/*
 * Dell WMI hotkeys
 *
 * Copyright (C) 2008 Red Hat <mjg@redhat.com>
 * Copyright (C) 2014-2015 Pali Rohár <pali.rohar@gmail.com>
 *
 * Portions based on wistron_btns.c:
 * Copyright (C) 2005 Miloslav Trmac <mitr@volny.cz>
 * Copyright (C) 2005 Bernhard Rosenkraenzer <bero@arklinux.org>
 * Copyright (C) 2005 Dmitry Torokhov <dtor@mail.ru>
 *
 *  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.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/input.h>
#include <linux/input/sparse-keymap.h>
#include <linux/acpi.h>
#include <linux/string.h>
#include <linux/dmi.h>
#include <acpi/video.h>
#include "dell-smbios.h"

MODULE_AUTHOR("Matthew Garrett <mjg@redhat.com>");
MODULE_AUTHOR("Pali Rohár <pali.rohar@gmail.com>");
MODULE_DESCRIPTION("Dell laptop WMI hotkeys driver");
MODULE_LICENSE("GPL");

#define DELL_EVENT_GUID "9DBB5994-A997-11DA-B012-B622A1EF5492"
#define DELL_DESCRIPTOR_GUID "8D9DDCBC-A997-11DA-B012-B622A1EF5492"

static u32 dell_wmi_interface_version;
static bool wmi_requires_smbios_request;

MODULE_ALIAS("wmi:"DELL_EVENT_GUID);
MODULE_ALIAS("wmi:"DELL_DESCRIPTOR_GUID);

static int __init dmi_matched(const struct dmi_system_id *dmi)
{
        wmi_requires_smbios_request = 1;
        return 1;
}

static const struct dmi_system_id dell_wmi_smbios_list[] __initconst = {
        {
                .callback = dmi_matched,
                .ident = "Dell Inspiron M5110",
                .matches = {
                        DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
                        DMI_MATCH(DMI_PRODUCT_NAME, "Inspiron M5110"),
                },
        },
        {
                .callback = dmi_matched,
                .ident = "Dell Vostro V131",
                .matches = {
                        DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
                        DMI_MATCH(DMI_PRODUCT_NAME, "Vostro V131"),
                },
        },
        { }
};

/*
 * Keymap for WMI events of type 0x0000
 *
 * Certain keys are flagged as KE_IGNORE. All of these are either
 * notifications (rather than requests for change) or are also sent
 * via the keyboard controller so should not be sent again.
 */
static const struct key_entry dell_wmi_keymap_type_0000[] __initconst = {
        { KE_IGNORE, 0x003a, { KEY_CAPSLOCK } },

        /* Key code is followed by brightness level */
        { KE_KEY,    0xe005, { KEY_BRIGHTNESSDOWN } },
        { KE_KEY,    0xe006, { KEY_BRIGHTNESSUP } },

        /* Battery health status button */
        { KE_KEY,    0xe007, { KEY_BATTERY } },

        /* Radio devices state change, key code is followed by other values */
        { KE_IGNORE, 0xe008, { KEY_RFKILL } },

        { KE_KEY,    0xe009, { KEY_EJECTCD } },

        /* Key code is followed by: next, active and attached devices */
        { KE_KEY,    0xe00b, { KEY_SWITCHVIDEOMODE } },

        /* Key code is followed by keyboard illumination level */
        { KE_IGNORE, 0xe00c, { KEY_KBDILLUMTOGGLE } },

        /* BIOS error detected */
        { KE_IGNORE, 0xe00d, { KEY_RESERVED } },

        /* Battery was removed or inserted */
        { KE_IGNORE, 0xe00e, { KEY_RESERVED } },

        /* Wifi Catcher */
        { KE_KEY,    0xe011, { KEY_PROG2 } },

        /* Ambient light sensor toggle */
        { KE_IGNORE, 0xe013, { KEY_RESERVED } },

        { KE_IGNORE, 0xe020, { KEY_MUTE } },

        /* Unknown, defined in ACPI DSDT */
        /* { KE_IGNORE, 0xe023, { KEY_RESERVED } }, */

        /* Untested, Dell Instant Launch key on Inspiron 7520 */
        /* { KE_IGNORE, 0xe024, { KEY_RESERVED } }, */

