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parkbd.c

/*
 *  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/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);

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