {
  				list_add(&req->list, &dev->rx_reqs);
  				continue;
  			}
  		}
  
  		/* Don't leave irqs off while doing memory copies */
  		spin_unlock_irqrestore(&dev->lock, flags);
  
  		if (len > current_rx_bytes)
  			size = current_rx_bytes;
  		else
  			size = len;
  
  		size -= copy_to_user(buf, current_rx_buf, size);
  		bytes_copied += size;
  		len -= size;
  		buf += size;
  
  		spin_lock_irqsave(&dev->lock, flags);
  
  		/* We've disconnected or reset so return. */
  		if (dev->reset_printer) {
  			list_add(&current_rx_req->list, &dev->rx_reqs);
  			spin_unlock_irqrestore(&dev->lock, flags);
  			mutex_unlock(&dev->lock_printer_io);
  			return -EAGAIN;
  		}
  
  		/* If we not returning all the data left in this RX request
  		 * buffer then adjust the amount of data left in the buffer.
  		 * Othewise if we are done with this RX request buffer then
  		 * requeue it to get any incoming data from the USB host.
  		 */
  		if (size < current_rx_bytes) {
  			current_rx_bytes -= size;
  			current_rx_buf += size;
  		} else {
  			list_add(&current_rx_req->list, &dev->rx_reqs);
  			current_rx_bytes = 0;
  			current_rx_buf = NULL;
  			current_rx_req = NULL;
  		}
  	}
  
  	dev->current_rx_req = current_rx_req;
  	dev->current_rx_bytes = current_rx_bytes;
  	dev->current_rx_buf = current_rx_buf;
  
  	spin_unlock_irqrestore(&dev->lock, flags);
  	mutex_unlock(&dev->lock_printer_io);
  
  	DBG(dev, "printer_read returned %d bytes\n", (int)bytes_copied);
  
  	if (bytes_copied)
  		return bytes_copied;
  	else
  		return -EAGAIN;
  }
  
  static ssize_t
  printer_write(struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
  {
  	struct printer_dev	*dev = fd->private_data;
  	unsigned long		flags;
  	size_t			size;	/* Amount of data in a TX request. */
  	size_t			bytes_copied = 0;
  	struct usb_request	*req;
  
  	DBG(dev, "printer_write trying to send %d bytes\n", (int)len);
  
  	if (len == 0)
  		return -EINVAL;
  
  	mutex_lock(&dev->lock_printer_io);
  	spin_lock_irqsave(&dev->lock, flags);
  
  	/* Check if a printer reset happens while we have interrupts on */
  	dev->reset_printer = 0;
  
  	/* Check if there is any available write buffers */
  	if (likely(list_empty(&dev->tx_reqs))) {
  		/* Turn interrupts back on before sleeping. */
  		spin_unlock_irqrestore(&dev->lock, flags);
  
  		/*
  		 * If write buffers are available check if this is
  		 * a NON-Blocking call or not.
  		 */
  		if (fd->f_flags & (O_NONBLOCK|O_NDELAY)) {
  			mutex_unlock(&dev->lock_printer_io);
  			return -EAGAIN;
  		}
  
  		/* Sleep until a write buffer is available */
  		wait_event_interruptible(dev->tx_wait,
  				(likely(!list_empty(&dev->tx_reqs))));
  		spin_lock_irqsave(&dev->lock, flags);
  	}
  
  	while (likely(!list_empty(&dev->tx_reqs)) && len) {
  
  		if (len > USB_BUFSIZE)
  			size = USB_BUFSIZE;
  		else
  			size = len;
  
  		req = container_of(dev->tx_reqs.next, struct usb_request,
  				list);
  		list_del_init(&req->list);
  
  		req->complete = tx_complete;
  		req->length = size;
  
  		/* Check if we need to send a zero length packet. */
  		if (len > size)
  			/* They will be more TX requests so no yet. */
  			req->zero = 0;
  		else
  			/* If the data amount is not a multiple of the
  			 * maxpacket size then send a zero length packet.
  			 */
  			req->zero = ((len % dev->in_ep->maxpacket) == 0);
  