        /* Dell Instant Launch key */
        { KE_KEY,    0xe025, { KEY_PROG4 } },

        /* Audio panel key */
        { KE_IGNORE, 0xe026, { KEY_RESERVED } },

        /* LCD Display On/Off Control key */
        { KE_KEY,    0xe027, { KEY_DISPLAYTOGGLE } },

        /* Untested, Multimedia key on Dell Vostro 3560 */
        /* { KE_IGNORE, 0xe028, { KEY_RESERVED } }, */

        /* Dell Instant Launch key */
        { KE_KEY,    0xe029, { KEY_PROG4 } },

        /* Untested, Windows Mobility Center button on Inspiron 7520 */
        /* { KE_IGNORE, 0xe02a, { KEY_RESERVED } }, */

        /* Unknown, defined in ACPI DSDT */
        /* { KE_IGNORE, 0xe02b, { KEY_RESERVED } }, */

        /* Untested, Dell Audio With Preset Switch button on Inspiron 7520 */
        /* { KE_IGNORE, 0xe02c, { KEY_RESERVED } }, */

        { KE_IGNORE, 0xe02e, { KEY_VOLUMEDOWN } },
        { KE_IGNORE, 0xe030, { KEY_VOLUMEUP } },
        { KE_IGNORE, 0xe033, { KEY_KBDILLUMUP } },
        { KE_IGNORE, 0xe034, { KEY_KBDILLUMDOWN } },
        { KE_IGNORE, 0xe03a, { KEY_CAPSLOCK } },

        /* NIC Link is Up */
        { KE_IGNORE, 0xe043, { KEY_RESERVED } },

        /* NIC Link is Down */
        { KE_IGNORE, 0xe044, { KEY_RESERVED } },

        /*
         * This entry is very suspicious!
         * Originally Matthew Garrett created this dell-wmi driver specially for
         * "button with a picture of a battery" which has event code 0xe045.
         * Later Mario Limonciello from Dell told us that event code 0xe045 is
         * reported by Num Lock and should be ignored because key is send also
         * by keyboard controller.
         * So for now we will ignore this event to prevent potential double
         * Num Lock key press.
         */
        { KE_IGNORE, 0xe045, { KEY_NUMLOCK } },

        /* Scroll lock and also going to tablet mode on portable devices */
        { KE_IGNORE, 0xe046, { KEY_SCROLLLOCK } },

        /* Untested, going from tablet mode on portable devices */
        /* { KE_IGNORE, 0xe047, { KEY_RESERVED } }, */

        /* Dell Support Center key */
        { KE_IGNORE, 0xe06e, { KEY_RESERVED } },

        { KE_IGNORE, 0xe0f7, { KEY_MUTE } },
        { KE_IGNORE, 0xe0f8, { KEY_VOLUMEDOWN } },
        { KE_IGNORE, 0xe0f9, { KEY_VOLUMEUP } },
};

struct dell_bios_keymap_entry {
        u16 scancode;
        u16 keycode;
};

struct dell_bios_hotkey_table {
        struct dmi_header header;
        struct dell_bios_keymap_entry keymap[];

};

struct dell_dmi_results {
        int err;
        int keymap_size;
        struct key_entry *keymap;
};

/* Uninitialized entries here are KEY_RESERVED == 0. */
static const u16 bios_to_linux_keycode[256] __initconst = {
        [0]     = KEY_MEDIA,
        [1]     = KEY_NEXTSONG,
        [2]     = KEY_PLAYPAUSE,
        [3]     = KEY_PREVIOUSSONG,
        [4]     = KEY_STOPCD,
        [5]     = KEY_UNKNOWN,
        [6]     = KEY_UNKNOWN,
        [7]     = KEY_UNKNOWN,
        [8]     = KEY_WWW,
        [9]     = KEY_UNKNOWN,
        [10]    = KEY_VOLUMEDOWN,
        [11]    = KEY_MUTE,
        [12]    = KEY_VOLUMEUP,
        [13]    = KEY_UNKNOWN,
        [14]    = KEY_BATTERY,
        [15]    = KEY_EJECTCD,
        [16]    = KEY_UNKNOWN,
        [17]    = KEY_SLEEP,
        [18]    = KEY_PROG1,
        [19]    = KEY_BRIGHTNESSDOWN,
        [20]    = KEY_BRIGHTNESSUP,
        [21]    = KEY_UNKNOWN,
        [22]    = KEY_KBDILLUMTOGGLE,
        [23]    = KEY_UNKNOWN,
        [24]    = KEY_SWITCHVIDEOMODE,
        [25]    = KEY_UNKNOWN,
        [26]    = KEY_UNKNOWN,
        [27]    = KEY_SWITCHVIDEOMODE,
        [28]    = KEY_UNKNOWN,
        [29]    = KEY_UNKNOWN,
        [30]    = KEY_PROG2,
        [31]    = KEY_UNKNOWN,
        [32]    = KEY_UNKNOWN,
        [33]    = KEY_UNKNOWN,
        [34]    = KEY_UNKNOWN,
        [35]    = KEY_UNKNOWN,
        [36]    = KEY_UNKNOWN,
        [37]    = KEY_UNKNOWN,
        [38]    = KEY_MICMUTE,
        [255]   = KEY_PROG3,
};

