adutux.c

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/*
 * 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)
 *
 * 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.
 *
 * derived from the Lego USB Tower driver 0.56:
 * Copyright (c) 2003 David Glance <[email protected]>
 *               2001 Juergen Stuber <[email protected]>
 * that was derived from USB Skeleton driver - 0.5
 * Copyright (c) 2001 Greg Kroah-Hartman ([email protected])
 *
 */

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/usb.h>
#include <linux/mutex.h>
#include <asm/uaccess.h>

#ifdef CONFIG_USB_DEBUG
static int debug = 5;
#else
static int debug = 1;
#endif

/* Use our own dbg macro */
#undef dbg
#define dbg(lvl, format, arg...)                    \
do {                                    \
    if (debug >= lvl)                       \
        printk(KERN_DEBUG "%s: " format "\n", __FILE__, ##arg); \
} while (0)


/* Version Information */
#define DRIVER_VERSION "v0.0.13"
#define DRIVER_AUTHOR "John Homppi"
#define DRIVER_DESC "adutux (see www.ontrak.net)"

/* Module parameters */
module_param(debug, int, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(debug, "Debug enabled or not");

/* 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)  /* 60 second timeout for a command */

/*
 * 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 void adu_debug_data(int level, const char *function, int size,
               const unsigned char *data)
{
    int i;

    if (debug < level)
        return;

    printk(KERN_DEBUG "%s: %s - length = %d, data = ",
           __FILE__, function, size);
    for (i = 0; i < size; ++i)
        printk("%.2x ", data[i]);
    printk("\n");
}

static void adu_abort_transfers(struct adu_device *dev)
{
    unsigned long flags;

    dbg(2," %s : enter", __func__);

    if (dev->udev == NULL) {
        dbg(1," %s : udev is null", __func__);
        goto exit;
    }

    /* 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);
        usb_kill_urb(dev->interrupt_out_urb);
    } else
        spin_unlock_irqrestore(&dev->buflock, flags);

exit:
    dbg(2," %s : leave", __func__);
}

static void adu_delete(struct adu_device *dev)
{
    dbg(2, "%s enter", __func__);

    /* 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);

    dbg(2, "%s : leave", __func__);
}

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

    dbg(4," %s : enter, status %d", __func__, status);
    adu_debug_data(5, __func__, urb->actual_length,
               urb->transfer_buffer);

    spin_lock(&dev->buflock);

    if (status != 0) {
        if ((status != -ENOENT) && (status != -ECONNRESET) &&
            (status != -ESHUTDOWN)) {
            dbg(1," %s : nonzero status received: %d",
                __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;
            dbg(2," %s reading  %d ", __func__,
                urb->actual_length);
        } else {
            dbg(1," %s : read_buffer overflow", __func__);
        }
    }

exit:
    dev->read_urb_finished = 1;
    spin_unlock(&dev->buflock);
    /* always wake up so we recover from errors */
    wake_up_interruptible(&dev->read_wait);
    adu_debug_data(5, __func__, urb->actual_length,
               urb->transfer_buffer);
    dbg(4," %s : leave, status %d", __func__, status);
}

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

    dbg(4," %s : enter, status %d", __func__, status);
    adu_debug_data(5,__func__, urb->actual_length, urb->transfer_buffer);

    if (status != 0) {
        if ((status != -ENOENT) &&
            (status != -ECONNRESET)) {
            dbg(1, " %s :nonzero status received: %d",
                __func__, status);
        }
        goto exit;
    }

    spin_lock(&dev->buflock);
    dev->out_urb_finished = 1;
    wake_up(&dev->write_wait);
    spin_unlock(&dev->buflock);
exit:

    adu_debug_data(5, __func__, urb->actual_length,
               urb->transfer_buffer);
    dbg(4," %s : leave, status %d", __func__, status);
}

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

    dbg(2,"%s : enter", __func__);

    subminor = iminor(inode);

    if ((retval = mutex_lock_interruptible(&adutux_mutex))) {
        dbg(2, "%s : mutex lock failed", __func__);
        goto exit_no_lock;
    }

    interface = usb_find_interface(&adu_driver, subminor);
    if (!interface) {
        printk(KERN_ERR "adutux: %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;
    dbg(2,"%s : open count %d", __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:
    dbg(2,"%s : leave, return value %d ", __func__, retval);
    return retval;
}

static void adu_release_internal(struct adu_device *dev)
{
    dbg(2," %s : enter", __func__);

    /* decrement our usage count for the device */
    --dev->open_count;
    dbg(2," %s : open count %d", __func__, dev->open_count);
    if (dev->open_count <= 0) {
        adu_abort_transfers(dev);
        dev->open_count = 0;
    }

    dbg(2," %s : leave", __func__);
}

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

    dbg(2," %s : enter", __func__);

    if (file == NULL) {
        dbg(1," %s : file is NULL", __func__);
        retval = -ENODEV;
        goto exit;
    }

    dev = file->private_data;
    if (dev == NULL) {
        dbg(1," %s : object is NULL", __func__);
        retval = -ENODEV;
        goto exit;
    }

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

    if (dev->open_count <= 0) {
        dbg(1," %s : device not opened", __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:
    dbg(2," %s : leave, return value %d", __func__, retval);
    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);

    dbg(2," %s : enter, count = %Zd, file=%p", __func__, count, file);

    dev = file->private_data;
    dbg(2," %s : dev=%p", __func__, dev);