  		/* Don't leave irqs off while doing memory copies */
  		spin_unlock_irqrestore(&dev->lock, flags);
  
  		if (copy_from_user(req->buf, buf, size)) {
  			list_add(&req->list, &dev->tx_reqs);
  			mutex_unlock(&dev->lock_printer_io);
  			return bytes_copied;
  		}
  
  		bytes_copied += size;
  		len -= size;
  		buf += size;
  
  		spin_lock_irqsave(&dev->lock, flags);
  
  		/* We've disconnected or reset so free the req and buffer */
  		if (dev->reset_printer) {
  			list_add(&req->list, &dev->tx_reqs);
  			spin_unlock_irqrestore(&dev->lock, flags);
  			mutex_unlock(&dev->lock_printer_io);
  			return -EAGAIN;
  		}
  
  		if (usb_ep_queue(dev->in_ep, req, GFP_ATOMIC)) {
  			list_add(&req->list, &dev->tx_reqs);
  			spin_unlock_irqrestore(&dev->lock, flags);
  			mutex_unlock(&dev->lock_printer_io);
  			return -EAGAIN;
  		}
  
  		list_add(&req->list, &dev->tx_reqs_active);
  
  	}
  
  	spin_unlock_irqrestore(&dev->lock, flags);
  	mutex_unlock(&dev->lock_printer_io);
  
  	DBG(dev, "printer_write sent %d bytes\n", (int)bytes_copied);
  
  	if (bytes_copied)
  		return bytes_copied;
  	else
  		return -EAGAIN;
  }
  
  static int
  printer_fsync(struct file *fd, loff_t start, loff_t end, int datasync)
  {
  	struct printer_dev	*dev = fd->private_data;
  	struct inode *inode = file_inode(fd);
  	unsigned long		flags;
  	int			tx_list_empty;
  
  	mutex_lock(&inode->i_mutex);
  	spin_lock_irqsave(&dev->lock, flags);
  	tx_list_empty = (likely(list_empty(&dev->tx_reqs)));
  	spin_unlock_irqrestore(&dev->lock, flags);
  
  	if (!tx_list_empty) {
  		/* Sleep until all data has been sent */
  		wait_event_interruptible(dev->tx_flush_wait,
  				(likely(list_empty(&dev->tx_reqs_active))));
  	}
  	mutex_unlock(&inode->i_mutex);
  
  	return 0;
  }
  
  static unsigned int
  printer_poll(struct file *fd, poll_table *wait)
  {
  	struct printer_dev	*dev = fd->private_data;
  	unsigned long		flags;
  	int			status = 0;
  
  	mutex_lock(&dev->lock_printer_io);
  	spin_lock_irqsave(&dev->lock, flags);
  	setup_rx_reqs(dev);
  	spin_unlock_irqrestore(&dev->lock, flags);
  	mutex_unlock(&dev->lock_printer_io);
  
  	poll_wait(fd, &dev->rx_wait, wait);
  	poll_wait(fd, &dev->tx_wait, wait);
  
  	spin_lock_irqsave(&dev->lock, flags);
  	if (likely(!list_empty(&dev->tx_reqs)))
  		status |= POLLOUT | POLLWRNORM;
  
  	if (likely(dev->current_rx_bytes) ||
  			likely(!list_empty(&dev->rx_buffers)))
  		status |= POLLIN | POLLRDNORM;
  
  	spin_unlock_irqrestore(&dev->lock, flags);
  
  	return status;
  }
  
  static long
  printer_ioctl(struct file *fd, unsigned int code, unsigned long arg)
  {
  	struct printer_dev	*dev = fd->private_data;
  	unsigned long		flags;
  	int			status = 0;
  
  	DBG(dev, "printer_ioctl: cmd=0x%4.4x, arg=%lu\n", code, arg);
  
