// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  ACPI-WMI mapping driver
 *
 *  Copyright (C) 2007-2008 Carlos Corbacho <carlos@strangeworlds.co.uk>
 *
 *  GUID parsing code from ldm.c is:
 *   Copyright (C) 2001,2002 Richard Russon <ldm@flatcap.org>
 *   Copyright (c) 2001-2007 Anton Altaparmakov
 *   Copyright (C) 2001,2002 Jakob Kemi <jakob.kemi@telia.com>
 *
 *  WMI bus infrastructure by Andrew Lutomirski and Darren Hart:
 *    Copyright (C) 2015 Andrew Lutomirski
 *    Copyright (C) 2017 VMware, Inc. All Rights Reserved.
 */

#define pr_fmt(fmt)     KBUILD_MODNAME ": " fmt

#include <linux/acpi.h>
#include <linux/device.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/uaccess.h>
#include <linux/uuid.h>
#include <linux/wmi.h>
#include <linux/fs.h>
#include <uapi/linux/wmi.h>

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

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 wmi_device dev;
        struct list_head list;
        struct guid_block gblock;
        struct miscdevice char_dev;
        struct mutex char_mutex;
        struct acpi_device *acpi_device;
        wmi_notify_handler handler;
        void *handler_data;
        u64 req_buf_size;

        bool read_takes_no_args;
};


/*
 * 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 platform_device *device);
static int acpi_wmi_probe(struct platform_device *device);

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

static struct platform_driver acpi_wmi_driver = {
        .driver = {
                .name = "acpi-wmi",
                .acpi_match_table = wmi_device_ids,
        },
        .probe = acpi_wmi_probe,
        .remove = acpi_wmi_remove,
};

/*
 * GUID parsing functions
 */

static bool find_guid(const char *guid_string, struct wmi_block **out)
{
        uuid_le guid_input;
        struct wmi_block *wblock;
        struct guid_block *block;

        if (uuid_le_to_bin(guid_string, &guid_input))
                return false;

        list_for_each_entry(wblock, &wmi_block_list, list) {
                block = &wblock->gblock;

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

static const void *find_guid_context(struct wmi_block *wblock,
                                      struct wmi_driver *wdriver)
{
        const struct wmi_device_id *id;
        uuid_le guid_input;

        if (wblock == NULL || wdriver == NULL)
                return NULL;
        if (wdriver->id_table == NULL)
                return NULL;

        id = wdriver->id_table;
        while (*id->guid_string) {
                if (uuid_le_to_bin(id->guid_string, &guid_input))
                        continue;
                if (!memcmp(wblock->gblock.guid, &guid_input, 16))
                        return id->context;
                id++;
        }
        return NULL;
}

static int get_subobj_info(acpi_handle handle, const char *pathname,
                           struct acpi_device_info **info)
{
        struct acpi_device_info *dummy_info, **info_ptr;
        acpi_handle subobj_handle;
        acpi_status status;

        status = acpi_get_handle(handle, (char *)pathname, &subobj_handle);
        if (status == AE_NOT_FOUND)
                return -ENOENT;
        else if (ACPI_FAILURE(status))
                return -EIO;

        info_ptr = info ? info : &dummy_info;
        status = acpi_get_object_info(subobj_handle, info_ptr);
        if (ACPI_FAILURE(status))
                return -EIO;

        if (!info)
                kfree(dummy_info);

        return 0;
}

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

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

        snprintf(method, 5, "WE%02X", block->notify_id);
        status = acpi_execute_simple_method(handle, method, enable);

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

/*
 * Exported WMI functions
 */

/**
 * set_required_buffer_size - Sets the buffer size needed for performing IOCTL
 * @wdev: A wmi bus device from a driver
 * @instance: Instance index
 *
 * Allocates memory needed for buffer, stores the buffer size in that memory
 */
int set_required_buffer_size(struct wmi_device *wdev, u64 length)
{
        struct wmi_block *wblock;

        wblock = container_of(wdev, struct wmi_block, dev);
        wblock->req_buf_size = length;

        return 0;
}
EXPORT_SYMBOL_GPL(set_required_buffer_size);

