// SPDX-License-Identifier: GPL-2.0-only
/*
 * Input driver for resistor ladder connected on ADC
 *
 * Copyright (c) 2016 Alexandre Belloni
 */

#include <linux/err.h>
#include <linux/iio/consumer.h>
#include <linux/iio/types.h>
#include <linux/input.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/property.h>
#include <linux/slab.h>

struct adc_keys_button {
        u32 voltage;
        u32 keycode;
};

struct adc_keys_state {
        struct iio_channel *channel;
        u32 num_keys;
        u32 last_key;
        u32 keyup_voltage;
        const struct adc_keys_button *map;
};

static void adc_keys_poll(struct input_dev *input)
{
        struct adc_keys_state *st = input_get_drvdata(input);
        int i, value, ret;
        u32 diff, closest = 0xffffffff;
        int keycode = 0;

        ret = iio_read_channel_processed(st->channel, &value);
        if (unlikely(ret < 0)) {
                /* Forcibly release key if any was pressed */
                value = st->keyup_voltage;
        } else {
                for (i = 0; i < st->num_keys; i++) {
                        diff = abs(st->map[i].voltage - value);
                        if (diff < closest) {
                                closest = diff;
                                keycode = st->map[i].keycode;
                        }
                }
        }

        if (abs(st->keyup_voltage - value) < closest)
                keycode = 0;

        if (st->last_key && st->last_key != keycode)
                input_report_key(input, st->last_key, 0);

        if (keycode)
                input_report_key(input, keycode, 1);

        input_sync(input);
        st->last_key = keycode;
}

static int adc_keys_load_keymap(struct device *dev, struct adc_keys_state *st)
{
        struct adc_keys_button *map;
        int i;

        st->num_keys = device_get_child_node_count(dev);
        if (st->num_keys == 0) {
                dev_err(dev, "keymap is missing\n");
                return -EINVAL;
        }

        map = devm_kmalloc_array(dev, st->num_keys, sizeof(*map), GFP_KERNEL);
        if (!map)
                return -ENOMEM;

        i = 0;
        device_for_each_child_node_scoped(dev, child) {
                if (fwnode_property_read_u32(child, "press-threshold-microvolt",
                                             &map[i].voltage)) {
                        dev_err(dev, "Key with invalid or missing voltage\n");
                        return -EINVAL;
                }
                map[i].voltage /= 1000;

                if (fwnode_property_read_u32(child, "linux,code",
                                             &map[i].keycode)) {
                        dev_err(dev, "Key with invalid or missing linux,code\n");
                        return -EINVAL;
                }

                i++;
        }

        st->map = map;
        return 0;
}

static int adc_keys_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct adc_keys_state *st;
        struct input_dev *input;
        enum iio_chan_type type;
        int i, value;
        int error;

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

        st->channel = devm_iio_channel_get(dev, "buttons");
        if (IS_ERR(st->channel))
                return PTR_ERR(st->channel);

        if (!st->channel->indio_dev)
                return -ENXIO;

        error = iio_get_channel_type(st->channel, &type);
        if (error < 0)
                return error;

        if (type != IIO_VOLTAGE) {
                dev_err(dev, "Incompatible channel type %d\n", type);
                return -EINVAL;
        }

        if (device_property_read_u32(dev, "keyup-threshold-microvolt",
                                     &st->keyup_voltage)) {
                dev_err(dev, "Invalid or missing keyup voltage\n");
                return -EINVAL;
        }
        st->keyup_voltage /= 1000;

        error = adc_keys_load_keymap(dev, st);
        if (error)
                return error;

        input = devm_input_allocate_device(dev);
        if (!input) {
                dev_err(dev, "failed to allocate input device\n");
                return -ENOMEM;
        }

        input_set_drvdata(input, st);

        input->name = pdev->name;
        input->phys = "adc-keys/input0";

        input->id.bustype = BUS_HOST;
        input->id.vendor = 0x0001;
        input->id.product = 0x0001;
        input->id.version = 0x0100;

        __set_bit(EV_KEY, input->evbit);
        for (i = 0; i < st->num_keys; i++)
                __set_bit(st->map[i].keycode, input->keybit);

        if (device_property_read_bool(dev, "autorepeat"))
                __set_bit(EV_REP, input->evbit);


        error = input_setup_polling(input, adc_keys_poll);
        if (error) {
                dev_err(dev, "Unable to set up polling: %d\n", error);
                return error;
        }

        if (!device_property_read_u32(dev, "poll-interval", &value))
                input_set_poll_interval(input, value);

        error = input_register_device(input);
        if (error) {
                dev_err(dev, "Unable to register input device: %d\n", error);
                return error;
        }

        return 0;
}

#ifdef CONFIG_OF
static const struct of_device_id adc_keys_of_match[] = {
        { .compatible = "adc-keys", },
        { }
};
MODULE_DEVICE_TABLE(of, adc_keys_of_match);
#endif

static struct platform_driver adc_keys_driver = {
        .driver = {
                .name = "adc_keys",
                .of_match_table = of_match_ptr(adc_keys_of_match),
        },
        .probe = adc_keys_probe,
};
module_platform_driver(adc_keys_driver);

MODULE_AUTHOR("Alexandre Belloni <alexandre.belloni@free-electrons.com>");
MODULE_DESCRIPTION("Input driver for resistor ladder connected on ADC");
MODULE_LICENSE("GPL v2");