  	/* handle ioctls */
  
  	spin_lock_irqsave(&dev->lock, flags);
  
  	switch (code) {
  	case GADGET_GET_PRINTER_STATUS:
  		status = (int)dev->printer_status;
  		break;
  	case GADGET_SET_PRINTER_STATUS:
  		dev->printer_status = (u8)arg;
  		break;
  	default:
  		/* could not handle ioctl */
  		DBG(dev, "printer_ioctl: ERROR cmd=0x%4.4xis not supported\n",
  				code);
  		status = -ENOTTY;
  	}
  
  	spin_unlock_irqrestore(&dev->lock, flags);
  
  	return status;
  }
  
  /* used after endpoint configuration */
  static const struct file_operations printer_io_operations = {
  	.owner =	THIS_MODULE,
  	.open =		printer_open,
  	.read =		printer_read,
  	.write =	printer_write,
  	.fsync =	printer_fsync,
  	.poll =		printer_poll,
  	.unlocked_ioctl = printer_ioctl,
  	.release =	printer_close,
  	.llseek =	noop_llseek,
  };
  
  /*-------------------------------------------------------------------------*/
  
  static int
  set_printer_interface(struct printer_dev *dev)
  {
  	int			result = 0;
  
  	dev->in_ep->desc = ep_desc(dev->gadget, &fs_ep_in_desc, &hs_ep_in_desc,
  				&ss_ep_in_desc);
  	dev->in_ep->driver_data = dev;
  
  	dev->out_ep->desc = ep_desc(dev->gadget, &fs_ep_out_desc,
  				    &hs_ep_out_desc, &ss_ep_out_desc);
  	dev->out_ep->driver_data = dev;
  
  	result = usb_ep_enable(dev->in_ep);
  	if (result != 0) {
  		DBG(dev, "enable %s --> %d\n", dev->in_ep->name, result);
  		goto done;
  	}
  
  	result = usb_ep_enable(dev->out_ep);
  	if (result != 0) {
  		DBG(dev, "enable %s --> %d\n", dev->in_ep->name, result);
  		goto done;
  	}
  
  done:
  	/* on error, disable any endpoints  */
  	if (result != 0) {
  		(void) usb_ep_disable(dev->in_ep);
  		(void) usb_ep_disable(dev->out_ep);
  		dev->in_ep->desc = NULL;
  		dev->out_ep->desc = NULL;
  	}
  
  	/* caller is responsible for cleanup on error */
  	return result;
  }
  
  static void printer_reset_interface(struct printer_dev *dev)
  {
  	if (dev->interface < 0)
  		return;
  
  	DBG(dev, "%s\n", __func__);
  
  	if (dev->in_ep->desc)
  		usb_ep_disable(dev->in_ep);
  
  	if (dev->out_ep->desc)
  		usb_ep_disable(dev->out_ep);
  
  	dev->in_ep->desc = NULL;
  	dev->out_ep->desc = NULL;
  	dev->interface = -1;
  }
  
  /* Change our operational Interface. */
  static int set_interface(struct printer_dev *dev, unsigned number)
  {
  	int			result = 0;
  
  	/* Free the current interface */
  	printer_reset_interface(dev);
  
  	result = set_printer_interface(dev);
  	if (result)
  		printer_reset_interface(dev);
  	else
  		dev->interface = number;
  
  	if (!result)
  		INFO(dev, "Using interface %x\n", number);
  
  	return result;
  }
  
  static void printer_soft_reset(struct printer_dev *dev)
  {
  	struct usb_request	*req;
  
  	INFO(dev, "Received Printer Reset Request\n");
  
  	if (usb_ep_disable(dev->in_ep))
  		DBG(dev, "Failed to disable USB in_ep\n");
  	if (usb_ep_disable(dev->out_ep))
  		DBG(dev, "Failed to disable USB out_ep\n");
  
  	if (dev->current_rx_req != NULL) {
  		list_add(&dev->current_rx_req->list, &dev->rx_reqs);
  		dev->current_rx_req = NULL;
  	}
  	dev->current_rx_bytes = 0;
  	dev->current_rx_buf = NULL;
  	dev->reset_printer = 1;
  
  	while (likely(!(list_empty(&dev->rx_buffers)))) {
  		req = container_of(dev->rx_buffers.next, struct usb_request,
  				list);
  		list_del_init(&req->list);
  		list_add(&req->list, &dev->rx_reqs);
  	}
  
  	while (likely(!(list_empty(&dev->rx_reqs_active)))) {
  		req = container_of(dev->rx_buffers.next, struct usb_request,
  				list);
  		list_del_init(&req->list);
  		list_add(&req->list, &dev->rx_reqs);
  	}
  