/**
 * wmi_evaluate_method - Evaluate a WMI method
 * @guid_string: 36 char string of the form fa50ff2b-f2e8-45de-83fa-65417f2f49ba
 * @instance: Instance index
 * @method_id: Method ID to call
 * &in: Buffer containing input for the method call
 * &out: Empty buffer to return the method results
 *
 * Call an ACPI-WMI method
 */
acpi_status wmi_evaluate_method(const char *guid_string, u8 instance,
u32 method_id, const struct acpi_buffer *in, struct acpi_buffer *out)
{
        struct wmi_block *wblock = NULL;

        if (!find_guid(guid_string, &wblock))
                return AE_ERROR;
        return wmidev_evaluate_method(&wblock->dev, instance, method_id,
                                      in, out);
}
EXPORT_SYMBOL_GPL(wmi_evaluate_method);

/**
 * wmidev_evaluate_method - Evaluate a WMI method
 * @wdev: A wmi bus device from a driver
 * @instance: Instance index
 * @method_id: Method ID to call
 * &in: Buffer containing input for the method call
 * &out: Empty buffer to return the method results
 *
 * Call an ACPI-WMI method
 */
acpi_status wmidev_evaluate_method(struct wmi_device *wdev, 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";

        wblock = container_of(wdev, struct wmi_block, dev);
        block = &wblock->gblock;
        handle = wblock->acpi_device->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(wmidev_evaluate_method);

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

        if (!out)
                return AE_BAD_PARAMETER;

        block = &wblock->gblock;
        handle = wblock->acpi_device->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 (instance == 0 && wblock->read_takes_no_args)
                input.count = 0;

        /*
         * If ACPI_WMI_EXPENSIVE, call the relevant WCxx method first to
         * enable collection.
         */
        if (block->flags & ACPI_WMI_EXPENSIVE) {
                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_execute_simple_method(handle, wc_method, 1);
        }

        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)) {
                status = acpi_execute_simple_method(handle, wc_method, 0);
        }

        return status;
}

/**
 * wmi_query_block - Return contents of a WMI block (deprecated)
 * @guid_string: 36 char string of the form fa50ff2b-f2e8-45de-83fa-65417f2f49ba
 * @instance: Instance index
 * &out: Empty buffer to return the contents of the data block to
 *
 * Return the contents of an ACPI-WMI data block to a buffer
 */
acpi_status wmi_query_block(const char *guid_string, u8 instance,
                            struct acpi_buffer *out)
{
        struct wmi_block *wblock;

        if (!guid_string)
                return AE_BAD_PARAMETER;

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

        return __query_block(wblock, instance, out);
}
EXPORT_SYMBOL_GPL(wmi_query_block);

union acpi_object *wmidev_block_query(struct wmi_device *wdev, u8 instance)
{
        struct acpi_buffer out = { ACPI_ALLOCATE_BUFFER, NULL };
        struct wmi_block *wblock = container_of(wdev, struct wmi_block, dev);

        if (ACPI_FAILURE(__query_block(wblock, instance, &out)))
                return NULL;

        return (union acpi_object *)out.pointer;
}
EXPORT_SYMBOL_GPL(wmidev_block_query);

/**
 * wmi_set_block - Write to a WMI block
 * @guid_string: 36 char string of the form fa50ff2b-f2e8-45de-83fa-65417f2f49ba
 * @instance: Instance index
 * &in: Buffer containing new values for the data block
 *
 * Write the contents of the input buffer to an ACPI-WMI data 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->acpi_device->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)
{
        pr_info("%pUL:\n", g->guid);
        if (g->flags & ACPI_WMI_EVENT)
                pr_info("\tnotify_id: 0x%02X\n", g->notify_id);
        else
                pr_info("\tobject_id: %2pE\n", g->object_id);
        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);
}

/**
 * wmi_install_notify_handler - Register handler for WMI events
 * @handler: Function to handle notifications
 * @data: Data to be returned to handler when event is fired
 *
 * Register a handler for events sent to the ACPI-WMI mapper device.
 */
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;
        uuid_le guid_input;

