// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  WMI hotkeys support for Dell All-In-One series
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/input.h>
#include <linux/input/sparse-keymap.h>
#include <linux/acpi.h>
#include <linux/string.h>

MODULE_DESCRIPTION("WMI hotkeys driver for Dell All-In-One series");
MODULE_LICENSE("GPL");

#define EVENT_GUID1 "284A0E6B-380E-472A-921F-E52786257FB4"
#define EVENT_GUID2 "02314822-307C-4F66-BF0E-48AEAEB26CC8"

struct dell_wmi_event {
        u16     length;
        /* 0x000: A hot key pressed or an event occurred
         * 0x00F: A sequence of hot keys are pressed */
        u16     type;
        u16     event[];
};

static const char *dell_wmi_aio_guids[] = {
        EVENT_GUID1,
        EVENT_GUID2,
        NULL
};

MODULE_ALIAS("wmi:"EVENT_GUID1);
MODULE_ALIAS("wmi:"EVENT_GUID2);

static const struct key_entry dell_wmi_aio_keymap[] = {
        { KE_KEY, 0xc0, { KEY_VOLUMEUP } },
        { KE_KEY, 0xc1, { KEY_VOLUMEDOWN } },
        { KE_KEY, 0xe030, { KEY_VOLUMEUP } },
        { KE_KEY, 0xe02e, { KEY_VOLUMEDOWN } },
        { KE_KEY, 0xe020, { KEY_MUTE } },
        { KE_KEY, 0xe027, { KEY_DISPLAYTOGGLE } },
        { KE_KEY, 0xe006, { KEY_BRIGHTNESSUP } },
        { KE_KEY, 0xe005, { KEY_BRIGHTNESSDOWN } },
        { KE_KEY, 0xe00b, { KEY_SWITCHVIDEOMODE } },
        { KE_END, 0 }
};

static struct input_dev *dell_wmi_aio_input_dev;

/*
 * The new WMI event data format will follow the dell_wmi_event structure
 * So, we will check if the buffer matches the format
 */
static bool dell_wmi_aio_event_check(u8 *buffer, int length)
{
        struct dell_wmi_event *event = (struct dell_wmi_event *)buffer;

        if (event == NULL || length < 6)
                return false;

        if ((event->type == 0 || event->type == 0xf) &&
                        event->length >= 2)
                return true;

        return false;
}

static void dell_wmi_aio_notify(u32 value, void *context)
{
        struct acpi_buffer response = { ACPI_ALLOCATE_BUFFER, NULL };
        union acpi_object *obj;
        struct dell_wmi_event *event;
        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) {
                unsigned int scancode = 0;

                switch (obj->type) {
                case ACPI_TYPE_INTEGER:
                        /* Most All-In-One correctly return integer scancode */
                        scancode = obj->integer.value;
                        sparse_keymap_report_event(dell_wmi_aio_input_dev,
                                scancode, 1, true);
                        break;
                case ACPI_TYPE_BUFFER:
                        if (dell_wmi_aio_event_check(obj->buffer.pointer,
                                                obj->buffer.length)) {
                                event = (struct dell_wmi_event *)
                                        obj->buffer.pointer;
                                scancode = event->event[0];
                        } else {
                                /* Broken machines return the scancode in a
                                   buffer */
                                if (obj->buffer.pointer &&
                                                obj->buffer.length > 0)
                                        scancode = obj->buffer.pointer[0];
                        }
                        if (scancode)
                                sparse_keymap_report_event(
                                        dell_wmi_aio_input_dev,
                                        scancode, 1, true);
                        break;
                }
        }
        kfree(obj);
}

static int __init dell_wmi_aio_input_setup(void)
{
        int err;

        dell_wmi_aio_input_dev = input_allocate_device();

        if (!dell_wmi_aio_input_dev)
                return -ENOMEM;

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

        err = sparse_keymap_setup(dell_wmi_aio_input_dev,
                        dell_wmi_aio_keymap, NULL);
        if (err) {
                pr_err("Unable to setup input device keymap\n");
                goto err_free_dev;
        }
        err = input_register_device(dell_wmi_aio_input_dev);
        if (err) {
                pr_info("Unable to register input device\n");
                goto err_free_dev;
        }
        return 0;

err_free_dev:
        input_free_device(dell_wmi_aio_input_dev);
        return err;
}

static const char *dell_wmi_aio_find(void)
{
        int i;

        for (i = 0; dell_wmi_aio_guids[i] != NULL; i++)
                if (wmi_has_guid(dell_wmi_aio_guids[i]))
                        return dell_wmi_aio_guids[i];

        return NULL;
}

static int __init dell_wmi_aio_init(void)
{
        int err;
        const char *guid;

        guid = dell_wmi_aio_find();
        if (!guid) {
                pr_warn("No known WMI GUID found\n");
                return -ENXIO;
        }

        err = dell_wmi_aio_input_setup();
        if (err)
                return err;

        err = wmi_install_notify_handler(guid, dell_wmi_aio_notify, NULL);
        if (err) {
                pr_err("Unable to register notify handler - %d\n", err);
                input_unregister_device(dell_wmi_aio_input_dev);
                return err;
        }

        return 0;
}

static void __exit dell_wmi_aio_exit(void)
{
        const char *guid;

        guid = dell_wmi_aio_find();
        wmi_remove_notify_handler(guid);
        input_unregister_device(dell_wmi_aio_input_dev);
}

module_init(dell_wmi_aio_init);
module_exit(dell_wmi_aio_exit);