// SPDX-License-Identifier: GPL-2.0
/*
 * GPIO line mux which acts as virtual gpiochip and provides a 1-to-many
 * mapping between virtual GPIOs and a real GPIO + multiplexer.
 *
 * Copyright (c) 2025 Jonas Jelonek <jelonek.jonas@gmail.com>
 */

#include <linux/gpio/consumer.h>
#include <linux/gpio/driver.h>
#include <linux/mod_devicetable.h>
#include <linux/mutex.h>
#include <linux/mux/consumer.h>
#include <linux/platform_device.h>

#define MUX_SELECT_DELAY_US     100

struct gpio_lmux {
        struct gpio_chip gc;
        struct mux_control *mux;
        struct gpio_desc *muxed_gpio;

        u32 num_gpio_mux_states;
        unsigned int gpio_mux_states[] __counted_by(num_gpio_mux_states);
};

static int gpio_lmux_gpio_get(struct gpio_chip *gc, unsigned int offset)
{
        struct gpio_lmux *glm = gpiochip_get_data(gc);
        int ret;

        ret = mux_control_select_delay(glm->mux, glm->gpio_mux_states[offset],
                                       MUX_SELECT_DELAY_US);
        if (ret < 0)
                return ret;

        ret = gpiod_get_raw_value_cansleep(glm->muxed_gpio);
        mux_control_deselect(glm->mux);
        return ret;
}

static int gpio_lmux_gpio_get_direction(struct gpio_chip *gc,
                                        unsigned int offset)
{
        return GPIO_LINE_DIRECTION_IN;
}

static int gpio_lmux_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct gpio_lmux *glm;
        unsigned int ngpio;
        size_t size;
        int ret;

        ngpio = device_property_count_u32(dev, "gpio-line-mux-states");
        if (!ngpio)
                return -EINVAL;

        size = struct_size(glm, gpio_mux_states, ngpio);
        glm = devm_kzalloc(dev, size, GFP_KERNEL);
        if (!glm)
                return -ENOMEM;

        glm->gc.base = -1;
        glm->gc.can_sleep = true;
        glm->gc.fwnode = dev_fwnode(dev);
        glm->gc.label = dev_name(dev);
        glm->gc.ngpio = ngpio;
        glm->gc.owner = THIS_MODULE;
        glm->gc.parent = dev;

        glm->gc.get = gpio_lmux_gpio_get;
        glm->gc.get_direction = gpio_lmux_gpio_get_direction;

        glm->mux = devm_mux_control_get(dev, NULL);
        if (IS_ERR(glm->mux))
                return dev_err_probe(dev, PTR_ERR(glm->mux),
                                     "could not get mux controller\n");

        glm->muxed_gpio = devm_gpiod_get(dev, "muxed", GPIOD_IN);
        if (IS_ERR(glm->muxed_gpio))
                return dev_err_probe(dev, PTR_ERR(glm->muxed_gpio),
                                     "could not get muxed-gpio\n");

        glm->num_gpio_mux_states = ngpio;
        ret = device_property_read_u32_array(dev, "gpio-line-mux-states",
                                             &glm->gpio_mux_states[0], ngpio);
        if (ret)
                return dev_err_probe(dev, ret, "could not get mux states\n");

        ret = devm_gpiochip_add_data(dev, &glm->gc, glm);
        if (ret)
                return dev_err_probe(dev, ret, "failed to add gpiochip\n");

        return 0;
}

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

static struct platform_driver gpio_lmux_driver = {
        .driver = {
                .name = "gpio-line-mux",
                .of_match_table = gpio_lmux_of_match,
        },
        .probe = gpio_lmux_probe,
};
module_platform_driver(gpio_lmux_driver);

MODULE_AUTHOR("Jonas Jelonek <jelonek.jonas@gmail.com>");
MODULE_DESCRIPTION("GPIO line mux driver");
MODULE_LICENSE("GPL");