// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Driver for   DEC VSXXX-AA mouse (hockey-puck mouse, ball or two rollers)
 *              DEC VSXXX-GA mouse (rectangular mouse, with ball)
 *              DEC VSXXX-AB tablet (digitizer with hair cross or stylus)
 *
 * Copyright (C) 2003-2004 by Jan-Benedict Glaw <jbglaw@lug-owl.de>
 *
 * The packet format was initially taken from a patch to GPM which is (C) 2001
 * by   Karsten Merker <merker@linuxtag.org>
 * and  Maciej W. Rozycki <macro@ds2.pg.gda.pl>
 * Later on, I had access to the device's documentation (referenced below).
 */

/*
 * Building an adaptor to DE9 / DB25 RS232
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *
 * DISCLAIMER: Use this description AT YOUR OWN RISK! I'll not pay for
 * anything if you break your mouse, your computer or whatever!
 *
 * In theory, this mouse is a simple RS232 device. In practice, it has got
 * a quite uncommon plug and the requirement to additionally get a power
 * supply at +5V and -12V.
 *
 * If you look at the socket/jack (_not_ at the plug), we use this pin
 * numbering:
 *    _______
 *   / 7 6 5 \
 *  | 4 --- 3 |
 *   \  2 1  /
 *    -------
 *
 *      DEC socket      DE9     DB25    Note
 *      1 (GND)         5       7       -
 *      2 (RxD)         2       3       -
 *      3 (TxD)         3       2       -
 *      4 (-12V)        -       -       Somewhere from the PSU. At ATX, it's
 *                                      the thin blue wire at pin 12 of the
 *                                      ATX power connector. Only required for
 *                                      VSXXX-AA/-GA mice.
 *      5 (+5V)         -       -       PSU (red wires of ATX power connector
 *                                      on pin 4, 6, 19 or 20) or HDD power
 *                                      connector (also red wire).
 *      6 (+12V)        -       -       HDD power connector, yellow wire. Only
 *                                      required for VSXXX-AB digitizer.
 *      7 (dev. avail.) -       -       The mouse shorts this one to pin 1.
 *                                      This way, the host computer can detect
 *                                      the mouse. To use it with the adaptor,
 *                                      simply don't connect this pin.
 *
 * So to get a working adaptor, you need to connect the mouse with three
 * wires to a RS232 port and two or three additional wires for +5V, +12V and
 * -12V to the PSU.
 *
 * Flow specification for the link is 4800, 8o1.
 *
 * The mice and tablet are described in "VCB02 Video Subsystem - Technical
 * Manual", DEC EK-104AA-TM-001. You'll find it at MANX, a search engine
 * specific for DEC documentation. Try
 * http://www.vt100.net/manx/details?pn=EK-104AA-TM-001;id=21;cp=1
 */

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

#define DRIVER_DESC "Driver for DEC VSXXX-AA and -GA mice and VSXXX-AB tablet"

MODULE_AUTHOR("Jan-Benedict Glaw <jbglaw@lug-owl.de>");
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_LICENSE("GPL");

#undef VSXXXAA_DEBUG
#ifdef VSXXXAA_DEBUG
#define DBG(x...) printk(x)
#else
#define DBG(x...) do {} while (0)
#endif

#define VSXXXAA_INTRO_MASK      0x80
#define VSXXXAA_INTRO_HEAD      0x80
#define IS_HDR_BYTE(x)                  \
        (((x) & VSXXXAA_INTRO_MASK) == VSXXXAA_INTRO_HEAD)

#define VSXXXAA_PACKET_MASK     0xe0
#define VSXXXAA_PACKET_REL      0x80
#define VSXXXAA_PACKET_ABS      0xc0
#define VSXXXAA_PACKET_POR      0xa0
#define MATCH_PACKET_TYPE(data, type)   \
        (((data) & VSXXXAA_PACKET_MASK) == (type))



struct vsxxxaa {
        struct input_dev *dev;
        struct serio *serio;
#define BUFLEN 15 /* At least 5 is needed for a full tablet packet */
        unsigned char buf[BUFLEN];
        unsigned char count;
        unsigned char version;
        unsigned char country;
        unsigned char type;
        char name[64];
        char phys[32];
};

static void vsxxxaa_drop_bytes(struct vsxxxaa *mouse, int num)
{
        if (num >= mouse->count) {
                mouse->count = 0;
        } else {
                memmove(mouse->buf, mouse->buf + num, BUFLEN - num);
                mouse->count -= num;
        }
}

static void vsxxxaa_queue_byte(struct vsxxxaa *mouse, unsigned char byte)
{
        if (mouse->count == BUFLEN) {
                printk(KERN_ERR "%s on %s: Dropping a byte of full buffer.\n",
                        mouse->name, mouse->phys);
                vsxxxaa_drop_bytes(mouse, 1);
        }