  	while (likely(!(list_empty(&dev->tx_reqs_active)))) {
  		req = container_of(dev->tx_reqs_active.next,
  				struct usb_request, list);
  		list_del_init(&req->list);
  		list_add(&req->list, &dev->tx_reqs);
  	}
  
  	if (usb_ep_enable(dev->in_ep))
  		DBG(dev, "Failed to enable USB in_ep\n");
  	if (usb_ep_enable(dev->out_ep))
  		DBG(dev, "Failed to enable USB out_ep\n");
  
  	wake_up_interruptible(&dev->rx_wait);
  	wake_up_interruptible(&dev->tx_wait);
  	wake_up_interruptible(&dev->tx_flush_wait);
  }
  
  /*-------------------------------------------------------------------------*/
  
  static bool gprinter_req_match(struct usb_function *f,
  			       const struct usb_ctrlrequest *ctrl)
  {
  	struct printer_dev	*dev = func_to_printer(f);
  	u16			w_index = le16_to_cpu(ctrl->wIndex);
  	u16			w_value = le16_to_cpu(ctrl->wValue);
  	u16			w_length = le16_to_cpu(ctrl->wLength);
  
  	if ((ctrl->bRequestType & USB_RECIP_MASK) != USB_RECIP_INTERFACE ||
  	    (ctrl->bRequestType & USB_TYPE_MASK) != USB_TYPE_CLASS)
  		return false;
  
  	switch (ctrl->bRequest) {
  	case GET_DEVICE_ID:
  		w_index >>= 8;
  		if (w_length <= PNP_STRING_LEN &&
  		    (USB_DIR_IN & ctrl->bRequestType))
  			break;
  		return false;
  	case GET_PORT_STATUS:
  		if (!w_value && w_length == 1 &&
  		    (USB_DIR_IN & ctrl->bRequestType))
  			break;
  		return false;
  	case SOFT_RESET:
  		if (!w_value && !w_length &&
  		   !(USB_DIR_IN & ctrl->bRequestType))
  			break;
  		/* fall through */
  	default:
  		return false;
  	}
  	return w_index == dev->interface;
  }
  
  /*
   * The setup() callback implements all the ep0 functionality that's not
   * handled lower down.
   */
  static int printer_func_setup(struct usb_function *f,
  		const struct usb_ctrlrequest *ctrl)
  {
  	struct printer_dev *dev = func_to_printer(f);
  	struct usb_composite_dev *cdev = f->config->cdev;
  	struct usb_request	*req = cdev->req;
  	int			value = -EOPNOTSUPP;
  	u16			wIndex = le16_to_cpu(ctrl->wIndex);
  	u16			wValue = le16_to_cpu(ctrl->wValue);
  	u16			wLength = le16_to_cpu(ctrl->wLength);
  
  	DBG(dev, "ctrl req%02x.%02x v%04x i%04x l%d\n",
  		ctrl->bRequestType, ctrl->bRequest, wValue, wIndex, wLength);
  
  	switch (ctrl->bRequestType&USB_TYPE_MASK) {
  	case USB_TYPE_CLASS:
  		switch (ctrl->bRequest) {
  		case GET_DEVICE_ID: /* Get the IEEE-1284 PNP String */
  			/* Only one printer interface is supported. */
  			if ((wIndex>>8) != dev->interface)
  				break;
  
  			value = (dev->pnp_string[0] << 8) | dev->pnp_string[1];
  			memcpy(req->buf, dev->pnp_string, value);
  			DBG(dev, "1284 PNP String: %x %s\n", value,
  					&dev->pnp_string[2]);
  			break;
  
  		case GET_PORT_STATUS: /* Get Port Status */
  			/* Only one printer interface is supported. */
  			if (wIndex != dev->interface)
  				break;
  
