text: // 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/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)
  {
  	struct acpi_device *adev = to_acpi_device(dev);
  
  	return chromeos_tbmc_query_switch(adev, adev->driver_data);
  }
  
  static void chromeos_tbmc_notify(struct acpi_device *adev, u32 event)
  {
  	acpi_pm_wakeup_event(&adev->dev);
  	switch (event) {
  	case 0x80:
  		chromeos_tbmc_query_switch(adev, adev->driver_data);
  		break;
  	default:
  		dev_err(&adev->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_add(struct acpi_device *adev)
  {
  	struct input_dev *idev;
  	struct device *dev = &adev->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);
  	adev->driver_data = 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);
  	return 0;
  }
  
  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 acpi_driver chromeos_tbmc_driver = {
  	.name = DRV_NAME,
  	.class = DRV_NAME,
  	.ids = chromeos_tbmc_acpi_device_ids,
  	.ops = {
  		.add = chromeos_tbmc_add,
  		.notify = chromeos_tbmc_notify,
  	},
  	.drv.pm = &chromeos_tbmc_pm_ops,
  };
  
  module_acpi_driver(chromeos_tbmc_driver);
  
  MODULE_LICENSE("GPL v2");
  MODULE_DESCRIPTION("ChromeOS ACPI tablet switch driver");
  