// SPDX-License-Identifier: GPL-2.0-only
/*
 * D-Link DIR-685 router I2C-based Touchkeys input driver
 * Copyright (C) 2017 Linus Walleij <linus.walleij@linaro.org>
 *
 * This is a one-off touchkey controller based on the Cypress Semiconductor
 * CY8C214 MCU with some firmware in its internal 8KB flash. The circuit
 * board inside the router is named E119921
 */

#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/input.h>
#include <linux/slab.h>
#include <linux/string_choices.h>
#include <linux/bitops.h>

struct dir685_touchkeys {
        struct device           *dev;
        struct i2c_client       *client;
        struct input_dev        *input;
        unsigned long           cur_key;
        u16                     codes[7];
};

static irqreturn_t dir685_tk_irq_thread(int irq, void *data)
{
        struct dir685_touchkeys *tk = data;
        const int num_bits = min_t(int, ARRAY_SIZE(tk->codes), 16);
        unsigned long changed;
        u8 buf[6];
        unsigned long key;
        int i;
        int err;

        memset(buf, 0, sizeof(buf));
        err = i2c_master_recv(tk->client, buf, sizeof(buf));
        if (err != sizeof(buf)) {
                dev_err(tk->dev, "short read %d\n", err);
                return IRQ_HANDLED;
        }

        dev_dbg(tk->dev, "IN: %*ph\n", (int)sizeof(buf), buf);
        key = be16_to_cpup((__be16 *) &buf[4]);

        /* Figure out if any bits went high or low since last message */
        changed = tk->cur_key ^ key;
        for_each_set_bit(i, &changed, num_bits) {
                dev_dbg(tk->dev, "key %d is %s\n", i,
                        str_down_up(test_bit(i, &key)));
                input_report_key(tk->input, tk->codes[i], test_bit(i, &key));
        }

        /* Store currently down keys */
        tk->cur_key = key;
        input_sync(tk->input);

        return IRQ_HANDLED;
}

static int dir685_tk_probe(struct i2c_client *client)
{
        static const u8 bl_data[] = { 0xa7, 0x40 };
        struct device *dev = &client->dev;
        struct dir685_touchkeys *tk;
        int err;
        int i;

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

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

        tk->client = client;
        tk->dev = dev;

        tk->input->keycodesize = sizeof(u16);
        tk->input->keycodemax = ARRAY_SIZE(tk->codes);
        tk->input->keycode = tk->codes;
        tk->codes[0] = KEY_UP;
        tk->codes[1] = KEY_DOWN;
        tk->codes[2] = KEY_LEFT;
        tk->codes[3] = KEY_RIGHT;
        tk->codes[4] = KEY_ENTER;
        tk->codes[5] = KEY_WPS_BUTTON;
        /*
         * This key appears in the vendor driver, but I have
         * not been able to activate it.
         */
        tk->codes[6] = KEY_RESERVED;

        __set_bit(EV_KEY, tk->input->evbit);
        for (i = 0; i < ARRAY_SIZE(tk->codes); i++)
                __set_bit(tk->codes[i], tk->input->keybit);
        __clear_bit(KEY_RESERVED, tk->input->keybit);

        tk->input->name = "D-Link DIR-685 touchkeys";
        tk->input->id.bustype = BUS_I2C;

        err = input_register_device(tk->input);
        if (err)
                return err;

        /* Set the brightness to max level */
        err = i2c_master_send(client, bl_data, sizeof(bl_data));
        if (err != sizeof(bl_data))
                dev_warn(tk->dev, "error setting brightness level\n");

        if (!client->irq) {
                dev_err(dev, "no IRQ on the I2C device\n");
                return -ENODEV;
        }
        err = devm_request_threaded_irq(dev, client->irq,
                                        NULL, dir685_tk_irq_thread,
                                        IRQF_ONESHOT,
                                        "dir685-tk", tk);
        if (err) {
                dev_err(dev, "can't request IRQ\n");
                return err;
        }

        return 0;
}

static const struct i2c_device_id dir685_tk_id[] = {
        { .name = "dir685tk" },
        { }
};
MODULE_DEVICE_TABLE(i2c, dir685_tk_id);

#ifdef CONFIG_OF
static const struct of_device_id dir685_tk_of_match[] = {
        { .compatible = "dlink,dir685-touchkeys" },
        {},
};
MODULE_DEVICE_TABLE(of, dir685_tk_of_match);
#endif

static struct i2c_driver dir685_tk_i2c_driver = {
        .driver = {
                .name   = "dlink-dir685-touchkeys",
                .of_match_table = of_match_ptr(dir685_tk_of_match),
        },
        .probe          = dir685_tk_probe,
        .id_table       = dir685_tk_id,
};
module_i2c_driver(dir685_tk_i2c_driver);

MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");
MODULE_DESCRIPTION("D-Link DIR-685 touchkeys driver");
MODULE_LICENSE("GPL");