/*
 * Supports for the button array on the Surface tablets.
 *
 * (C) Copyright 2016 Red Hat, Inc
 *
 * Based on soc_button_array.c:
 *
 * {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/i2c.h>
#include <linux/slab.h>
#include <linux/acpi.h>
#include <linux/gpio/consumer.h>
#include <linux/gpio_keys.h>
#include <linux/gpio.h>
#include <linux/platform_device.h>


#define SURFACE_BUTTON_OBJ_NAME		"TEV2"
#define MAX_NBUTTONS			4

/*
 * 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

/*
 * Power button, Home button, Volume buttons support is supposed to
 * be covered by drivers/input/misc/soc_button_array.c, which is implemented
 * according to "Windows ACPI Design Guide for SoC Platforms".
 * However surface 3 seems not to obey the specs, instead it uses
 * device TEV2(MSHW0028) for declaring the GPIOs. The gpios are also slightly
 * different in which the Home button is active high.
 * Compared to surfacepro3_button.c which also handles MSHW0028, the Surface 3
 * is a reduce platform and thus uses GPIOs, not ACPI events.
 * We choose an I2C driver here because we need to access the resources
 * declared under the device node, while surfacepro3_button.c only needs
 * the ACPI companion node.
 */
static const struct acpi_device_id surface3_acpi_match[] = {
	{ "MSHW0028", 0 },
	{ }
};
MODULE_DEVICE_TABLE(acpi, surface3_acpi_match);

struct surface3_button_info {
	const char *name;
	int acpi_index;
	unsigned int event_type;
	unsigned int event_code;
	bool autorepeat;
	bool wakeup;
	bool active_low;
};

struct surface3_button_data {
	struct platform_device *children[BUTTON_TYPES];
};

/*
 * Get the Nth GPIO number from the ACPI object.
 */
static int surface3_button_lookup_gpio(struct device *dev, int acpi_index)
{
	struct gpio_desc *desc;
	int gpio;

	desc = gpiod_get_index(dev, NULL, 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 *
surface3_button_device_create(struct i2c_client *client,
			      const struct surface3_button_info *button_info,
			      bool autorepeat)
{
	const struct surface3_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(&client->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 = surface3_button_lookup_gpio(&client->dev,
						   info->acpi_index);
		if (!gpio_is_valid(gpio))
			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 = info->active_low;
		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(&client->dev, gpio_keys_pdata);
	return ERR_PTR(error);
}

static int surface3_button_remove(struct i2c_client *client)
{
	struct surface3_button_data *priv = i2c_get_clientdata(client);

	int i;

	for (i = 0; i < BUTTON_TYPES; i++)
		if (priv->children[i])
			platform_device_unregister(priv->children[i]);

	return 0;
}

static struct surface3_button_info surface3_button_surface3[] = {
	{ "power", 0, EV_KEY, KEY_POWER, false, true, true },
	{ "home", 1, EV_KEY, KEY_LEFTMETA, false, true, false },
	{ "volume_up", 2, EV_KEY, KEY_VOLUMEUP, true, false, true },
	{ "volume_down", 3, EV_KEY, KEY_VOLUMEDOWN, true, false, true },
	{ }
};

static int surface3_button_probe(struct i2c_client *client,
				 const struct i2c_device_id *id)
{
	struct device *dev = &client->dev;
	struct surface3_button_data *priv;
	struct platform_device *pd;
	int i;
	int error;

	if (strncmp(acpi_device_bid(ACPI_COMPANION(&client->dev)),
		    SURFACE_BUTTON_OBJ_NAME,
		    strlen(SURFACE_BUTTON_OBJ_NAME)))
		return -ENODEV;

	error = gpiod_count(dev, NULL);
	if (error < 0) {
		dev_dbg(dev, "no GPIO attached, ignoring...\n");
		return error;
	}

	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
	if (!priv)
		return -ENOMEM;

	i2c_set_clientdata(client, priv);

	for (i = 0; i < BUTTON_TYPES; i++) {
		pd = surface3_button_device_create(client,
						   surface3_button_surface3,
						   i == 0);
		if (IS_ERR(pd)) {
			error = PTR_ERR(pd);
			if (error != -ENODEV) {
				surface3_button_remove(client);
				return error;
			}
			continue;
		}

		priv->children[i] = pd;
	}

	if (!priv->children[0] && !priv->children[1])
		return -ENODEV;

	return 0;
}

static const struct i2c_device_id surface3_id[] = {
	{ }
};
MODULE_DEVICE_TABLE(i2c, surface3_id);

static struct i2c_driver surface3_driver = {
	.probe = surface3_button_probe,
	.remove = surface3_button_remove,
	.id_table = surface3_id,
	.driver = {
		.name = "surface3",
		.acpi_match_table = ACPI_PTR(surface3_acpi_match),
	},
};
module_i2c_driver(surface3_driver);

MODULE_AUTHOR("Benjamin Tissoires <benjamin.tissoires@gmail.com>");
MODULE_DESCRIPTION("surface3 button array driver");
MODULE_LICENSE("GPL v2");