alphatrack.c

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/*
 * Frontier Designs Alphatrack driver
 *
 * Copyright (C) 2007 Michael Taht ([email protected])
 *
 * Based on the usbled driver and ldusb drivers by
 *
 * Copyright (C) 2004 Greg Kroah-Hartman ([email protected])
 * Copyright (C) 2005 Michael Hund <[email protected]>
 *
 * The ldusb driver was, in turn, derived from Lego USB Tower driver
 * Copyright (C) 2003 David Glance <[email protected]>
 *       2001-2004 Juergen Stuber <[email protected]>
 *
 *  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, version 2.
 *
 */

/* Note: this currently uses a dumb ringbuffer for reads and writes.
 * A more optimal driver would cache and kill off outstanding urbs that are
 * now invalid, and ignore ones that already were in the queue but valid
 * as we only have 30 commands for the alphatrack. In particular this is
 * key for getting lights to flash in time as otherwise many commands
 * can be buffered up before the light change makes it to the interface.
*/

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/kobject.h>
#include <linux/mutex.h>

#include <linux/uaccess.h>
#include <linux/input.h>
#include <linux/usb.h>
#include <linux/poll.h>

#include "alphatrack.h"

#define VENDOR_ID   0x165b
#define PRODUCT_ID  0xfad1

#ifdef CONFIG_USB_DYNAMIC_MINORS
#define USB_ALPHATRACK_MINOR_BASE   0
#else
/* FIXME 176 - is another driver's minor - apply for that */
#define USB_ALPHATRACK_MINOR_BASE   176
#endif

/* table of devices that work with this driver */
static const struct usb_device_id usb_alphatrack_table[] = {
    {USB_DEVICE(VENDOR_ID, PRODUCT_ID)},
    {}          /* Terminating entry */
};

MODULE_DEVICE_TABLE(usb, usb_alphatrack_table);
MODULE_VERSION("0.41");
MODULE_AUTHOR("Mike Taht <[email protected]>");
MODULE_DESCRIPTION("Alphatrack USB Driver");
MODULE_LICENSE("GPL");
MODULE_SUPPORTED_DEVICE("Frontier Designs Alphatrack Control Surface");

/* These aren't done yet */

#define SUPPRESS_EXTRA_ONLINE_EVENTS 0
#define BUFFERED_WRITES 0
#define SUPPRESS_EXTRA_OFFLINE_EVENTS 0
#define COMPRESS_FADER_EVENTS 0

#define BUFFERED_READS 1
#define RING_BUFFER_SIZE 512
#define WRITE_BUFFER_SIZE 34
#define ALPHATRACK_USB_TIMEOUT 10
#define OUTPUT_CMD_SIZE 8
#define INPUT_CMD_SIZE 12
#define ALPHATRACK_DEBUG 0

static int debug = ALPHATRACK_DEBUG;

/* Use our own dbg macro */
#define dbg_info(dev, format, arg...) do \
    { if (debug) dev_info(dev , format , ## arg); } while (0)

#define alphatrack_ocmd_info(dev, cmd, format, arg...)

#define alphatrack_icmd_info(dev, cmd, format, arg...)

/* Module parameters */

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

/* All interrupt in transfers are collected in a ring buffer to
 * avoid racing conditions and get better performance of the driver.
 */

static int ring_buffer_size = RING_BUFFER_SIZE;

module_param(ring_buffer_size, int, S_IRUGO);
MODULE_PARM_DESC(ring_buffer_size, "Read ring buffer size");

/* The write_buffer can one day contain more than one interrupt out transfer.
 */

static int write_buffer_size = WRITE_BUFFER_SIZE;
module_param(write_buffer_size, int, S_IRUGO);
MODULE_PARM_DESC(write_buffer_size, "Write buffer size");

/*
 * Increase the interval for debugging purposes.
 * or set to 1 to use the standard interval from the endpoint descriptors.
 */

static int min_interrupt_in_interval = ALPHATRACK_USB_TIMEOUT;
module_param(min_interrupt_in_interval, int, 0);
MODULE_PARM_DESC(min_interrupt_in_interval,
         "Minimum interrupt in interval in ms");

static int min_interrupt_out_interval = ALPHATRACK_USB_TIMEOUT;
module_param(min_interrupt_out_interval, int, 0);
MODULE_PARM_DESC(min_interrupt_out_interval,
         "Minimum interrupt out interval in ms");

