// SPDX-License-Identifier: GPL-2.0-only
/*
 * GPIO driven charlieplex keypad driver
 *
 * Copyright (c) 2026 Hugo Villeneuve <hvilleneuve@dimonoff.com>
 *
 * Based on matrix_keyboard.c
 */

#include <linux/bitops.h>
#include <linux/delay.h>
#include <linux/dev_printk.h>
#include <linux/device/devres.h>
#include <linux/err.h>
#include <linux/gpio/consumer.h>
#include <linux/input.h>
#include <linux/input/matrix_keypad.h>
#include <linux/math.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/property.h>
#include <linux/string_helpers.h>
#include <linux/types.h>

struct charlieplex_keypad {
        struct input_dev *input_dev;
        struct gpio_descs *line_gpios;
        unsigned int nlines;
        unsigned int settling_time_us;
        unsigned int debounce_threshold;
        unsigned int debounce_count;
        int debounce_code;
        int current_code;
};

static void charlieplex_keypad_report_key(struct input_dev *input)
{
        struct charlieplex_keypad *keypad = input_get_drvdata(input);
        const unsigned short *keycodes = input->keycode;

        if (keypad->current_code > 0) {
                input_event(input, EV_MSC, MSC_SCAN, keypad->current_code);
                input_report_key(input, keycodes[keypad->current_code], 0);
                input_sync(input);
        }

        if (keypad->debounce_code) {
                input_event(input, EV_MSC, MSC_SCAN, keypad->debounce_code);
                input_report_key(input, keycodes[keypad->debounce_code], 1);
                input_sync(input);
        }

        keypad->current_code = keypad->debounce_code;
}

static void charlieplex_keypad_check_switch_change(struct input_dev *input,
                                                   unsigned int code)
{
        struct charlieplex_keypad *keypad = input_get_drvdata(input);

        if (code != keypad->debounce_code) {
                keypad->debounce_count = 0;
                keypad->debounce_code = code;
        }

        if (keypad->debounce_code != keypad->current_code) {
                if (keypad->debounce_count++ >= keypad->debounce_threshold)
                        charlieplex_keypad_report_key(input);
        }
}

static int charlieplex_keypad_scan_line(struct charlieplex_keypad *keypad,
                                        unsigned int oline)
{
        struct gpio_descs *line_gpios = keypad->line_gpios;
        DECLARE_BITMAP(values, MATRIX_MAX_ROWS);
        int err;

        /* Activate only one line as output at a time. */
        gpiod_direction_output(line_gpios->desc[oline], 1);

        if (keypad->settling_time_us)
                fsleep(keypad->settling_time_us);

        /* Read input on all other lines. */
        err = gpiod_get_array_value_cansleep(line_gpios->ndescs, line_gpios->desc,
                                             line_gpios->info, values);

        gpiod_direction_input(line_gpios->desc[oline]);

        if (err)
                return err;

        for (unsigned int iline = 0; iline < keypad->nlines; iline++) {
                if (iline == oline)
                        continue; /* Do not read active output line. */

                /* Check if GPIO is asserted. */
                if (test_bit(iline, values))
                        return MATRIX_SCAN_CODE(oline, iline,
                                                get_count_order(keypad->nlines));
        }

        return 0;
}

static void charlieplex_keypad_poll(struct input_dev *input)
{
        struct charlieplex_keypad *keypad = input_get_drvdata(input);
        int code = 0;

        for (unsigned int oline = 0; oline < keypad->nlines; oline++) {
                code = charlieplex_keypad_scan_line(keypad, oline);
                if (code != 0)
                        break;
        }

        if (code >= 0)
                charlieplex_keypad_check_switch_change(input, code);
}

static int charlieplex_keypad_init_gpio(struct platform_device *pdev,
                                        struct charlieplex_keypad *keypad)
{
        char **pin_names;
        char label[32];

        snprintf(label, sizeof(label), "%s-pin", pdev->name);

        keypad->line_gpios = devm_gpiod_get_array(&pdev->dev, "line", GPIOD_IN);
        if (IS_ERR(keypad->line_gpios))
                return PTR_ERR(keypad->line_gpios);

        keypad->nlines = keypad->line_gpios->ndescs;

        if (keypad->nlines > MATRIX_MAX_ROWS)
                return -EINVAL;

        pin_names = devm_kasprintf_strarray(&pdev->dev, label, keypad->nlines);
        if (IS_ERR(pin_names))
                return PTR_ERR(pin_names);

        for (unsigned int i = 0; i < keypad->line_gpios->ndescs; i++)
                gpiod_set_consumer_name(keypad->line_gpios->desc[i], pin_names[i]);

        return 0;
}

static int charlieplex_keypad_probe(struct platform_device *pdev)
{
        struct charlieplex_keypad *keypad;
        struct input_dev *input_dev;
        unsigned int debounce_interval_ms = 5;
        unsigned int poll_interval_ms;
        int err;

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

        input_dev = devm_input_allocate_device(&pdev->dev);
        if (!input_dev)
                return -ENOMEM;

        keypad->input_dev = input_dev;

        err = device_property_read_u32(&pdev->dev, "poll-interval", &poll_interval_ms);
        if (err)
                return dev_err_probe(&pdev->dev, err,
                                     "failed to parse 'poll-interval' property\n");

        if (poll_interval_ms == 0)
                return dev_err_probe(&pdev->dev, -EINVAL, "invalid 'poll-interval' value\n");

        device_property_read_u32(&pdev->dev, "debounce-delay-ms", &debounce_interval_ms);
        device_property_read_u32(&pdev->dev, "settling-time-us", &keypad->settling_time_us);

        keypad->current_code = -1;
        keypad->debounce_code = -1;
        keypad->debounce_threshold = DIV_ROUND_UP(debounce_interval_ms, poll_interval_ms);

        err = charlieplex_keypad_init_gpio(pdev, keypad);
        if (err)
                return err;

        input_dev->name = pdev->name;
        input_dev->id.bustype = BUS_HOST;

        err = matrix_keypad_build_keymap(NULL, NULL, keypad->nlines,
                                         keypad->nlines, NULL, input_dev);
        if (err)
                return dev_err_probe(&pdev->dev, err, "failed to build keymap\n");

        if (device_property_read_bool(&pdev->dev, "autorepeat"))
                __set_bit(EV_REP, input_dev->evbit);

        input_set_capability(input_dev, EV_MSC, MSC_SCAN);

        err = input_setup_polling(input_dev, charlieplex_keypad_poll);
        if (err)
                return dev_err_probe(&pdev->dev, err, "unable to set up polling\n");

        input_set_poll_interval(input_dev, poll_interval_ms);

        input_set_drvdata(input_dev, keypad);

        err = input_register_device(keypad->input_dev);
        if (err)
                return err;

        return 0;
}

static const struct of_device_id charlieplex_keypad_dt_match[] = {
        { .compatible = "gpio-charlieplex-keypad" },
        { }
};
MODULE_DEVICE_TABLE(of, charlieplex_keypad_dt_match);

static struct platform_driver charlieplex_keypad_driver = {
        .probe          = charlieplex_keypad_probe,
        .driver         = {
                .name   = "charlieplex-keypad",
                .of_match_table = charlieplex_keypad_dt_match,
        },
};
module_platform_driver(charlieplex_keypad_driver);

MODULE_AUTHOR("Hugo Villeneuve <hvilleneuve@dimonoff.com>");
MODULE_DESCRIPTION("GPIO driven charlieplex keypad driver");
MODULE_LICENSE("GPL");