// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  Copyright (c) 2001 Paul Stewart
 *  Copyright (c) 2001 Vojtech Pavlik
 *
 *  HID char devices, giving access to raw HID device events.
 */

/*
 *
 * Should you need to contact me, the author, you can do so either by
 * e-mail - mail your message to Paul Stewart <stewart@wetlogic.net>
 */

#include <linux/poll.h>
#include <linux/slab.h>
#include <linux/sched/signal.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/input.h>
#include <linux/usb.h>
#include <linux/hid.h>
#include <linux/hiddev.h>
#include <linux/compat.h>
#include <linux/vmalloc.h>
#include <linux/nospec.h>
#include "usbhid.h"

#ifdef CONFIG_USB_DYNAMIC_MINORS
#define HIDDEV_MINOR_BASE       0
#define HIDDEV_MINORS           256
#else
#define HIDDEV_MINOR_BASE       96
#define HIDDEV_MINORS           16
#endif
#define HIDDEV_BUFFER_SIZE      2048

struct hiddev_list {
        struct hiddev_usage_ref buffer[HIDDEV_BUFFER_SIZE];
        int head;
        int tail;
        unsigned flags;
        struct fasync_struct *fasync;
        struct hiddev *hiddev;
        struct list_head node;
        struct mutex thread_lock;
};

/*
 * Find a report, given the report's type and ID.  The ID can be specified
 * indirectly by REPORT_ID_FIRST (which returns the first report of the given
 * type) or by (REPORT_ID_NEXT | old_id), which returns the next report of the
 * given type which follows old_id.
 */
static struct hid_report *
hiddev_lookup_report(struct hid_device *hid, struct hiddev_report_info *rinfo)
{
        unsigned int flags = rinfo->report_id & ~HID_REPORT_ID_MASK;
        unsigned int rid = rinfo->report_id & HID_REPORT_ID_MASK;
        struct hid_report_enum *report_enum;
        struct hid_report *report;
        struct list_head *list;

        if (rinfo->report_type < HID_REPORT_TYPE_MIN ||
            rinfo->report_type > HID_REPORT_TYPE_MAX)
                return NULL;

        report_enum = hid->report_enum +
                (rinfo->report_type - HID_REPORT_TYPE_MIN);

        switch (flags) {
        case 0: /* Nothing to do -- report_id is already set correctly */
                break;

        case HID_REPORT_ID_FIRST:
                if (list_empty(&report_enum->report_list))
                        return NULL;

                list = report_enum->report_list.next;
                report = list_entry(list, struct hid_report, list);
                rinfo->report_id = report->id;
                break;

        case HID_REPORT_ID_NEXT:
                report = report_enum->report_id_hash[rid];
                if (!report)
                        return NULL;

                list = report->list.next;
                if (list == &report_enum->report_list)
                        return NULL;

                report = list_entry(list, struct hid_report, list);
                rinfo->report_id = report->id;
                break;

        default:
                return NULL;
        }

        return report_enum->report_id_hash[rinfo->report_id];
}

/*
 * Perform an exhaustive search of the report table for a usage, given its
 * type and usage id.
 */
static struct hid_field *
hiddev_lookup_usage(struct hid_device *hid, struct hiddev_usage_ref *uref)
{
        int i, j;
        struct hid_report *report;
        struct hid_report_enum *report_enum;
        struct hid_field *field;

        if (uref->report_type < HID_REPORT_TYPE_MIN ||
            uref->report_type > HID_REPORT_TYPE_MAX)
                return NULL;

        report_enum = hid->report_enum +
                (uref->report_type - HID_REPORT_TYPE_MIN);

        list_for_each_entry(report, &report_enum->report_list, list) {
                for (i = 0; i < report->maxfield; i++) {
                        field = report->field[i];
                        for (j = 0; j < field->maxusage; j++) {
                                if (field->usage[j].hid == uref->usage_code) {
                                        uref->report_id = report->id;
                                        uref->field_index = i;
                                        uref->usage_index = j;
                                        return field;
                                }
                        }
                }
        }

        return NULL;
}

static void hiddev_send_event(struct hid_device *hid,
                              struct hiddev_usage_ref *uref)
{
        struct hiddev *hiddev = hid->hiddev;
        struct hiddev_list *list;
        unsigned long flags;