/* Structure to hold all of our device specific stuff */

struct usb_alphatrack {
    struct mutex mtx;   /* locks this structure */
    struct usb_interface *intf; /* save off the usb interface pointer */
    int open_count;     /* number of times this port has been opened */

    /* make gcc happy */
    struct alphatrack_icmd (*ring_buffer)[RING_BUFFER_SIZE];
    struct alphatrack_ocmd (*write_buffer)[WRITE_BUFFER_SIZE];
    unsigned int ring_head;
    unsigned int ring_tail;

    wait_queue_head_t read_wait;
    wait_queue_head_t write_wait;

    unsigned char *interrupt_in_buffer;
    unsigned char *oldi_buffer;
    struct usb_endpoint_descriptor *interrupt_in_endpoint;
    struct urb *interrupt_in_urb;
    int interrupt_in_interval;
    size_t interrupt_in_endpoint_size;
    int interrupt_in_running;
    int interrupt_in_done;

    char *interrupt_out_buffer;
    struct usb_endpoint_descriptor *interrupt_out_endpoint;
    struct urb *interrupt_out_urb;
    int interrupt_out_interval;
    size_t interrupt_out_endpoint_size;
    int interrupt_out_busy;

    atomic_t writes_pending;
    int event;      /* alternate interface to events */
    int fader;      /* 10 bits */
    int lights;     /* 23 bits */
    unsigned char dump_state;   /* 0 if disabled 1 if enabled */
    unsigned char enable;   /* 0 if disabled 1 if enabled */
    unsigned char offline;  /* if the device is out of range or asleep */
    unsigned char verbose;  /* be verbose in error reporting */
    unsigned char last_cmd[OUTPUT_CMD_SIZE];
    unsigned char screen[32];
};

/* prevent races between open() and disconnect() */
static DEFINE_MUTEX(disconnect_mutex);

/* forward declaration */

static struct usb_driver usb_alphatrack_driver;

static void usb_alphatrack_abort_transfers(struct usb_alphatrack *dev)
{
    /* shutdown transfer */
    if (dev->interrupt_in_running) {
        dev->interrupt_in_running = 0;
        if (dev->intf)
            usb_kill_urb(dev->interrupt_in_urb);
    }
    if (dev->interrupt_out_busy)
        if (dev->intf)
            usb_kill_urb(dev->interrupt_out_urb);
}

static void usb_alphatrack_delete(struct usb_alphatrack *dev)
{
    usb_alphatrack_abort_transfers(dev);
    usb_free_urb(dev->interrupt_in_urb);
    usb_free_urb(dev->interrupt_out_urb);
    kfree(dev->ring_buffer);
    kfree(dev->interrupt_in_buffer);
    kfree(dev->interrupt_out_buffer);
    kfree(dev);     /* fixme oldi_buffer */
}

static void usb_alphatrack_interrupt_in_callback(struct urb *urb)
{
    struct usb_alphatrack *dev = urb->context;
    unsigned int next_ring_head;
    int retval = -1;

    if (urb->status) {
        if (urb->status == -ENOENT ||
            urb->status == -ECONNRESET || urb->status == -ESHUTDOWN) {
            goto exit;
        } else {
            dbg_info(&dev->intf->dev,
                 "%s: nonzero status received: %d\n", __func__,
                 urb->status);
            goto resubmit;  /* maybe we can recover */
        }
    }

    if (urb->actual_length != INPUT_CMD_SIZE) {
        dev_warn(&dev->intf->dev,
             "Urb length was %d bytes!!"
             "Do something intelligent\n", urb->actual_length);
    } else {
        alphatrack_ocmd_info(&dev->intf->dev,
                     &(*dev->ring_buffer)[dev->ring_tail].cmd,
                     "%s", "bla");
        if (memcmp
            (dev->interrupt_in_buffer, dev->oldi_buffer,
             INPUT_CMD_SIZE) == 0) {
            goto resubmit;
        }
        memcpy(dev->oldi_buffer, dev->interrupt_in_buffer,
               INPUT_CMD_SIZE);

