wmi.c

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/*
 *  ACPI-WMI mapping driver
 *
 *  Copyright (C) 2007-2008 Carlos Corbacho <[email protected]>
 *
 *  GUID parsing code from ldm.c is:
 *   Copyright (C) 2001,2002 Richard Russon <[email protected]>
 *   Copyright (c) 2001-2007 Anton Altaparmakov
 *   Copyright (C) 2001,2002 Jakob Kemi <[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.
 *
 *  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/init.h>
#include <linux/types.h>
#include <linux/device.h>
#include <linux/list.h>
#include <linux/acpi.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <acpi/acpi_bus.h>
#include <acpi/acpi_drivers.h>

ACPI_MODULE_NAME("wmi");
MODULE_AUTHOR("Carlos Corbacho");
MODULE_DESCRIPTION("ACPI-WMI Mapping Driver");
MODULE_LICENSE("GPL");

#define ACPI_WMI_CLASS "wmi"

static DEFINE_MUTEX(wmi_data_lock);
static LIST_HEAD(wmi_block_list);

struct guid_block {
    char guid[16];
    union {
        char object_id[2];
        struct {
            unsigned char notify_id;
            unsigned char reserved;
        };
    };
    u8 instance_count;
    u8 flags;
};

struct wmi_block {
    struct list_head list;
    struct guid_block gblock;
    acpi_handle handle;
    wmi_notify_handler handler;
    void *handler_data;
    struct device dev;
};


/*
 * If the GUID data block is marked as expensive, we must enable and
 * explicitily disable data collection.
 */
#define ACPI_WMI_EXPENSIVE   0x1
#define ACPI_WMI_METHOD      0x2    /* GUID is a method */
#define ACPI_WMI_STRING      0x4    /* GUID takes & returns a string */
#define ACPI_WMI_EVENT       0x8    /* GUID is an event */

static bool debug_event;
module_param(debug_event, bool, 0444);
MODULE_PARM_DESC(debug_event,
         "Log WMI Events [0/1]");

static bool debug_dump_wdg;
module_param(debug_dump_wdg, bool, 0444);
MODULE_PARM_DESC(debug_dump_wdg,
         "Dump available WMI interfaces [0/1]");

static int acpi_wmi_remove(struct acpi_device *device, int type);
static int acpi_wmi_add(struct acpi_device *device);
static void acpi_wmi_notify(struct acpi_device *device, u32 event);

static const struct acpi_device_id wmi_device_ids[] = {
    {"PNP0C14", 0},
    {"pnp0c14", 0},
    {"", 0},
};
MODULE_DEVICE_TABLE(acpi, wmi_device_ids);

static struct acpi_driver acpi_wmi_driver = {
    .name = "wmi",
    .class = ACPI_WMI_CLASS,
    .ids = wmi_device_ids,
    .ops = {
        .add = acpi_wmi_add,
        .remove = acpi_wmi_remove,
        .notify = acpi_wmi_notify,
    },
};

/*
 * GUID parsing functions
 */

static int wmi_parse_hexbyte(const u8 *src)
{
    int h;
    int value;

    /* high part */
    h = value = hex_to_bin(src[0]);
    if (value < 0)
        return -1;

    /* low part */
    value = hex_to_bin(src[1]);
    if (value >= 0)
        return (h << 4) | value;
    return -1;
}

static void wmi_swap_bytes(u8 *src, u8 *dest)
{
    int i;

    for (i = 0; i <= 3; i++)
        memcpy(dest + i, src + (3 - i), 1);

    for (i = 0; i <= 1; i++)
        memcpy(dest + 4 + i, src + (5 - i), 1);

    for (i = 0; i <= 1; i++)
        memcpy(dest + 6 + i, src + (7 - i), 1);

    memcpy(dest + 8, src + 8, 8);
}

static bool wmi_parse_guid(const u8 *src, u8 *dest)
{
    static const int size[] = { 4, 2, 2, 2, 6 };
    int i, j, v;

    if (src[8]  != '-' || src[13] != '-' ||
        src[18] != '-' || src[23] != '-')
        return false;

    for (j = 0; j < 5; j++, src++) {
        for (i = 0; i < size[j]; i++, src += 2, *dest++ = v) {
            v = wmi_parse_hexbyte(src);
            if (v < 0)
                return false;
        }
    }

