[PATCH] USB: add ldusb driver

The following driver provides complete interrupt-in and interrupt-out
reports (raw data) to a user program. Until now it uses the
HIDIOCGDEVINFO ioctl call, because I don't know better :-(. Perhaps, it
will be ok for you - and I will be happy, if you assign 8 minor numbers.

I have tested it in several environments and it works very well for me.
However, it has a problem with two or more devices at the same hub, if
the two or more devices need 1 ms interrupt-in transfers. Unfortunately
more than one interrupt-in transfer every ms isn't possible (ehci
driver?). This is why the min_interrupt_in_interval and
min_interrupt_out_interval are increased to 2 ms (see the corresponding
module parameters). This way, I can use two devices simultaneously at
the same hub.

Signed-off-by: Michael Hund <mhund@ld-didactic.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 794 insertions, 0 deletions

diff --git a/drivers/usb/misc/ldusb.c b/drivers/usb/misc/ldusb.c
new file mode 100644
index 000000000000..66ec88354b93
--- /dev/null
+++ b/drivers/usb/misc/ldusb.c
@@ -0,0 +1,794 @@
+/**
+ * Generic USB driver for report based interrupt in/out devices
+ * like LD Didactic's USB devices. LD Didactic's USB devices are
+ * HID devices which do not use HID report definitons (they use
+ * raw interrupt in and our reports only for communication).
+ *
+ * This driver uses a ring buffer for time critical reading of
+ * interrupt in reports and provides read and write methods for
+ * raw interrupt reports (similar to the Windows HID driver).
+ * Devices based on the book USB COMPLETE by Jan Axelson may need
+ * such a compatibility to the Windows HID driver.
+ *
+ * Copyright (C) 2005 Michael Hund <mhund@ld-didactic.de>
+ *
+ *      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 Lego USB Tower driver
+ * Copyright (C) 2003 David Glance <advidgsf@sourceforge.net>
+ *               2001-2004 Juergen Stuber <starblue@users.sourceforge.net>
+ *
+ * V0.1  (mh) Initial version
+ * V0.11 (mh) Added raw support for HID 1.0 devices (no interrupt out endpoint)
+ */
+
+#include <linux/config.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+
+#include <asm/uaccess.h>
+#include <linux/input.h>
+#include <linux/usb.h>
+#include <linux/poll.h>
+
+/* Define these values to match your devices */
+#define USB_VENDOR_ID_LD                0x0f11  /* USB Vendor ID of LD Didactic GmbH */
+#define USB_DEVICE_ID_CASSY             0x1000  /* USB Product ID for all CASSY-S modules */
+#define USB_DEVICE_ID_POCKETCASSY       0x1010  /* USB Product ID for Pocket-CASSY */
+#define USB_DEVICE_ID_MOBILECASSY       0x1020  /* USB Product ID for Mobile-CASSY */
+#define USB_DEVICE_ID_JWM               0x1080  /* USB Product ID for Joule and Wattmeter */
+#define USB_DEVICE_ID_DMMP              0x1081  /* USB Product ID for Digital Multimeter P (reserved) */
+#define USB_DEVICE_ID_UMIP              0x1090  /* USB Product ID for UMI P */
+#define USB_DEVICE_ID_VIDEOCOM          0x1200  /* USB Product ID for VideoCom */
+#define USB_DEVICE_ID_COM3LAB           0x2000  /* USB Product ID for COM3LAB */
+#define USB_DEVICE_ID_TELEPORT          0x2010  /* USB Product ID for Terminal Adapter */
+#define USB_DEVICE_ID_NETWORKANALYSER   0x2020  /* USB Product ID for Network Analyser */
+#define USB_DEVICE_ID_POWERCONTROL      0x2030  /* USB Product ID for Controlling device for Power Electronics */
+
+#define USB_VENDOR_ID_VERNIER           0x08f7
+#define USB_DEVICE_ID_VERNIER_LABPRO    0x0001
+#define USB_DEVICE_ID_VERNIER_GOTEMP    0x0002
+#define USB_DEVICE_ID_VERNIER_SKIP      0x0003
+#define USB_DEVICE_ID_VERNIER_CYCLOPS   0x0004
+
+
+#ifdef CONFIG_USB_DYNAMIC_MINORS
+#define USB_LD_MINOR_BASE       0
+#else
+#define USB_LD_MINOR_BASE       176
+#endif
+
+/* table of devices that work with this driver */
+static struct usb_device_id ld_usb_table [] = {
+        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_CASSY) },
+        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_POCKETCASSY) },
+        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_MOBILECASSY) },
+        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_JWM) },
+        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_DMMP) },
