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// SPDX-License-Identifier: GPL-2.0-only
/*
* Parallel port to Keyboard port adapter driver for Linux
*
* Copyright (c) 1999-2004 Vojtech Pavlik
*/
/*
* 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(struct parport *pp)
{
struct pardev_cb parkbd_parport_cb;
memset(&parkbd_parport_cb, 0, sizeof(parkbd_parport_cb));
parkbd_parport_cb.irq_func = parkbd_interrupt;
parkbd_parport_cb.flags = PARPORT_FLAG_EXCL;
parkbd_dev = parport_register_dev_model(pp, "parkbd",
&parkbd_parport_cb, 0);
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 *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;
strscpy(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 void parkbd_attach(struct parport *pp)
{
if (pp->number != parkbd_pp_no) {
pr_debug("Not using parport%d.\n", pp->number);
return;
}
if (parkbd_getport(pp))
return;
parkbd_port = parkbd_allocate_serio();
if (!parkbd_port) {
parport_release(parkbd_dev);
parport_unregister_device(parkbd_dev);
return;
}
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;
}
static void parkbd_detach(struct parport *port)
{
if (!parkbd_port || port->number != parkbd_pp_no)
return;
parport_release(parkbd_dev);
serio_unregister_port(parkbd_port);
parport_unregister_device(parkbd_dev);
parkbd_port = NULL;
}
static struct parport_driver parkbd_parport_driver = {
.name = "parkbd",
.match_port = parkbd_attach,
.detach = parkbd_detach,
.devmodel = true,
};
module_parport_driver(parkbd_parport_driver);
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