        spin_lock_irqsave(&hiddev->list_lock, flags);
        list_for_each_entry(list, &hiddev->list, node) {
                if (uref->field_index != HID_FIELD_INDEX_NONE ||
                    (list->flags & HIDDEV_FLAG_REPORT) != 0) {
                        list->buffer[list->head] = *uref;
                        list->head = (list->head + 1) &
                                (HIDDEV_BUFFER_SIZE - 1);
                        kill_fasync(&list->fasync, SIGIO, POLL_IN);
                }
        }
        spin_unlock_irqrestore(&hiddev->list_lock, flags);

        wake_up_interruptible(&hiddev->wait);
}

/*
 * This is where hid.c calls into hiddev to pass an event that occurred over
 * the interrupt pipe
 */
void hiddev_hid_event(struct hid_device *hid, struct hid_field *field,
                      struct hid_usage *usage, __s32 value)
{
        unsigned type = field->report_type;
        struct hiddev_usage_ref uref;

        uref.report_type =
          (type == HID_INPUT_REPORT) ? HID_REPORT_TYPE_INPUT :
          ((type == HID_OUTPUT_REPORT) ? HID_REPORT_TYPE_OUTPUT :
           ((type == HID_FEATURE_REPORT) ? HID_REPORT_TYPE_FEATURE : 0));
        uref.report_id = field->report->id;
        uref.field_index = field->index;
        uref.usage_index = (usage - field->usage);
        uref.usage_code = usage->hid;
        uref.value = value;

        hiddev_send_event(hid, &uref);
}
EXPORT_SYMBOL_GPL(hiddev_hid_event);

void hiddev_report_event(struct hid_device *hid, struct hid_report *report)
{
        unsigned type = report->type;
        struct hiddev_usage_ref uref;

        memset(&uref, 0, sizeof(uref));
        uref.report_type =
          (type == HID_INPUT_REPORT) ? HID_REPORT_TYPE_INPUT :
          ((type == HID_OUTPUT_REPORT) ? HID_REPORT_TYPE_OUTPUT :
           ((type == HID_FEATURE_REPORT) ? HID_REPORT_TYPE_FEATURE : 0));
        uref.report_id = report->id;
        uref.field_index = HID_FIELD_INDEX_NONE;

        hiddev_send_event(hid, &uref);
}

/*
 * fasync file op
 */
static int hiddev_fasync(int fd, struct file *file, int on)
{
        struct hiddev_list *list = file->private_data;

        return fasync_helper(fd, file, on, &list->fasync);
}


/*
 * release file op
 */
static int hiddev_release(struct inode * inode, struct file * file)
{
        struct hiddev_list *list = file->private_data;
        unsigned long flags;

        spin_lock_irqsave(&list->hiddev->list_lock, flags);
        list_del(&list->node);
        spin_unlock_irqrestore(&list->hiddev->list_lock, flags);

        mutex_lock(&list->hiddev->existancelock);
        if (!--list->hiddev->open) {
                if (list->hiddev->exist) {
                        hid_hw_close(list->hiddev->hid);
                        hid_hw_power(list->hiddev->hid, PM_HINT_NORMAL);
                } else {
                        mutex_unlock(&list->hiddev->existancelock);
                        kfree(list->hiddev);
                        vfree(list);
                        return 0;
                }
        }

        mutex_unlock(&list->hiddev->existancelock);
        vfree(list);

        return 0;
}

static int __hiddev_open(struct hiddev *hiddev, struct file *file)
{
        struct hiddev_list *list;
        int error;

        lockdep_assert_held(&hiddev->existancelock);

        list = vzalloc(sizeof(*list));
        if (!list)
                return -ENOMEM;

        mutex_init(&list->thread_lock);
        list->hiddev = hiddev;

        if (!hiddev->open++) {
                error = hid_hw_power(hiddev->hid, PM_HINT_FULLON);
                if (error < 0)
                        goto err_drop_count;

                error = hid_hw_open(hiddev->hid);
                if (error < 0)
                        goto err_normal_power;
        }

        spin_lock_irq(&hiddev->list_lock);
        list_add_tail(&list->node, &hiddev->list);
        spin_unlock_irq(&hiddev->list_lock);

        file->private_data = list;

        return 0;

err_normal_power:
        hid_hw_power(hiddev->hid, PM_HINT_NORMAL);
err_drop_count:
        hiddev->open--;
        vfree(list);
        return error;
}