+        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_UMIP) },
+        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_VIDEOCOM) },
+        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_COM3LAB) },
+        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_TELEPORT) },
+        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_NETWORKANALYSER) },
+        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_POWERCONTROL) },
+        { USB_DEVICE(USB_VENDOR_ID_VERNIER, USB_DEVICE_ID_VERNIER_LABPRO) },
+        { USB_DEVICE(USB_VENDOR_ID_VERNIER, USB_DEVICE_ID_VERNIER_GOTEMP) },
+        { USB_DEVICE(USB_VENDOR_ID_VERNIER, USB_DEVICE_ID_VERNIER_SKIP) },
+        { USB_DEVICE(USB_VENDOR_ID_VERNIER, USB_DEVICE_ID_VERNIER_CYCLOPS) },
+        { }                                     /* Terminating entry */
+};
+MODULE_DEVICE_TABLE(usb, ld_usb_table);
+MODULE_VERSION("V0.11");
+MODULE_AUTHOR("Michael Hund <mhund@ld-didactic.de>");
+MODULE_DESCRIPTION("LD USB Driver");
+MODULE_LICENSE("GPL");
+MODULE_SUPPORTED_DEVICE("LD USB Devices");
+
+#ifdef CONFIG_USB_DEBUG
+        static int debug = 1;
+#else
+        static int debug = 0;
+#endif
+
+/* Use our own dbg macro */
+#define dbg_info(dev, format, arg...) do { if (debug) dev_info(dev , format , ## arg); } while (0)
+
+/* 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 = 128;
+module_param(ring_buffer_size, int, 0);
+MODULE_PARM_DESC(ring_buffer_size, "Read ring buffer size in reports");
+
+/* The write_buffer can contain more than one interrupt out transfer.
+ */
+static int write_buffer_size = 10;
+module_param(write_buffer_size, int, 0);
+MODULE_PARM_DESC(write_buffer_size, "Write buffer size in reports");
+
+/* As of kernel version 2.6.4 ehci-hcd uses an
+ * "only one interrupt transfer per frame" shortcut
+ * to simplify the scheduling of periodic transfers.
+ * This conflicts with our standard 1ms intervals for in and out URBs.
+ * We use default intervals of 2ms for in and 2ms for out transfers,
+ * which should be fast enough.
+ * Increase the interval to allow more devices that do interrupt transfers,
+ * or set to 1 to use the standard interval from the endpoint descriptors.
+ */
+static int min_interrupt_in_interval = 2;
+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 = 2;
+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 ld_usb {
+        struct semaphore        sem;            /* locks this structure */
+        struct usb_interface*   intf;           /* save off the usb interface pointer */
+
+        int                     open_count;     /* number of times this port has been opened */
+
+        char*                   ring_buffer;
+        unsigned int            ring_head;
+        unsigned int            ring_tail;
+
+        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                     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;
+};
+
+/* prevent races between open() and disconnect() */
+static DECLARE_MUTEX(disconnect_sem);
+
+static struct usb_driver ld_usb_driver;
+
+/**
+ *      ld_usb_abort_transfers
+ *      aborts transfers and frees associated data structures
+ */
+static void ld_usb_abort_transfers(struct ld_usb *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);
+}
+
+/**
+ *      ld_usb_delete
+ */
+static void ld_usb_delete(struct ld_usb *dev)
+{
+        ld_usb_abort_transfers(dev);
+
+        /* free data structures */
+        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);
+}
+
+/**
+ *      ld_usb_interrupt_in_callback
+ */
+static void ld_usb_interrupt_in_callback(struct urb *urb, struct pt_regs *regs)
+{
+        struct ld_usb *dev = urb->context;
+        size_t *actual_buffer;
+        unsigned int next_ring_head;
+        int retval;
+
+        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",
+                                 __FUNCTION__, urb->status);
+                        goto resubmit; /* maybe we can recover */
+                }
+        }
+
+        if (urb->actual_length > 0) {
+                next_ring_head = (dev->ring_head+1) % ring_buffer_size;
+                if (next_ring_head != dev->ring_tail) {
+                        actual_buffer = (size_t*)(dev->ring_buffer + dev->ring_head*(sizeof(size_t)+dev->interrupt_in_endpoint_size));
