/*
    Dell Airplane Mode Switch driver
    Copyright (C) 2014-2015  Pali Rohár <pali.rohar@gmail.com>

    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; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.
*/

#include <linux/module.h>
#include <linux/acpi.h>
#include <linux/rfkill.h>
#include <linux/input.h>

enum rbtn_type {
        RBTN_UNKNOWN,
        RBTN_TOGGLE,
        RBTN_SLIDER,
};

struct rbtn_data {
        enum rbtn_type type;
        struct rfkill *rfkill;
        struct input_dev *input_dev;
        bool suspended;
};


/*
 * acpi functions
 */

static enum rbtn_type rbtn_check(struct acpi_device *device)
{
        unsigned long long output;
        acpi_status status;

        status = acpi_evaluate_integer(device->handle, "CRBT", NULL, &output);
        if (ACPI_FAILURE(status))
                return RBTN_UNKNOWN;

        switch (output) {
        case 0:
        case 1:
                return RBTN_TOGGLE;
        case 2:
        case 3:
                return RBTN_SLIDER;
        default:
                return RBTN_UNKNOWN;
        }
}

static int rbtn_get(struct acpi_device *device)
{
        unsigned long long output;
        acpi_status status;

        status = acpi_evaluate_integer(device->handle, "GRBT", NULL, &output);
        if (ACPI_FAILURE(status))
                return -EINVAL;

        return !output;
}

static int rbtn_acquire(struct acpi_device *device, bool enable)
{
        struct acpi_object_list input;
        union acpi_object param;
        acpi_status status;

        param.type = ACPI_TYPE_INTEGER;
        param.integer.value = enable;
        input.count = 1;
        input.pointer = &param;

        status = acpi_evaluate_object(device->handle, "ARBT", &input, NULL);
        if (ACPI_FAILURE(status))
                return -EINVAL;

        return 0;
}


/*
 * rfkill device
 */

static void rbtn_rfkill_query(struct rfkill *rfkill, void *data)
{
        struct acpi_device *device = data;
        int state;

        state = rbtn_get(device);
        if (state < 0)
                return;

        rfkill_set_states(rfkill, state, state);
}

static int rbtn_rfkill_set_block(void *data, bool blocked)
{
        /* NOTE: setting soft rfkill state is not supported */
        return -EINVAL;
}

static const struct rfkill_ops rbtn_ops = {
        .query = rbtn_rfkill_query,
        .set_block = rbtn_rfkill_set_block,
};

static int rbtn_rfkill_init(struct acpi_device *device)
{
        struct rbtn_data *rbtn_data = device->driver_data;
        int ret;

        if (rbtn_data->rfkill)
                return 0;

        /*
         * NOTE: rbtn controls all radio devices, not only WLAN
         *       but rfkill interface does not support "ANY" type
         *       so "WLAN" type is used
         */
        rbtn_data->rfkill = rfkill_alloc("dell-rbtn", &device->dev,
                                         RFKILL_TYPE_WLAN, &rbtn_ops, device);
        if (!rbtn_data->rfkill)
                return -ENOMEM;

        ret = rfkill_register(rbtn_data->rfkill);
        if (ret) {
                rfkill_destroy(rbtn_data->rfkill);
                rbtn_data->rfkill = NULL;
                return ret;
        }

        return 0;
}

static void rbtn_rfkill_exit(struct acpi_device *device)
{
        struct rbtn_data *rbtn_data = device->driver_data;

        if (!rbtn_data->rfkill)
                return;

        rfkill_unregister(rbtn_data->rfkill);
        rfkill_destroy(rbtn_data->rfkill);
        rbtn_data->rfkill = NULL;
}

static void rbtn_rfkill_event(struct acpi_device *device)
{
        struct rbtn_data *rbtn_data = device->driver_data;

        if (rbtn_data->rfkill)
                rbtn_rfkill_query(rbtn_data->rfkill, device);
}


