drivers/platform/chrome/chromeos_tbmc.c

// 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 = ACPI_COMPANION(dev);
	int ret;

	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");