+                        /* actual_buffer gets urb->actual_length + interrupt_in_buffer */
+                        *actual_buffer = urb->actual_length;
+                        memcpy(actual_buffer+1, dev->interrupt_in_buffer, urb->actual_length);
+                        dev->ring_head = next_ring_head;
+                        dbg_info(&dev->intf->dev, "%s: received %d bytes\n",
+                                 __FUNCTION__, urb->actual_length);
+                } else
+                        dev_warn(&dev->intf->dev,
+                                 "Ring buffer overflow, %d bytes dropped\n",
+                                 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);
+}
+
+/**
+ *      ld_usb_interrupt_out_callback
+ */
+static void ld_usb_interrupt_out_callback(struct urb *urb, struct pt_regs *regs)
+{
+        struct ld_usb *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",
+                         __FUNCTION__, urb->status);
+
+        dev->interrupt_out_busy = 0;
+        wake_up_interruptible(&dev->write_wait);
+}
+
+/**
+ *      ld_usb_open
+ */
+static int ld_usb_open(struct inode *inode, struct file *file)
+{
+        struct ld_usb *dev;
+        int subminor;
+        int retval = 0;
+        struct usb_interface *interface;
+
+        nonseekable_open(inode, file);
+        subminor = iminor(inode);
+
+        down(&disconnect_sem);
+
+        interface = usb_find_interface(&ld_usb_driver, subminor);
+
+        if (!interface) {
+                err("%s - error, can't find device for minor %d\n",
+                     __FUNCTION__, subminor);
+                retval = -ENODEV;
+                goto unlock_disconnect_exit;
+        }
+
+        dev = usb_get_intfdata(interface);
+
+        if (!dev) {
+                retval = -ENODEV;
+                goto unlock_disconnect_exit;
+        }
+
+        /* lock this device */
+        if (down_interruptible(&dev->sem)) {
+                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,
+                         ld_usb_interrupt_in_callback,
+                         dev,
+                         dev->interrupt_in_interval);
+
+        dev->interrupt_in_running = 1;
+        dev->interrupt_in_done = 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:
+        up(&dev->sem);
+
+unlock_disconnect_exit:
+        up(&disconnect_sem);
+
+        return retval;
+}
+
+/**
+ *      ld_usb_release
+ */
+static int ld_usb_release(struct inode *inode, struct file *file)
+{
+        struct ld_usb *dev;
+        int retval = 0;
+
+        dev = file->private_data;
+
+        if (dev == NULL) {
+                retval = -ENODEV;
+                goto exit;
+        }
+
+        if (down_interruptible(&dev->sem)) {
+                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 */
+                up(&dev->sem);
+                /* unlock here as ld_usb_delete frees dev */
+                ld_usb_delete(dev);
+                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);
+        ld_usb_abort_transfers(dev);
+        dev->open_count = 0;
+
+unlock_exit:
+        up(&dev->sem);
+
+exit:
+        return retval;
+}
+
+/**
+ *      ld_usb_poll
+ */
+static unsigned int ld_usb_poll(struct file *file, poll_table *wait)
+{
+        struct ld_usb *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;
+}
+
+/**
+ *      ld_usb_read
+ */
+static ssize_t ld_usb_read(struct file *file, char __user *buffer, size_t count,
+                           loff_t *ppos)
+{
+        struct ld_usb *dev;
+        size_t *actual_buffer;
+        size_t bytes_to_read;
+        int retval = 0;
+
+        dev = file->private_data;
+
+        /* verify that we actually have some data to read */
+        if (count == 0)
+                goto exit;
+
+        /* lock this object */
+        if (down_interruptible(&dev->sem)) {
+                retval = -ERESTARTSYS;
+                goto exit;
+        }
+
+        /* verify that the device wasn't unplugged */
+        if (dev->intf == NULL) {
+                retval = -ENODEV;
+                err("No device or device unplugged %d\n", retval);
+                goto unlock_exit;
+        }
+
+        /* wait for data */