/*
 * input device
 */

static int rbtn_input_init(struct rbtn_data *rbtn_data)
{
        int ret;

        rbtn_data->input_dev = input_allocate_device();
        if (!rbtn_data->input_dev)
                return -ENOMEM;

        rbtn_data->input_dev->name = "DELL Wireless hotkeys";
        rbtn_data->input_dev->phys = "dellabce/input0";
        rbtn_data->input_dev->id.bustype = BUS_HOST;
        rbtn_data->input_dev->evbit[0] = BIT(EV_KEY);
        set_bit(KEY_RFKILL, rbtn_data->input_dev->keybit);

        ret = input_register_device(rbtn_data->input_dev);
        if (ret) {
                input_free_device(rbtn_data->input_dev);
                rbtn_data->input_dev = NULL;
                return ret;
        }

        return 0;
}

static void rbtn_input_exit(struct rbtn_data *rbtn_data)
{
        input_unregister_device(rbtn_data->input_dev);
        rbtn_data->input_dev = NULL;
}

static void rbtn_input_event(struct rbtn_data *rbtn_data)
{
        input_report_key(rbtn_data->input_dev, KEY_RFKILL, 1);
        input_sync(rbtn_data->input_dev);
        input_report_key(rbtn_data->input_dev, KEY_RFKILL, 0);
        input_sync(rbtn_data->input_dev);
}


/*
 * acpi driver
 */

static int rbtn_add(struct acpi_device *device);
static int rbtn_remove(struct acpi_device *device);
static void rbtn_notify(struct acpi_device *device, u32 event);

static const struct acpi_device_id rbtn_ids[] = {
        { "DELRBTN", 0 },
        { "DELLABCE", 0 },

        /*
         * This driver can also handle the "DELLABC6" device that
         * appears on the XPS 13 9350, but that device is disabled by
         * the DSDT unless booted with acpi_osi="!Windows 2012"
         * acpi_osi="!Windows 2013".
         *
         * According to Mario at Dell:
         *
         *  DELLABC6 is a custom interface that was created solely to
         *  have airplane mode support for Windows 7.  For Windows 10
         *  the proper interface is to use that which is handled by
         *  intel-hid. A OEM airplane mode driver is not used.
         *
         *  Since the kernel doesn't identify as Windows 7 it would be
         *  incorrect to do attempt to use that interface.
         *
         * Even if we override _OSI and bind to DELLABC6, we end up with
         * inconsistent behavior in which userspace can get out of sync
         * with the rfkill state as it conflicts with events from
         * intel-hid.
         *
         * The upshot is that it is better to just ignore DELLABC6
         * devices.
         */

        { "", 0 },
};

#ifdef CONFIG_PM_SLEEP
static void ACPI_SYSTEM_XFACE rbtn_clear_suspended_flag(void *context)
{
        struct rbtn_data *rbtn_data = context;

        rbtn_data->suspended = false;
}

static int rbtn_suspend(struct device *dev)
{
        struct acpi_device *device = to_acpi_device(dev);
        struct rbtn_data *rbtn_data = acpi_driver_data(device);

        rbtn_data->suspended = true;

        return 0;
}

static int rbtn_resume(struct device *dev)
{
        struct acpi_device *device = to_acpi_device(dev);
        struct rbtn_data *rbtn_data = acpi_driver_data(device);
        acpi_status status;

        /*
         * Upon resume, some BIOSes send an ACPI notification thet triggers
         * an unwanted input event. In order to ignore it, we use a flag
         * that we set at suspend and clear once we have received the extra
         * ACPI notification. Since ACPI notifications are delivered
         * asynchronously to drivers, we clear the flag from the workqueue
         * used to deliver the notifications. This should be enough
         * to have the flag cleared only after we received the extra
         * notification, if any.
         */
        status = acpi_os_execute(OSL_NOTIFY_HANDLER,
                         rbtn_clear_suspended_flag, rbtn_data);
        if (ACPI_FAILURE(status))
                rbtn_clear_suspended_flag(rbtn_data);

        return 0;
}
#endif

static SIMPLE_DEV_PM_OPS(rbtn_pm_ops, rbtn_suspend, rbtn_resume);

static struct acpi_driver rbtn_driver = {
        .name = "dell-rbtn",
        .ids = rbtn_ids,
        .drv.pm = &rbtn_pm_ops,
        .ops = {
                .add = rbtn_add,
                .remove = rbtn_remove,
                .notify = rbtn_notify,
        },
        .owner = THIS_MODULE,
};


/*
 * notifier export functions
 */

static bool auto_remove_rfkill = true;

static ATOMIC_NOTIFIER_HEAD(rbtn_chain_head);

static int rbtn_inc_count(struct device *dev, void *data)
{
        struct acpi_device *device = to_acpi_device(dev);
        struct rbtn_data *rbtn_data = device->driver_data;
        int *count = data;

        if (rbtn_data->type == RBTN_SLIDER)
                (*count)++;

        return 0;
}

static int rbtn_switch_dev(struct device *dev, void *data)
{
        struct acpi_device *device = to_acpi_device(dev);
        struct rbtn_data *rbtn_data = device->driver_data;
        bool enable = data;