/*
 * open file op
 */
static int hiddev_open(struct inode *inode, struct file *file)
{
        struct usb_interface *intf;
        struct hid_device *hid;
        struct hiddev *hiddev;
        int res;

        intf = usbhid_find_interface(iminor(inode));
        if (!intf)
                return -ENODEV;

        hid = usb_get_intfdata(intf);
        hiddev = hid->hiddev;

        mutex_lock(&hiddev->existancelock);
        res = hiddev->exist ? __hiddev_open(hiddev, file) : -ENODEV;
        mutex_unlock(&hiddev->existancelock);

        return res;
}

/*
 * "write" file op
 */
static ssize_t hiddev_write(struct file * file, const char __user * buffer, size_t count, loff_t *ppos)
{
        return -EINVAL;
}

/*
 * "read" file op
 */
static ssize_t hiddev_read(struct file * file, char __user * buffer, size_t count, loff_t *ppos)
{
        DEFINE_WAIT(wait);
        struct hiddev_list *list = file->private_data;
        int event_size;
        int retval;

        event_size = ((list->flags & HIDDEV_FLAG_UREF) != 0) ?
                sizeof(struct hiddev_usage_ref) : sizeof(struct hiddev_event);

        if (count < event_size)
                return 0;

        /* lock against other threads */
        retval = mutex_lock_interruptible(&list->thread_lock);
        if (retval)
                return -ERESTARTSYS;

        while (retval == 0) {
                if (list->head == list->tail) {
                        prepare_to_wait(&list->hiddev->wait, &wait, TASK_INTERRUPTIBLE);

                        while (list->head == list->tail) {
                                if (signal_pending(current)) {
                                        retval = -ERESTARTSYS;
                                        break;
                                }
                                if (!list->hiddev->exist) {
                                        retval = -EIO;
                                        break;
                                }
                                if (file->f_flags & O_NONBLOCK) {
                                        retval = -EAGAIN;
                                        break;
                                }

                                /* let O_NONBLOCK tasks run */
                                mutex_unlock(&list->thread_lock);
                                schedule();
                                if (mutex_lock_interruptible(&list->thread_lock)) {
                                        finish_wait(&list->hiddev->wait, &wait);
                                        return -EINTR;
                                }
                                set_current_state(TASK_INTERRUPTIBLE);
                        }
                        finish_wait(&list->hiddev->wait, &wait);

                }

                if (retval) {
                        mutex_unlock(&list->thread_lock);
                        return retval;
                }


                while (list->head != list->tail &&
                       retval + event_size <= count) {
                        if ((list->flags & HIDDEV_FLAG_UREF) == 0) {
                                if (list->buffer[list->tail].field_index != HID_FIELD_INDEX_NONE) {
                                        struct hiddev_event event;

                                        event.hid = list->buffer[list->tail].usage_code;
                                        event.value = list->buffer[list->tail].value;
                                        if (copy_to_user(buffer + retval, &event, sizeof(struct hiddev_event))) {
                                                mutex_unlock(&list->thread_lock);
                                                return -EFAULT;
                                        }
                                        retval += sizeof(struct hiddev_event);
                                }
                        } else {
                                if (list->buffer[list->tail].field_index != HID_FIELD_INDEX_NONE ||
                                    (list->flags & HIDDEV_FLAG_REPORT) != 0) {

                                        if (copy_to_user(buffer + retval, list->buffer + list->tail, sizeof(struct hiddev_usage_ref))) {
                                                mutex_unlock(&list->thread_lock);
                                                return -EFAULT;
                                        }
                                        retval += sizeof(struct hiddev_usage_ref);
                                }
                        }
                        list->tail = (list->tail + 1) & (HIDDEV_BUFFER_SIZE - 1);
                }

        }
        mutex_unlock(&list->thread_lock);

        return retval;
}

/*
 * "poll" file op
 * No kernel lock - fine
 */
static __poll_t hiddev_poll(struct file *file, poll_table *wait)
{
        struct hiddev_list *list = file->private_data;

        poll_wait(file, &list->hiddev->wait, wait);
        if (list->head != list->tail)
                return EPOLLIN | EPOLLRDNORM | EPOLLOUT;
        if (!list->hiddev->exist)
                return EPOLLERR | EPOLLHUP;
        return 0;
}