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

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

    /* verify that some data was requested */
    if (count == 0) {
        dbg(1," %s : read request of 0 bytes", __func__);
        goto exit;
    }

    timeout = COMMAND_TIMEOUT;
    dbg(2," %s : about to start looping", __func__);
    while (bytes_to_read) {
        int data_in_secondary = dev->secondary_tail - dev->secondary_head;
        dbg(2," %s : while, data_in_secondary=%d, status=%d",
            __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);
            if (i) {
                retval = bytes_read ? bytes_read : -EFAULT;
                goto exit;
            }
        } 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;
                dbg(2," %s : swap, read_buffer_length = %d",
                    __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);
                    dbg(2," %s : submitted already", __func__);
                } else {
                    /* we must initiate input */
                    dbg(2," %s : initiate input", __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;
                        }
                        dbg(2," %s : submit failed", __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) {
                    dbg(2," %s : timeout", __func__);
                    retval = bytes_read ? bytes_read : -ETIMEDOUT;
                    goto exit;
                }

                if (signal_pending(current)) {
                    dbg(2," %s : signal pending", __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);

    dbg(2," %s : leave, return value %d", __func__, retval);
    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;

    dbg(2," %s : enter, count = %Zd", __func__, count);

    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;
        printk(KERN_ERR "adutux: No device or device unplugged %d\n",
               retval);
        goto exit;
    }

    /* verify that we actually have some data to write */
    if (count == 0) {
        dbg(1," %s : write request of 0 bytes", __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)) {
                dbg(1," %s : interrupted", __func__);
                set_current_state(TASK_RUNNING);
                retval = -EINTR;
                goto exit_onqueue;
            }
            if (schedule_timeout(COMMAND_TIMEOUT) == 0) {
                dbg(1, "%s - command timed out.", __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;
            }

            dbg(4," %s : in progress, count = %Zd", __func__, count);
        } else {
            spin_unlock_irqrestore(&dev->buflock, flags);
            set_current_state(TASK_RUNNING);
            remove_wait_queue(&dev->write_wait, &waita);
            dbg(4," %s : sending, count = %Zd", __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;
            dbg(4," %s : buffer_size = %Zd, count = %Zd, bytes_to_write = %Zd",
                __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:
    dbg(2," %s : leave, return value %d", __func__, retval);
    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,
};

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;
    struct usb_host_interface *iface_desc;
    struct usb_endpoint_descriptor *endpoint;
    int retval = -ENODEV;
    int in_end_size;
    int out_end_size;
    int i;

    dbg(2," %s : enter", __func__);

    if (udev == NULL) {
        dev_err(&interface->dev, "udev is NULL.\n");
        goto exit;
    }

    /* allocate memory for our device state and initialize it */
    dev = kzalloc(sizeof(struct adu_device), GFP_KERNEL);
    if (dev == NULL) {
        dev_err(&interface->dev, "Out of memory\n");
        retval = -ENOMEM;
        goto exit;
    }

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

    iface_desc = &interface->altsetting[0];

    /* set up the endpoint information */
    for (i = 0; i < iface_desc->desc.bNumEndpoints; ++i) {
        endpoint = &iface_desc->endpoint[i].desc;

        if (usb_endpoint_is_int_in(endpoint))
            dev->interrupt_in_endpoint = endpoint;

        if (usb_endpoint_is_int_out(endpoint))
            dev->interrupt_out_endpoint = endpoint;
    }
    if (dev->interrupt_in_endpoint == NULL) {
        dev_err(&interface->dev, "interrupt in endpoint not found\n");
        goto error;
    }
    if (dev->interrupt_out_endpoint == NULL) {
        dev_err(&interface->dev, "interrupt out endpoint not found\n");
        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) {
        dev_err(&interface->dev, "Couldn't allocate read_buffer_primary\n");
        retval = -ENOMEM;
        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) {
        dev_err(&interface->dev, "Couldn't allocate read_buffer_secondary\n");
        retval = -ENOMEM;
        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) {
        dev_err(&interface->dev, "Couldn't allocate interrupt_in_buffer\n");
        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) {
        dev_err(&interface->dev, "Couldn't allocate interrupt_in_urb\n");
        goto error;
    }
    dev->interrupt_out_buffer = kmalloc(out_end_size, GFP_KERNEL);
    if (!dev->interrupt_out_buffer) {
        dev_err(&interface->dev, "Couldn't allocate interrupt_out_buffer\n");
        goto error;
    }
    dev->interrupt_out_urb = usb_alloc_urb(0, GFP_KERNEL);
    if (!dev->interrupt_out_urb) {
        dev_err(&interface->dev, "Couldn't allocate interrupt_out_urb\n");
        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");
        goto error;
    }
    dbg(2," %s : serial_number=%s", __func__, 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",
         udev->descriptor.idProduct, dev->serial_number,
         (dev->minor - ADU_MINOR_BASE));
exit:
    dbg(2," %s : leave, return value %p (dev)", __func__, dev);

    return retval;

error:
    adu_delete(dev);
    return retval;
}

static void adu_disconnect(struct usb_interface *interface)
{
    struct adu_device *dev;
    int minor;

    dbg(2," %s : enter", __func__);

    dev = usb_get_intfdata(interface);

    mutex_lock(&dev->mtx);  /* not interruptible */
    dev->udev = NULL;   /* poison */
    minor = dev->minor;
    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 */
    dbg(2," %s : open count %d", __func__, dev->open_count);
    if (!dev->open_count)
        adu_delete(dev);

    mutex_unlock(&adutux_mutex);

    dev_info(&interface->dev, "ADU device adutux%d now disconnected\n",
         (minor - ADU_MINOR_BASE));

    dbg(2," %s : leave", __func__);
}

/* 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");