+        if (dev->ring_head == dev->ring_tail) {
+                if (file->f_flags & O_NONBLOCK) {
+                        retval = -EAGAIN;
+                        goto unlock_exit;
+                }
+                retval = wait_event_interruptible(dev->read_wait, dev->interrupt_in_done);
+                if (retval < 0)
+                        goto unlock_exit;
+        }
+
+        /* actual_buffer contains actual_length + interrupt_in_buffer */
+        actual_buffer = (size_t*)(dev->ring_buffer + dev->ring_tail*(sizeof(size_t)+dev->interrupt_in_endpoint_size));
+        bytes_to_read = min(count, *actual_buffer);
+        if (bytes_to_read < *actual_buffer)
+                dev_warn(&dev->intf->dev, "Read buffer overflow, %d bytes dropped\n",
+                         *actual_buffer-bytes_to_read);
+
+        /* copy one interrupt_in_buffer from ring_buffer into userspace */
+        if (copy_to_user(buffer, actual_buffer+1, bytes_to_read)) {
+                retval = -EFAULT;
+                goto unlock_exit;
+        }
+        dev->ring_tail = (dev->ring_tail+1) % ring_buffer_size;
+
+        retval = bytes_to_read;
+
+unlock_exit:
+        /* unlock the device */
+        up(&dev->sem);
+
+exit:
+        return retval;
+}
+
+/**
+ *      ld_usb_write
+ */
+static ssize_t ld_usb_write(struct file *file, const char __user *buffer,
+                            size_t count, loff_t *ppos)
+{
+        struct ld_usb *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 (down_interruptible(&dev->sem)) {
+                retval = -ERESTARTSYS;
+                goto exit;
+        }
+
+        /* verify that the device wasn't unplugged */
+        if (dev->intf == NULL) {
+                retval = -ENODEV;
+                err("No device or device unplugged %d\n", 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 */
+        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, %d bytes dropped\n",count-bytes_to_write);
+        dbg_info(&dev->intf->dev, "%s: count = %d, bytes_to_write = %d\n", __FUNCTION__, 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) {
+                /* try HID_REQ_SET_REPORT=9 on control_endpoint instead of interrupt_out_endpoint */
+                retval = usb_control_msg(interface_to_usbdev(dev->intf),
+                                         usb_sndctrlpipe(interface_to_usbdev(dev->intf), 0),
+                                         9,
+                                         USB_TYPE_CLASS | USB_RECIP_INTERFACE | USB_DIR_OUT,
+                                         1 << 8, 0,
+                                         dev->interrupt_out_buffer,
+                                         bytes_to_write,
+                                         USB_CTRL_SET_TIMEOUT * HZ);
+                if (retval < 0)
+                        err("Couldn't submit HID_REQ_SET_REPORT %d\n", retval);
+                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,
+                         ld_usb_interrupt_out_callback,
+                         dev,
+                         dev->interrupt_out_interval);
+
+        dev->interrupt_out_busy = 1;
+        wmb();
+
+        retval = usb_submit_urb(dev->interrupt_out_urb, GFP_KERNEL);
+        if (retval) {
+                dev->interrupt_out_busy = 0;
+                err("Couldn't submit interrupt_out_urb %d\n", retval);
+                goto unlock_exit;
+        }
+        retval = bytes_to_write;
+
+unlock_exit:
+        /* unlock the device */
+        up(&dev->sem);
+
+exit:
+        return retval;
+}
+
+/* file operations needed when we register this driver */
+static struct file_operations ld_usb_fops = {
+        .owner =        THIS_MODULE,
+        .read  =        ld_usb_read,
+        .write =        ld_usb_write,
+        .open =         ld_usb_open,
+        .release =      ld_usb_release,
+        .poll =         ld_usb_poll,
+};
+
+/*
+ * 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 ld_usb_class = {
+        .name =         "ldusb%d",
+        .fops =         &ld_usb_fops,
+        .minor_base =   USB_LD_MINOR_BASE,
+};
+
+/**
+ *      ld_usb_probe
+ *
+ *      Called by the usb core when a new device is connected that it thinks
+ *      this driver might be interested in.
