/*
 * f_hid.c -- USB HID function driver
 *
 * Copyright (C) 2010 Fabien Chouteau <fabien.chouteau@barco.com>
 *
 * 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.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/hid.h>
#include <linux/cdev.h>
#include <linux/mutex.h>
#include <linux/poll.h>
#include <linux/uaccess.h>
#include <linux/wait.h>
#include <linux/sched.h>
#include <linux/usb/g_hid.h>

static int major, minors;
static struct class *hidg_class;

/*-------------------------------------------------------------------------*/
/*                            HID gadget struct                            */

struct f_hidg_req_list {
        struct usb_request      *req;
        unsigned int            pos;
        struct list_head        list;
};

struct f_hidg {
        /* configuration */
        unsigned char                   bInterfaceSubClass;
        unsigned char                   bInterfaceProtocol;
        unsigned short                  report_desc_length;
        char                            *report_desc;
        unsigned short                  report_length;

        /* recv report */
        struct list_head                completed_out_req;
        spinlock_t                      spinlock;
        wait_queue_head_t               read_queue;
        unsigned int                    qlen;

        /* send report */
        struct mutex                    lock;
        bool                            write_pending;
        wait_queue_head_t               write_queue;
        struct usb_request              *req;

        int                             minor;
        struct cdev                     cdev;
        struct usb_function             func;

        struct usb_ep                   *in_ep;
        struct usb_ep                   *out_ep;
};

static inline struct f_hidg *func_to_hidg(struct usb_function *f)
{
        return container_of(f, struct f_hidg, func);
}

/*-------------------------------------------------------------------------*/
/*                           Static descriptors                            */

static struct usb_interface_descriptor hidg_interface_desc = {
        .bLength                = sizeof hidg_interface_desc,
        .bDescriptorType        = USB_DT_INTERFACE,
        /* .bInterfaceNumber    = DYNAMIC */
        .bAlternateSetting      = 0,
        .bNumEndpoints          = 2,
        .bInterfaceClass        = USB_CLASS_HID,
        /* .bInterfaceSubClass  = DYNAMIC */
        /* .bInterfaceProtocol  = DYNAMIC */
        /* .iInterface          = DYNAMIC */
};

static struct hid_descriptor hidg_desc = {
        .bLength                        = sizeof hidg_desc,
        .bDescriptorType                = HID_DT_HID,
        .bcdHID                         = 0x0101,
        .bCountryCode                   = 0x00,
        .bNumDescriptors                = 0x1,
        /*.desc[0].bDescriptorType      = DYNAMIC */
        /*.desc[0].wDescriptorLenght    = DYNAMIC */
};

/* High-Speed Support */

static struct usb_endpoint_descriptor hidg_hs_in_ep_desc = {
        .bLength                = USB_DT_ENDPOINT_SIZE,
        .bDescriptorType        = USB_DT_ENDPOINT,
        .bEndpointAddress       = USB_DIR_IN,
        .bmAttributes           = USB_ENDPOINT_XFER_INT,
        /*.wMaxPacketSize       = DYNAMIC */
        .bInterval              = 4, /* FIXME: Add this field in the
                                      * HID gadget configuration?
                                      * (struct hidg_func_descriptor)
                                      */
};

static struct usb_endpoint_descriptor hidg_hs_out_ep_desc = {
        .bLength                = USB_DT_ENDPOINT_SIZE,
        .bDescriptorType        = USB_DT_ENDPOINT,
        .bEndpointAddress       = USB_DIR_OUT,
        .bmAttributes           = USB_ENDPOINT_XFER_INT,
        /*.wMaxPacketSize       = DYNAMIC */
        .bInterval              = 4, /* FIXME: Add this field in the
                                      * HID gadget configuration?
                                      * (struct hidg_func_descriptor)
                                      */
};

static struct usb_descriptor_header *hidg_hs_descriptors[] = {
        (struct usb_descriptor_header *)&hidg_interface_desc,
        (struct usb_descriptor_header *)&hidg_desc,
        (struct usb_descriptor_header *)&hidg_hs_in_ep_desc,
        (struct usb_descriptor_header *)&hidg_hs_out_ep_desc,
        NULL,
};