        DBG(KERN_INFO "Queueing byte 0x%02x\n", byte);

        mouse->buf[mouse->count++] = byte;
}

static void vsxxxaa_detection_done(struct vsxxxaa *mouse)
{
        switch (mouse->type) {
        case 0x02:
                strscpy(mouse->name, "DEC VSXXX-AA/-GA mouse",
                        sizeof(mouse->name));
                break;

        case 0x04:
                strscpy(mouse->name, "DEC VSXXX-AB digitizer",
                        sizeof(mouse->name));
                break;

        default:
                snprintf(mouse->name, sizeof(mouse->name),
                         "unknown DEC pointer device (type = 0x%02x)",
                         mouse->type);
                break;
        }

        printk(KERN_INFO
                "Found %s version 0x%02x from country 0x%02x on port %s\n",
                mouse->name, mouse->version, mouse->country, mouse->phys);
}

/*
 * Returns number of bytes to be dropped, 0 if packet is okay.
 */
static int vsxxxaa_check_packet(struct vsxxxaa *mouse, int packet_len)
{
        int i;

        /* First byte must be a header byte */
        if (!IS_HDR_BYTE(mouse->buf[0])) {
                DBG("vsck: len=%d, 1st=0x%02x\n", packet_len, mouse->buf[0]);
                return 1;
        }

        /* Check all following bytes */
        for (i = 1; i < packet_len; i++) {
                if (IS_HDR_BYTE(mouse->buf[i])) {
                        printk(KERN_ERR
                                "Need to drop %d bytes of a broken packet.\n",
                                i - 1);
                        DBG(KERN_INFO "check: len=%d, b[%d]=0x%02x\n",
                            packet_len, i, mouse->buf[i]);
                        return i - 1;
                }
        }

        return 0;
}

static inline int vsxxxaa_smells_like_packet(struct vsxxxaa *mouse,
                                             unsigned char type, size_t len)
{
        return mouse->count >= len && MATCH_PACKET_TYPE(mouse->buf[0], type);
}

static void vsxxxaa_handle_REL_packet(struct vsxxxaa *mouse)
{
        struct input_dev *dev = mouse->dev;
        unsigned char *buf = mouse->buf;
        int left, middle, right;
        int dx, dy;

        /*
         * Check for normal stream packets. This is three bytes,
         * with the first byte's 3 MSB set to 100.
         *
         * [0]: 1       0       0       SignX   SignY   Left    Middle  Right
         * [1]: 0       dx      dx      dx      dx      dx      dx      dx
         * [2]: 0       dy      dy      dy      dy      dy      dy      dy
         */

        /*
         * Low 7 bit of byte 1 are abs(dx), bit 7 is
         * 0, bit 4 of byte 0 is direction.
         */
        dx = buf[1] & 0x7f;
        dx *= ((buf[0] >> 4) & 0x01) ? 1 : -1;

        /*
         * Low 7 bit of byte 2 are abs(dy), bit 7 is
         * 0, bit 3 of byte 0 is direction.
         */
        dy = buf[2] & 0x7f;
        dy *= ((buf[0] >> 3) & 0x01) ? -1 : 1;

        /*
         * Get button state. It's the low three bits
         * (for three buttons) of byte 0.
         */
        left    = buf[0] & 0x04;
        middle  = buf[0] & 0x02;
        right   = buf[0] & 0x01;

        vsxxxaa_drop_bytes(mouse, 3);

        DBG(KERN_INFO "%s on %s: dx=%d, dy=%d, buttons=%s%s%s\n",
            mouse->name, mouse->phys, dx, dy,
            left ? "L" : "l", middle ? "M" : "m", right ? "R" : "r");

        /*
         * Report what we've found so far...
         */
        input_report_key(dev, BTN_LEFT, left);
        input_report_key(dev, BTN_MIDDLE, middle);
        input_report_key(dev, BTN_RIGHT, right);
        input_report_key(dev, BTN_TOUCH, 0);
        input_report_rel(dev, REL_X, dx);
        input_report_rel(dev, REL_Y, dy);
        input_sync(dev);
}

static void vsxxxaa_handle_ABS_packet(struct vsxxxaa *mouse)
{
        struct input_dev *dev = mouse->dev;
        unsigned char *buf = mouse->buf;
        int left, middle, right, touch;
        int x, y;

        /*
         * Tablet position / button packet
         *
         * [0]: 1       1       0       B4      B3      B2      B1      Pr
         * [1]: 0       0       X5      X4      X3      X2      X1      X0
         * [2]: 0       0       X11     X10     X9      X8      X7      X6
         * [3]: 0       0       Y5      Y4      Y3      Y2      Y1      Y0
         * [4]: 0       0       Y11     Y10     Y9      Y8      Y7      Y6
         */