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

        if (uuid_le_to_bin(guid, &guid_input))
                return AE_BAD_PARAMETER;

        list_for_each_entry(block, &wmi_block_list, list) {
                acpi_status wmi_status;

                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);

/**
 * wmi_uninstall_notify_handler - Unregister handler for WMI events
 *
 * Unregister handler for events sent to the ACPI-WMI mapper device.
 */
acpi_status wmi_remove_notify_handler(const char *guid)
{
        struct wmi_block *block;
        acpi_status status = AE_NOT_EXIST;
        uuid_le guid_input;

        if (!guid)
                return AE_BAD_PARAMETER;

        if (uuid_le_to_bin(guid, &guid_input))
                return AE_BAD_PARAMETER;

        list_for_each_entry(block, &wmi_block_list, list) {
                acpi_status wmi_status;

                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);

/**
 * wmi_get_event_data - Get WMI data associated with an event
 *
 * @event: Event to find
 * @out: Buffer to hold event data. out->pointer should be freed with kfree()
 *
 * Returns extra data associated with an event in WMI.
 */
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;

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

        list_for_each_entry(wblock, &wmi_block_list, list) {
                gblock = &wblock->gblock;

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

        return AE_NOT_FOUND;
}
EXPORT_SYMBOL_GPL(wmi_get_event_data);

/**
 * wmi_has_guid - Check if a GUID is available
 * @guid_string: 36 char string of the form fa50ff2b-f2e8-45de-83fa-65417f2f49ba
 *
 * Check if a given GUID is defined by _WDG
 */
bool wmi_has_guid(const char *guid_string)
{
        return find_guid(guid_string, NULL);
}
EXPORT_SYMBOL_GPL(wmi_has_guid);

/**
 * wmi_get_acpi_device_uid() - Get _UID name of ACPI device that defines GUID
 * @guid_string: 36 char string of the form fa50ff2b-f2e8-45de-83fa-65417f2f49ba
 *
 * Find the _UID of ACPI device associated with this WMI GUID.
 *
 * Return: The ACPI _UID field value or NULL if the WMI GUID was not found
 */
char *wmi_get_acpi_device_uid(const char *guid_string)
{
        struct wmi_block *wblock = NULL;

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

        return acpi_device_uid(wblock->acpi_device);
}
EXPORT_SYMBOL_GPL(wmi_get_acpi_device_uid);

static struct wmi_block *dev_to_wblock(struct device *dev)
{
        return container_of(dev, struct wmi_block, dev.dev);
}

static struct wmi_device *dev_to_wdev(struct device *dev)
{
        return container_of(dev, struct wmi_device, dev);
}

/*
 * sysfs interface
 */
static ssize_t modalias_show(struct device *dev, struct device_attribute *attr,
                             char *buf)
{
        struct wmi_block *wblock = dev_to_wblock(dev);

        return sprintf(buf, "wmi:%pUL\n", wblock->gblock.guid);
}
static DEVICE_ATTR_RO(modalias);

static ssize_t guid_show(struct device *dev, struct device_attribute *attr,
                         char *buf)
{
        struct wmi_block *wblock = dev_to_wblock(dev);

        return sprintf(buf, "%pUL\n", wblock->gblock.guid);
}
static DEVICE_ATTR_RO(guid);

static ssize_t instance_count_show(struct device *dev,
                                   struct device_attribute *attr, char *buf)
{
        struct wmi_block *wblock = dev_to_wblock(dev);

        return sprintf(buf, "%d\n", (int)wblock->gblock.instance_count);
}
static DEVICE_ATTR_RO(instance_count);

static ssize_t expensive_show(struct device *dev,
                              struct device_attribute *attr, char *buf)
{
        struct wmi_block *wblock = dev_to_wblock(dev);

        return sprintf(buf, "%d\n",
                       (wblock->gblock.flags & ACPI_WMI_EXPENSIVE) != 0);
}
static DEVICE_ATTR_RO(expensive);