/* Full-Speed Support */

static struct usb_endpoint_descriptor hidg_fs_in_ep_desc = {
        .bLength                = USB_DT_ENDPOINT_SIZE,
        .bDescriptorType        = USB_DT_ENDPOINT,
        .bEndpointAddress       = USB_DIR_IN,
        .bmAttributes           = USB_ENDPOINT_XFER_INT,
        /*.wMaxPacketSize       = DYNAMIC */
        .bInterval              = 10, /* FIXME: Add this field in the
                                       * HID gadget configuration?
                                       * (struct hidg_func_descriptor)
                                       */
};

static struct usb_endpoint_descriptor hidg_fs_out_ep_desc = {
        .bLength                = USB_DT_ENDPOINT_SIZE,
        .bDescriptorType        = USB_DT_ENDPOINT,
        .bEndpointAddress       = USB_DIR_OUT,
        .bmAttributes           = USB_ENDPOINT_XFER_INT,
        /*.wMaxPacketSize       = DYNAMIC */
        .bInterval              = 10, /* FIXME: Add this field in the
                                       * HID gadget configuration?
                                       * (struct hidg_func_descriptor)
                                       */
};

static struct usb_descriptor_header *hidg_fs_descriptors[] = {
        (struct usb_descriptor_header *)&hidg_interface_desc,
        (struct usb_descriptor_header *)&hidg_desc,
        (struct usb_descriptor_header *)&hidg_fs_in_ep_desc,
        (struct usb_descriptor_header *)&hidg_fs_out_ep_desc,
        NULL,
};

/*-------------------------------------------------------------------------*/
/*                              Char Device                                */

static ssize_t f_hidg_read(struct file *file, char __user *buffer,
                        size_t count, loff_t *ptr)
{
        struct f_hidg *hidg = file->private_data;
        struct f_hidg_req_list *list;
        struct usb_request *req;
        unsigned long flags;
        int ret;

        if (!count)
                return 0;

        if (!access_ok(VERIFY_WRITE, buffer, count))
                return -EFAULT;

        spin_lock_irqsave(&hidg->spinlock, flags);

#define READ_COND (!list_empty(&hidg->completed_out_req))

        /* wait for at least one buffer to complete */
        while (!READ_COND) {
                spin_unlock_irqrestore(&hidg->spinlock, flags);
                if (file->f_flags & O_NONBLOCK)
                        return -EAGAIN;

                if (wait_event_interruptible(hidg->read_queue, READ_COND))
                        return -ERESTARTSYS;

                spin_lock_irqsave(&hidg->spinlock, flags);
        }

        /* pick the first one */
        list = list_first_entry(&hidg->completed_out_req,
                                struct f_hidg_req_list, list);
        req = list->req;
        count = min_t(unsigned int, count, req->actual - list->pos);
        spin_unlock_irqrestore(&hidg->spinlock, flags);

        /* copy to user outside spinlock */
        count -= copy_to_user(buffer, req->buf + list->pos, count);
        list->pos += count;

        /*
         * if this request is completely handled and transfered to
         * userspace, remove its entry from the list and requeue it
         * again. Otherwise, we will revisit it again upon the next
         * call, taking into account its current read position.
         */
        if (list->pos == req->actual) {
                spin_lock_irqsave(&hidg->spinlock, flags);
                list_del(&list->list);
                kfree(list);
                spin_unlock_irqrestore(&hidg->spinlock, flags);

                req->length = hidg->report_length;
                ret = usb_ep_queue(hidg->out_ep, req, GFP_KERNEL);
                if (ret < 0)
                        return ret;
        }

        return count;
}

static void f_hidg_req_complete(struct usb_ep *ep, struct usb_request *req)
{
        struct f_hidg *hidg = (struct f_hidg *)ep->driver_data;

        if (req->status != 0) {
                ERROR(hidg->func.config->cdev,
                        "End Point Request ERROR: %d\n", req->status);
        }

        hidg->write_pending = 0;
        wake_up(&hidg->write_queue);
}

static ssize_t f_hidg_write(struct file *file, const char __user *buffer,
                            size_t count, loff_t *offp)
{
        struct f_hidg *hidg  = file->private_data;
        ssize_t status = -ENOMEM;

        if (!access_ok(VERIFY_READ, buffer, count))
                return -EFAULT;

        mutex_lock(&hidg->lock);