+ */
+static int ld_usb_probe(struct usb_interface *intf, const struct usb_device_id *id)
+{
+        struct usb_device *udev = interface_to_usbdev(intf);
+        struct ld_usb *dev = NULL;
+        struct usb_host_interface *iface_desc;
+        struct usb_endpoint_descriptor *endpoint;
+        char *buffer;
+        int i;
+        int retval = -ENOMEM;
+
+        /* allocate memory for our device state and intialize it */
+
+        dev = kmalloc(sizeof(*dev), GFP_KERNEL);
+        if (dev == NULL) {
+                dev_err(&intf->dev, "Out of memory\n");
+                goto exit;
+        }
+        memset(dev, 0x00, sizeof(*dev));
+        init_MUTEX(&dev->sem);
+        dev->intf = intf;
+        init_waitqueue_head(&dev->read_wait);
+        init_waitqueue_head(&dev->write_wait);
+
+        /* workaround for early firmware versions on fast computers */
+        if ((le16_to_cpu(udev->descriptor.idVendor) == USB_VENDOR_ID_LD) &&
+            ((le16_to_cpu(udev->descriptor.idProduct) == USB_DEVICE_ID_CASSY) ||
+             (le16_to_cpu(udev->descriptor.idProduct) == USB_DEVICE_ID_COM3LAB)) &&
+            (le16_to_cpu(udev->descriptor.bcdDevice) <= 0x103)) {
+                buffer = kmalloc(256, GFP_KERNEL);
+                /* usb_string makes SETUP+STALL to leave always ControlReadLoop */
+                usb_string(udev, 255, buffer, 256);
+                kfree(buffer);
+        }
+
+        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 (((endpoint->bEndpointAddress & USB_ENDPOINT_DIR_MASK) == USB_DIR_IN) &&
+                    ((endpoint->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK) == USB_ENDPOINT_XFER_INT)) {
+                        dev->interrupt_in_endpoint = endpoint;
+                }
+
+                if (((endpoint->bEndpointAddress & USB_ENDPOINT_DIR_MASK) == USB_DIR_OUT) &&
+                    ((endpoint->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK) == USB_ENDPOINT_XFER_INT)) {
+                        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);
+        dev->ring_buffer = kmalloc(ring_buffer_size*(sizeof(size_t)+dev->interrupt_in_endpoint_size), GFP_KERNEL);
+        if (!dev->ring_buffer) {
+                dev_err(&intf->dev, "Couldn't allocate ring_buffer\n");
+                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->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;
+        dev->interrupt_out_buffer = kmalloc(write_buffer_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->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);
+
+        retval = usb_register_dev(intf, &ld_usb_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, "LD USB Device #%d now attached to major %d minor %d\n",
+                (intf->minor - USB_LD_MINOR_BASE), USB_MAJOR, intf->minor);
+
+exit:
+        return retval;
+
+error:
+        ld_usb_delete(dev);
+
+        return retval;
+}
+
+/**
+ *      ld_usb_disconnect
+ *
+ *      Called by the usb core when the device is removed from the system.
+ */
+static void ld_usb_disconnect(struct usb_interface *intf)
+{
+        struct ld_usb *dev;
+        int minor;
+
+        down(&disconnect_sem);
+
+        dev = usb_get_intfdata(intf);
+        usb_set_intfdata(intf, NULL);
+
+        down(&dev->sem);
+
+        minor = intf->minor;
+
+        /* give back our minor */
+        usb_deregister_dev(intf, &ld_usb_class);
+
+        /* if the device is not opened, then we clean up right now */
+        if (!dev->open_count) {
+                up(&dev->sem);
+                ld_usb_delete(dev);
+        } else {
+                dev->intf = NULL;
+                up(&dev->sem);
+        }
+
+        up(&disconnect_sem);
+
+        dev_info(&intf->dev, "LD USB Device #%d now disconnected\n",
+                 (minor - USB_LD_MINOR_BASE));
+}
+
+/* usb specific object needed to register this driver with the usb subsystem */
+static struct usb_driver ld_usb_driver = {
+        .owner =        THIS_MODULE,
+        .name =         "ldusb",
+        .probe =        ld_usb_probe,
+        .disconnect =   ld_usb_disconnect,
+        .id_table =     ld_usb_table,
+};
+
+/**
+ *      ld_usb_init
+ */
+static int __init ld_usb_init(void)
+{
+        int retval;
+
+        /* register this driver with the USB subsystem */
+        retval = usb_register(&ld_usb_driver);
+        if (retval)
+                err("usb_register failed for the "__FILE__" driver. Error number %d\n", retval);
+
+        return retval;
+}
+
+/**
+ *      ld_usb_exit
+ */
+static void __exit ld_usb_exit(void)
+{
+        /* deregister this driver with the USB subsystem */
+        usb_deregister(&ld_usb_driver);
+}
+
+module_init(ld_usb_init);
+module_exit(ld_usb_exit);
+