static struct attribute *wmi_attrs[] = {
        &dev_attr_modalias.attr,
        &dev_attr_guid.attr,
        &dev_attr_instance_count.attr,
        &dev_attr_expensive.attr,
        NULL,
};
ATTRIBUTE_GROUPS(wmi);

static ssize_t notify_id_show(struct device *dev, struct device_attribute *attr,
                              char *buf)
{
        struct wmi_block *wblock = dev_to_wblock(dev);

        return sprintf(buf, "%02X\n", (unsigned int)wblock->gblock.notify_id);
}
static DEVICE_ATTR_RO(notify_id);

static struct attribute *wmi_event_attrs[] = {
        &dev_attr_notify_id.attr,
        NULL,
};
ATTRIBUTE_GROUPS(wmi_event);

static ssize_t object_id_show(struct device *dev, struct device_attribute *attr,
                              char *buf)
{
        struct wmi_block *wblock = dev_to_wblock(dev);

        return sprintf(buf, "%c%c\n", wblock->gblock.object_id[0],
                       wblock->gblock.object_id[1]);
}
static DEVICE_ATTR_RO(object_id);

static ssize_t setable_show(struct device *dev, struct device_attribute *attr,
                            char *buf)
{
        struct wmi_device *wdev = dev_to_wdev(dev);

        return sprintf(buf, "%d\n", (int)wdev->setable);
}
static DEVICE_ATTR_RO(setable);

static struct attribute *wmi_data_attrs[] = {
        &dev_attr_object_id.attr,
        &dev_attr_setable.attr,
        NULL,
};
ATTRIBUTE_GROUPS(wmi_data);

static struct attribute *wmi_method_attrs[] = {
        &dev_attr_object_id.attr,
        NULL,
};
ATTRIBUTE_GROUPS(wmi_method);

static int wmi_dev_uevent(struct device *dev, struct kobj_uevent_env *env)
{
        struct wmi_block *wblock = dev_to_wblock(dev);

        if (add_uevent_var(env, "MODALIAS=wmi:%pUL", wblock->gblock.guid))
                return -ENOMEM;

        if (add_uevent_var(env, "WMI_GUID=%pUL", wblock->gblock.guid))
                return -ENOMEM;

        return 0;
}

static void wmi_dev_release(struct device *dev)
{
        struct wmi_block *wblock = dev_to_wblock(dev);

        kfree(wblock);
}

static int wmi_dev_match(struct device *dev, struct device_driver *driver)
{
        struct wmi_driver *wmi_driver =
                container_of(driver, struct wmi_driver, driver);
        struct wmi_block *wblock = dev_to_wblock(dev);
        const struct wmi_device_id *id = wmi_driver->id_table;

        if (id == NULL)
                return 0;

        while (*id->guid_string) {
                uuid_le driver_guid;

                if (WARN_ON(uuid_le_to_bin(id->guid_string, &driver_guid)))
                        continue;
                if (!memcmp(&driver_guid, wblock->gblock.guid, 16))
                        return 1;

                id++;
        }

        return 0;
}
static int wmi_char_open(struct inode *inode, struct file *filp)
{
        const char *driver_name = filp->f_path.dentry->d_iname;
        struct wmi_block *wblock = NULL;
        struct wmi_block *next = NULL;

        list_for_each_entry_safe(wblock, next, &wmi_block_list, list) {
                if (!wblock->dev.dev.driver)
                        continue;
                if (strcmp(driver_name, wblock->dev.dev.driver->name) == 0) {
                        filp->private_data = wblock;
                        break;
                }
        }

        if (!filp->private_data)
                return -ENODEV;

        return nonseekable_open(inode, filp);
}

static ssize_t wmi_char_read(struct file *filp, char __user *buffer,
        size_t length, loff_t *offset)
{
        struct wmi_block *wblock = filp->private_data;

        return simple_read_from_buffer(buffer, length, offset,
                                       &wblock->req_buf_size,
                                       sizeof(wblock->req_buf_size));
}

static long wmi_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
        struct wmi_ioctl_buffer __user *input =
                (struct wmi_ioctl_buffer __user *) arg;
        struct wmi_block *wblock = filp->private_data;
        struct wmi_ioctl_buffer *buf = NULL;
        struct wmi_driver *wdriver = NULL;
        int ret;

        if (_IOC_TYPE(cmd) != WMI_IOC)
                return -ENOTTY;