  			*(u8 *)req->buf = dev->printer_status;
  			value = min_t(u16, wLength, 1);
  			break;
  
  		case SOFT_RESET: /* Soft Reset */
  			/* Only one printer interface is supported. */
  			if (wIndex != dev->interface)
  				break;
  
  			printer_soft_reset(dev);
  
  			value = 0;
  			break;
  
  		default:
  			goto unknown;
  		}
  		break;
  
  	default:
  unknown:
  		VDBG(dev,
  			"unknown ctrl req%02x.%02x v%04x i%04x l%d\n",
  			ctrl->bRequestType, ctrl->bRequest,
  			wValue, wIndex, wLength);
  		break;
  	}
  	/* host either stalls (value < 0) or reports success */
  	if (value >= 0) {
  		req->length = value;
  		req->zero = value < wLength;
  		value = usb_ep_queue(cdev->gadget->ep0, req, GFP_ATOMIC);
  		if (value < 0) {
  			ERROR(dev, "%s:%d Error!\n", __func__, __LINE__);
  			req->status = 0;
  		}
  	}
  	return value;
  }
  
  static int printer_func_bind(struct usb_configuration *c,
  		struct usb_function *f)
  {
  	struct usb_gadget *gadget = c->cdev->gadget;
  	struct printer_dev *dev = func_to_printer(f);
  	struct device *pdev;
  	struct usb_composite_dev *cdev = c->cdev;
  	struct usb_ep *in_ep;
  	struct usb_ep *out_ep = NULL;
  	struct usb_request *req;
  	dev_t devt;
  	int id;
  	int ret;
  	u32 i;
  
  	id = usb_interface_id(c, f);
  	if (id < 0)
  		return id;
  	intf_desc.bInterfaceNumber = id;
  
  	/* finish hookup to lower layer ... */
  	dev->gadget = gadget;
  
  	/* all we really need is bulk IN/OUT */
  	in_ep = usb_ep_autoconfig(cdev->gadget, &fs_ep_in_desc);
  	if (!in_ep) {
  autoconf_fail:
  		dev_err(&cdev->gadget->dev, "can't autoconfigure on %s\n",
  			cdev->gadget->name);
  		return -ENODEV;
  	}
  	in_ep->driver_data = in_ep;	/* claim */
  
  	out_ep = usb_ep_autoconfig(cdev->gadget, &fs_ep_out_desc);
  	if (!out_ep)
  		goto autoconf_fail;
  	out_ep->driver_data = out_ep;	/* claim */
  
  	/* assumes that all endpoints are dual-speed */
  	hs_ep_in_desc.bEndpointAddress = fs_ep_in_desc.bEndpointAddress;
  	hs_ep_out_desc.bEndpointAddress = fs_ep_out_desc.bEndpointAddress;
  	ss_ep_in_desc.bEndpointAddress = fs_ep_in_desc.bEndpointAddress;
  	ss_ep_out_desc.bEndpointAddress = fs_ep_out_desc.bEndpointAddress;
  
  	ret = usb_assign_descriptors(f, fs_printer_function,
  			hs_printer_function, ss_printer_function);
  	if (ret)
  		return ret;
  
  	dev->in_ep = in_ep;
  	dev->out_ep = out_ep;
  
  	ret = -ENOMEM;
  	for (i = 0; i < dev->q_len; i++) {
  		req = printer_req_alloc(dev->in_ep, USB_BUFSIZE, GFP_KERNEL);
  		if (!req)
  			goto fail_tx_reqs;
  		list_add(&req->list, &dev->tx_reqs);
  	}
  
  	for (i = 0; i < dev->q_len; i++) {
  		req = printer_req_alloc(dev->out_ep, USB_BUFSIZE, GFP_KERNEL);
  		if (!req)
  			goto fail_rx_reqs;
  		list_add(&req->list, &dev->rx_reqs);
  	}
  
  	/* Setup the sysfs files for the printer gadget. */
  	devt = MKDEV(major, dev->minor);
  	pdev = device_create(usb_gadget_class, NULL, devt,
  				  NULL, "g_printer%d", dev->minor);
  	if (IS_ERR(pdev)) {
  		ERROR(dev, "Failed to create device: g_printer\n");
  		ret = PTR_ERR(pdev);
  		goto fail_rx_reqs;
  	}
  