/*
 * Keymap for WMI events of type 0x0010
 *
 * These are applied if the 0xB2 DMI hotkey table is present and doesn't
 * override them.
 */
static const struct key_entry dell_wmi_keymap_type_0010[] __initconst = {
        /* Fn-lock */
        { KE_IGNORE, 0x151, { KEY_RESERVED } },

        /* Change keyboard illumination */
        { KE_IGNORE, 0x152, { KEY_KBDILLUMTOGGLE } },

        /*
         * Radio disable (notify only -- there is no model for which the
         * WMI event is supposed to trigger an action).
         */
        { KE_IGNORE, 0x153, { KEY_RFKILL } },

        /* RGB keyboard backlight control */
        { KE_IGNORE, 0x154, { KEY_RESERVED } },

        /* Stealth mode toggle */
        { KE_IGNORE, 0x155, { KEY_RESERVED } },
};

/*
 * Keymap for WMI events of type 0x0011
 */
static const struct key_entry dell_wmi_keymap_type_0011[] __initconst = {
        /* Battery unplugged */
        { KE_IGNORE, 0xfff0, { KEY_RESERVED } },

        /* Battery inserted */
        { KE_IGNORE, 0xfff1, { KEY_RESERVED } },

        /* Keyboard backlight level changed */
        { KE_IGNORE, 0x01e1, { KEY_RESERVED } },
        { KE_IGNORE, 0x02ea, { KEY_RESERVED } },
        { KE_IGNORE, 0x02eb, { KEY_RESERVED } },
        { KE_IGNORE, 0x02ec, { KEY_RESERVED } },
        { KE_IGNORE, 0x02f6, { KEY_RESERVED } },
};

static struct input_dev *dell_wmi_input_dev;

static void dell_wmi_process_key(int type, int code)
{
        const struct key_entry *key;

        key = sparse_keymap_entry_from_scancode(dell_wmi_input_dev,
                                                (type << 16) | code);
        if (!key) {
                pr_info("Unknown key with type 0x%04x and code 0x%04x pressed\n",
                        type, code);
                return;
        }

        pr_debug("Key with type 0x%04x and code 0x%04x pressed\n", type, code);

        /* Don't report brightness notifications that will also come via ACPI */
        if ((key->keycode == KEY_BRIGHTNESSUP ||
             key->keycode == KEY_BRIGHTNESSDOWN) &&
            acpi_video_handles_brightness_key_presses())
                return;

        if (type == 0x0000 && code == 0xe025 && !wmi_requires_smbios_request)
                return;

        sparse_keymap_report_entry(dell_wmi_input_dev, key, 1, true);
}

static void dell_wmi_notify(u32 value, void *context)
{
        struct acpi_buffer response = { ACPI_ALLOCATE_BUFFER, NULL };
        union acpi_object *obj;
        acpi_status status;
        acpi_size buffer_size;
        u16 *buffer_entry, *buffer_end;
        int len, i;

        status = wmi_get_event_data(value, &response);
        if (status != AE_OK) {
                pr_warn("bad event status 0x%x\n", status);
                return;
        }

        obj = (union acpi_object *)response.pointer;
        if (!obj) {
                pr_warn("no response\n");
                return;
        }

        if (obj->type != ACPI_TYPE_BUFFER) {
                pr_warn("bad response type %x\n", obj->type);
                kfree(obj);
                return;
        }

        pr_debug("Received WMI event (%*ph)\n",
                obj->buffer.length, obj->buffer.pointer);

        buffer_entry = (u16 *)obj->buffer.pointer;
        buffer_size = obj->buffer.length/2;
        buffer_end = buffer_entry + buffer_size;