#define WRITE_COND (!hidg->write_pending)

        /* write queue */
        while (!WRITE_COND) {
                mutex_unlock(&hidg->lock);
                if (file->f_flags & O_NONBLOCK)
                        return -EAGAIN;

                if (wait_event_interruptible_exclusive(
                                hidg->write_queue, WRITE_COND))
                        return -ERESTARTSYS;

                mutex_lock(&hidg->lock);
        }

        count  = min_t(unsigned, count, hidg->report_length);
        status = copy_from_user(hidg->req->buf, buffer, count);

        if (status != 0) {
                ERROR(hidg->func.config->cdev,
                        "copy_from_user error\n");
                mutex_unlock(&hidg->lock);
                return -EINVAL;
        }

        hidg->req->status   = 0;
        hidg->req->zero     = 0;
        hidg->req->length   = count;
        hidg->req->complete = f_hidg_req_complete;
        hidg->req->context  = hidg;
        hidg->write_pending = 1;

        status = usb_ep_queue(hidg->in_ep, hidg->req, GFP_ATOMIC);
        if (status < 0) {
                ERROR(hidg->func.config->cdev,
                        "usb_ep_queue error on int endpoint %zd\n", status);
                hidg->write_pending = 0;
                wake_up(&hidg->write_queue);
        } else {
                status = count;
        }

        mutex_unlock(&hidg->lock);

        return status;
}

static unsigned int f_hidg_poll(struct file *file, poll_table *wait)
{
        struct f_hidg   *hidg  = file->private_data;
        unsigned int    ret = 0;

        poll_wait(file, &hidg->read_queue, wait);
        poll_wait(file, &hidg->write_queue, wait);

        if (WRITE_COND)
                ret |= POLLOUT | POLLWRNORM;

        if (READ_COND)
                ret |= POLLIN | POLLRDNORM;

        return ret;
}

#undef WRITE_COND
#undef READ_COND

static int f_hidg_release(struct inode *inode, struct file *fd)
{
        fd->private_data = NULL;
        return 0;
}

static int f_hidg_open(struct inode *inode, struct file *fd)
{
        struct f_hidg *hidg =
                container_of(inode->i_cdev, struct f_hidg, cdev);

        fd->private_data = hidg;

        return 0;
}

/*-------------------------------------------------------------------------*/
/*                                usb_function                             */

static struct usb_request *hidg_alloc_ep_req(struct usb_ep *ep, unsigned length)
{
        struct usb_request *req;

        req = usb_ep_alloc_request(ep, GFP_ATOMIC);
        if (req) {
                req->length = length;
                req->buf = kmalloc(length, GFP_ATOMIC);
                if (!req->buf) {
                        usb_ep_free_request(ep, req);
                        req = NULL;
                }
        }
        return req;
}

static void hidg_set_report_complete(struct usb_ep *ep, struct usb_request *req)
{
        struct f_hidg *hidg = (struct f_hidg *) req->context;
        struct f_hidg_req_list *req_list;
        unsigned long flags;

        req_list = kzalloc(sizeof(*req_list), GFP_ATOMIC);
        if (!req_list)
                return;

        req_list->req = req;

        spin_lock_irqsave(&hidg->spinlock, flags);
        list_add_tail(&req_list->list, &hidg->completed_out_req);
        spin_unlock_irqrestore(&hidg->spinlock, flags);

        wake_up(&hidg->read_queue);
}

static int hidg_setup(struct usb_function *f,
                const struct usb_ctrlrequest *ctrl)
{
        struct f_hidg                   *hidg = func_to_hidg(f);
        struct usb_composite_dev        *cdev = f->config->cdev;
        struct usb_request              *req  = cdev->req;
        int status = 0;
        __u16 value, length;

        value   = __le16_to_cpu(ctrl->wValue);
        length  = __le16_to_cpu(ctrl->wLength);

        VDBG(cdev, "hid_setup crtl_request : bRequestType:0x%x bRequest:0x%x "
                "Value:0x%x\n", ctrl->bRequestType, ctrl->bRequest, value);

        switch ((ctrl->bRequestType << 8) | ctrl->bRequest) {
        case ((USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8
                  | HID_REQ_GET_REPORT):
                VDBG(cdev, "get_report\n");