    return true;
}

/*
 * Convert a raw GUID to the ACII string representation
 */
static int wmi_gtoa(const char *in, char *out)
{
    int i;

    for (i = 3; i >= 0; i--)
        out += sprintf(out, "%02X", in[i] & 0xFF);

    out += sprintf(out, "-");
    out += sprintf(out, "%02X", in[5] & 0xFF);
    out += sprintf(out, "%02X", in[4] & 0xFF);
    out += sprintf(out, "-");
    out += sprintf(out, "%02X", in[7] & 0xFF);
    out += sprintf(out, "%02X", in[6] & 0xFF);
    out += sprintf(out, "-");
    out += sprintf(out, "%02X", in[8] & 0xFF);
    out += sprintf(out, "%02X", in[9] & 0xFF);
    out += sprintf(out, "-");

    for (i = 10; i <= 15; i++)
        out += sprintf(out, "%02X", in[i] & 0xFF);

    *out = '\0';
    return 0;
}

static bool find_guid(const char *guid_string, struct wmi_block **out)
{
    char tmp[16], guid_input[16];
    struct wmi_block *wblock;
    struct guid_block *block;
    struct list_head *p;

    wmi_parse_guid(guid_string, tmp);
    wmi_swap_bytes(tmp, guid_input);

    list_for_each(p, &wmi_block_list) {
        wblock = list_entry(p, struct wmi_block, list);
        block = &wblock->gblock;

        if (memcmp(block->guid, guid_input, 16) == 0) {
            if (out)
                *out = wblock;
            return 1;
        }
    }
    return 0;
}

static acpi_status wmi_method_enable(struct wmi_block *wblock, int enable)
{
    struct guid_block *block = NULL;
    char method[5];
    struct acpi_object_list input;
    union acpi_object params[1];
    acpi_status status;
    acpi_handle handle;

    block = &wblock->gblock;
    handle = wblock->handle;

    if (!block)
        return AE_NOT_EXIST;

    input.count = 1;
    input.pointer = params;
    params[0].type = ACPI_TYPE_INTEGER;
    params[0].integer.value = enable;

    snprintf(method, 5, "WE%02X", block->notify_id);
    status = acpi_evaluate_object(handle, method, &input, NULL);

    if (status != AE_OK && status != AE_NOT_FOUND)
        return status;
    else
        return AE_OK;
}

/*
 * Exported WMI functions
 */
acpi_status wmi_evaluate_method(const char *guid_string, u8 instance,
u32 method_id, const struct acpi_buffer *in, struct acpi_buffer *out)
{
    struct guid_block *block = NULL;
    struct wmi_block *wblock = NULL;
    acpi_handle handle;
    acpi_status status;
    struct acpi_object_list input;
    union acpi_object params[3];
    char method[5] = "WM";

    if (!find_guid(guid_string, &wblock))
        return AE_ERROR;

    block = &wblock->gblock;
    handle = wblock->handle;

    if (!(block->flags & ACPI_WMI_METHOD))
        return AE_BAD_DATA;

    if (block->instance_count < instance)
        return AE_BAD_PARAMETER;

    input.count = 2;
    input.pointer = params;
    params[0].type = ACPI_TYPE_INTEGER;
    params[0].integer.value = instance;
    params[1].type = ACPI_TYPE_INTEGER;
    params[1].integer.value = method_id;

    if (in) {
        input.count = 3;

        if (block->flags & ACPI_WMI_STRING) {
            params[2].type = ACPI_TYPE_STRING;
        } else {
            params[2].type = ACPI_TYPE_BUFFER;
        }
        params[2].buffer.length = in->length;
        params[2].buffer.pointer = in->pointer;
    }

    strncat(method, block->object_id, 2);

    status = acpi_evaluate_object(handle, method, &input, out);

    return status;
}
EXPORT_SYMBOL_GPL(wmi_evaluate_method);

acpi_status wmi_query_block(const char *guid_string, u8 instance,
struct acpi_buffer *out)
{
    struct guid_block *block = NULL;
    struct wmi_block *wblock = NULL;
    acpi_handle handle, wc_handle;
    acpi_status status, wc_status = AE_ERROR;
    struct acpi_object_list input, wc_input;
    union acpi_object wc_params[1], wq_params[1];
    char method[5];
    char wc_method[5] = "WC";

    if (!guid_string || !out)
        return AE_BAD_PARAMETER;

    if (!find_guid(guid_string, &wblock))
        return AE_ERROR;

    block = &wblock->gblock;
    handle = wblock->handle;

    if (block->instance_count < instance)
        return AE_BAD_PARAMETER;

