// SPDX-License-Identifier: GPL-2.0+
/*
 * adutux - driver for ADU devices from Ontrak Control Systems
 * This is an experimental driver. Use at your own risk.
 * This driver is not supported by Ontrak Control Systems.
 *
 * Copyright (c) 2003 John Homppi (SCO, leave this notice here)
 *
 * derived from the Lego USB Tower driver 0.56:
 * Copyright (c) 2003 David Glance <davidgsf@sourceforge.net>
 *               2001 Juergen Stuber <stuber@loria.fr>
 * that was derived from USB Skeleton driver - 0.5
 * Copyright (c) 2001 Greg Kroah-Hartman (greg@kroah.com)
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/sched/signal.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/usb.h>
#include <linux/mutex.h>
#include <linux/uaccess.h>

#define DRIVER_AUTHOR "John Homppi"
#define DRIVER_DESC "adutux (see www.ontrak.net)"

/* Define these values to match your device */
#define ADU_VENDOR_ID 0x0a07
#define ADU_PRODUCT_ID 0x0064

/* table of devices that work with this driver */
static const struct usb_device_id device_table[] = {
        { USB_DEVICE(ADU_VENDOR_ID, ADU_PRODUCT_ID) },          /* ADU100 */
        { USB_DEVICE(ADU_VENDOR_ID, ADU_PRODUCT_ID+20) },       /* ADU120 */
        { USB_DEVICE(ADU_VENDOR_ID, ADU_PRODUCT_ID+30) },       /* ADU130 */
        { USB_DEVICE(ADU_VENDOR_ID, ADU_PRODUCT_ID+100) },      /* ADU200 */
        { USB_DEVICE(ADU_VENDOR_ID, ADU_PRODUCT_ID+108) },      /* ADU208 */
        { USB_DEVICE(ADU_VENDOR_ID, ADU_PRODUCT_ID+118) },      /* ADU218 */
        { } /* Terminating entry */
};

MODULE_DEVICE_TABLE(usb, device_table);

#ifdef CONFIG_USB_DYNAMIC_MINORS
#define ADU_MINOR_BASE  0
#else
#define ADU_MINOR_BASE  67
#endif

/* we can have up to this number of device plugged in at once */
#define MAX_DEVICES     16

#define COMMAND_TIMEOUT (2*HZ)

/*
 * The locking scheme is a vanilla 3-lock:
 *   adu_device.buflock: A spinlock, covers what IRQs touch.
 *   adutux_mutex:       A Static lock to cover open_count. It would also cover
 *                       any globals, but we don't have them in 2.6.
 *   adu_device.mtx:     A mutex to hold across sleepers like copy_from_user.
 *                       It covers all of adu_device, except the open_count
 *                       and what .buflock covers.
 */

/* Structure to hold all of our device specific stuff */
struct adu_device {
        struct mutex            mtx;
        struct usb_device *udev; /* save off the usb device pointer */
        struct usb_interface *interface;
        unsigned int            minor; /* the starting minor number for this device */
        char                    serial_number[8];

        int                     open_count; /* number of times this port has been opened */

        char            *read_buffer_primary;
        int                     read_buffer_length;
        char            *read_buffer_secondary;
        int                     secondary_head;
        int                     secondary_tail;
        spinlock_t              buflock;

        wait_queue_head_t       read_wait;
        wait_queue_head_t       write_wait;

        char            *interrupt_in_buffer;
        struct usb_endpoint_descriptor *interrupt_in_endpoint;
        struct urb      *interrupt_in_urb;
        int                     read_urb_finished;

        char            *interrupt_out_buffer;
        struct usb_endpoint_descriptor *interrupt_out_endpoint;
        struct urb      *interrupt_out_urb;
        int                     out_urb_finished;
};

static DEFINE_MUTEX(adutux_mutex);

static struct usb_driver adu_driver;

static inline void adu_debug_data(struct device *dev, const char *function,
                                  int size, const unsigned char *data)
{
        dev_dbg(dev, "%s - length = %d, data = %*ph\n",
                function, size, size, data);
}