                /* send an empty report */
                length = min_t(unsigned, length, hidg->report_length);
                memset(req->buf, 0x0, length);

                goto respond;
                break;

        case ((USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8
                  | HID_REQ_GET_PROTOCOL):
                VDBG(cdev, "get_protocol\n");
                goto stall;
                break;

        case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8
                  | HID_REQ_SET_REPORT):
                VDBG(cdev, "set_report | wLenght=%d\n", ctrl->wLength);
                goto stall;
                break;

        case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8
                  | HID_REQ_SET_PROTOCOL):
                VDBG(cdev, "set_protocol\n");
                goto stall;
                break;

        case ((USB_DIR_IN | USB_TYPE_STANDARD | USB_RECIP_INTERFACE) << 8
                  | USB_REQ_GET_DESCRIPTOR):
                switch (value >> 8) {
                case HID_DT_HID:
                        VDBG(cdev, "USB_REQ_GET_DESCRIPTOR: HID\n");
                        length = min_t(unsigned short, length,
                                                   hidg_desc.bLength);
                        memcpy(req->buf, &hidg_desc, length);
                        goto respond;
                        break;
                case HID_DT_REPORT:
                        VDBG(cdev, "USB_REQ_GET_DESCRIPTOR: REPORT\n");
                        length = min_t(unsigned short, length,
                                                   hidg->report_desc_length);
                        memcpy(req->buf, hidg->report_desc, length);
                        goto respond;
                        break;

                default:
                        VDBG(cdev, "Unknown descriptor request 0x%x\n",
                                 value >> 8);
                        goto stall;
                        break;
                }
                break;

        default:
                VDBG(cdev, "Unknown request 0x%x\n",
                         ctrl->bRequest);
                goto stall;
                break;
        }

stall:
        return -EOPNOTSUPP;

respond:
        req->zero = 0;
        req->length = length;
        status = usb_ep_queue(cdev->gadget->ep0, req, GFP_ATOMIC);
        if (status < 0)
                ERROR(cdev, "usb_ep_queue error on ep0 %d\n", value);
        return status;
}

static void hidg_disable(struct usb_function *f)
{
        struct f_hidg *hidg = func_to_hidg(f);
        struct f_hidg_req_list *list, *next;

        usb_ep_disable(hidg->in_ep);
        hidg->in_ep->driver_data = NULL;

        usb_ep_disable(hidg->out_ep);
        hidg->out_ep->driver_data = NULL;

        list_for_each_entry_safe(list, next, &hidg->completed_out_req, list) {
                list_del(&list->list);
                kfree(list);
        }
}

static int hidg_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
{
        struct usb_composite_dev                *cdev = f->config->cdev;
        struct f_hidg                           *hidg = func_to_hidg(f);
        int i, status = 0;

        VDBG(cdev, "hidg_set_alt intf:%d alt:%d\n", intf, alt);

        if (hidg->in_ep != NULL) {
                /* restart endpoint */
                if (hidg->in_ep->driver_data != NULL)
                        usb_ep_disable(hidg->in_ep);

                status = config_ep_by_speed(f->config->cdev->gadget, f,
                                            hidg->in_ep);
                if (status) {
                        ERROR(cdev, "config_ep_by_speed FAILED!\n");
                        goto fail;
                }
                status = usb_ep_enable(hidg->in_ep);
                if (status < 0) {
                        ERROR(cdev, "Enable IN endpoint FAILED!\n");
                        goto fail;
                }
                hidg->in_ep->driver_data = hidg;
        }


        if (hidg->out_ep != NULL) {
                /* restart endpoint */
                if (hidg->out_ep->driver_data != NULL)
                        usb_ep_disable(hidg->out_ep);

                status = config_ep_by_speed(f->config->cdev->gadget, f,
                                            hidg->out_ep);
                if (status) {
                        ERROR(cdev, "config_ep_by_speed FAILED!\n");
                        goto fail;
                }
                status = usb_ep_enable(hidg->out_ep);
                if (status < 0) {
                        ERROR(cdev, "Enable IN endpoint FAILED!\n");
                        goto fail;
                }
                hidg->out_ep->driver_data = hidg;