#if SUPPRESS_EXTRA_OFFLINE_EVENTS
        if (dev->offline == 2 && dev->interrupt_in_buffer[1] == 0xff)
            goto resubmit;
        if (dev->offline == 1 && dev->interrupt_in_buffer[1] == 0xff) {
            dev->offline = 2;
            goto resubmit;
        }
/* Always pass one offline event up the stack */
        if (dev->offline > 0 && dev->interrupt_in_buffer[1] != 0xff)
            dev->offline = 0;
        if (dev->offline == 0 && dev->interrupt_in_buffer[1] == 0xff)
            dev->offline = 1;
#endif
        dbg_info(&dev->intf->dev, "%s: head, tail are %x, %x\n",
             __func__, dev->ring_head, dev->ring_tail);
        next_ring_head = (dev->ring_head + 1) % ring_buffer_size;

        if (next_ring_head != dev->ring_tail) {
            memcpy(&((*dev->ring_buffer)[dev->ring_head]),
                   dev->interrupt_in_buffer, urb->actual_length);
            dev->ring_head = next_ring_head;
            retval = 0;
            memset(dev->interrupt_in_buffer, 0, urb->actual_length);
        } else {
            dev_warn(&dev->intf->dev,
                 "Ring buffer overflow, %d bytes dropped\n",
                 urb->actual_length);
            memset(dev->interrupt_in_buffer, 0, urb->actual_length);
        }
    }

resubmit:
    /* resubmit if we're still running */
    if (dev->interrupt_in_running && dev->intf) {
        retval = usb_submit_urb(dev->interrupt_in_urb, GFP_ATOMIC);
        if (retval)
            dev_err(&dev->intf->dev,
                "usb_submit_urb failed (%d)\n", retval);
    }

exit:
    dev->interrupt_in_done = 1;
    wake_up_interruptible(&dev->read_wait);
}

static void usb_alphatrack_interrupt_out_callback(struct urb *urb)
{
    struct usb_alphatrack *dev = urb->context;

    /* sync/async unlink faults aren't errors */
    if (urb->status && !(urb->status == -ENOENT ||
                 urb->status == -ECONNRESET ||
                 urb->status == -ESHUTDOWN))
        dbg_info(&dev->intf->dev,
             "%s - nonzero write interrupt status received: %d\n",
             __func__, urb->status);
    atomic_dec(&dev->writes_pending);
    dev->interrupt_out_busy = 0;
    wake_up_interruptible(&dev->write_wait);
}

static int usb_alphatrack_open(struct inode *inode, struct file *file)
{
    struct usb_alphatrack *dev;
    int subminor;
    int retval = 0;
    struct usb_interface *interface;

    nonseekable_open(inode, file);
    subminor = iminor(inode);

    mutex_lock(&disconnect_mutex);

    interface = usb_find_interface(&usb_alphatrack_driver, subminor);

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

    dev = usb_get_intfdata(interface);

    if (!dev) {
        retval = -ENODEV;
        goto unlock_disconnect_exit;
    }

    /* lock this device */
    if (mutex_lock_interruptible(&dev->mtx)) {
        retval = -ERESTARTSYS;
        goto unlock_disconnect_exit;
    }

    /* allow opening only once */
    if (dev->open_count) {
        retval = -EBUSY;
        goto unlock_exit;
    }
    dev->open_count = 1;

    /* initialize in direction */
    dev->ring_head = 0;
    dev->ring_tail = 0;
    usb_fill_int_urb(dev->interrupt_in_urb,
             interface_to_usbdev(interface),
             usb_rcvintpipe(interface_to_usbdev(interface),
                    dev->interrupt_in_endpoint->
                    bEndpointAddress),
             dev->interrupt_in_buffer,
             dev->interrupt_in_endpoint_size,
             usb_alphatrack_interrupt_in_callback, dev,
             dev->interrupt_in_interval);

    dev->interrupt_in_running = 1;
    dev->interrupt_in_done = 0;
    dev->enable = 1;
    dev->offline = 0;

    retval = usb_submit_urb(dev->interrupt_in_urb, GFP_KERNEL);
    if (retval) {
        dev_err(&interface->dev,
            "Couldn't submit interrupt_in_urb %d\n", retval);
        dev->interrupt_in_running = 0;
        dev->open_count = 0;
        goto unlock_exit;
    }

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

unlock_exit:
    mutex_unlock(&dev->mtx);

unlock_disconnect_exit:
    mutex_unlock(&disconnect_mutex);

    return retval;
}

static int usb_alphatrack_release(struct inode *inode, struct file *file)
{
    struct usb_alphatrack *dev;
    int retval = 0;

    dev = file->private_data;