        /*
         * Get X/Y position. Y axis needs to be inverted since VSXXX-AB
         * counts down->top while monitor counts top->bottom.
         */
        x = ((buf[2] & 0x3f) << 6) | (buf[1] & 0x3f);
        y = ((buf[4] & 0x3f) << 6) | (buf[3] & 0x3f);
        y = 1023 - y;

        /*
         * Get button state. It's bits <4..1> of byte 0.
         */
        left    = buf[0] & 0x02;
        middle  = buf[0] & 0x04;
        right   = buf[0] & 0x08;
        touch   = buf[0] & 0x10;

        vsxxxaa_drop_bytes(mouse, 5);

        DBG(KERN_INFO "%s on %s: x=%d, y=%d, buttons=%s%s%s%s\n",
            mouse->name, mouse->phys, x, y,
            left ? "L" : "l", middle ? "M" : "m",
            right ? "R" : "r", touch ? "T" : "t");

        /*
         * Report what we've found so far...
         */
        input_report_key(dev, BTN_LEFT, left);
        input_report_key(dev, BTN_MIDDLE, middle);
        input_report_key(dev, BTN_RIGHT, right);
        input_report_key(dev, BTN_TOUCH, touch);
        input_report_abs(dev, ABS_X, x);
        input_report_abs(dev, ABS_Y, y);
        input_sync(dev);
}

static void vsxxxaa_handle_POR_packet(struct vsxxxaa *mouse)
{
        struct input_dev *dev = mouse->dev;
        unsigned char *buf = mouse->buf;
        int left, middle, right;
        unsigned char error;

        /*
         * Check for Power-On-Reset packets. These are sent out
         * after plugging the mouse in, or when explicitly
         * requested by sending 'T'.
         *
         * [0]: 1       0       1       0       R3      R2      R1      R0
         * [1]: 0       M2      M1      M0      D3      D2      D1      D0
         * [2]: 0       E6      E5      E4      E3      E2      E1      E0
         * [3]: 0       0       0       0       0       Left    Middle  Right
         *
         * M: manufacturer location code
         * R: revision code
         * E: Error code. If it's in the range of 0x00..0x1f, only some
         *    minor problem occurred. Errors >= 0x20 are considered bad
         *    and the device may not work properly...
         * D: <0010> == mouse, <0100> == tablet
         */

        mouse->version = buf[0] & 0x0f;
        mouse->country = (buf[1] >> 4) & 0x07;
        mouse->type = buf[1] & 0x0f;
        error = buf[2] & 0x7f;

        /*
         * Get button state. It's the low three bits
         * (for three buttons) of byte 0. Maybe even the bit <3>
         * has some meaning if a tablet is attached.
         */
        left    = buf[0] & 0x04;
        middle  = buf[0] & 0x02;
        right   = buf[0] & 0x01;

        vsxxxaa_drop_bytes(mouse, 4);
        vsxxxaa_detection_done(mouse);

        if (error <= 0x1f) {
                /* No (serious) error. Report buttons */
                input_report_key(dev, BTN_LEFT, left);
                input_report_key(dev, BTN_MIDDLE, middle);
                input_report_key(dev, BTN_RIGHT, right);
                input_report_key(dev, BTN_TOUCH, 0);
                input_sync(dev);

                if (error != 0)
                        printk(KERN_INFO "Your %s on %s reports error=0x%02x\n",
                                mouse->name, mouse->phys, error);

        }

        /*
         * If the mouse was hot-plugged, we need to force differential mode
         * now... However, give it a second to recover from it's reset.
         */
        printk(KERN_NOTICE
                "%s on %s: Forcing standard packet format, "
                "incremental streaming mode and 72 samples/sec\n",
                mouse->name, mouse->phys);
        serio_write(mouse->serio, 'S'); /* Standard format */
        mdelay(50);
        serio_write(mouse->serio, 'R'); /* Incremental */
        mdelay(50);
        serio_write(mouse->serio, 'L'); /* 72 samples/sec */
}

static void vsxxxaa_parse_buffer(struct vsxxxaa *mouse)
{
        unsigned char *buf = mouse->buf;
        int stray_bytes;

        /*
         * Parse buffer to death...
         */
        do {
                /*
                 * Out of sync? Throw away what we don't understand. Each
                 * packet starts with a byte whose bit 7 is set. Unhandled
                 * packets (ie. which we don't know about or simply b0rk3d
                 * data...) will get shifted out of the buffer after some
                 * activity on the mouse.
                 */
                while (mouse->count > 0 && !IS_HDR_BYTE(buf[0])) {
                        printk(KERN_ERR "%s on %s: Dropping a byte to regain "
                                "sync with mouse data stream...\n",
                                mouse->name, mouse->phys);
                        vsxxxaa_drop_bytes(mouse, 1);
                }