                /*
                 * allocate a bunch of read buffers and queue them all at once.
                 */
                for (i = 0; i < hidg->qlen && status == 0; i++) {
                        struct usb_request *req =
                                        hidg_alloc_ep_req(hidg->out_ep,
                                                          hidg->report_length);
                        if (req) {
                                req->complete = hidg_set_report_complete;
                                req->context  = hidg;
                                status = usb_ep_queue(hidg->out_ep, req,
                                                      GFP_ATOMIC);
                                if (status)
                                        ERROR(cdev, "%s queue req --> %d\n",
                                                hidg->out_ep->name, status);
                        } else {
                                usb_ep_disable(hidg->out_ep);
                                hidg->out_ep->driver_data = NULL;
                                status = -ENOMEM;
                                goto fail;
                        }
                }
        }

fail:
        return status;
}

const struct file_operations f_hidg_fops = {
        .owner          = THIS_MODULE,
        .open           = f_hidg_open,
        .release        = f_hidg_release,
        .write          = f_hidg_write,
        .read           = f_hidg_read,
        .poll           = f_hidg_poll,
        .llseek         = noop_llseek,
};

static int __init hidg_bind(struct usb_configuration *c, struct usb_function *f)
{
        struct usb_ep           *ep;
        struct f_hidg           *hidg = func_to_hidg(f);
        int                     status;
        dev_t                   dev;

        /* allocate instance-specific interface IDs, and patch descriptors */
        status = usb_interface_id(c, f);
        if (status < 0)
                goto fail;
        hidg_interface_desc.bInterfaceNumber = status;

        /* allocate instance-specific endpoints */
        status = -ENODEV;
        ep = usb_ep_autoconfig(c->cdev->gadget, &hidg_fs_in_ep_desc);
        if (!ep)
                goto fail;
        ep->driver_data = c->cdev;      /* claim */
        hidg->in_ep = ep;

        ep = usb_ep_autoconfig(c->cdev->gadget, &hidg_fs_out_ep_desc);
        if (!ep)
                goto fail;
        ep->driver_data = c->cdev;      /* claim */
        hidg->out_ep = ep;

        /* preallocate request and buffer */
        status = -ENOMEM;
        hidg->req = usb_ep_alloc_request(hidg->in_ep, GFP_KERNEL);
        if (!hidg->req)
                goto fail;

        hidg->req->buf = kmalloc(hidg->report_length, GFP_KERNEL);
        if (!hidg->req->buf)
                goto fail;

        /* set descriptor dynamic values */
        hidg_interface_desc.bInterfaceSubClass = hidg->bInterfaceSubClass;
        hidg_interface_desc.bInterfaceProtocol = hidg->bInterfaceProtocol;
        hidg_hs_in_ep_desc.wMaxPacketSize = cpu_to_le16(hidg->report_length);
        hidg_fs_in_ep_desc.wMaxPacketSize = cpu_to_le16(hidg->report_length);
        hidg_hs_out_ep_desc.wMaxPacketSize = cpu_to_le16(hidg->report_length);
        hidg_fs_out_ep_desc.wMaxPacketSize = cpu_to_le16(hidg->report_length);
        hidg_desc.desc[0].bDescriptorType = HID_DT_REPORT;
        hidg_desc.desc[0].wDescriptorLength =
                cpu_to_le16(hidg->report_desc_length);

        hidg_hs_in_ep_desc.bEndpointAddress =
                hidg_fs_in_ep_desc.bEndpointAddress;
        hidg_hs_out_ep_desc.bEndpointAddress =
                hidg_fs_out_ep_desc.bEndpointAddress;

        status = usb_assign_descriptors(f, hidg_fs_descriptors,
                        hidg_hs_descriptors, NULL);
        if (status)
                goto fail;

        mutex_init(&hidg->lock);
        spin_lock_init(&hidg->spinlock);
        init_waitqueue_head(&hidg->write_queue);
        init_waitqueue_head(&hidg->read_queue);
        INIT_LIST_HEAD(&hidg->completed_out_req);