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

    if (mutex_lock_interruptible(&dev->mtx)) {
        retval = -ERESTARTSYS;
        goto exit;
    }

    if (dev->open_count != 1) {
        retval = -ENODEV;
        goto unlock_exit;
    }

    if (dev->intf == NULL) {
        /* the device was unplugged before the file was released */
        mutex_unlock(&dev->mtx);
        /* unlock here as usb_alphatrack_delete frees dev */
        usb_alphatrack_delete(dev);
        retval = -ENODEV;
        goto exit;
    }

    /* wait until write transfer is finished */
    if (dev->interrupt_out_busy)
        wait_event_interruptible_timeout(dev->write_wait,
                         !dev->interrupt_out_busy,
                         2 * HZ);
    usb_alphatrack_abort_transfers(dev);
    dev->open_count = 0;

unlock_exit:
    mutex_unlock(&dev->mtx);

exit:
    return retval;
}

static unsigned int usb_alphatrack_poll(struct file *file, poll_table *wait)
{
    struct usb_alphatrack *dev;
    unsigned int mask = 0;

    dev = file->private_data;

    poll_wait(file, &dev->read_wait, wait);
    poll_wait(file, &dev->write_wait, wait);

    if (dev->ring_head != dev->ring_tail)
        mask |= POLLIN | POLLRDNORM;
    if (!dev->interrupt_out_busy)
        mask |= POLLOUT | POLLWRNORM;

    return mask;
}

static ssize_t usb_alphatrack_read(struct file *file, char __user *buffer,
                   size_t count, loff_t *ppos)
{
    struct usb_alphatrack *dev;
    int retval = 0;

    int c = 0;

    dev = file->private_data;

    /* verify that we actually have some data to read */
    if (count == 0)
        goto exit;

    /* lock this object */
    if (mutex_lock_interruptible(&dev->mtx)) {
        retval = -ERESTARTSYS;
        goto exit;
    }

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

    while (dev->ring_head == dev->ring_tail) {
        if (file->f_flags & O_NONBLOCK) {
            retval = -EAGAIN;
            goto unlock_exit;
        }
        dev->interrupt_in_done = 0;
        retval =
            wait_event_interruptible(dev->read_wait,
                         dev->interrupt_in_done);
        if (retval < 0)
            goto unlock_exit;
    }

    alphatrack_ocmd_info(&dev->intf->dev,
                 &(*dev->ring_buffer)[dev->ring_tail].cmd, "%s",
                 ": copying to userspace");

    c = 0;
    while ((c < count) && (dev->ring_tail != dev->ring_head)) {
        if (copy_to_user
            (&buffer[c], &(*dev->ring_buffer)[dev->ring_tail],
             INPUT_CMD_SIZE)) {
            retval = -EFAULT;
            goto unlock_exit;
        }
        dev->ring_tail = (dev->ring_tail + 1) % ring_buffer_size;
        c += INPUT_CMD_SIZE;
        dbg_info(&dev->intf->dev, "%s: head, tail are %x, %x\n",
             __func__, dev->ring_head, dev->ring_tail);
    }
    retval = c;

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

exit:
    return retval;
}

static ssize_t usb_alphatrack_write(struct file *file,
                    const char __user *buffer, size_t count,
                    loff_t *ppos)
{
    struct usb_alphatrack *dev;
    size_t bytes_to_write;
    int retval = 0;

    dev = file->private_data;

    /* verify that we actually have some data to write */
    if (count == 0)
        goto exit;

    /* lock this object */
    if (mutex_lock_interruptible(&dev->mtx)) {
        retval = -ERESTARTSYS;
        goto exit;
    }

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

    /* wait until previous transfer is finished */
    if (dev->interrupt_out_busy) {
        if (file->f_flags & O_NONBLOCK) {
            retval = -EAGAIN;
            goto unlock_exit;
        }
        retval =
            wait_event_interruptible(dev->write_wait,
                         !dev->interrupt_out_busy);
        if (retval < 0)
            goto unlock_exit;
    }

    /* write the data into interrupt_out_buffer from userspace */
    /* FIXME - if you write more than 12 bytes this breaks */
    bytes_to_write =
        min(count, write_buffer_size * dev->interrupt_out_endpoint_size);
    if (bytes_to_write < count)
        dev_warn(&dev->intf->dev,
             "Write buffer overflow, %zd bytes dropped\n",
             count - bytes_to_write);

    dbg_info(&dev->intf->dev, "%s: count = %zd, bytes_to_write = %zd\n",
         __func__, count, bytes_to_write);