  	/*
  	 * Register a character device as an interface to a user mode
  	 * program that handles the printer specific functionality.
  	 */
  	cdev_init(&dev->printer_cdev, &printer_io_operations);
  	dev->printer_cdev.owner = THIS_MODULE;
  	ret = cdev_add(&dev->printer_cdev, devt, 1);
  	if (ret) {
  		ERROR(dev, "Failed to open char device\n");
  		goto fail_cdev_add;
  	}
  
  	return 0;
  
  fail_cdev_add:
  	device_destroy(usb_gadget_class, devt);
  
  fail_rx_reqs:
  	while (!list_empty(&dev->rx_reqs)) {
  		req = container_of(dev->rx_reqs.next, struct usb_request, list);
  		list_del(&req->list);
  		printer_req_free(dev->out_ep, req);
  	}
  
  fail_tx_reqs:
  	while (!list_empty(&dev->tx_reqs)) {
  		req = container_of(dev->tx_reqs.next, struct usb_request, list);
  		list_del(&req->list);
  		printer_req_free(dev->in_ep, req);
  	}
  
  	return ret;
  
  }
  
  static int printer_func_set_alt(struct usb_function *f,
  		unsigned intf, unsigned alt)
  {
  	struct printer_dev *dev = func_to_printer(f);
  	int ret = -ENOTSUPP;
  
  	if (!alt)
  		ret = set_interface(dev, intf);
  
  	return ret;
  }
  
  static void printer_func_disable(struct usb_function *f)
  {
  	struct printer_dev *dev = func_to_printer(f);
  	unsigned long		flags;
  
  	DBG(dev, "%s\n", __func__);
  
  	spin_lock_irqsave(&dev->lock, flags);
  	printer_reset_interface(dev);
  	spin_unlock_irqrestore(&dev->lock, flags);
  }
  
  static inline struct f_printer_opts
  *to_f_printer_opts(struct config_item *item)
  {
  	return container_of(to_config_group(item), struct f_printer_opts,
  			    func_inst.group);
  }
  
  CONFIGFS_ATTR_STRUCT(f_printer_opts);
  CONFIGFS_ATTR_OPS(f_printer_opts);
  
  static void printer_attr_release(struct config_item *item)
  {
  	struct f_printer_opts *opts = to_f_printer_opts(item);
  
  	usb_put_function_instance(&opts->func_inst);
  }
  
  static struct configfs_item_operations printer_item_ops = {
  	.release	= printer_attr_release,
  	.show_attribute	= f_printer_opts_attr_show,
  	.store_attribute = f_printer_opts_attr_store,
  };
  
  static ssize_t f_printer_opts_pnp_string_show(struct f_printer_opts *opts,
  					      char *page)
  {
  	int result;
  
  	mutex_lock(&opts->lock);
  	result = strlcpy(page, opts->pnp_string + 2, PNP_STRING_LEN - 2);
  	mutex_unlock(&opts->lock);
  
  	return result;
  }
  
  static ssize_t f_printer_opts_pnp_string_store(struct f_printer_opts *opts,
  					       const char *page, size_t len)
  {
  	int result, l;
  
  	mutex_lock(&opts->lock);
  	result = strlcpy(opts->pnp_string + 2, page, PNP_STRING_LEN - 2);
  	l = strlen(opts->pnp_string + 2) + 2;
  	opts->pnp_string[0] = (l >> 8) & 0xFF;
  	opts->pnp_string[1] = l & 0xFF;
  	mutex_unlock(&opts->lock);
  
  	return result;
  }
  
  static struct f_printer_opts_attribute f_printer_opts_pnp_string =
  	__CONFIGFS_ATTR(pnp_string, S_IRUGO | S_IWUSR,
  			f_printer_opts_pnp_string_show,
  			f_printer_opts_pnp_string_store);
  
  static ssize_t f_printer_opts_q_len_show(struct f_printer_opts *opts,
  					 char *page)
  {
  	int result;
  
  	mutex_lock(&opts->lock);
  	result = sprintf(page, "%d\n", opts->q_len);
  	mutex_unlock(&opts->lock);
  
  	return result;
  }
  
  static ssize_t f_printer_opts_q_len_store(struct f_printer_opts *opts,
  					  const char *page, size_t len)
  {
  	int ret;
  	u16 num;
  
  	mutex_lock(&opts->lock);
  	if (opts->refcnt) {
  		ret = -EBUSY;
  		goto end;
  	}
  
  	ret = kstrtou16(page, 0, &num);
  	if (ret)
  		goto end;
  
