// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2016 Texas Instruments Incorporated - http://www.ti.com/
 *
 * A generic driver to read multiple gpio lines and translate the
 * encoded numeric value into an input event.
 */

#include <linux/bitmap.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/minmax.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/property.h>
#include <linux/types.h>

struct gpio_decoder {
        struct gpio_descs *input_gpios;
        struct device *dev;
        u32 axis;
        u32 last_stable;
};

static int gpio_decoder_get_gpios_state(struct gpio_decoder *decoder)
{
        struct gpio_descs *gpios = decoder->input_gpios;
        DECLARE_BITMAP(values, 32);
        unsigned int size;
        int err;

        size = min(gpios->ndescs, 32U);
        err = gpiod_get_array_value_cansleep(size, gpios->desc, gpios->info, values);
        if (err) {
                dev_err(decoder->dev, "Error reading GPIO: %d\n", err);
                return err;
        }

        return bitmap_read(values, 0, size);
}

static void gpio_decoder_poll_gpios(struct input_dev *input)
{
        struct gpio_decoder *decoder = input_get_drvdata(input);
        int state;

        state = gpio_decoder_get_gpios_state(decoder);
        if (state >= 0 && state != decoder->last_stable) {
                input_report_abs(input, decoder->axis, state);
                input_sync(input);
                decoder->last_stable = state;
        }
}

static int gpio_decoder_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct gpio_decoder *decoder;
        struct input_dev *input;
        u32 max;
        int err;

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

        decoder->dev = dev;
        device_property_read_u32(dev, "linux,axis", &decoder->axis);

        decoder->input_gpios = devm_gpiod_get_array(dev, NULL, GPIOD_IN);
        if (IS_ERR(decoder->input_gpios))
                return dev_err_probe(dev, PTR_ERR(decoder->input_gpios),
                                     "unable to acquire input gpios\n");

        if (decoder->input_gpios->ndescs < 2)
                return dev_err_probe(dev, -EINVAL, "not enough gpios found\n");

        if (decoder->input_gpios->ndescs > 31)
                return dev_err_probe(dev, -EINVAL, "too many gpios found\n");

        if (device_property_read_u32(dev, "decoder-max-value", &max))
                max = BIT(decoder->input_gpios->ndescs) - 1;

        input = devm_input_allocate_device(dev);
        if (!input)
                return -ENOMEM;

        input_set_drvdata(input, decoder);

        input->name = pdev->name;
        input->id.bustype = BUS_HOST;
        input_set_abs_params(input, decoder->axis, 0, max, 0, 0);

        err = input_setup_polling(input, gpio_decoder_poll_gpios);
        if (err)
                return dev_err_probe(dev, err, "failed to set up polling\n");

        err = input_register_device(input);
        if (err)
                return dev_err_probe(dev, err, "failed to register input device\n");

        return 0;
}

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

static struct platform_driver gpio_decoder_driver = {
        .probe          = gpio_decoder_probe,
        .driver         = {
                .name   = "gpio-decoder",
                .of_match_table = gpio_decoder_of_match,
        }
};
module_platform_driver(gpio_decoder_driver);

MODULE_DESCRIPTION("GPIO decoder input driver");
MODULE_AUTHOR("Vignesh R <vigneshr@ti.com>");
MODULE_LICENSE("GPL v2");