/*
 * 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/gpio.h>
#include <linux/platform_device.h>

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, 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 *
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;

        for (info = button_info; info->name; info++)
                if (info->autorepeat == autorepeat)
                        n_buttons++;

        gpio_keys_pdata = devm_kzalloc(&pdev->dev,
                                       sizeof(*gpio_keys_pdata) +
                                        sizeof(*gpio_keys) * n_buttons,
                                       GFP_KERNEL);
        if (!gpio_keys_pdata)
                return ERR_PTR(-ENOMEM);

        gpio_keys = (void *)(gpio_keys_pdata + 1);
        n_buttons = 0;

        for (info = button_info; info->name; info++) {
                if (info->autorepeat != autorepeat)
                        continue;

                gpio = soc_button_lookup_gpio(&pdev->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 = 1;
                gpio_keys[n_buttons].desc = info->name;
                gpio_keys[n_buttons].wakeup = info->wakeup;
                /* These devices often use cheap buttons, use 50 ms debounce */
                gpio_keys[n_buttons].debounce_interval = 50;
                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_get_acpi_object_int(const union acpi_object *obj)
{
        if (obj->type != ACPI_TYPE_INTEGER)
                return -1;

        return obj->integer.value;
}

/* Parse a single ACPI0011 _DSD button descriptor */
static int soc_button_parse_btn_desc(struct device *dev,
                                     const union acpi_object *desc,
                                     int collection_uid,
                                     struct soc_button_info *info)
{
        int upage, usage;

        if (desc->type != ACPI_TYPE_PACKAGE ||
            desc->package.count != 5 ||
            /* First byte should be 1 (control) */
            soc_button_get_acpi_object_int(&desc->package.elements[0]) != 1 ||
            /* Third byte should be collection uid */
            soc_button_get_acpi_object_int(&desc->package.elements[2]) !=
                                                            collection_uid) {
                dev_err(dev, "Invalid ACPI Button Descriptor\n");
                return -ENODEV;
        }

        info->event_type = EV_KEY;
        info->acpi_index =
                soc_button_get_acpi_object_int(&desc->package.elements[1]);
        upage = soc_button_get_acpi_object_int(&desc->package.elements[3]);
        usage = soc_button_get_acpi_object_int(&desc->package.elements[4]);

        /*
         * The UUID: fa6bd625-9ce8-470d-a2c7-b3ca36c4282e descriptors use HID
         * usage page and usage codes, but otherwise the device is not HID
         * compliant: it uses one irq per button instead of generating HID
         * input reports and some buttons should generate wakeups where as
         * others should not, so we cannot use the HID subsystem.
         *
         * Luckily all devices only use a few usage page + usage combinations,
         * so we can simply check for the known combinations here.
         */
        if (upage == 0x01 && usage == 0x81) {
                info->name = "power";
                info->event_code = KEY_POWER;
                info->wakeup = true;
        } else if (upage == 0x07 && usage == 0xe3) {
                info->name = "home";
                info->event_code = KEY_LEFTMETA;
                info->wakeup = true;
        } else if (upage == 0x0c && usage == 0xe9) {
                info->name = "volume_up";
                info->event_code = KEY_VOLUMEUP;
                info->autorepeat = true;
        } else if (upage == 0x0c && usage == 0xea) {
                info->name = "volume_down";
                info->event_code = KEY_VOLUMEDOWN;
                info->autorepeat = true;
        } else {
                dev_warn(dev, "Unknown button index %d upage %02x usage %02x, ignoring\n",
                         info->acpi_index, upage, usage);
                info->name = "unknown";
                info->event_code = KEY_RESERVED;
        }

        return 0;
}

/* ACPI0011 _DSD btns descriptors UUID: fa6bd625-9ce8-470d-a2c7-b3ca36c4282e */
static const u8 btns_desc_uuid[16] = {
        0x25, 0xd6, 0x6b, 0xfa, 0xe8, 0x9c, 0x0d, 0x47,
        0xa2, 0xc7, 0xb3, 0xca, 0x36, 0xc4, 0x28, 0x2e
};

/* Parse ACPI0011 _DSD button descriptors */
static struct soc_button_info *soc_button_get_button_info(struct device *dev)
{
        struct acpi_buffer buf = { ACPI_ALLOCATE_BUFFER };
        const union acpi_object *desc, *el0, *uuid, *btns_desc = NULL;
        struct soc_button_info *button_info;
        acpi_status status;
        int i, btn, collection_uid = -1;

        status = acpi_evaluate_object_typed(ACPI_HANDLE(dev), "_DSD", NULL,
                                            &buf, ACPI_TYPE_PACKAGE);
        if (ACPI_FAILURE(status)) {
                dev_err(dev, "ACPI _DSD object not found\n");
                return ERR_PTR(-ENODEV);
        }

        /* Look for the Button Descriptors UUID */
        desc = buf.pointer;
        for (i = 0; (i + 1) < desc->package.count; i += 2) {
                uuid = &desc->package.elements[i];

                if (uuid->type != ACPI_TYPE_BUFFER ||
                    uuid->buffer.length != 16 ||
                    desc->package.elements[i + 1].type != ACPI_TYPE_PACKAGE) {
                        break;
                }

                if (memcmp(uuid->buffer.pointer, btns_desc_uuid, 16) == 0) {
                        btns_desc = &desc->package.elements[i + 1];
                        break;
                }
        }

        if (!btns_desc) {
                dev_err(dev, "ACPI Button Descriptors not found\n");
                button_info = ERR_PTR(-ENODEV);
                goto out;
        }

        /* The first package describes the collection */
        el0 = &btns_desc->package.elements[0];
        if (el0->type == ACPI_TYPE_PACKAGE &&
            el0->package.count == 5 &&
            /* First byte should be 0 (collection) */
            soc_button_get_acpi_object_int(&el0->package.elements[0]) == 0 &&
            /* Third byte should be 0 (top level collection) */
            soc_button_get_acpi_object_int(&el0->package.elements[2]) == 0) {
                collection_uid = soc_button_get_acpi_object_int(
                                                &el0->package.elements[1]);
        }
        if (collection_uid == -1) {
                dev_err(dev, "Invalid Button Collection Descriptor\n");
                button_info = ERR_PTR(-ENODEV);
                goto out;
        }

        /* There are package.count - 1 buttons + 1 terminating empty entry */
        button_info = devm_kcalloc(dev, btns_desc->package.count,
                                   sizeof(*button_info), GFP_KERNEL);
        if (!button_info) {
                button_info = ERR_PTR(-ENOMEM);
                goto out;
        }

        /* Parse the button descriptors */
        for (i = 1, btn = 0; i < btns_desc->package.count; i++, btn++) {
                if (soc_button_parse_btn_desc(dev,
                                              &btns_desc->package.elements[i],
                                              collection_uid,
                                              &button_info[btn])) {
                        button_info = ERR_PTR(-ENODEV);
                        goto out;
                }
        }

out:
        kfree(buf.pointer);
        return button_info;
}

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;

        if (!id->driver_data) {
                button_info = soc_button_get_button_info(dev);
                if (IS_ERR(button_info))
                        return PTR_ERR(button_info);
        } else {
                button_info = (struct soc_button_info *)id->driver_data;
        }

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

        priv = devm_kzalloc(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;

        if (!id->driver_data)
                devm_kfree(dev, button_info);

        return 0;
}

/*
 * 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"
 */
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 },
        { "ACPI0011", 0 },
        { }
};

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");