/*
 *  Parallel port to Keyboard port adapter driver for Linux
 *
 *  Copyright (c) 1999-2004 Vojtech Pavlik
 */

/*
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 */

/*
 * To connect an AT or XT keyboard to the parallel port, a fairly simple adapter
 * can be made:
 * 
 *  Parallel port            Keyboard port
 *
 *     +5V --------------------- +5V (4)
 *  
 *                 ______
 *     +5V -------|______|--.
 *                          |
 *     ACK (10) ------------|
 *                          |--- KBD CLOCK (5)
 *     STROBE (1) ---|<|----'
 *     
 *                 ______
 *     +5V -------|______|--.
 *                          |
 *     BUSY (11) -----------|
 *                          |--- KBD DATA (1)
 *     AUTOFD (14) --|<|----'
 *
 *     GND (18-25) ------------- GND (3)
 *     
 * The diodes can be fairly any type, and the resistors should be somewhere
 * around 5 kOhm, but the adapter will likely work without the resistors,
 * too.
 *
 * The +5V source can be taken either from USB, from mouse or keyboard ports,
 * or from a joystick port. Unfortunately, the parallel port of a PC doesn't
 * have a +5V pin, and feeding the keyboard from signal pins is out of question
 * with 300 mA power reqirement of a typical AT keyboard.
 */

#include <linux/module.h>
#include <linux/parport.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/serio.h>

MODULE_AUTHOR("Vojtech Pavlik <vojtech@ucw.cz>");
MODULE_DESCRIPTION("Parallel port to Keyboard port adapter driver");
MODULE_LICENSE("GPL");

static unsigned int parkbd_pp_no;
module_param_named(port, parkbd_pp_no, int, 0);
MODULE_PARM_DESC(port, "Parallel port the adapter is connected to (default is 0)");

static unsigned int parkbd_mode = SERIO_8042;
module_param_named(mode, parkbd_mode, uint, 0);
MODULE_PARM_DESC(mode, "Mode of operation: XT = 0/AT = 1 (default)");

#define PARKBD_CLOCK    0x01    /* Strobe & Ack */
#define PARKBD_DATA     0x02    /* AutoFd & Busy */

static int parkbd_buffer;
static int parkbd_counter;
static unsigned long parkbd_last;
static int parkbd_writing;
static unsigned long parkbd_start;

static struct pardevice *parkbd_dev;
static struct serio *parkbd_port;

static int parkbd_readlines(void)
{
        return (parport_read_status(parkbd_dev->port) >> 6) ^ 2;
}

static void parkbd_writelines(int data)
{
        parport_write_control(parkbd_dev->port, (~data & 3) | 0x10);
}

static int parkbd_write(struct serio *port, unsigned char c)
{
        unsigned char p;

        if (!parkbd_mode) return -1;

        p = c ^ (c >> 4);
        p = p ^ (p >> 2);
        p = p ^ (p >> 1);

        parkbd_counter = 0;
        parkbd_writing = 1;
        parkbd_buffer = c | (((int) (~p & 1)) << 8) | 0x600;

        parkbd_writelines(2);

        return 0;
}

static void parkbd_interrupt(void *dev_id)
{

        if (parkbd_writing) {

                if (parkbd_counter && ((parkbd_counter == 11) || time_after(jiffies, parkbd_last + HZ/100))) {
                        parkbd_counter = 0;
                        parkbd_buffer = 0;
                        parkbd_writing = 0;
                        parkbd_writelines(3);
                        return;
                }

                parkbd_writelines(((parkbd_buffer >> parkbd_counter++) & 1) | 2);

                if (parkbd_counter == 11) {
                        parkbd_counter = 0;
                        parkbd_buffer = 0;
                        parkbd_writing = 0;
                        parkbd_writelines(3);
                }

        } else {

                if ((parkbd_counter == parkbd_mode + 10) || time_after(jiffies, parkbd_last + HZ/100)) {
                        parkbd_counter = 0;
                        parkbd_buffer = 0;
                }

                parkbd_buffer |= (parkbd_readlines() >> 1) << parkbd_counter++;

                if (parkbd_counter == parkbd_mode + 10)
                        serio_interrupt(parkbd_port, (parkbd_buffer >> (2 - parkbd_mode)) & 0xff, 0);
        }

        parkbd_last = jiffies;
}

static int parkbd_getport(void)
{
        struct parport *pp;

        pp = parport_find_number(parkbd_pp_no);

        if (pp == NULL) {
                printk(KERN_ERR "parkbd: no such parport\n");
                return -ENODEV;
        }

        parkbd_dev = parport_register_device(pp, "parkbd", NULL, NULL, parkbd_interrupt, PARPORT_DEV_EXCL, NULL);
        parport_put_port(pp);

        if (!parkbd_dev)
                return -ENODEV;

        if (parport_claim(parkbd_dev)) {
                parport_unregister_device(parkbd_dev);
                return -EBUSY;
        }

        parkbd_start = jiffies;

        return 0;
}

static struct serio * __init parkbd_allocate_serio(void)
{
        struct serio *serio;

        serio = kzalloc(sizeof(struct serio), GFP_KERNEL);
        if (serio) {
                serio->id.type = parkbd_mode;
                serio->write = parkbd_write,
                strlcpy(serio->name, "PARKBD AT/XT keyboard adapter", sizeof(serio->name));
                snprintf(serio->phys, sizeof(serio->phys), "%s/serio0", parkbd_dev->port->name);
        }

        return serio;
}

static int __init parkbd_init(void)
{
        int err;

        err = parkbd_getport();
        if (err)
                return err;

        parkbd_port = parkbd_allocate_serio();
        if (!parkbd_port) {
                parport_release(parkbd_dev);
                return -ENOMEM;
        }

        parkbd_writelines(3);

        serio_register_port(parkbd_port);

        printk(KERN_INFO "serio: PARKBD %s adapter on %s\n",
                        parkbd_mode ? "AT" : "XT", parkbd_dev->port->name);

        return 0;
}

static void __exit parkbd_exit(void)
{
        parport_release(parkbd_dev);
        serio_unregister_port(parkbd_port);
        parport_unregister_device(parkbd_dev);
}

module_init(parkbd_init);
module_exit(parkbd_exit);