        /* make sure we're not calling a higher instance than exists*/
        if (_IOC_NR(cmd) >= wblock->gblock.instance_count)
                return -EINVAL;

        mutex_lock(&wblock->char_mutex);
        buf = wblock->handler_data;
        if (get_user(buf->length, &input->length)) {
                dev_dbg(&wblock->dev.dev, "Read length from user failed\n");
                ret = -EFAULT;
                goto out_ioctl;
        }
        /* if it's too small, abort */
        if (buf->length < wblock->req_buf_size) {
                dev_err(&wblock->dev.dev,
                        "Buffer %lld too small, need at least %lld\n",
                        buf->length, wblock->req_buf_size);
                ret = -EINVAL;
                goto out_ioctl;
        }
        /* if it's too big, warn, driver will only use what is needed */
        if (buf->length > wblock->req_buf_size)
                dev_warn(&wblock->dev.dev,
                        "Buffer %lld is bigger than required %lld\n",
                        buf->length, wblock->req_buf_size);

        /* copy the structure from userspace */
        if (copy_from_user(buf, input, wblock->req_buf_size)) {
                dev_dbg(&wblock->dev.dev, "Copy %llu from user failed\n",
                        wblock->req_buf_size);
                ret = -EFAULT;
                goto out_ioctl;
        }

        /* let the driver do any filtering and do the call */
        wdriver = container_of(wblock->dev.dev.driver,
                               struct wmi_driver, driver);
        if (!try_module_get(wdriver->driver.owner)) {
                ret = -EBUSY;
                goto out_ioctl;
        }
        ret = wdriver->filter_callback(&wblock->dev, cmd, buf);
        module_put(wdriver->driver.owner);
        if (ret)
                goto out_ioctl;

        /* return the result (only up to our internal buffer size) */
        if (copy_to_user(input, buf, wblock->req_buf_size)) {
                dev_dbg(&wblock->dev.dev, "Copy %llu to user failed\n",
                        wblock->req_buf_size);
                ret = -EFAULT;
        }

out_ioctl:
        mutex_unlock(&wblock->char_mutex);
        return ret;
}

static const struct file_operations wmi_fops = {
        .owner          = THIS_MODULE,
        .read           = wmi_char_read,
        .open           = wmi_char_open,
        .unlocked_ioctl = wmi_ioctl,
        .compat_ioctl   = compat_ptr_ioctl,
};

static int wmi_dev_probe(struct device *dev)
{
        struct wmi_block *wblock = dev_to_wblock(dev);
        struct wmi_driver *wdriver =
                container_of(dev->driver, struct wmi_driver, driver);
        int ret = 0;
        char *buf;

        if (ACPI_FAILURE(wmi_method_enable(wblock, 1)))
                dev_warn(dev, "failed to enable device -- probing anyway\n");

        if (wdriver->probe) {
                ret = wdriver->probe(dev_to_wdev(dev),
                                find_guid_context(wblock, wdriver));
                if (ret != 0)
                        goto probe_failure;
        }

        /* driver wants a character device made */
        if (wdriver->filter_callback) {
                /* check that required buffer size declared by driver or MOF */
                if (!wblock->req_buf_size) {
                        dev_err(&wblock->dev.dev,
                                "Required buffer size not set\n");
                        ret = -EINVAL;
                        goto probe_failure;
                }

                wblock->handler_data = kmalloc(wblock->req_buf_size,
                                               GFP_KERNEL);
                if (!wblock->handler_data) {
                        ret = -ENOMEM;
                        goto probe_failure;
                }