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

    if (dev->interrupt_out_endpoint == NULL) {
        dev_err(&dev->intf->dev, "Endpoint should not be be null!\n");
        goto unlock_exit;
    }

    /* send off the urb */
    usb_fill_int_urb(dev->interrupt_out_urb,
             interface_to_usbdev(dev->intf),
             usb_sndintpipe(interface_to_usbdev(dev->intf),
                    dev->interrupt_out_endpoint->
                    bEndpointAddress),
             dev->interrupt_out_buffer, bytes_to_write,
             usb_alphatrack_interrupt_out_callback, dev,
             dev->interrupt_out_interval);
    dev->interrupt_out_busy = 1;
    atomic_inc(&dev->writes_pending);
    wmb();

    retval = usb_submit_urb(dev->interrupt_out_urb, GFP_KERNEL);
    if (retval) {
        dev->interrupt_out_busy = 0;
        dev_err(&dev->intf->dev,
            "Couldn't submit interrupt_out_urb %d\n", retval);
        atomic_dec(&dev->writes_pending);
        goto unlock_exit;
    }
    retval = bytes_to_write;

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

exit:
    return retval;
}

/* file operations needed when we register this driver */
static const struct file_operations usb_alphatrack_fops = {
    .owner = THIS_MODULE,
    .read = usb_alphatrack_read,
    .write = usb_alphatrack_write,
    .open = usb_alphatrack_open,
    .release = usb_alphatrack_release,
    .poll = usb_alphatrack_poll,
    .llseek = no_llseek,
};

/*
 * usb class driver info in order to get a minor number from the usb core,
 * and to have the device registered with the driver core
 */

static struct usb_class_driver usb_alphatrack_class = {
    .name = "alphatrack%d",
    .fops = &usb_alphatrack_fops,
    .minor_base = USB_ALPHATRACK_MINOR_BASE,
};

static int usb_alphatrack_probe(struct usb_interface *intf,
                const struct usb_device_id *id)
{
    struct usb_device *udev = interface_to_usbdev(intf);
    struct usb_alphatrack *dev = NULL;
    struct usb_host_interface *iface_desc;
    struct usb_endpoint_descriptor *endpoint;
    int i;
    int true_size;
    int retval = -ENOMEM;

    /* allocate memory for our device state and initialize it */

    dev = kzalloc(sizeof(*dev), GFP_KERNEL);
    if (dev == NULL) {
        dev_err(&intf->dev, "Out of memory\n");
        goto exit;
    }
    mutex_init(&dev->mtx);
    dev->intf = intf;
    init_waitqueue_head(&dev->read_wait);
    init_waitqueue_head(&dev->write_wait);

    iface_desc = intf->cur_altsetting;

    /* 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(&intf->dev, "Interrupt in endpoint not found\n");
        goto error;
    }
    if (dev->interrupt_out_endpoint == NULL)
        dev_warn(&intf->dev,
             "Interrupt out endpoint not found"
             "(using control endpoint instead)\n");

    dev->interrupt_in_endpoint_size =
        le16_to_cpu(dev->interrupt_in_endpoint->wMaxPacketSize);

    if (dev->interrupt_in_endpoint_size != 64)
        dev_warn(&intf->dev, "Interrupt in endpoint size is not 64!\n");

    if (ring_buffer_size == 0)
        ring_buffer_size = RING_BUFFER_SIZE;

    true_size = min(ring_buffer_size, RING_BUFFER_SIZE);

    /* FIXME - there are more usb_alloc routines for dma correctness.
       Needed? */
    dev->ring_buffer =
        kmalloc((true_size * sizeof(struct alphatrack_icmd)), GFP_KERNEL);

    if (!dev->ring_buffer) {
        dev_err(&intf->dev,
            "Couldn't allocate input ring_buffer of size %d\n",
            true_size);
        goto error;
    }

    dev->interrupt_in_buffer =
        kmalloc(dev->interrupt_in_endpoint_size, GFP_KERNEL);