    /* Check GUID is a data block */
    if (block->flags & (ACPI_WMI_EVENT | ACPI_WMI_METHOD))
        return AE_ERROR;

    input.count = 1;
    input.pointer = wq_params;
    wq_params[0].type = ACPI_TYPE_INTEGER;
    wq_params[0].integer.value = instance;

    /*
     * If ACPI_WMI_EXPENSIVE, call the relevant WCxx method first to
     * enable collection.
     */
    if (block->flags & ACPI_WMI_EXPENSIVE) {
        wc_input.count = 1;
        wc_input.pointer = wc_params;
        wc_params[0].type = ACPI_TYPE_INTEGER;
        wc_params[0].integer.value = 1;

        strncat(wc_method, block->object_id, 2);

        /*
         * Some GUIDs break the specification by declaring themselves
         * expensive, but have no corresponding WCxx method. So we
         * should not fail if this happens.
         */
        wc_status = acpi_get_handle(handle, wc_method, &wc_handle);
        if (ACPI_SUCCESS(wc_status))
            wc_status = acpi_evaluate_object(handle, wc_method,
                &wc_input, NULL);
    }

    strcpy(method, "WQ");
    strncat(method, block->object_id, 2);

    status = acpi_evaluate_object(handle, method, &input, out);

    /*
     * If ACPI_WMI_EXPENSIVE, call the relevant WCxx method, even if
     * the WQxx method failed - we should disable collection anyway.
     */
    if ((block->flags & ACPI_WMI_EXPENSIVE) && ACPI_SUCCESS(wc_status)) {
        wc_params[0].integer.value = 0;
        status = acpi_evaluate_object(handle,
        wc_method, &wc_input, NULL);
    }

    return status;
}
EXPORT_SYMBOL_GPL(wmi_query_block);

acpi_status wmi_set_block(const char *guid_string, u8 instance,
const struct acpi_buffer *in)
{
    struct guid_block *block = NULL;
    struct wmi_block *wblock = NULL;
    acpi_handle handle;
    struct acpi_object_list input;
    union acpi_object params[2];
    char method[5] = "WS";

    if (!guid_string || !in)
        return AE_BAD_DATA;

    if (!find_guid(guid_string, &wblock))
        return AE_ERROR;

    block = &wblock->gblock;
    handle = wblock->handle;

    if (block->instance_count < instance)
        return AE_BAD_PARAMETER;

    /* Check GUID is a data block */
    if (block->flags & (ACPI_WMI_EVENT | ACPI_WMI_METHOD))
        return AE_ERROR;

    input.count = 2;
    input.pointer = params;
    params[0].type = ACPI_TYPE_INTEGER;
    params[0].integer.value = instance;

    if (block->flags & ACPI_WMI_STRING) {
        params[1].type = ACPI_TYPE_STRING;
    } else {
        params[1].type = ACPI_TYPE_BUFFER;
    }
    params[1].buffer.length = in->length;
    params[1].buffer.pointer = in->pointer;

    strncat(method, block->object_id, 2);

    return acpi_evaluate_object(handle, method, &input, NULL);
}
EXPORT_SYMBOL_GPL(wmi_set_block);

static void wmi_dump_wdg(const struct guid_block *g)
{
    char guid_string[37];

    wmi_gtoa(g->guid, guid_string);

    pr_info("%s:\n", guid_string);
    pr_info("\tobject_id: %c%c\n", g->object_id[0], g->object_id[1]);
    pr_info("\tnotify_id: %02X\n", g->notify_id);
    pr_info("\treserved: %02X\n", g->reserved);
    pr_info("\tinstance_count: %d\n", g->instance_count);
    pr_info("\tflags: %#x", g->flags);
    if (g->flags) {
        if (g->flags & ACPI_WMI_EXPENSIVE)
            pr_cont(" ACPI_WMI_EXPENSIVE");
        if (g->flags & ACPI_WMI_METHOD)
            pr_cont(" ACPI_WMI_METHOD");
        if (g->flags & ACPI_WMI_STRING)
            pr_cont(" ACPI_WMI_STRING");
        if (g->flags & ACPI_WMI_EVENT)
            pr_cont(" ACPI_WMI_EVENT");
    }
    pr_cont("\n");