                buf = kasprintf(GFP_KERNEL, "wmi/%s", wdriver->driver.name);
                if (!buf) {
                        ret = -ENOMEM;
                        goto probe_string_failure;
                }
                wblock->char_dev.minor = MISC_DYNAMIC_MINOR;
                wblock->char_dev.name = buf;
                wblock->char_dev.fops = &wmi_fops;
                wblock->char_dev.mode = 0444;
                ret = misc_register(&wblock->char_dev);
                if (ret) {
                        dev_warn(dev, "failed to register char dev: %d\n", ret);
                        ret = -ENOMEM;
                        goto probe_misc_failure;
                }
        }

        return 0;

probe_misc_failure:
        kfree(buf);
probe_string_failure:
        kfree(wblock->handler_data);
probe_failure:
        if (ACPI_FAILURE(wmi_method_enable(wblock, 0)))
                dev_warn(dev, "failed to disable device\n");
        return ret;
}

static int wmi_dev_remove(struct device *dev)
{
        struct wmi_block *wblock = dev_to_wblock(dev);
        struct wmi_driver *wdriver =
                container_of(dev->driver, struct wmi_driver, driver);
        int ret = 0;

        if (wdriver->filter_callback) {
                misc_deregister(&wblock->char_dev);
                kfree(wblock->char_dev.name);
                kfree(wblock->handler_data);
        }

        if (wdriver->remove)
                ret = wdriver->remove(dev_to_wdev(dev));

        if (ACPI_FAILURE(wmi_method_enable(wblock, 0)))
                dev_warn(dev, "failed to disable device\n");

        return ret;
}

static struct class wmi_bus_class = {
        .name = "wmi_bus",
};

static struct bus_type wmi_bus_type = {
        .name = "wmi",
        .dev_groups = wmi_groups,
        .match = wmi_dev_match,
        .uevent = wmi_dev_uevent,
        .probe = wmi_dev_probe,
        .remove = wmi_dev_remove,
};

static const struct device_type wmi_type_event = {
        .name = "event",
        .groups = wmi_event_groups,
        .release = wmi_dev_release,
};

static const struct device_type wmi_type_method = {
        .name = "method",
        .groups = wmi_method_groups,
        .release = wmi_dev_release,
};

static const struct device_type wmi_type_data = {
        .name = "data",
        .groups = wmi_data_groups,
        .release = wmi_dev_release,
};

static int wmi_create_device(struct device *wmi_bus_dev,
                             const struct guid_block *gblock,
                             struct wmi_block *wblock,
                             struct acpi_device *device)
{
        struct acpi_device_info *info;
        char method[5];
        int result;

        if (gblock->flags & ACPI_WMI_EVENT) {
                wblock->dev.dev.type = &wmi_type_event;
                goto out_init;
        }

        if (gblock->flags & ACPI_WMI_METHOD) {
                wblock->dev.dev.type = &wmi_type_method;
                mutex_init(&wblock->char_mutex);
                goto out_init;
        }

        /*
         * Data Block Query Control Method (WQxx by convention) is
         * required per the WMI documentation. If it is not present,
         * we ignore this data block.
         */
        strcpy(method, "WQ");
        strncat(method, wblock->gblock.object_id, 2);
        result = get_subobj_info(device->handle, method, &info);

        if (result) {
                dev_warn(wmi_bus_dev,
                         "%s data block query control method not found\n",
                         method);
                return result;
        }

        wblock->dev.dev.type = &wmi_type_data;

        /*
         * The Microsoft documentation specifically states:
         *
         *   Data blocks registered with only a single instance
         *   can ignore the parameter.
         *
         * ACPICA will get mad at us if we call the method with the wrong number
         * of arguments, so check what our method expects.  (On some Dell
         * laptops, WQxx may not be a method at all.)
         */
        if (info->type != ACPI_TYPE_METHOD || info->param_count == 0)
                wblock->read_takes_no_args = true;

        kfree(info);

        strcpy(method, "WS");
        strncat(method, wblock->gblock.object_id, 2);
        result = get_subobj_info(device->handle, method, NULL);

        if (result == 0)
                wblock->dev.setable = true;