        /*
         * BIOS/ACPI on devices with WMI interface version 0 does not clear
         * buffer before filling it. So next time when BIOS/ACPI send WMI event
         * which is smaller as previous then it contains garbage in buffer from
         * previous event.
         *
         * BIOS/ACPI on devices with WMI interface version 1 clears buffer and
         * sometimes send more events in buffer at one call.
         *
         * So to prevent reading garbage from buffer we will process only first
         * one event on devices with WMI interface version 0.
         */
        if (dell_wmi_interface_version == 0 && buffer_entry < buffer_end)
                if (buffer_end > buffer_entry + buffer_entry[0] + 1)
                        buffer_end = buffer_entry + buffer_entry[0] + 1;

        while (buffer_entry < buffer_end) {

                len = buffer_entry[0];
                if (len == 0)
                        break;

                len++;

                if (buffer_entry + len > buffer_end) {
                        pr_warn("Invalid length of WMI event\n");
                        break;
                }

                pr_debug("Process buffer (%*ph)\n", len*2, buffer_entry);

                switch (buffer_entry[1]) {
                case 0x0000: /* One key pressed or event occurred */
                        if (len > 2)
                                dell_wmi_process_key(0x0000, buffer_entry[2]);
                        /* Other entries could contain additional information */
                        break;
                case 0x0010: /* Sequence of keys pressed */
                case 0x0011: /* Sequence of events occurred */
                        for (i = 2; i < len; ++i)
                                dell_wmi_process_key(buffer_entry[1],
                                                     buffer_entry[i]);
                        break;
                default: /* Unknown event */
                        pr_info("Unknown WMI event type 0x%x\n",
                                (int)buffer_entry[1]);
                        break;
                }

                buffer_entry += len;

        }

        kfree(obj);
}

static bool have_scancode(u32 scancode, const struct key_entry *keymap, int len)
{
        int i;

        for (i = 0; i < len; i++)
                if (keymap[i].code == scancode)
                        return true;

        return false;
}

static void __init handle_dmi_entry(const struct dmi_header *dm,
                                    void *opaque)

{
        struct dell_dmi_results *results = opaque;
        struct dell_bios_hotkey_table *table;
        int hotkey_num, i, pos = 0;
        struct key_entry *keymap;

        if (results->err || results->keymap)
                return;         /* We already found the hotkey table. */

        if (dm->type != 0xb2)
                return;

        table = container_of(dm, struct dell_bios_hotkey_table, header);

        hotkey_num = (table->header.length -
                      sizeof(struct dell_bios_hotkey_table)) /
                                sizeof(struct dell_bios_keymap_entry);
        if (hotkey_num < 1) {
                /*
                 * Historically, dell-wmi would ignore a DMI entry of
                 * fewer than 7 bytes.  Sizes between 4 and 8 bytes are
                 * nonsensical (both the header and all entries are 4
                 * bytes), so we approximate the old behavior by
                 * ignoring tables with fewer than one entry.
                 */
                return;
        }

        keymap = kcalloc(hotkey_num, sizeof(struct key_entry), GFP_KERNEL);
        if (!keymap) {
                results->err = -ENOMEM;
                return;
        }

        for (i = 0; i < hotkey_num; i++) {
                const struct dell_bios_keymap_entry *bios_entry =
                                        &table->keymap[i];

                /* Uninitialized entries are 0 aka KEY_RESERVED. */
                u16 keycode = (bios_entry->keycode <
                               ARRAY_SIZE(bios_to_linux_keycode)) ?
                        bios_to_linux_keycode[bios_entry->keycode] :
                        KEY_RESERVED;