        /* create char device */
        cdev_init(&hidg->cdev, &f_hidg_fops);
        dev = MKDEV(major, hidg->minor);
        status = cdev_add(&hidg->cdev, dev, 1);
        if (status)
                goto fail;

        device_create(hidg_class, NULL, dev, NULL, "%s%d", "hidg", hidg->minor);

        return 0;

fail:
        ERROR(f->config->cdev, "hidg_bind FAILED\n");
        if (hidg->req != NULL) {
                kfree(hidg->req->buf);
                if (hidg->in_ep != NULL)
                        usb_ep_free_request(hidg->in_ep, hidg->req);
        }

        usb_free_all_descriptors(f);
        return status;
}

static void hidg_unbind(struct usb_configuration *c, struct usb_function *f)
{
        struct f_hidg *hidg = func_to_hidg(f);

        device_destroy(hidg_class, MKDEV(major, hidg->minor));
        cdev_del(&hidg->cdev);

        /* disable/free request and end point */
        usb_ep_disable(hidg->in_ep);
        usb_ep_dequeue(hidg->in_ep, hidg->req);
        kfree(hidg->req->buf);
        usb_ep_free_request(hidg->in_ep, hidg->req);

        usb_free_all_descriptors(f);

        kfree(hidg->report_desc);
        kfree(hidg);
}

/*-------------------------------------------------------------------------*/
/*                                 Strings                                 */

#define CT_FUNC_HID_IDX 0

static struct usb_string ct_func_string_defs[] = {
        [CT_FUNC_HID_IDX].s     = "HID Interface",
        {},                     /* end of list */
};

static struct usb_gadget_strings ct_func_string_table = {
        .language       = 0x0409,       /* en-US */
        .strings        = ct_func_string_defs,
};

static struct usb_gadget_strings *ct_func_strings[] = {
        &ct_func_string_table,
        NULL,
};

/*-------------------------------------------------------------------------*/
/*                             usb_configuration                           */

int __init hidg_bind_config(struct usb_configuration *c,
                            struct hidg_func_descriptor *fdesc, int index)
{
        struct f_hidg *hidg;
        int status;

        if (index >= minors)
                return -ENOENT;

        /* maybe allocate device-global string IDs, and patch descriptors */
        if (ct_func_string_defs[CT_FUNC_HID_IDX].id == 0) {
                status = usb_string_id(c->cdev);
                if (status < 0)
                        return status;
                ct_func_string_defs[CT_FUNC_HID_IDX].id = status;
                hidg_interface_desc.iInterface = status;
        }

        /* allocate and initialize one new instance */
        hidg = kzalloc(sizeof *hidg, GFP_KERNEL);
        if (!hidg)
                return -ENOMEM;

        hidg->minor = index;
        hidg->bInterfaceSubClass = fdesc->subclass;
        hidg->bInterfaceProtocol = fdesc->protocol;
        hidg->report_length = fdesc->report_length;
        hidg->report_desc_length = fdesc->report_desc_length;
        hidg->report_desc = kmemdup(fdesc->report_desc,
                                    fdesc->report_desc_length,
                                    GFP_KERNEL);
        if (!hidg->report_desc) {
                kfree(hidg);
                return -ENOMEM;
        }

        hidg->func.name    = "hid";
        hidg->func.strings = ct_func_strings;
        hidg->func.bind    = hidg_bind;
        hidg->func.unbind  = hidg_unbind;
        hidg->func.set_alt = hidg_set_alt;
        hidg->func.disable = hidg_disable;
        hidg->func.setup   = hidg_setup;

        /* this could me made configurable at some point */
        hidg->qlen         = 4;

        status = usb_add_function(c, &hidg->func);
        if (status)
                kfree(hidg);

        return status;
}

int __init ghid_setup(struct usb_gadget *g, int count)
{
        int status;
        dev_t dev;

        hidg_class = class_create(THIS_MODULE, "hidg");

        status = alloc_chrdev_region(&dev, 0, count, "hidg");
        if (!status) {
                major = MAJOR(dev);
                minors = count;
        }

        return status;
}

void ghid_cleanup(void)
{
        if (major) {
                unregister_chrdev_region(MKDEV(major, 0), minors);
                major = minors = 0;
        }

        class_destroy(hidg_class);
        hidg_class = NULL;
}