}

static void wmi_notify_debug(u32 value, void *context)
{
    struct acpi_buffer response = { ACPI_ALLOCATE_BUFFER, NULL };
    union acpi_object *obj;
    acpi_status status;

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

    obj = (union acpi_object *)response.pointer;

    if (!obj)
        return;

    pr_info("DEBUG Event ");
    switch(obj->type) {
    case ACPI_TYPE_BUFFER:
        pr_cont("BUFFER_TYPE - length %d\n", obj->buffer.length);
        break;
    case ACPI_TYPE_STRING:
        pr_cont("STRING_TYPE - %s\n", obj->string.pointer);
        break;
    case ACPI_TYPE_INTEGER:
        pr_cont("INTEGER_TYPE - %llu\n", obj->integer.value);
        break;
    case ACPI_TYPE_PACKAGE:
        pr_cont("PACKAGE_TYPE - %d elements\n", obj->package.count);
        break;
    default:
        pr_cont("object type 0x%X\n", obj->type);
    }
    kfree(obj);
}

acpi_status wmi_install_notify_handler(const char *guid,
wmi_notify_handler handler, void *data)
{
    struct wmi_block *block;
    acpi_status status = AE_NOT_EXIST;
    char tmp[16], guid_input[16];
    struct list_head *p;

    if (!guid || !handler)
        return AE_BAD_PARAMETER;

    wmi_parse_guid(guid, tmp);
    wmi_swap_bytes(tmp, guid_input);

    list_for_each(p, &wmi_block_list) {
        acpi_status wmi_status;
        block = list_entry(p, struct wmi_block, list);

        if (memcmp(block->gblock.guid, guid_input, 16) == 0) {
            if (block->handler &&
                block->handler != wmi_notify_debug)
                return AE_ALREADY_ACQUIRED;

            block->handler = handler;
            block->handler_data = data;

            wmi_status = wmi_method_enable(block, 1);
            if ((wmi_status != AE_OK) ||
                ((wmi_status == AE_OK) && (status == AE_NOT_EXIST)))
                status = wmi_status;
        }
    }

    return status;
}
EXPORT_SYMBOL_GPL(wmi_install_notify_handler);

acpi_status wmi_remove_notify_handler(const char *guid)
{
    struct wmi_block *block;
    acpi_status status = AE_NOT_EXIST;
    char tmp[16], guid_input[16];
    struct list_head *p;

    if (!guid)
        return AE_BAD_PARAMETER;

    wmi_parse_guid(guid, tmp);
    wmi_swap_bytes(tmp, guid_input);

    list_for_each(p, &wmi_block_list) {
        acpi_status wmi_status;
        block = list_entry(p, struct wmi_block, list);

        if (memcmp(block->gblock.guid, guid_input, 16) == 0) {
            if (!block->handler ||
                block->handler == wmi_notify_debug)
                return AE_NULL_ENTRY;

            if (debug_event) {
                block->handler = wmi_notify_debug;
                status = AE_OK;
            } else {
                wmi_status = wmi_method_enable(block, 0);
                block->handler = NULL;
                block->handler_data = NULL;
                if ((wmi_status != AE_OK) ||
                    ((wmi_status == AE_OK) &&
                     (status == AE_NOT_EXIST)))
                    status = wmi_status;
            }
        }
    }

    return status;
}
EXPORT_SYMBOL_GPL(wmi_remove_notify_handler);

acpi_status wmi_get_event_data(u32 event, struct acpi_buffer *out)
{
    struct acpi_object_list input;
    union acpi_object params[1];
    struct guid_block *gblock;
    struct wmi_block *wblock;
    struct list_head *p;

    input.count = 1;
    input.pointer = params;
    params[0].type = ACPI_TYPE_INTEGER;
    params[0].integer.value = event;

    list_for_each(p, &wmi_block_list) {
        wblock = list_entry(p, struct wmi_block, list);
        gblock = &wblock->gblock;

        if ((gblock->flags & ACPI_WMI_EVENT) &&
            (gblock->notify_id == event))
            return acpi_evaluate_object(wblock->handle, "_WED",
                &input, out);
    }

    return AE_NOT_FOUND;
}
EXPORT_SYMBOL_GPL(wmi_get_event_data);

bool wmi_has_guid(const char *guid_string)
{
    return find_guid(guid_string, NULL);
}
EXPORT_SYMBOL_GPL(wmi_has_guid);