/**
 * adu_abort_transfers
 *      aborts transfers and frees associated data structures
 */
static void adu_abort_transfers(struct adu_device *dev)
{
        unsigned long flags;

        if (dev->udev == NULL)
                return;

        /* shutdown transfer */

        /* XXX Anchor these instead */
        spin_lock_irqsave(&dev->buflock, flags);
        if (!dev->read_urb_finished) {
                spin_unlock_irqrestore(&dev->buflock, flags);
                usb_kill_urb(dev->interrupt_in_urb);
        } else
                spin_unlock_irqrestore(&dev->buflock, flags);

        spin_lock_irqsave(&dev->buflock, flags);
        if (!dev->out_urb_finished) {
                spin_unlock_irqrestore(&dev->buflock, flags);
                wait_event_timeout(dev->write_wait, dev->out_urb_finished,
                        COMMAND_TIMEOUT);
                usb_kill_urb(dev->interrupt_out_urb);
        } else
                spin_unlock_irqrestore(&dev->buflock, flags);
}

static void adu_delete(struct adu_device *dev)
{
        /* free data structures */
        usb_free_urb(dev->interrupt_in_urb);
        usb_free_urb(dev->interrupt_out_urb);
        kfree(dev->read_buffer_primary);
        kfree(dev->read_buffer_secondary);
        kfree(dev->interrupt_in_buffer);
        kfree(dev->interrupt_out_buffer);
        kfree(dev);
}

static void adu_interrupt_in_callback(struct urb *urb)
{
        struct adu_device *dev = urb->context;
        int status = urb->status;
        unsigned long flags;

        adu_debug_data(&dev->udev->dev, __func__,
                       urb->actual_length, urb->transfer_buffer);

        spin_lock_irqsave(&dev->buflock, flags);

        if (status != 0) {
                if ((status != -ENOENT) && (status != -ECONNRESET) &&
                        (status != -ESHUTDOWN)) {
                        dev_dbg(&dev->udev->dev,
                                "%s : nonzero status received: %d\n",
                                __func__, status);
                }
                goto exit;
        }

        if (urb->actual_length > 0 && dev->interrupt_in_buffer[0] != 0x00) {
                if (dev->read_buffer_length <
                    (4 * usb_endpoint_maxp(dev->interrupt_in_endpoint)) -
                     (urb->actual_length)) {
                        memcpy (dev->read_buffer_primary +
                                dev->read_buffer_length,
                                dev->interrupt_in_buffer, urb->actual_length);

                        dev->read_buffer_length += urb->actual_length;
                        dev_dbg(&dev->udev->dev,"%s reading  %d\n", __func__,
                                urb->actual_length);
                } else {
                        dev_dbg(&dev->udev->dev,"%s : read_buffer overflow\n",
                                __func__);
                }
        }

exit:
        dev->read_urb_finished = 1;
        spin_unlock_irqrestore(&dev->buflock, flags);
        /* always wake up so we recover from errors */
        wake_up_interruptible(&dev->read_wait);
}

static void adu_interrupt_out_callback(struct urb *urb)
{
        struct adu_device *dev = urb->context;
        int status = urb->status;
        unsigned long flags;

        adu_debug_data(&dev->udev->dev, __func__,
                       urb->actual_length, urb->transfer_buffer);

        if (status != 0) {
                if ((status != -ENOENT) &&
                    (status != -ECONNRESET)) {
                        dev_dbg(&dev->udev->dev,
                                "%s :nonzero status received: %d\n", __func__,
                                status);
                }
                return;
        }

        spin_lock_irqsave(&dev->buflock, flags);
        dev->out_urb_finished = 1;
        wake_up(&dev->write_wait);
        spin_unlock_irqrestore(&dev->buflock, flags);
}