/*
 * "ioctl" file op
 */
static noinline int hiddev_ioctl_usage(struct hiddev *hiddev, unsigned int cmd, void __user *user_arg)
{
        struct hid_device *hid = hiddev->hid;
        struct hiddev_report_info rinfo;
        struct hiddev_usage_ref_multi *uref_multi = NULL;
        struct hiddev_usage_ref *uref;
        struct hid_report *report;
        struct hid_field *field;
        int i;

        uref_multi = kmalloc_obj(struct hiddev_usage_ref_multi);
        if (!uref_multi)
                return -ENOMEM;
        uref = &uref_multi->uref;
        if (cmd == HIDIOCGUSAGES || cmd == HIDIOCSUSAGES) {
                if (copy_from_user(uref_multi, user_arg,
                                   sizeof(*uref_multi)))
                        goto fault;
        } else {
                if (copy_from_user(uref, user_arg, sizeof(*uref)))
                        goto fault;
        }

        switch (cmd) {
        case HIDIOCGUCODE:
                rinfo.report_type = uref->report_type;
                rinfo.report_id = uref->report_id;
                if ((report = hiddev_lookup_report(hid, &rinfo)) == NULL)
                        goto inval;

                if (uref->field_index >= report->maxfield)
                        goto inval;
                uref->field_index = array_index_nospec(uref->field_index,
                                                       report->maxfield);

                field = report->field[uref->field_index];
                if (uref->usage_index >= field->maxusage)
                        goto inval;
                uref->usage_index = array_index_nospec(uref->usage_index,
                                                       field->maxusage);

                uref->usage_code = field->usage[uref->usage_index].hid;

                if (copy_to_user(user_arg, uref, sizeof(*uref)))
                        goto fault;

                goto goodreturn;

        default:
                if (cmd != HIDIOCGUSAGE &&
                    cmd != HIDIOCGUSAGES &&
                    uref->report_type == HID_REPORT_TYPE_INPUT)
                        goto inval;

                if (uref->report_id == HID_REPORT_ID_UNKNOWN) {
                        field = hiddev_lookup_usage(hid, uref);
                        if (field == NULL)
                                goto inval;
                } else {
                        rinfo.report_type = uref->report_type;
                        rinfo.report_id = uref->report_id;
                        if ((report = hiddev_lookup_report(hid, &rinfo)) == NULL)
                                goto inval;

                        if (uref->field_index >= report->maxfield)
                                goto inval;
                        uref->field_index = array_index_nospec(uref->field_index,
                                                               report->maxfield);

                        field = report->field[uref->field_index];

                        if (cmd == HIDIOCGCOLLECTIONINDEX) {
                                if (uref->usage_index >= field->maxusage)
                                        goto inval;
                                uref->usage_index =
                                        array_index_nospec(uref->usage_index,
                                                           field->maxusage);
                        } else if (uref->usage_index >= field->report_count)
                                goto inval;
                }

                if (cmd == HIDIOCGUSAGES || cmd == HIDIOCSUSAGES) {
                        if (uref_multi->num_values > HID_MAX_MULTI_USAGES ||
                            uref->usage_index + uref_multi->num_values >
                            field->report_count)
                                goto inval;

                        uref->usage_index =
                                array_index_nospec(uref->usage_index,
                                                   field->report_count -
                                                   uref_multi->num_values);
                }

                switch (cmd) {
                case HIDIOCGUSAGE:
                        if (uref->usage_index >= field->report_count)
                                goto inval;
                        uref->value = field->value[uref->usage_index];
                        if (copy_to_user(user_arg, uref, sizeof(*uref)))
                                goto fault;
                        goto goodreturn;

                case HIDIOCSUSAGE:
                        if (uref->usage_index >= field->report_count)
                                goto inval;
                        field->value[uref->usage_index] = uref->value;
                        goto goodreturn;

