/*
   * Supports for the button array on SoC tablets originally running
   * Windows 8.
   *
   * (C) Copyright 2014 Intel Corporation
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License
   * as published by the Free Software Foundation; version 2
   * of the License.
   */
  
  #include <linux/module.h>
  #include <linux/input.h>
  #include <linux/init.h>
  #include <linux/kernel.h>
  #include <linux/acpi.h>
  #include <linux/gpio/consumer.h>
  #include <linux/gpio_keys.h>
  #include <linux/platform_device.h>
  
  /*
   * Definition of buttons on the tablet. The ACPI index of each button
   * is defined in section 2.8.7.2 of "Windows ACPI Design Guide for SoC
   * Platforms"
   */
  #define MAX_NBUTTONS	5
  
  struct soc_button_info {
  	const char *name;
  	int acpi_index;
  	unsigned int event_type;
  	unsigned int event_code;
  	bool autorepeat;
  	bool wakeup;
  };
  
  /*
   * Some of the buttons like volume up/down are auto repeat, while others
   * are not. To support both, we register two platform devices, and put
   * buttons into them based on whether the key should be auto repeat.
   */
  #define BUTTON_TYPES	2
  
  struct soc_button_data {
  	struct platform_device *children[BUTTON_TYPES];
  };
  
  /*
   * Get the Nth GPIO number from the ACPI object.
   */
  static int soc_button_lookup_gpio(struct device *dev, int acpi_index)
  {
  	struct gpio_desc *desc;
  	int gpio;
  
  	desc = gpiod_get_index(dev, KBUILD_MODNAME, acpi_index, GPIOD_ASIS);
  	if (IS_ERR(desc))
  		return PTR_ERR(desc);
  
  	gpio = desc_to_gpio(desc);
  
  	gpiod_put(desc);
  
  	return gpio;
  }
  
  static struct platform_device *
  soc_button_device_create(struct platform_device *pdev,
  			 const struct soc_button_info *button_info,
  			 bool autorepeat)
  {
  	const struct soc_button_info *info;
  	struct platform_device *pd;
  	struct gpio_keys_button *gpio_keys;
  	struct gpio_keys_platform_data *gpio_keys_pdata;
  	int n_buttons = 0;
  	int gpio;
  	int error;
  
  	gpio_keys_pdata = devm_kzalloc(&pdev->dev,
  				       sizeof(*gpio_keys_pdata) +
  					sizeof(*gpio_keys) * MAX_NBUTTONS,
  				       GFP_KERNEL);
  	if (!gpio_keys_pdata)
  		return ERR_PTR(-ENOMEM);
  
  	gpio_keys = (void *)(gpio_keys_pdata + 1);
  
  	for (info = button_info; info->name; info++) {
  		if (info->autorepeat != autorepeat)
  			continue;
  
  		gpio = soc_button_lookup_gpio(&pdev->dev, info->acpi_index);
  		if (gpio < 0)
  			continue;
  
  		gpio_keys[n_buttons].type = info->event_type;
  		gpio_keys[n_buttons].code = info->event_code;
  		gpio_keys[n_buttons].gpio = gpio;
  		gpio_keys[n_buttons].active_low = 1;
  		gpio_keys[n_buttons].desc = info->name;
  		gpio_keys[n_buttons].wakeup = info->wakeup;
  		n_buttons++;
  	}
  
  	if (n_buttons == 0) {
  		error = -ENODEV;
  		goto err_free_mem;
  	}
  
  	gpio_keys_pdata->buttons = gpio_keys;
  	gpio_keys_pdata->nbuttons = n_buttons;
  	gpio_keys_pdata->rep = autorepeat;
  
  	pd = platform_device_alloc("gpio-keys", PLATFORM_DEVID_AUTO);
  	if (!pd) {
  		error = -ENOMEM;
  		goto err_free_mem;
  	}
  
  	error = platform_device_add_data(pd, gpio_keys_pdata,
  					 sizeof(*gpio_keys_pdata));
  	if (error)
  		goto err_free_pdev;
  
  	error = platform_device_add(pd);
  	if (error)
  		goto err_free_pdev;
  
  	return pd;
  
  err_free_pdev:
  	platform_device_put(pd);
  err_free_mem:
  	devm_kfree(&pdev->dev, gpio_keys_pdata);
  	return ERR_PTR(error);
  }
  
  static int soc_button_remove(struct platform_device *pdev)
  {
  	struct soc_button_data *priv = platform_get_drvdata(pdev);
  
  	int i;
  
  	for (i = 0; i < BUTTON_TYPES; i++)
  		if (priv->children[i])
  			platform_device_unregister(priv->children[i]);
  
  	return 0;
  }
  
  static int soc_button_probe(struct platform_device *pdev)
  {
  	struct device *dev = &pdev->dev;
  	const struct acpi_device_id *id;
  	struct soc_button_info *button_info;
  	struct soc_button_data *priv;
  	struct platform_device *pd;
  	int i;
  	int error;
  
  	id = acpi_match_device(dev->driver->acpi_match_table, dev);
  	if (!id)
  		return -ENODEV;
  
  	button_info = (struct soc_button_info *)id->driver_data;
  
  	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
  	if (!priv)
  		return -ENOMEM;
  
  	platform_set_drvdata(pdev, priv);
  
  	for (i = 0; i < BUTTON_TYPES; i++) {
  		pd = soc_button_device_create(pdev, button_info, i == 0);
  		if (IS_ERR(pd)) {
  			error = PTR_ERR(pd);
  			if (error != -ENODEV) {
  				soc_button_remove(pdev);
  				return error;
  			}
  			continue;
  		}
  
  		priv->children[i] = pd;
  	}
  
  	if (!priv->children[0] && !priv->children[1])
  		return -ENODEV;
  
  	return 0;
  }
  
  static struct soc_button_info soc_button_PNP0C40[] = {
  	{ "power", 0, EV_KEY, KEY_POWER, false, true },
  	{ "home", 1, EV_KEY, KEY_LEFTMETA, false, true },
  	{ "volume_up", 2, EV_KEY, KEY_VOLUMEUP, true, false },
  	{ "volume_down", 3, EV_KEY, KEY_VOLUMEDOWN, true, false },
  	{ "rotation_lock", 4, EV_SW, SW_ROTATE_LOCK, false, false },
  	{ }
  };
  
  static const struct acpi_device_id soc_button_acpi_match[] = {
  	{ "PNP0C40", (unsigned long)soc_button_PNP0C40 },
  	{ }
  };
  
  MODULE_DEVICE_TABLE(acpi, soc_button_acpi_match);
  
  static struct platform_driver soc_button_driver = {
  	.probe          = soc_button_probe,
  	.remove		= soc_button_remove,
  	.driver		= {
  		.name = KBUILD_MODNAME,
  		.acpi_match_table = ACPI_PTR(soc_button_acpi_match),
  	},
  };
  module_platform_driver(soc_button_driver);
  
  MODULE_LICENSE("GPL");