static int adu_open(struct inode *inode, struct file *file)
{
        struct adu_device *dev = NULL;
        struct usb_interface *interface;
        int subminor;
        int retval;

        subminor = iminor(inode);

        retval = mutex_lock_interruptible(&adutux_mutex);
        if (retval)
                goto exit_no_lock;

        interface = usb_find_interface(&adu_driver, subminor);
        if (!interface) {
                pr_err("%s - error, can't find device for minor %d\n",
                       __func__, subminor);
                retval = -ENODEV;
                goto exit_no_device;
        }

        dev = usb_get_intfdata(interface);
        if (!dev || !dev->udev) {
                retval = -ENODEV;
                goto exit_no_device;
        }

        /* check that nobody else is using the device */
        if (dev->open_count) {
                retval = -EBUSY;
                goto exit_no_device;
        }

        ++dev->open_count;
        dev_dbg(&dev->udev->dev, "%s: open count %d\n", __func__,
                dev->open_count);

        /* save device in the file's private structure */
        file->private_data = dev;

        /* initialize in direction */
        dev->read_buffer_length = 0;

        /* fixup first read by having urb waiting for it */
        usb_fill_int_urb(dev->interrupt_in_urb, dev->udev,
                         usb_rcvintpipe(dev->udev,
                                        dev->interrupt_in_endpoint->bEndpointAddress),
                         dev->interrupt_in_buffer,
                         usb_endpoint_maxp(dev->interrupt_in_endpoint),
                         adu_interrupt_in_callback, dev,
                         dev->interrupt_in_endpoint->bInterval);
        dev->read_urb_finished = 0;
        if (usb_submit_urb(dev->interrupt_in_urb, GFP_KERNEL))
                dev->read_urb_finished = 1;
        /* we ignore failure */
        /* end of fixup for first read */

        /* initialize out direction */
        dev->out_urb_finished = 1;

        retval = 0;

exit_no_device:
        mutex_unlock(&adutux_mutex);
exit_no_lock:
        return retval;
}

static void adu_release_internal(struct adu_device *dev)
{
        /* decrement our usage count for the device */
        --dev->open_count;
        dev_dbg(&dev->udev->dev, "%s : open count %d\n", __func__,
                dev->open_count);
        if (dev->open_count <= 0) {
                adu_abort_transfers(dev);
                dev->open_count = 0;
        }
}

static int adu_release(struct inode *inode, struct file *file)
{
        struct adu_device *dev;
        int retval = 0;

        if (file == NULL) {
                retval = -ENODEV;
                goto exit;
        }

        dev = file->private_data;
        if (dev == NULL) {
                retval = -ENODEV;
                goto exit;
        }

        mutex_lock(&adutux_mutex); /* not interruptible */

        if (dev->open_count <= 0) {
                dev_dbg(&dev->udev->dev, "%s : device not opened\n", __func__);
                retval = -ENODEV;
                goto unlock;
        }

        adu_release_internal(dev);
        if (dev->udev == NULL) {
                /* the device was unplugged before the file was released */
                if (!dev->open_count)   /* ... and we're the last user */
                        adu_delete(dev);
        }
unlock:
        mutex_unlock(&adutux_mutex);
exit:
        return retval;
}

static ssize_t adu_read(struct file *file, __user char *buffer, size_t count,
                        loff_t *ppos)
{
        struct adu_device *dev;
        size_t bytes_read = 0;
        size_t bytes_to_read = count;
        int i;
        int retval = 0;
        int timeout = 0;
        int should_submit = 0;
        unsigned long flags;
        DECLARE_WAITQUEUE(wait, current);

        dev = file->private_data;
        if (mutex_lock_interruptible(&dev->mtx))
                return -ERESTARTSYS;

        /* verify that the device wasn't unplugged */
        if (dev->udev == NULL) {
                retval = -ENODEV;
                pr_err("No device or device unplugged %d\n", retval);
                goto exit;
        }

