// SPDX-License-Identifier: GPL-2.0+
/*
 * 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>
 *
 * Derived from Lego USB Tower driver
 * Copyright (C) 2003 David Glance <advidgsf@sourceforge.net>
 *               2001-2004 Juergen Stuber <starblue@users.sourceforge.net>
 */

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

#include <linux/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_LD_CASSY          0x1000  /* USB Product ID of CASSY-S modules with 8 bytes endpoint size */
#define USB_DEVICE_ID_LD_CASSY2         0x1001  /* USB Product ID of CASSY-S modules with 64 bytes endpoint size */
#define USB_DEVICE_ID_LD_POCKETCASSY    0x1010  /* USB Product ID of Pocket-CASSY */
#define USB_DEVICE_ID_LD_POCKETCASSY2   0x1011  /* USB Product ID of Pocket-CASSY 2 (reserved) */
#define USB_DEVICE_ID_LD_MOBILECASSY    0x1020  /* USB Product ID of Mobile-CASSY */
#define USB_DEVICE_ID_LD_MOBILECASSY2   0x1021  /* USB Product ID of Mobile-CASSY 2 (reserved) */
#define USB_DEVICE_ID_LD_MICROCASSYVOLTAGE      0x1031  /* USB Product ID of Micro-CASSY Voltage */
#define USB_DEVICE_ID_LD_MICROCASSYCURRENT      0x1032  /* USB Product ID of Micro-CASSY Current */
#define USB_DEVICE_ID_LD_MICROCASSYTIME         0x1033  /* USB Product ID of Micro-CASSY Time (reserved) */
#define USB_DEVICE_ID_LD_MICROCASSYTEMPERATURE  0x1035  /* USB Product ID of Micro-CASSY Temperature */
#define USB_DEVICE_ID_LD_MICROCASSYPH           0x1038  /* USB Product ID of Micro-CASSY pH */
#define USB_DEVICE_ID_LD_POWERANALYSERCASSY     0x1040  /* USB Product ID of Power Analyser CASSY */
#define USB_DEVICE_ID_LD_CONVERTERCONTROLLERCASSY       0x1042  /* USB Product ID of Converter Controller CASSY */
#define USB_DEVICE_ID_LD_MACHINETESTCASSY       0x1043  /* USB Product ID of Machine Test CASSY */
#define USB_DEVICE_ID_LD_JWM            0x1080  /* USB Product ID of Joule and Wattmeter */
#define USB_DEVICE_ID_LD_DMMP           0x1081  /* USB Product ID of Digital Multimeter P (reserved) */
#define USB_DEVICE_ID_LD_UMIP           0x1090  /* USB Product ID of UMI P */
#define USB_DEVICE_ID_LD_UMIC           0x10A0  /* USB Product ID of UMI C */
#define USB_DEVICE_ID_LD_UMIB           0x10B0  /* USB Product ID of UMI B */
#define USB_DEVICE_ID_LD_XRAY           0x1100  /* USB Product ID of X-Ray Apparatus 55481 */
#define USB_DEVICE_ID_LD_XRAY2          0x1101  /* USB Product ID of X-Ray Apparatus 554800 */
#define USB_DEVICE_ID_LD_XRAYCT         0x1110  /* USB Product ID of X-Ray Apparatus CT 554821*/
#define USB_DEVICE_ID_LD_VIDEOCOM       0x1200  /* USB Product ID of VideoCom */
#define USB_DEVICE_ID_LD_MOTOR          0x1210  /* USB Product ID of Motor (reserved) */
#define USB_DEVICE_ID_LD_COM3LAB        0x2000  /* USB Product ID of COM3LAB */
#define USB_DEVICE_ID_LD_TELEPORT       0x2010  /* USB Product ID of Terminal Adapter */
#define USB_DEVICE_ID_LD_NETWORKANALYSER 0x2020 /* USB Product ID of Network Analyser */
#define USB_DEVICE_ID_LD_POWERCONTROL   0x2030  /* USB Product ID of Converter Control Unit */
#define USB_DEVICE_ID_LD_MACHINETEST    0x2040  /* USB Product ID of Machine Test System */
#define USB_DEVICE_ID_LD_MOSTANALYSER   0x2050  /* USB Product ID of MOST Protocol Analyser */
#define USB_DEVICE_ID_LD_MOSTANALYSER2  0x2051  /* USB Product ID of MOST Protocol Analyser 2 */
#define USB_DEVICE_ID_LD_ABSESP         0x2060  /* USB Product ID of ABS ESP */
#define USB_DEVICE_ID_LD_AUTODATABUS    0x2070  /* USB Product ID of Automotive Data Buses */
#define USB_DEVICE_ID_LD_MCT            0x2080  /* USB Product ID of Microcontroller technique */
#define USB_DEVICE_ID_LD_HYBRID         0x2090  /* USB Product ID of Automotive Hybrid */
#define USB_DEVICE_ID_LD_HEATCONTROL    0x20A0  /* USB Product ID of Heat control */