 out_init:
        wblock->dev.dev.bus = &wmi_bus_type;
        wblock->dev.dev.parent = wmi_bus_dev;

        dev_set_name(&wblock->dev.dev, "%pUL", gblock->guid);

        device_initialize(&wblock->dev.dev);

        return 0;
}

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

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

static bool guid_already_parsed(struct acpi_device *device,
                                const u8 *guid)
{
        struct wmi_block *wblock;

        list_for_each_entry(wblock, &wmi_block_list, list) {
                if (memcmp(wblock->gblock.guid, guid, 16) == 0) {
                        /*
                         * Because we historically didn't track the relationship
                         * between GUIDs and ACPI nodes, we don't know whether
                         * we need to suppress GUIDs that are unique on a
                         * given node but duplicated across nodes.
                         */
                        dev_warn(&device->dev, "duplicate WMI GUID %pUL (first instance was on %s)\n",
                                 guid, dev_name(&wblock->acpi_device->dev));
                        return true;
                }
        }

        return false;
}

/*
 * Parse the _WDG method for the GUID data blocks
 */
static int parse_wdg(struct device *wmi_bus_dev, struct acpi_device *device)
{
        struct acpi_buffer out = {ACPI_ALLOCATE_BUFFER, NULL};
        const struct guid_block *gblock;
        struct wmi_block *wblock, *next;
        union acpi_object *obj;
        acpi_status status;
        int retval = 0;
        u32 i, total;

        status = acpi_evaluate_object(device->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]);

                /*
                 * 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(device, gblock[i].guid))
                        continue;

                wblock = kzalloc(sizeof(struct wmi_block), GFP_KERNEL);
                if (!wblock) {
                        retval = -ENOMEM;
                        break;
                }

                wblock->acpi_device = device;
                wblock->gblock = gblock[i];

                retval = wmi_create_device(wmi_bus_dev, &gblock[i], wblock, device);
                if (retval) {
                        kfree(wblock);
                        continue;
                }

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

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

        /*
         * Now that all of the devices are created, add them to the
         * device tree and probe subdrivers.
         */
        list_for_each_entry_safe(wblock, next, &wmi_block_list, list) {
                if (wblock->acpi_device != device)
                        continue;

                retval = device_add(&wblock->dev.dev);
                if (retval) {
                        dev_err(wmi_bus_dev, "failed to register %pUL\n",
                                wblock->gblock.guid);
                        if (debug_event)
                                wmi_method_enable(wblock, 0);
                        list_del(&wblock->list);
                        put_device(&wblock->dev.dev);
                }
        }

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_handler(acpi_handle handle, u32 event,
                                    void *context)
{
        struct guid_block *block;
        struct wmi_block *wblock;
        bool found_it = false;

        list_for_each_entry(wblock, &wmi_block_list, list) {
                block = &wblock->gblock;

                if (wblock->acpi_device->handle == handle &&
                    (block->flags & ACPI_WMI_EVENT) &&
                    (block->notify_id == event))
                {
                        found_it = true;
                        break;
                }
        }

        if (!found_it)
                return;

        /* If a driver is bound, then notify the driver. */
        if (wblock->dev.dev.driver) {
                struct wmi_driver *driver;
                struct acpi_object_list input;
                union acpi_object params[1];
                struct acpi_buffer evdata = { ACPI_ALLOCATE_BUFFER, NULL };
                acpi_status status;

                driver = container_of(wblock->dev.dev.driver,
                                      struct wmi_driver, driver);

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

                status = acpi_evaluate_object(wblock->acpi_device->handle,
                                              "_WED", &input, &evdata);
                if (ACPI_FAILURE(status)) {
                        dev_warn(&wblock->dev.dev,
                                 "failed to get event data\n");
                        return;
                }

                if (driver->notify)
                        driver->notify(&wblock->dev,
                                       (union acpi_object *)evdata.pointer);

                kfree(evdata.pointer);
        } else if (wblock->handler) {
                /* Legacy handler */
                wblock->handler(event, wblock->handler_data);
        }

        if (debug_event) {
                pr_info("DEBUG Event GUID: %pUL\n",
                        wblock->gblock.guid);
        }

        acpi_bus_generate_netlink_event(
                wblock->acpi_device->pnp.device_class,
                dev_name(&wblock->dev.dev),
                event, 0);

