// SPDX-License-Identifier: GPL-2.0-only
/*
 * EETI Egalax serial touchscreen driver
 *
 * Copyright (c) 2015 Zoltán Böszörményi <zboszor@pr.hu>
 *
 * based on the
 *
 * Hampshire serial touchscreen driver (Copyright (c) 2010 Adam Bennett)
 */


#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     "EETI Egalax serial touchscreen driver"

/*
 * Definitions & global arrays.
 */

#define EGALAX_FORMAT_MAX_LENGTH        6
#define EGALAX_FORMAT_START_BIT         BIT(7)
#define EGALAX_FORMAT_PRESSURE_BIT      BIT(6)
#define EGALAX_FORMAT_TOUCH_BIT         BIT(0)
#define EGALAX_FORMAT_RESOLUTION_MASK   0x06

#define EGALAX_MIN_XC                   0
#define EGALAX_MAX_XC                   0x4000
#define EGALAX_MIN_YC                   0
#define EGALAX_MAX_YC                   0x4000

/*
 * Per-touchscreen data.
 */
struct egalax {
        struct input_dev *input;
        struct serio *serio;
        int idx;
        u8 data[EGALAX_FORMAT_MAX_LENGTH];
        char phys[32];
};

static void egalax_process_data(struct egalax *egalax)
{
        struct input_dev *dev = egalax->input;
        u8 *data = egalax->data;
        u16 x, y;
        u8 shift;
        u8 mask;

        shift = 3 - ((data[0] & EGALAX_FORMAT_RESOLUTION_MASK) >> 1);
        mask = 0xff >> (shift + 1);

        x = (((u16)(data[1] & mask) << 7) | (data[2] & 0x7f)) << shift;
        y = (((u16)(data[3] & mask) << 7) | (data[4] & 0x7f)) << shift;

        input_report_key(dev, BTN_TOUCH, data[0] & EGALAX_FORMAT_TOUCH_BIT);
        input_report_abs(dev, ABS_X, x);
        input_report_abs(dev, ABS_Y, y);
        input_sync(dev);
}

static irqreturn_t egalax_interrupt(struct serio *serio,
                                    unsigned char data, unsigned int flags)
{
        struct egalax *egalax = serio_get_drvdata(serio);
        int pkt_len;

        egalax->data[egalax->idx++] = data;

        if (likely(egalax->data[0] & EGALAX_FORMAT_START_BIT)) {
                pkt_len = egalax->data[0] & EGALAX_FORMAT_PRESSURE_BIT ? 6 : 5;
                if (pkt_len == egalax->idx) {
                        egalax_process_data(egalax);
                        egalax->idx = 0;
                }
        } else {
                dev_dbg(&serio->dev, "unknown/unsynchronized data: %x\n",
                        egalax->data[0]);
                egalax->idx = 0;
        }

        return IRQ_HANDLED;
}

/*
 * egalax_connect() is the routine that is called when someone adds a
 * new serio device that supports egalax protocol and registers it as
 * an input device. This is usually accomplished using inputattach.
 */
static int egalax_connect(struct serio *serio, struct serio_driver *drv)
{
        struct egalax *egalax;
        struct input_dev *input_dev;
        int error;

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

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

        input_dev->name = "EETI eGalaxTouch Serial TouchScreen";
        input_dev->phys = egalax->phys;
        input_dev->id.bustype = BUS_RS232;
        input_dev->id.vendor = SERIO_EGALAX;
        input_dev->id.product = 0;
        input_dev->id.version = 0x0001;
        input_dev->dev.parent = &serio->dev;

        input_set_capability(input_dev, EV_KEY, BTN_TOUCH);
        input_set_abs_params(input_dev, ABS_X,
                             EGALAX_MIN_XC, EGALAX_MAX_XC, 0, 0);
        input_set_abs_params(input_dev, ABS_Y,
                             EGALAX_MIN_YC, EGALAX_MAX_YC, 0, 0);

        serio_set_drvdata(serio, egalax);

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

        error = input_register_device(input_dev);
        if (error)
                goto err_close_serio;

        return 0;

err_close_serio:
        serio_close(serio);
err_reset_drvdata:
        serio_set_drvdata(serio, NULL);
err_free_mem:
        input_free_device(input_dev);
        kfree(egalax);
        return error;
}

static void egalax_disconnect(struct serio *serio)
{
        struct egalax *egalax = serio_get_drvdata(serio);

        serio_close(serio);
        serio_set_drvdata(serio, NULL);
        input_unregister_device(egalax->input);
        kfree(egalax);
}

/*
 * The serio driver structure.
 */

static const struct serio_device_id egalax_serio_ids[] = {
        {
                .type   = SERIO_RS232,
                .proto  = SERIO_EGALAX,
                .id     = SERIO_ANY,
                .extra  = SERIO_ANY,
        },
        { 0 }
};

MODULE_DEVICE_TABLE(serio, egalax_serio_ids);

static struct serio_driver egalax_drv = {
        .driver         = {
                .name   = "egalax",
        },
        .description    = DRIVER_DESC,
        .id_table       = egalax_serio_ids,
        .interrupt      = egalax_interrupt,
        .connect        = egalax_connect,
        .disconnect     = egalax_disconnect,
};
module_serio_driver(egalax_drv);

MODULE_AUTHOR("Zoltán Böszörményi <zboszor@pr.hu>");
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_LICENSE("GPL v2");