                /*
                 * Log if we find an entry in the DMI table that we don't
                 * understand.  If this happens, we should figure out what
                 * the entry means and add it to bios_to_linux_keycode.
                 */
                if (keycode == KEY_RESERVED) {
                        pr_info("firmware scancode 0x%x maps to unrecognized keycode 0x%x\n",
                                bios_entry->scancode, bios_entry->keycode);
                        continue;
                }

                if (keycode == KEY_KBDILLUMTOGGLE)
                        keymap[pos].type = KE_IGNORE;
                else
                        keymap[pos].type = KE_KEY;
                keymap[pos].code = bios_entry->scancode;
                keymap[pos].keycode = keycode;

                pos++;
        }

        results->keymap = keymap;
        results->keymap_size = pos;
}

static int __init dell_wmi_input_setup(void)
{
        struct dell_dmi_results dmi_results = {};
        struct key_entry *keymap;
        int err, i, pos = 0;

        dell_wmi_input_dev = input_allocate_device();
        if (!dell_wmi_input_dev)
                return -ENOMEM;

        dell_wmi_input_dev->name = "Dell WMI hotkeys";
        dell_wmi_input_dev->phys = "wmi/input0";
        dell_wmi_input_dev->id.bustype = BUS_HOST;

        if (dmi_walk(handle_dmi_entry, &dmi_results)) {
                /*
                 * Historically, dell-wmi ignored dmi_walk errors.  A failure
                 * is certainly surprising, but it probably just indicates
                 * a very old laptop.
                 */
                pr_warn("no DMI; using the old-style hotkey interface\n");
        }

        if (dmi_results.err) {
                err = dmi_results.err;
                goto err_free_dev;
        }

        keymap = kcalloc(dmi_results.keymap_size +
                         ARRAY_SIZE(dell_wmi_keymap_type_0000) +
                         ARRAY_SIZE(dell_wmi_keymap_type_0010) +
                         ARRAY_SIZE(dell_wmi_keymap_type_0011) +
                         1,
                         sizeof(struct key_entry), GFP_KERNEL);
        if (!keymap) {
                kfree(dmi_results.keymap);
                err = -ENOMEM;
                goto err_free_dev;
        }

        /* Append table with events of type 0x0010 which comes from DMI */
        for (i = 0; i < dmi_results.keymap_size; i++) {
                keymap[pos] = dmi_results.keymap[i];
                keymap[pos].code |= (0x0010 << 16);
                pos++;
        }

        kfree(dmi_results.keymap);

        /* Append table with extra events of type 0x0010 which are not in DMI */
        for (i = 0; i < ARRAY_SIZE(dell_wmi_keymap_type_0010); i++) {
                const struct key_entry *entry = &dell_wmi_keymap_type_0010[i];

                /*
                 * Check if we've already found this scancode.  This takes
                 * quadratic time, but it doesn't matter unless the list
                 * of extra keys gets very long.
                 */
                if (dmi_results.keymap_size &&
                    have_scancode(entry->code | (0x0010 << 16),
                                  keymap, dmi_results.keymap_size)
                   )
                        continue;

                keymap[pos] = *entry;
                keymap[pos].code |= (0x0010 << 16);
                pos++;
        }

        /* Append table with events of type 0x0011 */
        for (i = 0; i < ARRAY_SIZE(dell_wmi_keymap_type_0011); i++) {
                keymap[pos] = dell_wmi_keymap_type_0011[i];
                keymap[pos].code |= (0x0011 << 16);
                pos++;
        }

        /*
         * Now append also table with "legacy" events of type 0x0000. Some of
         * them are reported also on laptops which have scancodes in DMI.
         */
        for (i = 0; i < ARRAY_SIZE(dell_wmi_keymap_type_0000); i++) {
                keymap[pos] = dell_wmi_keymap_type_0000[i];
                pos++;
        }

        keymap[pos].type = KE_END;

        err = sparse_keymap_setup(dell_wmi_input_dev, keymap, NULL);
        /*
         * Sparse keymap library makes a copy of keymap so we don't need the
         * original one that was allocated.
         */
        kfree(keymap);
        if (err)
                goto err_free_dev;

        err = input_register_device(dell_wmi_input_dev);
        if (err)
                goto err_free_keymap;

        return 0;

 err_free_keymap:
        sparse_keymap_free(dell_wmi_input_dev);
 err_free_dev:
        input_free_device(dell_wmi_input_dev);
        return err;
}

static void dell_wmi_input_destroy(void)
{
        sparse_keymap_free(dell_wmi_input_dev);
        input_unregister_device(dell_wmi_input_dev);
}