#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 const struct usb_device_id ld_usb_table[] = {
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_CASSY) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_CASSY2) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_POCKETCASSY) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_POCKETCASSY2) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_MOBILECASSY) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_MOBILECASSY2) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_MICROCASSYVOLTAGE) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_MICROCASSYCURRENT) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_MICROCASSYTIME) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_MICROCASSYTEMPERATURE) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_MICROCASSYPH) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_POWERANALYSERCASSY) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_CONVERTERCONTROLLERCASSY) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_MACHINETESTCASSY) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_JWM) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_DMMP) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_UMIP) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_UMIC) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_UMIB) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_XRAY) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_XRAY2) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_VIDEOCOM) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_MOTOR) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_COM3LAB) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_TELEPORT) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_NETWORKANALYSER) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_POWERCONTROL) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_MACHINETEST) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_MOSTANALYSER) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_MOSTANALYSER2) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_ABSESP) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_AUTODATABUS) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_MCT) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_HYBRID) },
        { USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_HEATCONTROL) },
        { }                                     /* Terminating entry */
};
MODULE_DEVICE_TABLE(usb, ld_usb_table);
MODULE_AUTHOR("Michael Hund <mhund@ld-didactic.de>");
MODULE_DESCRIPTION("LD USB Driver");
MODULE_LICENSE("GPL");

/* 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, 0000);
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, 0000);
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, 0000);
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, 0000);
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 mutex            mutex;          /* locks this structure */
        struct usb_interface    *intf;          /* save off the usb interface pointer */
        unsigned long           disconnected:1;

        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;
        int                     buffer_overflow;
        spinlock_t              rbsl;

        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;
};

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;
                usb_kill_urb(dev->interrupt_in_urb);
        }
        if (dev->interrupt_out_busy)
                usb_kill_urb(dev->interrupt_out_urb);
}

/*
 *      ld_usb_delete
 */
static void ld_usb_delete(struct ld_usb *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 ld_usb *dev = urb->context;
        size_t *actual_buffer;
        unsigned int next_ring_head;
        int status = urb->status;
        unsigned long flags;
        int retval;

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

        spin_lock_irqsave(&dev->rbsl, flags);
        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;
                        dev_dbg(&dev->intf->dev, "%s: received %d bytes\n",
                                __func__, urb->actual_length);
                } else {
                        dev_warn(&dev->intf->dev,
                                 "Ring buffer overflow, %d bytes dropped\n",
                                 urb->actual_length);
                        dev->buffer_overflow = 1;
                }
        }

resubmit:
        /* resubmit if we're still running */
        if (dev->interrupt_in_running && !dev->buffer_overflow) {
                retval = usb_submit_urb(dev->interrupt_in_urb, GFP_ATOMIC);
                if (retval) {
                        dev_err(&dev->intf->dev,
                                "usb_submit_urb failed (%d)\n", retval);
                        dev->buffer_overflow = 1;
                }
        }
        spin_unlock_irqrestore(&dev->rbsl, flags);
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 ld_usb *dev = urb->context;
        int status = urb->status;

        /* sync/async unlink faults aren't errors */
        if (status && !(status == -ENOENT ||
                        status == -ECONNRESET ||
                        status == -ESHUTDOWN))
                dev_dbg(&dev->intf->dev,
                        "%s - nonzero write interrupt status received: %d\n",
                        __func__, 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;
        struct usb_interface *interface;

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

        interface = usb_find_interface(&ld_usb_driver, subminor);

        if (!interface) {
                printk(KERN_ERR "%s - error, can't find device for minor %d\n",
                       __func__, subminor);
                return -ENODEV;
        }

        dev = usb_get_intfdata(interface);

        if (!dev)
                return -ENODEV;

        /* lock this device */
        if (mutex_lock_interruptible(&dev->mutex))
                return -ERESTARTSYS;

        /* 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;
        dev->buffer_overflow = 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:
        mutex_unlock(&dev->mutex);

        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;
        }

        mutex_lock(&dev->mutex);

        if (dev->open_count != 1) {
                retval = -ENODEV;
                goto unlock_exit;
        }
        if (dev->disconnected) {
                /* the device was unplugged before the file was released */
                mutex_unlock(&dev->mutex);
                /* 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:
        mutex_unlock(&dev->mutex);

exit:
        return retval;
}

/*
 *      ld_usb_poll
 */
static __poll_t ld_usb_poll(struct file *file, poll_table *wait)
{
        struct ld_usb *dev;
        __poll_t mask = 0;

        dev = file->private_data;

        if (dev->disconnected)
                return EPOLLERR | EPOLLHUP;

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

        if (dev->ring_head != dev->ring_tail)
                mask |= EPOLLIN | EPOLLRDNORM;
        if (!dev->interrupt_out_busy)
                mask |= EPOLLOUT | EPOLLWRNORM;

        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;
        int rv;

        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->mutex)) {
                retval = -ERESTARTSYS;
                goto exit;
        }

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

        /* wait for data */
        spin_lock_irq(&dev->rbsl);
        while (dev->ring_head == dev->ring_tail) {
                dev->interrupt_in_done = 0;
                spin_unlock_irq(&dev->rbsl);
                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;

                spin_lock_irq(&dev->rbsl);
        }
        spin_unlock_irq(&dev->rbsl);

