// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * ACPI Direct App Launch driver
 *
 * Copyright (C) 2024 Armin Wolf <W_Armin@gmx.de>
 * Copyright (C) 2022 Arvid Norlander <lkml@vorapal.se>
 * Copyright (C) 2007-2010 Angelo Arrifano <miknix@gmail.com>
 *
 * Information gathered from disassembled dsdt and from here:
 * <https://archive.org/details/microsoft-acpi-dirapplaunch>
 */

#include <linux/acpi.h>
#include <linux/device.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/input.h>
#include <linux/input/sparse-keymap.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/platform_device.h>
#include <linux/printk.h>
#include <linux/slab.h>
#include <linux/sysfs.h>
#include <linux/types.h>

#include <linux/unaligned.h>

#define DRIVER_NAME     "quickstart"

/*
 * There will be two events:
 * 0x02 - Button was pressed while device was off/sleeping.
 * 0x80 - Button was pressed while device was up.
 */
#define QUICKSTART_EVENT_RUNTIME        0x80

struct quickstart_data {
        struct device *dev;
        struct mutex input_lock;        /* Protects input sequence during notify */
        struct input_dev *input_device;
        char input_name[32];
        char phys[32];
        u32 id;
};

/*
 * Knowing what these buttons do require system specific knowledge.
 * This could be done by matching on DMI data in a long quirk table.
 * However, it is easier to leave it up to user space to figure this out.
 *
 * Using for example udev hwdb the scancode 0x1 can be remapped suitably.
 */
static const struct key_entry quickstart_keymap[] = {
        { KE_KEY, 0x1, { KEY_UNKNOWN } },
        { KE_END, 0 },
};

static ssize_t button_id_show(struct device *dev, struct device_attribute *attr, char *buf)
{
        struct quickstart_data *data = dev_get_drvdata(dev);

        return sysfs_emit(buf, "%u\n", data->id);
}
static DEVICE_ATTR_RO(button_id);

static struct attribute *quickstart_attrs[] = {
        &dev_attr_button_id.attr,
        NULL
};
ATTRIBUTE_GROUPS(quickstart);

static void quickstart_notify(acpi_handle handle, u32 event, void *context)
{
        struct quickstart_data *data = context;

        switch (event) {
        case QUICKSTART_EVENT_RUNTIME:
                mutex_lock(&data->input_lock);
                sparse_keymap_report_event(data->input_device, 0x1, 1, true);
                mutex_unlock(&data->input_lock);

                acpi_bus_generate_netlink_event(DRIVER_NAME, dev_name(data->dev), event, 0);
                break;
        default:
                dev_err(data->dev, FW_INFO "Unexpected ACPI notify event (%u)\n", event);
                break;
        }
}

/*
 * The GHID ACPI method is used to indicate the "role" of the button.
 * However, all the meanings of these values are vendor defined.
 *
 * We do however expose this value to user space.
 */
static int quickstart_get_ghid(struct quickstart_data *data)
{
        struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
        acpi_handle handle = ACPI_HANDLE(data->dev);
        union acpi_object *obj;
        acpi_status status;
        int ret = 0;

        /*
         * This returns a buffer telling the button usage ID,
         * and triggers pending notify events (The ones before booting).
         */
        status = acpi_evaluate_object_typed(handle, "GHID", NULL, &buffer, ACPI_TYPE_BUFFER);
        if (ACPI_FAILURE(status))
                return -EIO;

        obj = buffer.pointer;
        if (!obj)
                return -ENODATA;

        /*
         * Quoting the specification:
         * "The GHID method can return a BYTE, WORD, or DWORD.
         *  The value must be encoded in little-endian byte
         *  order (least significant byte first)."
         */
        switch (obj->buffer.length) {
        case 1:
                data->id = obj->buffer.pointer[0];
                break;
        case 2:
                data->id = get_unaligned_le16(obj->buffer.pointer);
                break;
        case 4:
                data->id = get_unaligned_le32(obj->buffer.pointer);
                break;
        default:
                dev_err(data->dev,
                        FW_BUG "GHID method returned buffer of unexpected length %u\n",
                        obj->buffer.length);
                ret = -EIO;
                break;
        }

        kfree(obj);

        return ret;
}

static void quickstart_notify_remove(void *context)
{
        struct quickstart_data *data = context;
        acpi_handle handle;

        handle = ACPI_HANDLE(data->dev);

        acpi_remove_notify_handler(handle, ACPI_DEVICE_NOTIFY, quickstart_notify);
}

static int quickstart_probe(struct platform_device *pdev)
{
        struct quickstart_data *data;
        acpi_handle handle;
        acpi_status status;
        int ret;

        handle = ACPI_HANDLE(&pdev->dev);
        if (!handle)
                return -ENODEV;

        data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
        if (!data)
                return -ENOMEM;

        data->dev = &pdev->dev;
        dev_set_drvdata(&pdev->dev, data);

        ret = devm_mutex_init(&pdev->dev, &data->input_lock);
        if (ret < 0)
                return ret;

        /*
         * We have to initialize the device wakeup before evaluating GHID because
         * doing so will notify the device if the button was used to wake the machine
         * from S5.
         */
        device_init_wakeup(&pdev->dev, true);

        ret = quickstart_get_ghid(data);
        if (ret < 0)
                return ret;

        data->input_device = devm_input_allocate_device(&pdev->dev);
        if (!data->input_device)
                return -ENOMEM;

        ret = sparse_keymap_setup(data->input_device, quickstart_keymap, NULL);
        if (ret < 0)
                return ret;

        snprintf(data->input_name, sizeof(data->input_name), "Quickstart Button %u", data->id);
        snprintf(data->phys, sizeof(data->phys), DRIVER_NAME "/input%u", data->id);

        data->input_device->name = data->input_name;
        data->input_device->phys = data->phys;
        data->input_device->id.bustype = BUS_HOST;

        ret = input_register_device(data->input_device);
        if (ret < 0)
                return ret;

        status = acpi_install_notify_handler(handle, ACPI_DEVICE_NOTIFY, quickstart_notify, data);
        if (ACPI_FAILURE(status))
                return -EIO;

        return devm_add_action_or_reset(&pdev->dev, quickstart_notify_remove, data);
}

static const struct acpi_device_id quickstart_device_ids[] = {
        { "PNP0C32" },
        { }
};
MODULE_DEVICE_TABLE(acpi, quickstart_device_ids);

static struct platform_driver quickstart_platform_driver = {
        .driver = {
                .name = DRIVER_NAME,
                .dev_groups = quickstart_groups,
                .probe_type = PROBE_PREFER_ASYNCHRONOUS,
                .acpi_match_table = quickstart_device_ids,
        },
        .probe = quickstart_probe,
};
module_platform_driver(quickstart_platform_driver);

MODULE_AUTHOR("Armin Wolf <W_Armin@gmx.de>");
MODULE_AUTHOR("Arvid Norlander <lkml@vorpal.se>");
MODULE_AUTHOR("Angelo Arrifano");
MODULE_DESCRIPTION("ACPI Direct App Launch driver");
MODULE_LICENSE("GPL");