// SPDX-License-Identifier: GPL-2.0
// Driver to detect Tablet Mode for ChromeOS convertible.
//
// Copyright (C) 2017 Google, Inc.
// Author: Gwendal Grignou <gwendal@chromium.org>
//
// On Chromebook using ACPI, this device listens for notification
// from GOOG0006 and issue method TBMC to retrieve the status.
//
// GOOG0006 issues the notification when it receives EC_HOST_EVENT_MODE_CHANGE
// from the EC.
// Method TBMC reads EC_ACPI_MEM_DEVICE_ORIENTATION byte from the shared
// memory region.

#include <linux/acpi.h>
#include <linux/input.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/printk.h>

#define DRV_NAME "chromeos_tbmc"
#define ACPI_DRV_NAME "GOOG0006"

static int chromeos_tbmc_query_switch(struct acpi_device *adev,
                                     struct input_dev *idev)
{
        unsigned long long state;
        acpi_status status;

        status = acpi_evaluate_integer(adev->handle, "TBMC", NULL, &state);
        if (ACPI_FAILURE(status))
                return -ENODEV;

        /* input layer checks if event is redundant */
        input_report_switch(idev, SW_TABLET_MODE, state);
        input_sync(idev);

        return 0;
}

static __maybe_unused int chromeos_tbmc_resume(struct device *dev)
{
        return chromeos_tbmc_query_switch(ACPI_COMPANION(dev), dev_get_drvdata(dev));
}

static void chromeos_tbmc_notify(acpi_handle handle, u32 event, void *data)
{
        struct device *dev = data;

        acpi_pm_wakeup_event(dev);
        switch (event) {
        case 0x80:
                chromeos_tbmc_query_switch(ACPI_COMPANION(dev), dev_get_drvdata(dev));
                break;
        default:
                dev_err(dev, "Unexpected event: 0x%08X\n", event);
        }
}

static int chromeos_tbmc_open(struct input_dev *idev)
{
        struct acpi_device *adev = input_get_drvdata(idev);

        return chromeos_tbmc_query_switch(adev, idev);
}

static int chromeos_tbmc_probe(struct platform_device *pdev)
{
        struct input_dev *idev;
        struct device *dev = &pdev->dev;
        struct acpi_device *adev;
        int ret;

        adev = ACPI_COMPANION(dev);
        if (!adev)
                return -ENODEV;

        idev = devm_input_allocate_device(dev);
        if (!idev)
                return -ENOMEM;

        idev->name = "Tablet Mode Switch";
        idev->phys = acpi_device_hid(adev);

        idev->id.bustype = BUS_HOST;
        idev->id.version = 1;
        idev->id.product = 0;
        idev->open = chromeos_tbmc_open;

        input_set_drvdata(idev, adev);
        platform_set_drvdata(pdev, idev);

        input_set_capability(idev, EV_SW, SW_TABLET_MODE);
        ret = input_register_device(idev);
        if (ret) {
                dev_err(dev, "cannot register input device\n");
                return ret;
        }
        device_init_wakeup(dev, true);

        ret = acpi_dev_install_notify_handler(adev, ACPI_DEVICE_NOTIFY,
                                              chromeos_tbmc_notify, dev);
        if (ret) {
                dev_err(dev, "cannot install ACPI notify handler\n");
                device_init_wakeup(dev, false);
                return ret;
        }

        return 0;
}

static void chromeos_tbmc_remove(struct platform_device *pdev)
{
        acpi_dev_remove_notify_handler(ACPI_COMPANION(&pdev->dev),
                                       ACPI_DEVICE_NOTIFY, chromeos_tbmc_notify);
        device_init_wakeup(&pdev->dev, false);
}

static const struct acpi_device_id chromeos_tbmc_acpi_device_ids[] = {
        { ACPI_DRV_NAME, 0 },
        { }
};
MODULE_DEVICE_TABLE(acpi, chromeos_tbmc_acpi_device_ids);

static SIMPLE_DEV_PM_OPS(chromeos_tbmc_pm_ops, NULL,
                chromeos_tbmc_resume);

static struct platform_driver chromeos_tbmc_driver = {
        .probe = chromeos_tbmc_probe,
        .remove = chromeos_tbmc_remove,
        .driver = {
                .name = DRV_NAME,
                .acpi_match_table = chromeos_tbmc_acpi_device_ids,
                .pm = &chromeos_tbmc_pm_ops,
        },
};

module_platform_driver(chromeos_tbmc_driver);

MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("ChromeOS ACPI tablet switch driver");