                case HIDIOCGCOLLECTIONINDEX:
                        i = field->usage[uref->usage_index].collection_index;
                        kfree(uref_multi);
                        return i;
                case HIDIOCGUSAGES:
                        for (i = 0; i < uref_multi->num_values; i++)
                                uref_multi->values[i] =
                                    field->value[uref->usage_index + i];
                        if (copy_to_user(user_arg, uref_multi,
                                         sizeof(*uref_multi)))
                                goto fault;
                        goto goodreturn;
                case HIDIOCSUSAGES:
                        for (i = 0; i < uref_multi->num_values; i++)
                                field->value[uref->usage_index + i] =
                                    uref_multi->values[i];
                        goto goodreturn;
                }

goodreturn:
                kfree(uref_multi);
                return 0;
fault:
                kfree(uref_multi);
                return -EFAULT;
inval:
                kfree(uref_multi);
                return -EINVAL;
        }
}

static noinline int hiddev_ioctl_string(struct hiddev *hiddev, unsigned int cmd, void __user *user_arg)
{
        struct hid_device *hid = hiddev->hid;
        struct usb_device *dev = hid_to_usb_dev(hid);
        int idx, len;
        char *buf;

        if (get_user(idx, (int __user *)user_arg))
                return -EFAULT;

        if ((buf = kmalloc(HID_STRING_SIZE, GFP_KERNEL)) == NULL)
                return -ENOMEM;

        if ((len = usb_string(dev, idx, buf, HID_STRING_SIZE-1)) < 0) {
                kfree(buf);
                return -EINVAL;
        }

        if (copy_to_user(user_arg+sizeof(int), buf, len+1)) {
                kfree(buf);
                return -EFAULT;
        }

        kfree(buf);

        return len;
}

static long hiddev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
        struct hiddev_list *list = file->private_data;
        struct hiddev *hiddev = list->hiddev;
        struct hid_device *hid;
        struct hiddev_collection_info cinfo;
        struct hiddev_report_info rinfo;
        struct hiddev_field_info finfo;
        struct hiddev_devinfo dinfo;
        struct hid_report *report;
        struct hid_field *field;
        void __user *user_arg = (void __user *)arg;
        int i, r = -EINVAL;

        /* Called without BKL by compat methods so no BKL taken */

        mutex_lock(&hiddev->existancelock);
        if (!hiddev->exist) {
                r = -ENODEV;
                goto ret_unlock;
        }

        hid = hiddev->hid;

        switch (cmd) {

        case HIDIOCGVERSION:
                r = put_user(HID_VERSION, (int __user *)arg) ?
                        -EFAULT : 0;
                break;

        case HIDIOCAPPLICATION:
                if (arg >= hid->maxapplication)
                        break;

                for (i = 0; i < hid->maxcollection; i++)
                        if (hid->collection[i].type ==
                            HID_COLLECTION_APPLICATION && arg-- == 0)
                                break;

                if (i < hid->maxcollection)
                        r = hid->collection[i].usage;
                break;

        case HIDIOCGDEVINFO:
                {
                        struct usb_device *dev = hid_to_usb_dev(hid);
                        struct usbhid_device *usbhid = hid->driver_data;

                        memset(&dinfo, 0, sizeof(dinfo));

                        dinfo.bustype = BUS_USB;
                        dinfo.busnum = dev->bus->busnum;
                        dinfo.devnum = dev->devnum;
                        dinfo.ifnum = usbhid->ifnum;
                        dinfo.vendor = le16_to_cpu(dev->descriptor.idVendor);
                        dinfo.product = le16_to_cpu(dev->descriptor.idProduct);
                        dinfo.version = le16_to_cpu(dev->descriptor.bcdDevice);
                        dinfo.num_applications = hid->maxapplication;

                        r = copy_to_user(user_arg, &dinfo, sizeof(dinfo)) ?
                                -EFAULT : 0;
                        break;
                }

        case HIDIOCGFLAG:
                r = put_user(list->flags, (int __user *)arg) ?
                        -EFAULT : 0;
                break;

        case HIDIOCSFLAG:
                {
                        int newflags;

                        if (get_user(newflags, (int __user *)arg)) {
                                r = -EFAULT;
                                break;
                        }

                        if ((newflags & ~HIDDEV_FLAGS) != 0 ||
                            ((newflags & HIDDEV_FLAG_REPORT) != 0 &&
                             (newflags & HIDDEV_FLAG_UREF) == 0))
                                break;

                        list->flags = newflags;

