// SPDX-License-Identifier: GPL-2.0-only
/*
 * TSC-40 serial touchscreen driver. It should be compatible with
 * TSC-10 and 25.
 *
 * Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/input.h>
#include <linux/serio.h>

#define PACKET_LENGTH  5
struct tsc_ser {
        struct input_dev *dev;
        struct serio *serio;
        u32 idx;
        unsigned char data[PACKET_LENGTH];
        char phys[32];
};

static void tsc_process_data(struct tsc_ser *ptsc)
{
        struct input_dev *dev = ptsc->dev;
        u8 *data = ptsc->data;
        u32 x;
        u32 y;

        x = ((data[1] & 0x03) << 8) | data[2];
        y = ((data[3] & 0x03) << 8) | data[4];

        input_report_abs(dev, ABS_X, x);
        input_report_abs(dev, ABS_Y, y);
        input_report_key(dev, BTN_TOUCH, 1);

        input_sync(dev);
}

static irqreturn_t tsc_interrupt(struct serio *serio,
                unsigned char data, unsigned int flags)
{
        struct tsc_ser *ptsc = serio_get_drvdata(serio);
        struct input_dev *dev = ptsc->dev;

        ptsc->data[ptsc->idx] = data;
        switch (ptsc->idx++) {
        case 0:
                if (unlikely((data & 0x3e) != 0x10)) {
                        dev_dbg(&serio->dev,
                                "unsynchronized packet start (0x%02x)\n", data);
                        ptsc->idx = 0;
                } else if (!(data & 0x01)) {
                        input_report_key(dev, BTN_TOUCH, 0);
                        input_sync(dev);
                        ptsc->idx = 0;
                }
                break;

        case 1:
        case 3:
                if (unlikely(data & 0xfc)) {
                        dev_dbg(&serio->dev,
                                "unsynchronized data 0x%02x at offset %d\n",
                                data, ptsc->idx - 1);
                        ptsc->idx = 0;
                }
                break;

        case 4:
                tsc_process_data(ptsc);
                ptsc->idx = 0;
                break;
        }

        return IRQ_HANDLED;
}

static int tsc_connect(struct serio *serio, struct serio_driver *drv)
{
        struct tsc_ser *ptsc;
        struct input_dev *input_dev;
        int error;

        ptsc = kzalloc_obj(*ptsc);
        input_dev = input_allocate_device();
        if (!ptsc || !input_dev) {
                error = -ENOMEM;
                goto fail1;
        }

        ptsc->serio = serio;
        ptsc->dev = input_dev;
        scnprintf(ptsc->phys, sizeof(ptsc->phys), "%s/input0", serio->phys);

        input_dev->name = "TSC-10/25/40 Serial TouchScreen";
        input_dev->phys = ptsc->phys;
        input_dev->id.bustype = BUS_RS232;
        input_dev->id.vendor = SERIO_TSC40;
        input_dev->id.product = 40;
        input_dev->id.version = 0x0001;
        input_dev->dev.parent = &serio->dev;

        input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
        __set_bit(BTN_TOUCH, input_dev->keybit);
        input_set_abs_params(ptsc->dev, ABS_X, 0, 0x3ff, 0, 0);
        input_set_abs_params(ptsc->dev, ABS_Y, 0, 0x3ff, 0, 0);

        serio_set_drvdata(serio, ptsc);

        error = serio_open(serio, drv);
        if (error)
                goto fail2;

        error = input_register_device(ptsc->dev);
        if (error)
                goto fail3;

        return 0;

fail3:
        serio_close(serio);
fail2:
        serio_set_drvdata(serio, NULL);
fail1:
        input_free_device(input_dev);
        kfree(ptsc);
        return error;
}

static void tsc_disconnect(struct serio *serio)
{
        struct tsc_ser *ptsc = serio_get_drvdata(serio);

        serio_close(serio);

        input_unregister_device(ptsc->dev);
        kfree(ptsc);

        serio_set_drvdata(serio, NULL);
}

static const struct serio_device_id tsc_serio_ids[] = {
        {
                .type   = SERIO_RS232,
                .proto  = SERIO_TSC40,
                .id     = SERIO_ANY,
                .extra  = SERIO_ANY,
        },
        { 0 }
};
MODULE_DEVICE_TABLE(serio, tsc_serio_ids);

#define DRIVER_DESC    "TSC-10/25/40 serial touchscreen driver"

static struct serio_driver tsc_drv = {
        .driver = {
                .name   = "tsc40",
        },
        .description    = DRIVER_DESC,
        .id_table       = tsc_serio_ids,
        .interrupt      = tsc_interrupt,
        .connect        = tsc_connect,
        .disconnect     = tsc_disconnect,
};

module_serio_driver(tsc_drv);

MODULE_AUTHOR("Sebastian Andrzej Siewior <bigeasy@linutronix.de>");
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_LICENSE("GPL v2");