// SPDX-License-Identifier: GPL-2.0+
//
// Gateworks I2C PLD GPIO expander
//
// Copyright (C) 2019 Linus Walleij <linus.walleij@linaro.org>
//
// Based on code and know-how from the OpenWrt driver:
// Copyright (C) 2009 Gateworks Corporation
// Authors: Chris Lang, Imre Kaloz

#include <linux/bits.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/gpio/driver.h>
#include <linux/i2c.h>
#include <linux/module.h>

/**
 * struct gw_pld - State container for Gateworks PLD
 * @chip: GPIO chip instance
 * @client: I2C client
 * @out: shadow register for the output bute
 */
struct gw_pld {
        struct gpio_chip chip;
        struct i2c_client *client;
        u8 out;
};

/*
 * The Gateworks I2C PLD chip only expose one read and one write register.
 * Writing a "one" bit (to match the reset state) lets that pin be used as an
 * input. It is an open-drain model.
 */
static int gw_pld_input8(struct gpio_chip *gc, unsigned offset)
{
        struct gw_pld *gw = gpiochip_get_data(gc);

        gw->out |= BIT(offset);
        return i2c_smbus_write_byte(gw->client, gw->out);
}

static int gw_pld_get8(struct gpio_chip *gc, unsigned offset)
{
        struct gw_pld *gw = gpiochip_get_data(gc);
        s32 val;

        val = i2c_smbus_read_byte(gw->client);

        return (val < 0) ? 0 : !!(val & BIT(offset));
}

static int gw_pld_output8(struct gpio_chip *gc, unsigned offset, int value)
{
        struct gw_pld *gw = gpiochip_get_data(gc);

        if (value)
                gw->out |= BIT(offset);
        else
                gw->out &= ~BIT(offset);

        return i2c_smbus_write_byte(gw->client, gw->out);
}

static int gw_pld_set8(struct gpio_chip *gc, unsigned int offset, int value)
{
        return gw_pld_output8(gc, offset, value);
}

static int gw_pld_probe(struct i2c_client *client)
{
        struct device *dev = &client->dev;
        struct gw_pld *gw;
        int ret;

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

        gw->chip.base = -1;
        gw->chip.can_sleep = true;
        gw->chip.parent = dev;
        gw->chip.owner = THIS_MODULE;
        gw->chip.label = dev_name(dev);
        gw->chip.ngpio = 8;
        gw->chip.direction_input = gw_pld_input8;
        gw->chip.get = gw_pld_get8;
        gw->chip.direction_output = gw_pld_output8;
        gw->chip.set = gw_pld_set8;
        gw->client = client;

        /*
         * The Gateworks I2C PLD chip does not properly send the acknowledge
         * bit at all times, but we can still use the standard i2c_smbus
         * functions by simply ignoring this bit.
         */
        client->flags |= I2C_M_IGNORE_NAK;
        gw->out = 0xFF;

        i2c_set_clientdata(client, gw);

        ret = devm_gpiochip_add_data(dev, &gw->chip, gw);
        if (ret)
                return ret;

        dev_info(dev, "registered Gateworks PLD GPIO device\n");

        return 0;
}

static const struct i2c_device_id gw_pld_id[] = {
        { "gw-pld", },
        { }
};
MODULE_DEVICE_TABLE(i2c, gw_pld_id);

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

static struct i2c_driver gw_pld_driver = {
        .driver = {
                .name = "gw_pld",
                .of_match_table = gw_pld_dt_ids,
        },
        .probe = gw_pld_probe,
        .id_table = gw_pld_id,
};
module_i2c_driver(gw_pld_driver);

MODULE_DESCRIPTION("Gateworks I2C PLD GPIO expander");
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");