        if (rbtn_data->type != RBTN_SLIDER)
                return 0;

        if (enable)
                rbtn_rfkill_init(device);
        else
                rbtn_rfkill_exit(device);

        return 0;
}

int dell_rbtn_notifier_register(struct notifier_block *nb)
{
        bool first;
        int count;
        int ret;

        count = 0;
        ret = driver_for_each_device(&rbtn_driver.drv, NULL, &count,
                                     rbtn_inc_count);
        if (ret || count == 0)
                return -ENODEV;

        first = !rbtn_chain_head.head;

        ret = atomic_notifier_chain_register(&rbtn_chain_head, nb);
        if (ret != 0)
                return ret;

        if (auto_remove_rfkill && first)
                ret = driver_for_each_device(&rbtn_driver.drv, NULL,
                                             (void *)false, rbtn_switch_dev);

        return ret;
}
EXPORT_SYMBOL_GPL(dell_rbtn_notifier_register);

int dell_rbtn_notifier_unregister(struct notifier_block *nb)
{
        int ret;

        ret = atomic_notifier_chain_unregister(&rbtn_chain_head, nb);
        if (ret != 0)
                return ret;

        if (auto_remove_rfkill && !rbtn_chain_head.head)
                ret = driver_for_each_device(&rbtn_driver.drv, NULL,
                                             (void *)true, rbtn_switch_dev);

        return ret;
}
EXPORT_SYMBOL_GPL(dell_rbtn_notifier_unregister);


/*
 * acpi driver functions
 */

static int rbtn_add(struct acpi_device *device)
{
        struct rbtn_data *rbtn_data;
        enum rbtn_type type;
        int ret = 0;

        type = rbtn_check(device);
        if (type == RBTN_UNKNOWN) {
                dev_info(&device->dev, "Unknown device type\n");
                return -EINVAL;
        }

        ret = rbtn_acquire(device, true);
        if (ret < 0) {
                dev_err(&device->dev, "Cannot enable device\n");
                return ret;
        }

        rbtn_data = devm_kzalloc(&device->dev, sizeof(*rbtn_data), GFP_KERNEL);
        if (!rbtn_data)
                return -ENOMEM;

        rbtn_data->type = type;
        device->driver_data = rbtn_data;

        switch (rbtn_data->type) {
        case RBTN_TOGGLE:
                ret = rbtn_input_init(rbtn_data);
                break;
        case RBTN_SLIDER:
                if (auto_remove_rfkill && rbtn_chain_head.head)
                        ret = 0;
                else
                        ret = rbtn_rfkill_init(device);
                break;
        default:
                ret = -EINVAL;
        }

        return ret;

}

static int rbtn_remove(struct acpi_device *device)
{
        struct rbtn_data *rbtn_data = device->driver_data;

        switch (rbtn_data->type) {
        case RBTN_TOGGLE:
                rbtn_input_exit(rbtn_data);
                break;
        case RBTN_SLIDER:
                rbtn_rfkill_exit(device);
                break;
        default:
                break;
        }

        rbtn_acquire(device, false);
        device->driver_data = NULL;

        return 0;
}

static void rbtn_notify(struct acpi_device *device, u32 event)
{
        struct rbtn_data *rbtn_data = device->driver_data;

        /*
         * Some BIOSes send a notification at resume.
         * Ignore it to prevent unwanted input events.
         */
        if (rbtn_data->suspended) {
                dev_dbg(&device->dev, "ACPI notification ignored\n");
                return;
        }

        if (event != 0x80) {
                dev_info(&device->dev, "Received unknown event (0x%x)\n",
                         event);
                return;
        }

        switch (rbtn_data->type) {
        case RBTN_TOGGLE:
                rbtn_input_event(rbtn_data);
                break;
        case RBTN_SLIDER:
                rbtn_rfkill_event(device);
                atomic_notifier_call_chain(&rbtn_chain_head, event, device);
                break;
        default:
                break;
        }
}


/*
 * module functions
 */

module_acpi_driver(rbtn_driver);

module_param(auto_remove_rfkill, bool, 0444);

MODULE_PARM_DESC(auto_remove_rfkill, "Automatically remove rfkill devices when "
                                     "other modules start receiving events "
                                     "from this module and re-add them when "
                                     "the last module stops receiving events "
                                     "(default true)");
MODULE_DEVICE_TABLE(acpi, rbtn_ids);
MODULE_DESCRIPTION("Dell Airplane Mode Switch driver");
MODULE_AUTHOR("Pali Rohár <pali.rohar@gmail.com>");
MODULE_LICENSE("GPL");