/*
 * Descriptor buffer is 128 byte long and contains:
 *
 *       Name             Offset  Length  Value
 * Vendor Signature          0       4    "DELL"
 * Object Signature          4       4    " WMI"
 * WMI Interface Version     8       4    <version>
 * WMI buffer length        12       4    4096
 */
static int __init dell_wmi_check_descriptor_buffer(void)
{
        struct acpi_buffer out = { ACPI_ALLOCATE_BUFFER, NULL };
        union acpi_object *obj;
        acpi_status status;
        u32 *buffer;

        status = wmi_query_block(DELL_DESCRIPTOR_GUID, 0, &out);
        if (ACPI_FAILURE(status)) {
                pr_err("Cannot read Dell descriptor buffer - %d\n", status);
                return status;
        }

        obj = (union acpi_object *)out.pointer;
        if (!obj) {
                pr_err("Dell descriptor buffer is empty\n");
                return -EINVAL;
        }

        if (obj->type != ACPI_TYPE_BUFFER) {
                pr_err("Cannot read Dell descriptor buffer\n");
                kfree(obj);
                return -EINVAL;
        }

        if (obj->buffer.length != 128) {
                pr_err("Dell descriptor buffer has invalid length (%d)\n",
                        obj->buffer.length);
                if (obj->buffer.length < 16) {
                        kfree(obj);
                        return -EINVAL;
                }
        }

        buffer = (u32 *)obj->buffer.pointer;

        if (buffer[0] != 0x4C4C4544 && buffer[1] != 0x494D5720)
                pr_warn("Dell descriptor buffer has invalid signature (%*ph)\n",
                        8, buffer);

        if (buffer[2] != 0 && buffer[2] != 1)
                pr_warn("Dell descriptor buffer has unknown version (%d)\n",
                        buffer[2]);

        if (buffer[3] != 4096)
                pr_warn("Dell descriptor buffer has invalid buffer length (%d)\n",
                        buffer[3]);

        dell_wmi_interface_version = buffer[2];

        pr_info("Detected Dell WMI interface version %u\n",
                dell_wmi_interface_version);

        kfree(obj);
        return 0;
}

/*
 * According to Dell SMBIOS documentation:
 *
 * 17  3  Application Program Registration
 *
 *     cbArg1 Application ID 1 = 0x00010000
 *     cbArg2 Application ID 2
 *            QUICKSET/DCP = 0x51534554 "QSET"
 *            ALS Driver   = 0x416c7353 "AlsS"
 *            Latitude ON  = 0x4c6f6e52 "LonR"
 *     cbArg3 Application version or revision number
 *     cbArg4 0 = Unregister application
 *            1 = Register application
 *     cbRes1 Standard return codes (0, -1, -2)
 */

static int dell_wmi_events_set_enabled(bool enable)
{
        struct calling_interface_buffer *buffer;
        int ret;

        buffer = dell_smbios_get_buffer();
        buffer->input[0] = 0x10000;
        buffer->input[1] = 0x51534554;
        buffer->input[3] = enable;
        dell_smbios_send_request(17, 3);
        ret = buffer->output[0];
        dell_smbios_release_buffer();

        return dell_smbios_error(ret);
}

static int __init dell_wmi_init(void)
{
        int err;
        acpi_status status;

        if (!wmi_has_guid(DELL_EVENT_GUID) ||
            !wmi_has_guid(DELL_DESCRIPTOR_GUID)) {
                pr_warn("Dell WMI GUID were not found\n");
                return -ENODEV;
        }

        err = dell_wmi_check_descriptor_buffer();
        if (err)
                return err;

        err = dell_wmi_input_setup();
        if (err)
                return err;

        status = wmi_install_notify_handler(DELL_EVENT_GUID,
                                         dell_wmi_notify, NULL);
        if (ACPI_FAILURE(status)) {
                dell_wmi_input_destroy();
                pr_err("Unable to register notify handler - %d\n", status);
                return -ENODEV;
        }

        dmi_check_system(dell_wmi_smbios_list);

        if (wmi_requires_smbios_request) {
                err = dell_wmi_events_set_enabled(true);
                if (err) {
                        pr_err("Failed to enable WMI events\n");
                        wmi_remove_notify_handler(DELL_EVENT_GUID);
                        dell_wmi_input_destroy();
                        return err;
                }
        }

        return 0;
}
module_init(dell_wmi_init);

static void __exit dell_wmi_exit(void)
{
        if (wmi_requires_smbios_request)
                dell_wmi_events_set_enabled(false);
        wmi_remove_notify_handler(DELL_EVENT_GUID);
        dell_wmi_input_destroy();
}
module_exit(dell_wmi_exit);