        /* verify that some data was requested */
        if (count == 0) {
                dev_dbg(&dev->udev->dev, "%s : read request of 0 bytes\n",
                        __func__);
                goto exit;
        }

        timeout = COMMAND_TIMEOUT;
        dev_dbg(&dev->udev->dev, "%s : about to start looping\n", __func__);
        while (bytes_to_read) {
                int data_in_secondary = dev->secondary_tail - dev->secondary_head;
                dev_dbg(&dev->udev->dev,
                        "%s : while, data_in_secondary=%d, status=%d\n",
                        __func__, data_in_secondary,
                        dev->interrupt_in_urb->status);

                if (data_in_secondary) {
                        /* drain secondary buffer */
                        int amount = bytes_to_read < data_in_secondary ? bytes_to_read : data_in_secondary;
                        i = copy_to_user(buffer, dev->read_buffer_secondary+dev->secondary_head, amount);
                        if (i) {
                                retval = -EFAULT;
                                goto exit;
                        }
                        dev->secondary_head += (amount - i);
                        bytes_read += (amount - i);
                        bytes_to_read -= (amount - i);
                } else {
                        /* we check the primary buffer */
                        spin_lock_irqsave (&dev->buflock, flags);
                        if (dev->read_buffer_length) {
                                /* we secure access to the primary */
                                char *tmp;
                                dev_dbg(&dev->udev->dev,
                                        "%s : swap, read_buffer_length = %d\n",
                                        __func__, dev->read_buffer_length);
                                tmp = dev->read_buffer_secondary;
                                dev->read_buffer_secondary = dev->read_buffer_primary;
                                dev->read_buffer_primary = tmp;
                                dev->secondary_head = 0;
                                dev->secondary_tail = dev->read_buffer_length;
                                dev->read_buffer_length = 0;
                                spin_unlock_irqrestore(&dev->buflock, flags);
                                /* we have a free buffer so use it */
                                should_submit = 1;
                        } else {
                                /* even the primary was empty - we may need to do IO */
                                if (!dev->read_urb_finished) {
                                        /* somebody is doing IO */
                                        spin_unlock_irqrestore(&dev->buflock, flags);
                                        dev_dbg(&dev->udev->dev,
                                                "%s : submitted already\n",
                                                __func__);
                                } else {
                                        /* we must initiate input */
                                        dev_dbg(&dev->udev->dev,
                                                "%s : initiate input\n",
                                                __func__);
                                        dev->read_urb_finished = 0;
                                        spin_unlock_irqrestore(&dev->buflock, flags);

                                        usb_fill_int_urb(dev->interrupt_in_urb, dev->udev,
                                                        usb_rcvintpipe(dev->udev,
                                                                dev->interrupt_in_endpoint->bEndpointAddress),
                                                         dev->interrupt_in_buffer,
                                                         usb_endpoint_maxp(dev->interrupt_in_endpoint),
                                                         adu_interrupt_in_callback,
                                                         dev,
                                                         dev->interrupt_in_endpoint->bInterval);
                                        retval = usb_submit_urb(dev->interrupt_in_urb, GFP_KERNEL);
                                        if (retval) {
                                                dev->read_urb_finished = 1;
                                                if (retval == -ENOMEM) {
                                                        retval = bytes_read ? bytes_read : -ENOMEM;
                                                }
                                                dev_dbg(&dev->udev->dev,
                                                        "%s : submit failed\n",
                                                        __func__);
                                                goto exit;
                                        }
                                }

                                /* we wait for I/O to complete */
                                set_current_state(TASK_INTERRUPTIBLE);
                                add_wait_queue(&dev->read_wait, &wait);
                                spin_lock_irqsave(&dev->buflock, flags);
                                if (!dev->read_urb_finished) {
                                        spin_unlock_irqrestore(&dev->buflock, flags);
                                        timeout = schedule_timeout(COMMAND_TIMEOUT);
                                } else {
                                        spin_unlock_irqrestore(&dev->buflock, flags);
                                        set_current_state(TASK_RUNNING);
                                }
                                remove_wait_queue(&dev->read_wait, &wait);