/*
 * sysfs interface
 */
static ssize_t modalias_show(struct device *dev, struct device_attribute *attr,
                 char *buf)
{
    char guid_string[37];
    struct wmi_block *wblock;

    wblock = dev_get_drvdata(dev);
    if (!wblock)
        return -ENOMEM;

    wmi_gtoa(wblock->gblock.guid, guid_string);

    return sprintf(buf, "wmi:%s\n", guid_string);
}

static struct device_attribute wmi_dev_attrs[] = {
    __ATTR_RO(modalias),
    __ATTR_NULL
};

static int wmi_dev_uevent(struct device *dev, struct kobj_uevent_env *env)
{
    char guid_string[37];

    struct wmi_block *wblock;

    if (add_uevent_var(env, "MODALIAS="))
        return -ENOMEM;

    wblock = dev_get_drvdata(dev);
    if (!wblock)
        return -ENOMEM;

    wmi_gtoa(wblock->gblock.guid, guid_string);

    strcpy(&env->buf[env->buflen - 1], "wmi:");
    memcpy(&env->buf[env->buflen - 1 + 4], guid_string, 36);
    env->buflen += 40;

    return 0;
}

static void wmi_dev_free(struct device *dev)
{
    struct wmi_block *wmi_block = container_of(dev, struct wmi_block, dev);

    kfree(wmi_block);
}

static struct class wmi_class = {
    .name = "wmi",
    .dev_release = wmi_dev_free,
    .dev_uevent = wmi_dev_uevent,
    .dev_attrs = wmi_dev_attrs,
};

static int wmi_create_device(const struct guid_block *gblock,
                 struct wmi_block *wblock, acpi_handle handle)
{
    char guid_string[37];

    wblock->dev.class = &wmi_class;

    wmi_gtoa(gblock->guid, guid_string);
    dev_set_name(&wblock->dev, guid_string);

    dev_set_drvdata(&wblock->dev, wblock);

    return device_register(&wblock->dev);
}

static void wmi_free_devices(void)
{
    struct wmi_block *wblock, *next;

    /* Delete devices for all the GUIDs */
    list_for_each_entry_safe(wblock, next, &wmi_block_list, list) {
        list_del(&wblock->list);
        if (wblock->dev.class)
            device_unregister(&wblock->dev);
        else
            kfree(wblock);
    }
}

static bool guid_already_parsed(const char *guid_string)
{
    struct wmi_block *wblock;

    list_for_each_entry(wblock, &wmi_block_list, list)
        if (memcmp(wblock->gblock.guid, guid_string, 16) == 0)
            return true;

    return false;
}

/*
 * Parse the _WDG method for the GUID data blocks
 */
static acpi_status parse_wdg(acpi_handle handle)
{
    struct acpi_buffer out = {ACPI_ALLOCATE_BUFFER, NULL};
    union acpi_object *obj;
    const struct guid_block *gblock;
    struct wmi_block *wblock;
    acpi_status status;
    int retval;
    u32 i, total;

    status = acpi_evaluate_object(handle, "_WDG", NULL, &out);
    if (ACPI_FAILURE(status))
        return -ENXIO;

    obj = (union acpi_object *) out.pointer;
    if (!obj)
        return -ENXIO;

    if (obj->type != ACPI_TYPE_BUFFER) {
        retval = -ENXIO;
        goto out_free_pointer;
    }

    gblock = (const struct guid_block *)obj->buffer.pointer;
    total = obj->buffer.length / sizeof(struct guid_block);

    for (i = 0; i < total; i++) {
        if (debug_dump_wdg)
            wmi_dump_wdg(&gblock[i]);

        wblock = kzalloc(sizeof(struct wmi_block), GFP_KERNEL);
        if (!wblock)
            return AE_NO_MEMORY;

        wblock->handle = handle;
        wblock->gblock = gblock[i];