    if (!dev->interrupt_in_buffer) {
        dev_err(&intf->dev, "Couldn't allocate interrupt_in_buffer\n");
        goto error;
    }
    dev->oldi_buffer = kmalloc(dev->interrupt_in_endpoint_size, GFP_KERNEL);
    if (!dev->oldi_buffer) {
        dev_err(&intf->dev, "Couldn't allocate old buffer\n");
        goto error;
    }
    dev->interrupt_in_urb = usb_alloc_urb(0, GFP_KERNEL);
    if (!dev->interrupt_in_urb) {
        dev_err(&intf->dev, "Couldn't allocate interrupt_in_urb\n");
        goto error;
    }

    dev->interrupt_out_endpoint_size =
        dev->interrupt_out_endpoint ? le16_to_cpu(dev->
                              interrupt_out_endpoint->
                              wMaxPacketSize) : udev->
        descriptor.bMaxPacketSize0;

    if (dev->interrupt_out_endpoint_size != 64)
        dev_warn(&intf->dev,
             "Interrupt out endpoint size is not 64!)\n");

    if (write_buffer_size == 0)
        write_buffer_size = WRITE_BUFFER_SIZE;
    true_size = min(write_buffer_size, WRITE_BUFFER_SIZE);

    dev->interrupt_out_buffer =
        kmalloc(true_size * dev->interrupt_out_endpoint_size, GFP_KERNEL);

    if (!dev->interrupt_out_buffer) {
        dev_err(&intf->dev, "Couldn't allocate interrupt_out_buffer\n");
        goto error;
    }

    dev->write_buffer =
        kmalloc(true_size * sizeof(struct alphatrack_ocmd), GFP_KERNEL);

    if (!dev->write_buffer) {
        dev_err(&intf->dev, "Couldn't allocate write_buffer\n");
        goto error;
    }

    dev->interrupt_out_urb = usb_alloc_urb(0, GFP_KERNEL);
    if (!dev->interrupt_out_urb) {
        dev_err(&intf->dev, "Couldn't allocate interrupt_out_urb\n");
        goto error;
    }
    dev->interrupt_in_interval =
        min_interrupt_in_interval >
        dev->interrupt_in_endpoint->
        bInterval ? min_interrupt_in_interval : dev->interrupt_in_endpoint->
        bInterval;
    if (dev->interrupt_out_endpoint)
        dev->interrupt_out_interval =
            min_interrupt_out_interval >
            dev->interrupt_out_endpoint->
            bInterval ? min_interrupt_out_interval : dev->
            interrupt_out_endpoint->bInterval;

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

    atomic_set(&dev->writes_pending, 0);
    retval = usb_register_dev(intf, &usb_alphatrack_class);
    if (retval) {
        /* something prevented us from registering this driver */
        dev_err(&intf->dev,
            "Not able to get a minor for this device.\n");
        usb_set_intfdata(intf, NULL);
        goto error;
    }

    /* let the user know what node this device is now attached to */
    dev_info(&intf->dev,
         "Alphatrack Device #%d now attached to major %d minor %d\n",
         (intf->minor - USB_ALPHATRACK_MINOR_BASE), USB_MAJOR,
         intf->minor);

exit:
    return retval;

error:
    usb_alphatrack_delete(dev);

    return retval;
}

static void usb_alphatrack_disconnect(struct usb_interface *intf)
{
    struct usb_alphatrack *dev;
    int minor;

    mutex_lock(&disconnect_mutex);

    dev = usb_get_intfdata(intf);
    usb_set_intfdata(intf, NULL);

    mutex_lock(&dev->mtx);

    minor = intf->minor;

    /* give back our minor */
    usb_deregister_dev(intf, &usb_alphatrack_class);

    /* if the device is not opened, then we clean up right now */
    if (!dev->open_count) {
        mutex_unlock(&dev->mtx);
        usb_alphatrack_delete(dev);
    } else {
        dev->intf = NULL;
        mutex_unlock(&dev->mtx);
    }

    atomic_set(&dev->writes_pending, 0);
    mutex_unlock(&disconnect_mutex);

    dev_info(&intf->dev, "Alphatrack Surface #%d now disconnected\n",
         (minor - USB_ALPHATRACK_MINOR_BASE));
}

/* usb specific object needed to register this driver with the usb subsystem */
static struct usb_driver usb_alphatrack_driver = {
    .name = "alphatrack",
    .probe = usb_alphatrack_probe,
    .disconnect = usb_alphatrack_disconnect,
    .id_table = usb_alphatrack_table,
};

module_usb_driver(usb_alphatrack_driver);