                                if (timeout <= 0) {
                                        dev_dbg(&dev->udev->dev,
                                                "%s : timeout\n", __func__);
                                        retval = bytes_read ? bytes_read : -ETIMEDOUT;
                                        goto exit;
                                }

                                if (signal_pending(current)) {
                                        dev_dbg(&dev->udev->dev,
                                                "%s : signal pending\n",
                                                __func__);
                                        retval = bytes_read ? bytes_read : -EINTR;
                                        goto exit;
                                }
                        }
                }
        }

        retval = bytes_read;
        /* if the primary buffer is empty then use it */
        spin_lock_irqsave(&dev->buflock, flags);
        if (should_submit && dev->read_urb_finished) {
                dev->read_urb_finished = 0;
                spin_unlock_irqrestore(&dev->buflock, flags);
                usb_fill_int_urb(dev->interrupt_in_urb, dev->udev,
                                 usb_rcvintpipe(dev->udev,
                                        dev->interrupt_in_endpoint->bEndpointAddress),
                                dev->interrupt_in_buffer,
                                usb_endpoint_maxp(dev->interrupt_in_endpoint),
                                adu_interrupt_in_callback,
                                dev,
                                dev->interrupt_in_endpoint->bInterval);
                if (usb_submit_urb(dev->interrupt_in_urb, GFP_KERNEL) != 0)
                        dev->read_urb_finished = 1;
                /* we ignore failure */
        } else {
                spin_unlock_irqrestore(&dev->buflock, flags);
        }

exit:
        /* unlock the device */
        mutex_unlock(&dev->mtx);

        return retval;
}

static ssize_t adu_write(struct file *file, const __user char *buffer,
                         size_t count, loff_t *ppos)
{
        DECLARE_WAITQUEUE(waita, current);
        struct adu_device *dev;
        size_t bytes_written = 0;
        size_t bytes_to_write;
        size_t buffer_size;
        unsigned long flags;
        int retval;

        dev = file->private_data;

        retval = mutex_lock_interruptible(&dev->mtx);
        if (retval)
                goto exit_nolock;

        /* verify that the device wasn't unplugged */
        if (dev->udev == NULL) {
                retval = -ENODEV;
                pr_err("No device or device unplugged %d\n", retval);
                goto exit;
        }

        /* verify that we actually have some data to write */
        if (count == 0) {
                dev_dbg(&dev->udev->dev, "%s : write request of 0 bytes\n",
                        __func__);
                goto exit;
        }

        while (count > 0) {
                add_wait_queue(&dev->write_wait, &waita);
                set_current_state(TASK_INTERRUPTIBLE);
                spin_lock_irqsave(&dev->buflock, flags);
                if (!dev->out_urb_finished) {
                        spin_unlock_irqrestore(&dev->buflock, flags);

                        mutex_unlock(&dev->mtx);
                        if (signal_pending(current)) {
                                dev_dbg(&dev->udev->dev, "%s : interrupted\n",
                                        __func__);
                                set_current_state(TASK_RUNNING);
                                retval = -EINTR;
                                goto exit_onqueue;
                        }
                        if (schedule_timeout(COMMAND_TIMEOUT) == 0) {
                                dev_dbg(&dev->udev->dev,
                                        "%s - command timed out.\n", __func__);
                                retval = -ETIMEDOUT;
                                goto exit_onqueue;
                        }
                        remove_wait_queue(&dev->write_wait, &waita);
                        retval = mutex_lock_interruptible(&dev->mtx);
                        if (retval) {
                                retval = bytes_written ? bytes_written : retval;
                                goto exit_nolock;
                        }

                        dev_dbg(&dev->udev->dev,
                                "%s : in progress, count = %zd\n",
                                __func__, count);
                } else {
                        spin_unlock_irqrestore(&dev->buflock, flags);
                        set_current_state(TASK_RUNNING);
                        remove_wait_queue(&dev->write_wait, &waita);
                        dev_dbg(&dev->udev->dev, "%s : sending, count = %zd\n",
                                __func__, count);