        /* 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));
        if (*actual_buffer > dev->interrupt_in_endpoint_size) {
                retval = -EIO;
                goto unlock_exit;
        }
        bytes_to_read = min(count, *actual_buffer);
        if (bytes_to_read < *actual_buffer)
                dev_warn(&dev->intf->dev, "Read buffer overflow, %zu 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;
        }
        retval = bytes_to_read;

        spin_lock_irq(&dev->rbsl);
        dev->ring_tail = (dev->ring_tail + 1) % ring_buffer_size;

        if (dev->buffer_overflow) {
                dev->buffer_overflow = 0;
                spin_unlock_irq(&dev->rbsl);
                rv = usb_submit_urb(dev->interrupt_in_urb, GFP_KERNEL);
                if (rv < 0)
                        dev->buffer_overflow = 1;
        } else {
                spin_unlock_irq(&dev->rbsl);
        }

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

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

        /* verify that the device wasn't unplugged */
        if (dev->disconnected) {
                retval = -ENODEV;
                printk(KERN_ERR "ldusb: 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, %zu bytes dropped\n",
                        count - bytes_to_write);
        dev_dbg(&dev->intf->dev, "%s: count = %zu, bytes_to_write = %zu\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) {
                /* 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);
                if (retval < 0)
                        dev_err(&dev->intf->dev,
                                "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;
                dev_err(&dev->intf->dev,
                        "Couldn't submit interrupt_out_urb %d\n", retval);
                goto unlock_exit;
        }
        retval = bytes_to_write;

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

exit:
        return retval;
}

/* file operations needed when we register this driver */
static const 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 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;
        char *buffer;
        int retval = -ENOMEM;
        int res;

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

        dev = kzalloc_obj(*dev);
        if (!dev)
                goto exit;
        mutex_init(&dev->mutex);
        spin_lock_init(&dev->rbsl);
        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_LD_CASSY) ||
             (le16_to_cpu(udev->descriptor.idProduct) == USB_DEVICE_ID_LD_COM3LAB)) &&
            (le16_to_cpu(udev->descriptor.bcdDevice) <= 0x103)) {
                buffer = kmalloc(256, GFP_KERNEL);
                if (!buffer)
                        goto error;
                /* usb_string makes SETUP+STALL to leave always ControlReadLoop */
                usb_string(udev, 255, buffer, 256);
                kfree(buffer);
        }

        iface_desc = intf->cur_altsetting;

        res = usb_find_last_int_in_endpoint(iface_desc,
                        &dev->interrupt_in_endpoint);
        if (res) {
                dev_err(&intf->dev, "Interrupt in endpoint not found\n");
                retval = res;
                goto error;
        }

        res = usb_find_last_int_out_endpoint(iface_desc,
                        &dev->interrupt_out_endpoint);
        if (res)
                dev_warn(&intf->dev, "Interrupt out endpoint not found (using control endpoint instead)\n");

        dev->interrupt_in_endpoint_size = usb_endpoint_maxp(dev->interrupt_in_endpoint);
        dev->ring_buffer = kcalloc(ring_buffer_size,
                        sizeof(size_t) + dev->interrupt_in_endpoint_size,
                        GFP_KERNEL);
        if (!dev->ring_buffer)
                goto error;
        dev->interrupt_in_buffer = kmalloc(dev->interrupt_in_endpoint_size, GFP_KERNEL);
        if (!dev->interrupt_in_buffer)
                goto error;
        dev->interrupt_in_urb = usb_alloc_urb(0, GFP_KERNEL);
        if (!dev->interrupt_in_urb)
                goto error;
        dev->interrupt_out_endpoint_size = dev->interrupt_out_endpoint ? usb_endpoint_maxp(dev->interrupt_out_endpoint) :
                                                                         udev->descriptor.bMaxPacketSize0;
        dev->interrupt_out_buffer =
                kmalloc_array(write_buffer_size,
                              dev->interrupt_out_endpoint_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;
        dev->interrupt_in_interval = max_t(int, min_interrupt_in_interval,
                                           dev->interrupt_in_endpoint->bInterval);
        if (dev->interrupt_out_endpoint)
                dev->interrupt_out_interval = max_t(int, 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;

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

        minor = intf->minor;

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

        usb_poison_urb(dev->interrupt_in_urb);
        usb_poison_urb(dev->interrupt_out_urb);

        mutex_lock(&dev->mutex);

        /* if the device is not opened, then we clean up right now */
        if (!dev->open_count) {
                mutex_unlock(&dev->mutex);
                ld_usb_delete(dev);
        } else {
                dev->disconnected = 1;
                /* wake up pollers */
                wake_up_interruptible_all(&dev->read_wait);
                wake_up_interruptible_all(&dev->write_wait);
                mutex_unlock(&dev->mutex);
        }

        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 = {
        .name =         "ldusb",
        .probe =        ld_usb_probe,
        .disconnect =   ld_usb_disconnect,
        .id_table =     ld_usb_table,
};

module_usb_driver(ld_usb_driver);