}

static int acpi_wmi_remove(struct platform_device *device)
{
        struct acpi_device *acpi_device = ACPI_COMPANION(&device->dev);

        acpi_remove_notify_handler(acpi_device->handle, ACPI_DEVICE_NOTIFY,
                                   acpi_wmi_notify_handler);
        acpi_remove_address_space_handler(acpi_device->handle,
                                ACPI_ADR_SPACE_EC, &acpi_wmi_ec_space_handler);
        wmi_free_devices(acpi_device);
        device_destroy(&wmi_bus_class, MKDEV(0, 0));

        return 0;
}

static int acpi_wmi_probe(struct platform_device *device)
{
        struct acpi_device *acpi_device;
        struct device *wmi_bus_dev;
        acpi_status status;
        int error;

        acpi_device = ACPI_COMPANION(&device->dev);
        if (!acpi_device) {
                dev_err(&device->dev, "ACPI companion is missing\n");
                return -ENODEV;
        }

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

        status = acpi_install_notify_handler(acpi_device->handle,
                                             ACPI_DEVICE_NOTIFY,
                                             acpi_wmi_notify_handler,
                                             NULL);
        if (ACPI_FAILURE(status)) {
                dev_err(&device->dev, "Error installing notify handler\n");
                error = -ENODEV;
                goto err_remove_ec_handler;
        }

        wmi_bus_dev = device_create(&wmi_bus_class, &device->dev, MKDEV(0, 0),
                                    NULL, "wmi_bus-%s", dev_name(&device->dev));
        if (IS_ERR(wmi_bus_dev)) {
                error = PTR_ERR(wmi_bus_dev);
                goto err_remove_notify_handler;
        }
        dev_set_drvdata(&device->dev, wmi_bus_dev);

        error = parse_wdg(wmi_bus_dev, acpi_device);
        if (error) {
                pr_err("Failed to parse WDG method\n");
                goto err_remove_busdev;
        }

        return 0;

err_remove_busdev:
        device_destroy(&wmi_bus_class, MKDEV(0, 0));

err_remove_notify_handler:
        acpi_remove_notify_handler(acpi_device->handle, ACPI_DEVICE_NOTIFY,
                                   acpi_wmi_notify_handler);

err_remove_ec_handler:
        acpi_remove_address_space_handler(acpi_device->handle,
                                          ACPI_ADR_SPACE_EC,
                                          &acpi_wmi_ec_space_handler);

        return error;
}

int __must_check __wmi_driver_register(struct wmi_driver *driver,
                                       struct module *owner)
{
        driver->driver.owner = owner;
        driver->driver.bus = &wmi_bus_type;

        return driver_register(&driver->driver);
}
EXPORT_SYMBOL(__wmi_driver_register);

void wmi_driver_unregister(struct wmi_driver *driver)
{
        driver_unregister(&driver->driver);
}
EXPORT_SYMBOL(wmi_driver_unregister);

static int __init acpi_wmi_init(void)
{
        int error;

        if (acpi_disabled)
                return -ENODEV;

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

        error = bus_register(&wmi_bus_type);
        if (error)
                goto err_unreg_class;

        error = platform_driver_register(&acpi_wmi_driver);
        if (error) {
                pr_err("Error loading mapper\n");
                goto err_unreg_bus;
        }

        return 0;

err_unreg_bus:
        bus_unregister(&wmi_bus_type);

err_unreg_class:
        class_unregister(&wmi_bus_class);

        return error;
}

static void __exit acpi_wmi_exit(void)
{
        platform_driver_unregister(&acpi_wmi_driver);
        bus_unregister(&wmi_bus_type);
        class_unregister(&wmi_bus_class);
}

subsys_initcall_sync(acpi_wmi_init);
module_exit(acpi_wmi_exit);