                        /* write the data into interrupt_out_buffer from userspace */
                        buffer_size = usb_endpoint_maxp(dev->interrupt_out_endpoint);
                        bytes_to_write = count > buffer_size ? buffer_size : count;
                        dev_dbg(&dev->udev->dev,
                                "%s : buffer_size = %zd, count = %zd, bytes_to_write = %zd\n",
                                __func__, buffer_size, count, bytes_to_write);

                        if (copy_from_user(dev->interrupt_out_buffer, buffer, bytes_to_write) != 0) {
                                retval = -EFAULT;
                                goto exit;
                        }

                        /* send off the urb */
                        usb_fill_int_urb(
                                dev->interrupt_out_urb,
                                dev->udev,
                                usb_sndintpipe(dev->udev, dev->interrupt_out_endpoint->bEndpointAddress),
                                dev->interrupt_out_buffer,
                                bytes_to_write,
                                adu_interrupt_out_callback,
                                dev,
                                dev->interrupt_out_endpoint->bInterval);
                        dev->interrupt_out_urb->actual_length = bytes_to_write;
                        dev->out_urb_finished = 0;
                        retval = usb_submit_urb(dev->interrupt_out_urb, GFP_KERNEL);
                        if (retval < 0) {
                                dev->out_urb_finished = 1;
                                dev_err(&dev->udev->dev, "Couldn't submit "
                                        "interrupt_out_urb %d\n", retval);
                                goto exit;
                        }

                        buffer += bytes_to_write;
                        count -= bytes_to_write;

                        bytes_written += bytes_to_write;
                }
        }
        mutex_unlock(&dev->mtx);
        return bytes_written;

exit:
        mutex_unlock(&dev->mtx);
exit_nolock:
        return retval;

exit_onqueue:
        remove_wait_queue(&dev->write_wait, &waita);
        return retval;
}

/* file operations needed when we register this driver */
static const struct file_operations adu_fops = {
        .owner = THIS_MODULE,
        .read  = adu_read,
        .write = adu_write,
        .open = adu_open,
        .release = adu_release,
        .llseek = noop_llseek,
};

/*
 * usb class driver info in order to get a minor number from the usb core,
 * and to have the device registered with devfs and the driver core
 */
static struct usb_class_driver adu_class = {
        .name = "usb/adutux%d",
        .fops = &adu_fops,
        .minor_base = ADU_MINOR_BASE,
};

/**
 * adu_probe
 *
 * Called by the usb core when a new device is connected that it thinks
 * this driver might be interested in.
 */
static int adu_probe(struct usb_interface *interface,
                     const struct usb_device_id *id)
{
        struct usb_device *udev = interface_to_usbdev(interface);
        struct adu_device *dev = NULL;
        int retval = -ENOMEM;
        int in_end_size;
        int out_end_size;
        int res;

        /* allocate memory for our device state and initialize it */
        dev = kzalloc(sizeof(struct adu_device), GFP_KERNEL);
        if (!dev)
                return -ENOMEM;

        mutex_init(&dev->mtx);
        spin_lock_init(&dev->buflock);
        dev->udev = udev;
        init_waitqueue_head(&dev->read_wait);
        init_waitqueue_head(&dev->write_wait);

        res = usb_find_common_endpoints_reverse(&interface->altsetting[0],
                        NULL, NULL,
                        &dev->interrupt_in_endpoint,
                        &dev->interrupt_out_endpoint);
        if (res) {
                dev_err(&interface->dev, "interrupt endpoints not found\n");
                retval = res;
                goto error;
        }

        in_end_size = usb_endpoint_maxp(dev->interrupt_in_endpoint);
        out_end_size = usb_endpoint_maxp(dev->interrupt_out_endpoint);

        dev->read_buffer_primary = kmalloc((4 * in_end_size), GFP_KERNEL);
        if (!dev->read_buffer_primary)
                goto error;

