// SPDX-License-Identifier: GPL-2.0-or-later
  #include <linux/module.h>
  #include <linux/sched/signal.h>
  #include <linux/acpi.h>
  #include <acpi/button.h>

  MODULE_AUTHOR("Josh Triplett");
  MODULE_DESCRIPTION("ACPI Tiny Power Button Driver");
  MODULE_LICENSE("GPL");
  
  static int power_signal __read_mostly = CONFIG_ACPI_TINY_POWER_BUTTON_SIGNAL;
  module_param(power_signal, int, 0644);
  MODULE_PARM_DESC(power_signal, "Power button sends this signal to init");
  
  static const struct acpi_device_id tiny_power_button_device_ids[] = {
  	{ ACPI_BUTTON_HID_POWER, 0 },
  	{ ACPI_BUTTON_HID_POWERF, 0 },
  	{ "", 0 },
  };
  MODULE_DEVICE_TABLE(acpi, tiny_power_button_device_ids);
  
  static int acpi_noop_add_remove(struct acpi_device *device)
  {
  	return 0;
  }
  
  static void acpi_tiny_power_button_notify(struct acpi_device *device, u32 event)
  {
  	kill_cad_pid(power_signal, 1);
  }
  
  static struct acpi_driver acpi_tiny_power_button_driver = {
  	.name = "tiny-power-button",
  	.class = "tiny-power-button",
  	.ids = tiny_power_button_device_ids,
  	.ops = {
  		.add = acpi_noop_add_remove,
  		.remove = acpi_noop_add_remove,
  		.notify = acpi_tiny_power_button_notify,
  	},
  };
  
  module_driver(acpi_tiny_power_button_driver,
  		acpi_bus_register_driver,
  		acpi_bus_unregister_driver);