f_hid.c

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/*
 * f_hid.c -- USB HID function driver
 *
 * Copyright (C) 2010 Fabien Chouteau <[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; 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);

    /* copy descriptors */
    f->descriptors = usb_copy_descriptors(hidg_fs_descriptors);
    if (!f->descriptors)
        goto fail;

    if (gadget_is_dualspeed(c->cdev->gadget)) {
        hidg_hs_in_ep_desc.bEndpointAddress =
            hidg_fs_in_ep_desc.bEndpointAddress;
        hidg_hs_out_ep_desc.bEndpointAddress =
            hidg_fs_out_ep_desc.bEndpointAddress;
        f->hs_descriptors = usb_copy_descriptors(hidg_hs_descriptors);
        if (!f->hs_descriptors)
            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_descriptors(f->hs_descriptors);
    usb_free_descriptors(f->descriptors);

    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);

    /* free descriptors copies */
    usb_free_descriptors(f->hs_descriptors);
    usb_free_descriptors(f->descriptors);

    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;
}