// SPDX-License-Identifier: GPL-2.0-only
/*
 * Fujitsu serial touchscreen driver
 *
 * Copyright (c) Dmitry Torokhov <dtor@mail.ru>
 */


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

#define DRIVER_DESC     "Fujitsu serial touchscreen driver"

MODULE_AUTHOR("Dmitry Torokhov <dtor@mail.ru>");
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_LICENSE("GPL");

#define FUJITSU_LENGTH 5

/*
 * Per-touchscreen data.
 */
struct fujitsu {
        struct input_dev *dev;
        struct serio *serio;
        int idx;
        unsigned char data[FUJITSU_LENGTH];
        char phys[32];
};

/*
 * Decode serial data (5 bytes per packet)
 * First byte
 * 1 C 0 0 R S S S
 * Where C is 1 while in calibration mode (which we don't use)
 * R is 1 when no coordinate corection was done.
 * S are button state
 */
static irqreturn_t fujitsu_interrupt(struct serio *serio,
                                     unsigned char data, unsigned int flags)
{
        struct fujitsu *fujitsu = serio_get_drvdata(serio);
        struct input_dev *dev = fujitsu->dev;

        if (fujitsu->idx == 0) {
                /* resync skip until start of frame */
                if ((data & 0xf0) != 0x80)
                        return IRQ_HANDLED;
        } else {
                /* resync skip garbage */
                if (data & 0x80) {
                        fujitsu->idx = 0;
                        return IRQ_HANDLED;
                }
        }

        fujitsu->data[fujitsu->idx++] = data;
        if (fujitsu->idx == FUJITSU_LENGTH) {
                input_report_abs(dev, ABS_X,
                                 (fujitsu->data[2] << 7) | fujitsu->data[1]);
                input_report_abs(dev, ABS_Y,
                                 (fujitsu->data[4] << 7) | fujitsu->data[3]);
                input_report_key(dev, BTN_TOUCH,
                                 (fujitsu->data[0] & 0x03) != 2);
                input_sync(dev);
                fujitsu->idx = 0;
        }

        return IRQ_HANDLED;
}

/*
 * fujitsu_disconnect() is the opposite of fujitsu_connect()
 */
static void fujitsu_disconnect(struct serio *serio)
{
        struct fujitsu *fujitsu = serio_get_drvdata(serio);

        input_get_device(fujitsu->dev);
        input_unregister_device(fujitsu->dev);
        serio_close(serio);
        serio_set_drvdata(serio, NULL);
        input_put_device(fujitsu->dev);
        kfree(fujitsu);
}

/*
 * fujitsu_connect() is the routine that is called when someone adds a
 * new serio device that supports the Fujitsu protocol and registers it
 * as input device.
 */
static int fujitsu_connect(struct serio *serio, struct serio_driver *drv)
{
        struct fujitsu *fujitsu;
        struct input_dev *input_dev;
        int err;

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

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

        input_dev->name = "Fujitsu Serial Touchscreen";
        input_dev->phys = fujitsu->phys;
        input_dev->id.bustype = BUS_RS232;
        input_dev->id.vendor = SERIO_FUJITSU;
        input_dev->id.product = 0;
        input_dev->id.version = 0x0100;
        input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
        input_dev->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH);

        input_set_abs_params(input_dev, ABS_X, 0, 4096, 0, 0);
        input_set_abs_params(input_dev, ABS_Y, 0, 4096, 0, 0);
        serio_set_drvdata(serio, fujitsu);

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

        err = input_register_device(fujitsu->dev);
        if (err)
                goto fail3;

        return 0;

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

/*
 * The serio driver structure.
 */
static const struct serio_device_id fujitsu_serio_ids[] = {
        {
                .type   = SERIO_RS232,
                .proto  = SERIO_FUJITSU,
                .id     = SERIO_ANY,
                .extra  = SERIO_ANY,
        },
        { 0 }
};

MODULE_DEVICE_TABLE(serio, fujitsu_serio_ids);

static struct serio_driver fujitsu_drv = {
        .driver         = {
                .name   = "fujitsu_ts",
        },
        .description    = DRIVER_DESC,
        .id_table       = fujitsu_serio_ids,
        .interrupt      = fujitsu_interrupt,
        .connect        = fujitsu_connect,
        .disconnect     = fujitsu_disconnect,
};

module_serio_driver(fujitsu_drv);