        /*
          Some WMI devices, like those for nVidia hooks, have a
          duplicate GUID. It's not clear what we should do in this
          case yet, so for now, we'll just ignore the duplicate
          for device creation.
        */
        if (!guid_already_parsed(gblock[i].guid)) {
            retval = wmi_create_device(&gblock[i], wblock, handle);
            if (retval) {
                wmi_free_devices();
                goto out_free_pointer;
            }
        }

        list_add_tail(&wblock->list, &wmi_block_list);

        if (debug_event) {
            wblock->handler = wmi_notify_debug;
            wmi_method_enable(wblock, 1);
        }
    }

    retval = 0;

out_free_pointer:
    kfree(out.pointer);

    return retval;
}

/*
 * WMI can have EmbeddedControl access regions. In which case, we just want to
 * hand these off to the EC driver.
 */
static acpi_status
acpi_wmi_ec_space_handler(u32 function, acpi_physical_address address,
              u32 bits, u64 *value,
              void *handler_context, void *region_context)
{
    int result = 0, i = 0;
    u8 temp = 0;

    if ((address > 0xFF) || !value)
        return AE_BAD_PARAMETER;

    if (function != ACPI_READ && function != ACPI_WRITE)
        return AE_BAD_PARAMETER;

    if (bits != 8)
        return AE_BAD_PARAMETER;

    if (function == ACPI_READ) {
        result = ec_read(address, &temp);
        (*value) |= ((u64)temp) << i;
    } else {
        temp = 0xff & ((*value) >> i);
        result = ec_write(address, temp);
    }

    switch (result) {
    case -EINVAL:
        return AE_BAD_PARAMETER;
        break;
    case -ENODEV:
        return AE_NOT_FOUND;
        break;
    case -ETIME:
        return AE_TIME;
        break;
    default:
        return AE_OK;
    }
}

static void acpi_wmi_notify(struct acpi_device *device, u32 event)
{
    struct guid_block *block;
    struct wmi_block *wblock;
    struct list_head *p;
    char guid_string[37];

    list_for_each(p, &wmi_block_list) {
        wblock = list_entry(p, struct wmi_block, list);
        block = &wblock->gblock;

        if ((block->flags & ACPI_WMI_EVENT) &&
            (block->notify_id == event)) {
            if (wblock->handler)
                wblock->handler(event, wblock->handler_data);
            if (debug_event) {
                wmi_gtoa(wblock->gblock.guid, guid_string);
                pr_info("DEBUG Event GUID: %s\n", guid_string);
            }

            acpi_bus_generate_netlink_event(
                device->pnp.device_class, dev_name(&device->dev),
                event, 0);
            break;
        }
    }
}

static int acpi_wmi_remove(struct acpi_device *device, int type)
{
    acpi_remove_address_space_handler(device->handle,
                ACPI_ADR_SPACE_EC, &acpi_wmi_ec_space_handler);
    wmi_free_devices();

    return 0;
}

static int acpi_wmi_add(struct acpi_device *device)
{
    acpi_status status;
    int error;

    status = acpi_install_address_space_handler(device->handle,
                            ACPI_ADR_SPACE_EC,
                            &acpi_wmi_ec_space_handler,
                            NULL, NULL);
    if (ACPI_FAILURE(status)) {
        pr_err("Error installing EC region handler\n");
        return -ENODEV;
    }

    error = parse_wdg(device->handle);
    if (error) {
        acpi_remove_address_space_handler(device->handle,
                          ACPI_ADR_SPACE_EC,
                          &acpi_wmi_ec_space_handler);
        pr_err("Failed to parse WDG method\n");
        return error;
    }

    return 0;
}

static int __init acpi_wmi_init(void)
{
    int error;

    if (acpi_disabled)
        return -ENODEV;

    error = class_register(&wmi_class);
    if (error)
        return error;

    error = acpi_bus_register_driver(&acpi_wmi_driver);
    if (error) {
        pr_err("Error loading mapper\n");
        class_unregister(&wmi_class);
        return error;
    }

    pr_info("Mapper loaded\n");
    return 0;
}

static void __exit acpi_wmi_exit(void)
{
    acpi_bus_unregister_driver(&acpi_wmi_driver);
    class_unregister(&wmi_class);

    pr_info("Mapper unloaded\n");
}

subsys_initcall(acpi_wmi_init);
module_exit(acpi_wmi_exit);