        /* debug code prime the buffer */
        memset(dev->read_buffer_primary, 'a', in_end_size);
        memset(dev->read_buffer_primary + in_end_size, 'b', in_end_size);
        memset(dev->read_buffer_primary + (2 * in_end_size), 'c', in_end_size);
        memset(dev->read_buffer_primary + (3 * in_end_size), 'd', in_end_size);

        dev->read_buffer_secondary = kmalloc((4 * in_end_size), GFP_KERNEL);
        if (!dev->read_buffer_secondary)
                goto error;

        /* debug code prime the buffer */
        memset(dev->read_buffer_secondary, 'e', in_end_size);
        memset(dev->read_buffer_secondary + in_end_size, 'f', in_end_size);
        memset(dev->read_buffer_secondary + (2 * in_end_size), 'g', in_end_size);
        memset(dev->read_buffer_secondary + (3 * in_end_size), 'h', in_end_size);

        dev->interrupt_in_buffer = kmalloc(in_end_size, GFP_KERNEL);
        if (!dev->interrupt_in_buffer)
                goto error;

        /* debug code prime the buffer */
        memset(dev->interrupt_in_buffer, 'i', in_end_size);

        dev->interrupt_in_urb = usb_alloc_urb(0, GFP_KERNEL);
        if (!dev->interrupt_in_urb)
                goto error;
        dev->interrupt_out_buffer = kmalloc(out_end_size, GFP_KERNEL);
        if (!dev->interrupt_out_buffer)
                goto error;
        dev->interrupt_out_urb = usb_alloc_urb(0, GFP_KERNEL);
        if (!dev->interrupt_out_urb)
                goto error;

        if (!usb_string(udev, udev->descriptor.iSerialNumber, dev->serial_number,
                        sizeof(dev->serial_number))) {
                dev_err(&interface->dev, "Could not retrieve serial number\n");
                retval = -EIO;
                goto error;
        }
        dev_dbg(&interface->dev,"serial_number=%s", dev->serial_number);

        /* we can register the device now, as it is ready */
        usb_set_intfdata(interface, dev);

        retval = usb_register_dev(interface, &adu_class);

        if (retval) {
                /* something prevented us from registering this driver */
                dev_err(&interface->dev, "Not able to get a minor for this device.\n");
                usb_set_intfdata(interface, NULL);
                goto error;
        }

        dev->minor = interface->minor;

        /* let the user know what node this device is now attached to */
        dev_info(&interface->dev, "ADU%d %s now attached to /dev/usb/adutux%d\n",
                 le16_to_cpu(udev->descriptor.idProduct), dev->serial_number,
                 (dev->minor - ADU_MINOR_BASE));

        return 0;

error:
        adu_delete(dev);
        return retval;
}

/**
 * adu_disconnect
 *
 * Called by the usb core when the device is removed from the system.
 */
static void adu_disconnect(struct usb_interface *interface)
{
        struct adu_device *dev;

        dev = usb_get_intfdata(interface);

        mutex_lock(&dev->mtx);  /* not interruptible */
        dev->udev = NULL;       /* poison */
        usb_deregister_dev(interface, &adu_class);
        mutex_unlock(&dev->mtx);

        mutex_lock(&adutux_mutex);
        usb_set_intfdata(interface, NULL);

        /* if the device is not opened, then we clean up right now */
        if (!dev->open_count)
                adu_delete(dev);

        mutex_unlock(&adutux_mutex);
}

/* usb specific object needed to register this driver with the usb subsystem */
static struct usb_driver adu_driver = {
        .name = "adutux",
        .probe = adu_probe,
        .disconnect = adu_disconnect,
        .id_table = device_table,
};

module_usb_driver(adu_driver);

MODULE_AUTHOR(DRIVER_AUTHOR);
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_LICENSE("GPL");