                        r = 0;
                        break;
                }

        case HIDIOCGSTRING:
                r = hiddev_ioctl_string(hiddev, cmd, user_arg);
                break;

        case HIDIOCINITREPORT:
                usbhid_init_reports(hid);
                hiddev->initialized = true;
                r = 0;
                break;

        case HIDIOCGREPORT:
                if (copy_from_user(&rinfo, user_arg, sizeof(rinfo))) {
                        r = -EFAULT;
                        break;
                }

                if (rinfo.report_type == HID_REPORT_TYPE_OUTPUT)
                        break;

                report = hiddev_lookup_report(hid, &rinfo);
                if (report == NULL)
                        break;

                hid_hw_request(hid, report, HID_REQ_GET_REPORT);
                hid_hw_wait(hid);

                r = 0;
                break;

        case HIDIOCSREPORT:
                if (copy_from_user(&rinfo, user_arg, sizeof(rinfo))) {
                        r = -EFAULT;
                        break;
                }

                if (rinfo.report_type == HID_REPORT_TYPE_INPUT)
                        break;

                report = hiddev_lookup_report(hid, &rinfo);
                if (report == NULL)
                        break;

                hid_hw_request(hid, report, HID_REQ_SET_REPORT);
                hid_hw_wait(hid);

                r = 0;
                break;

        case HIDIOCGREPORTINFO:
                if (copy_from_user(&rinfo, user_arg, sizeof(rinfo))) {
                        r = -EFAULT;
                        break;
                }

                report = hiddev_lookup_report(hid, &rinfo);
                if (report == NULL)
                        break;

                rinfo.num_fields = report->maxfield;

                r = copy_to_user(user_arg, &rinfo, sizeof(rinfo)) ?
                        -EFAULT : 0;
                break;

        case HIDIOCGFIELDINFO:
                if (copy_from_user(&finfo, user_arg, sizeof(finfo))) {
                        r = -EFAULT;
                        break;
                }

                rinfo.report_type = finfo.report_type;
                rinfo.report_id = finfo.report_id;

                report = hiddev_lookup_report(hid, &rinfo);
                if (report == NULL)
                        break;

                if (finfo.field_index >= report->maxfield)
                        break;
                finfo.field_index = array_index_nospec(finfo.field_index,
                                                       report->maxfield);

                field = report->field[finfo.field_index];
                memset(&finfo, 0, sizeof(finfo));
                finfo.report_type = rinfo.report_type;
                finfo.report_id = rinfo.report_id;
                finfo.field_index = field->report_count - 1;
                finfo.maxusage = field->maxusage;
                finfo.flags = field->flags;
                finfo.physical = field->physical;
                finfo.logical = field->logical;
                finfo.application = field->application;
                finfo.logical_minimum = field->logical_minimum;
                finfo.logical_maximum = field->logical_maximum;
                finfo.physical_minimum = field->physical_minimum;
                finfo.physical_maximum = field->physical_maximum;
                finfo.unit_exponent = field->unit_exponent;
                finfo.unit = field->unit;

                r = copy_to_user(user_arg, &finfo, sizeof(finfo)) ?
                        -EFAULT : 0;
                break;

        case HIDIOCGUCODE:
        case HIDIOCGUSAGE:
        case HIDIOCSUSAGE:
        case HIDIOCGUSAGES:
        case HIDIOCSUSAGES:
        case HIDIOCGCOLLECTIONINDEX:
                if (!hiddev->initialized) {
                        usbhid_init_reports(hid);
                        hiddev->initialized = true;
                }
                r = hiddev_ioctl_usage(hiddev, cmd, user_arg);
                break;

        case HIDIOCGCOLLECTIONINFO:
                if (copy_from_user(&cinfo, user_arg, sizeof(cinfo))) {
                        r = -EFAULT;
                        break;
                }

                if (cinfo.index >= hid->maxcollection)
                        break;
                cinfo.index = array_index_nospec(cinfo.index,
                                                 hid->maxcollection);

                cinfo.type = hid->collection[cinfo.index].type;
                cinfo.usage = hid->collection[cinfo.index].usage;
                cinfo.level = hid->collection[cinfo.index].level;

                r = copy_to_user(user_arg, &cinfo, sizeof(cinfo)) ?
                        -EFAULT : 0;
                break;

