/*
 * 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;

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

        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");