  	opts->q_len = (unsigned)num;
  	ret = len;
  end:
  	mutex_unlock(&opts->lock);
  	return ret;
  }
  
  static struct f_printer_opts_attribute f_printer_opts_q_len =
  	__CONFIGFS_ATTR(q_len, S_IRUGO | S_IWUSR, f_printer_opts_q_len_show,
  			f_printer_opts_q_len_store);
  
  static struct configfs_attribute *printer_attrs[] = {
  	&f_printer_opts_pnp_string.attr,
  	&f_printer_opts_q_len.attr,
  	NULL,
  };
  
  static struct config_item_type printer_func_type = {
  	.ct_item_ops	= &printer_item_ops,
  	.ct_attrs	= printer_attrs,
  	.ct_owner	= THIS_MODULE,
  };
  
  static inline int gprinter_get_minor(void)
  {
  	int ret;
  
  	ret = ida_simple_get(&printer_ida, 0, 0, GFP_KERNEL);
  	if (ret >= PRINTER_MINORS) {
  		ida_simple_remove(&printer_ida, ret);
  		ret = -ENODEV;
  	}
  
  	return ret;
  }
  
  static inline void gprinter_put_minor(int minor)
  {
  	ida_simple_remove(&printer_ida, minor);
  }
  
  static int gprinter_setup(int);
  static void gprinter_cleanup(void);
  
  static void gprinter_free_inst(struct usb_function_instance *f)
  {
  	struct f_printer_opts *opts;
  
  	opts = container_of(f, struct f_printer_opts, func_inst);
  
  	mutex_lock(&printer_ida_lock);
  
  	gprinter_put_minor(opts->minor);
  	if (idr_is_empty(&printer_ida.idr))
  		gprinter_cleanup();
  
  	mutex_unlock(&printer_ida_lock);
  
  	kfree(opts);
  }
  
  static struct usb_function_instance *gprinter_alloc_inst(void)
  {
  	struct f_printer_opts *opts;
  	struct usb_function_instance *ret;
  	int status = 0;
  
  	opts = kzalloc(sizeof(*opts), GFP_KERNEL);
  	if (!opts)
  		return ERR_PTR(-ENOMEM);
  
  	mutex_init(&opts->lock);
  	opts->func_inst.free_func_inst = gprinter_free_inst;
  	ret = &opts->func_inst;
  
  	mutex_lock(&printer_ida_lock);
  
  	if (idr_is_empty(&printer_ida.idr)) {
  		status = gprinter_setup(PRINTER_MINORS);
  		if (status) {
  			ret = ERR_PTR(status);
  			kfree(opts);
  			goto unlock;
  		}
  	}
  
  	opts->minor = gprinter_get_minor();
  	if (opts->minor < 0) {
  		ret = ERR_PTR(opts->minor);
  		kfree(opts);
  		if (idr_is_empty(&printer_ida.idr))
  			gprinter_cleanup();
  		goto unlock;
  	}
  	config_group_init_type_name(&opts->func_inst.group, "",
  				    &printer_func_type);
  
  unlock:
  	mutex_unlock(&printer_ida_lock);
  	return ret;
  }
  
  static void gprinter_free(struct usb_function *f)
  {
  	struct printer_dev *dev = func_to_printer(f);
  	struct f_printer_opts *opts;
  
  	opts = container_of(f->fi, struct f_printer_opts, func_inst);
  	kfree(dev);
  	mutex_lock(&opts->lock);
  	--opts->refcnt;
  	mutex_unlock(&opts->lock);
  }
  
  static void printer_func_unbind(struct usb_configuration *c,
  		struct usb_function *f)
  {
  	struct printer_dev	*dev;
  	struct usb_request	*req;
  
  	dev = func_to_printer(f);
  
  	device_destroy(usb_gadget_class, MKDEV(major, dev->minor));
  
  	/* Remove Character Device */
  	cdev_del(&dev->printer_cdev);
  
  	/* we must already have been disconnected ... no i/o may be active */
  	WARN_ON(!list_empty(&dev->tx_reqs_active));
  	WARN_ON(!list_empty(&dev->rx_reqs_active));
  