        default:
                if (_IOC_TYPE(cmd) != 'H' || _IOC_DIR(cmd) != _IOC_READ)
                        break;

                if (_IOC_NR(cmd) == _IOC_NR(HIDIOCGNAME(0))) {
                        int len = strlen(hid->name) + 1;
                        if (len > _IOC_SIZE(cmd))
                                 len = _IOC_SIZE(cmd);
                        r = copy_to_user(user_arg, hid->name, len) ?
                                -EFAULT : len;
                        break;
                }

                if (_IOC_NR(cmd) == _IOC_NR(HIDIOCGPHYS(0))) {
                        int len = strlen(hid->phys) + 1;
                        if (len > _IOC_SIZE(cmd))
                                len = _IOC_SIZE(cmd);
                        r = copy_to_user(user_arg, hid->phys, len) ?
                                -EFAULT : len;
                        break;
                }
        }

ret_unlock:
        mutex_unlock(&hiddev->existancelock);
        return r;
}

static const struct file_operations hiddev_fops = {
        .owner =        THIS_MODULE,
        .read =         hiddev_read,
        .write =        hiddev_write,
        .poll =         hiddev_poll,
        .open =         hiddev_open,
        .release =      hiddev_release,
        .unlocked_ioctl =       hiddev_ioctl,
        .fasync =       hiddev_fasync,
        .compat_ioctl   = compat_ptr_ioctl,
        .llseek         = noop_llseek,
};

static char *hiddev_devnode(const struct device *dev, umode_t *mode)
{
        return kasprintf(GFP_KERNEL, "usb/%s", dev_name(dev));
}

static struct usb_class_driver hiddev_class = {
        .name =         "hiddev%d",
        .devnode =      hiddev_devnode,
        .fops =         &hiddev_fops,
        .minor_base =   HIDDEV_MINOR_BASE,
};

/*
 * This is where hid.c calls us to connect a hid device to the hiddev driver
 */
int hiddev_connect(struct hid_device *hid, unsigned int force)
{
        struct hiddev *hiddev;
        struct usbhid_device *usbhid = hid->driver_data;
        int retval;

        if (!force) {
                unsigned int i;
                for (i = 0; i < hid->maxcollection; i++)
                        if (hid->collection[i].type ==
                            HID_COLLECTION_APPLICATION &&
                            !IS_INPUT_APPLICATION(hid->collection[i].usage))
                                break;

                if (i == hid->maxcollection)
                        return -EINVAL;
        }

        if (!(hiddev = kzalloc_obj(struct hiddev)))
                return -ENOMEM;

        init_waitqueue_head(&hiddev->wait);
        INIT_LIST_HEAD(&hiddev->list);
        spin_lock_init(&hiddev->list_lock);
        mutex_init(&hiddev->existancelock);
        hid->hiddev = hiddev;
        hiddev->hid = hid;
        hiddev->exist = 1;
        retval = usb_register_dev(usbhid->intf, &hiddev_class);
        if (retval) {
                hid_err(hid, "Not able to get a minor for this device\n");
                hid->hiddev = NULL;
                kfree(hiddev);
                return retval;
        }

        /*
         * If HID_QUIRK_NO_INIT_REPORTS is set, make sure we don't initialize
         * the reports.
         */
        hiddev->initialized = hid->quirks & HID_QUIRK_NO_INIT_REPORTS;

        hiddev->minor = usbhid->intf->minor;

        return 0;
}

/*
 * This is where hid.c calls us to disconnect a hiddev device from the
 * corresponding hid device (usually because the usb device has disconnected)
 */
static struct usb_class_driver hiddev_class;
void hiddev_disconnect(struct hid_device *hid)
{
        struct hiddev *hiddev = hid->hiddev;
        struct usbhid_device *usbhid = hid->driver_data;

        usb_deregister_dev(usbhid->intf, &hiddev_class);

        mutex_lock(&hiddev->existancelock);
        hiddev->exist = 0;

        if (hiddev->open) {
                hid_hw_close(hiddev->hid);
                wake_up_interruptible(&hiddev->wait);
                mutex_unlock(&hiddev->existancelock);
        } else {
                mutex_unlock(&hiddev->existancelock);
                kfree(hiddev);
        }
}