                /*
                 * Check for packets we know about.
                 */

                if (vsxxxaa_smells_like_packet(mouse, VSXXXAA_PACKET_REL, 3)) {
                        /* Check for broken packet */
                        stray_bytes = vsxxxaa_check_packet(mouse, 3);
                        if (!stray_bytes)
                                vsxxxaa_handle_REL_packet(mouse);

                } else if (vsxxxaa_smells_like_packet(mouse,
                                                      VSXXXAA_PACKET_ABS, 5)) {
                        /* Check for broken packet */
                        stray_bytes = vsxxxaa_check_packet(mouse, 5);
                        if (!stray_bytes)
                                vsxxxaa_handle_ABS_packet(mouse);

                } else if (vsxxxaa_smells_like_packet(mouse,
                                                      VSXXXAA_PACKET_POR, 4)) {
                        /* Check for broken packet */
                        stray_bytes = vsxxxaa_check_packet(mouse, 4);
                        if (!stray_bytes)
                                vsxxxaa_handle_POR_packet(mouse);

                } else {
                        break; /* No REL, ABS or POR packet found */
                }

                if (stray_bytes > 0) {
                        printk(KERN_ERR "Dropping %d bytes now...\n",
                                stray_bytes);
                        vsxxxaa_drop_bytes(mouse, stray_bytes);
                }

        } while (1);
}

static irqreturn_t vsxxxaa_interrupt(struct serio *serio,
                                     unsigned char data, unsigned int flags)
{
        struct vsxxxaa *mouse = serio_get_drvdata(serio);

        vsxxxaa_queue_byte(mouse, data);
        vsxxxaa_parse_buffer(mouse);

        return IRQ_HANDLED;
}

static void vsxxxaa_disconnect(struct serio *serio)
{
        struct vsxxxaa *mouse = serio_get_drvdata(serio);

        serio_close(serio);
        serio_set_drvdata(serio, NULL);
        input_unregister_device(mouse->dev);
        kfree(mouse);
}

static int vsxxxaa_connect(struct serio *serio, struct serio_driver *drv)
{
        struct vsxxxaa *mouse;
        struct input_dev *input_dev;
        int err = -ENOMEM;

        mouse = kzalloc_obj(*mouse);
        input_dev = input_allocate_device();
        if (!mouse || !input_dev)
                goto fail1;

        mouse->dev = input_dev;
        mouse->serio = serio;
        strlcat(mouse->name, "DEC VSXXX-AA/-GA mouse or VSXXX-AB digitizer",
                 sizeof(mouse->name));
        snprintf(mouse->phys, sizeof(mouse->phys), "%s/input0", serio->phys);

        input_dev->name = mouse->name;
        input_dev->phys = mouse->phys;
        input_dev->id.bustype = BUS_RS232;
        input_dev->dev.parent = &serio->dev;

        __set_bit(EV_KEY, input_dev->evbit);            /* We have buttons */
        __set_bit(EV_REL, input_dev->evbit);
        __set_bit(EV_ABS, input_dev->evbit);
        __set_bit(BTN_LEFT, input_dev->keybit);         /* We have 3 buttons */
        __set_bit(BTN_MIDDLE, input_dev->keybit);
        __set_bit(BTN_RIGHT, input_dev->keybit);
        __set_bit(BTN_TOUCH, input_dev->keybit);        /* ...and Tablet */
        __set_bit(REL_X, input_dev->relbit);
        __set_bit(REL_Y, input_dev->relbit);
        input_set_abs_params(input_dev, ABS_X, 0, 1023, 0, 0);
        input_set_abs_params(input_dev, ABS_Y, 0, 1023, 0, 0);

        serio_set_drvdata(serio, mouse);

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

        /*
         * Request selftest. Standard packet format and differential
         * mode will be requested after the device ID'ed successfully.
         */
        serio_write(serio, 'T'); /* Test */

        err = input_register_device(input_dev);
        if (err)
                goto fail3;

        return 0;

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

static struct serio_device_id vsxxaa_serio_ids[] = {
        {
                .type   = SERIO_RS232,
                .proto  = SERIO_VSXXXAA,
                .id     = SERIO_ANY,
                .extra  = SERIO_ANY,
        },
        { 0 }
};

MODULE_DEVICE_TABLE(serio, vsxxaa_serio_ids);

static struct serio_driver vsxxxaa_drv = {
        .driver         = {
                .name   = "vsxxxaa",
        },
        .description    = DRIVER_DESC,
        .id_table       = vsxxaa_serio_ids,
        .connect        = vsxxxaa_connect,
        .interrupt      = vsxxxaa_interrupt,
        .disconnect     = vsxxxaa_disconnect,
};

module_serio_driver(vsxxxaa_drv);