  	/* Free all memory for this driver. */
  	while (!list_empty(&dev->tx_reqs)) {
  		req = container_of(dev->tx_reqs.next, struct usb_request,
  				list);
  		list_del(&req->list);
  		printer_req_free(dev->in_ep, req);
  	}
  
  	if (dev->current_rx_req != NULL)
  		printer_req_free(dev->out_ep, dev->current_rx_req);
  
  	while (!list_empty(&dev->rx_reqs)) {
  		req = container_of(dev->rx_reqs.next,
  				struct usb_request, list);
  		list_del(&req->list);
  		printer_req_free(dev->out_ep, req);
  	}
  
  	while (!list_empty(&dev->rx_buffers)) {
  		req = container_of(dev->rx_buffers.next,
  				struct usb_request, list);
  		list_del(&req->list);
  		printer_req_free(dev->out_ep, req);
  	}
  	usb_free_all_descriptors(f);
  }
  
  static struct usb_function *gprinter_alloc(struct usb_function_instance *fi)
  {
  	struct printer_dev	*dev;
  	struct f_printer_opts	*opts;
  
  	opts = container_of(fi, struct f_printer_opts, func_inst);
  
  	mutex_lock(&opts->lock);
  	if (opts->minor >= minors) {
  		mutex_unlock(&opts->lock);
  		return ERR_PTR(-ENOENT);
  	}
  
  	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
  	if (!dev) {
  		mutex_unlock(&opts->lock);
  		return ERR_PTR(-ENOMEM);
  	}
  
  	++opts->refcnt;
  	dev->minor = opts->minor;
  	dev->pnp_string = opts->pnp_string;
  	dev->q_len = opts->q_len;
  	mutex_unlock(&opts->lock);
  
  	dev->function.name = "printer";
  	dev->function.bind = printer_func_bind;
  	dev->function.setup = printer_func_setup;
  	dev->function.unbind = printer_func_unbind;
  	dev->function.set_alt = printer_func_set_alt;
  	dev->function.disable = printer_func_disable;
  	dev->function.req_match = gprinter_req_match;
  	dev->function.free_func = gprinter_free;
  
  	INIT_LIST_HEAD(&dev->tx_reqs);
  	INIT_LIST_HEAD(&dev->rx_reqs);
  	INIT_LIST_HEAD(&dev->rx_buffers);
  	INIT_LIST_HEAD(&dev->tx_reqs_active);
  	INIT_LIST_HEAD(&dev->rx_reqs_active);
  
  	spin_lock_init(&dev->lock);
  	mutex_init(&dev->lock_printer_io);
  	init_waitqueue_head(&dev->rx_wait);
  	init_waitqueue_head(&dev->tx_wait);
  	init_waitqueue_head(&dev->tx_flush_wait);
  
  	dev->interface = -1;
  	dev->printer_cdev_open = 0;
  	dev->printer_status = PRINTER_NOT_ERROR;
  	dev->current_rx_req = NULL;
  	dev->current_rx_bytes = 0;
  	dev->current_rx_buf = NULL;
  
  	return &dev->function;
  }
  
  DECLARE_USB_FUNCTION_INIT(printer, gprinter_alloc_inst, gprinter_alloc);
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Craig Nadler");
  
  static int gprinter_setup(int count)
  {
  	int status;
  	dev_t devt;
  
  	usb_gadget_class = class_create(THIS_MODULE, "usb_printer_gadget");
  	if (IS_ERR(usb_gadget_class)) {
  		status = PTR_ERR(usb_gadget_class);
  		usb_gadget_class = NULL;
  		pr_err("unable to create usb_gadget class %d\n", status);
  		return status;
  	}
  
  	status = alloc_chrdev_region(&devt, 0, count, "USB printer gadget");
  	if (status) {
  		pr_err("alloc_chrdev_region %d\n", status);
  		class_destroy(usb_gadget_class);
  		usb_gadget_class = NULL;
  		return status;
  	}
  
  	major = MAJOR(devt);
  	minors = count;
  
  	return status;
  }
  
  static void gprinter_cleanup(void)
  {
  	if (major) {
  		unregister_chrdev_region(MKDEV(major, 0), minors);
  		major = minors = 0;
  	}
  	class_destroy(usb_gadget_class);
  	usb_gadget_class = NULL;
  }
  