1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 *  Parallel port to Keyboard port adapter driver for Linux
4 *
5 *  Copyright (c) 1999-2004 Vojtech Pavlik
6 */
7
8
9/*
10 * To connect an AT or XT keyboard to the parallel port, a fairly simple adapter
11 * can be made:
12 *
13 *  Parallel port            Keyboard port
14 *
15 *     +5V --------------------- +5V (4)
16 *
17 *                 ______
18 *     +5V -------|______|--.
19 *                          |
20 *     ACK (10) ------------|
21 *                          |--- KBD CLOCK (5)
22 *     STROBE (1) ---|<|----'
23 *
24 *                 ______
25 *     +5V -------|______|--.
26 *                          |
27 *     BUSY (11) -----------|
28 *                          |--- KBD DATA (1)
29 *     AUTOFD (14) --|<|----'
30 *
31 *     GND (18-25) ------------- GND (3)
32 *
33 * The diodes can be fairly any type, and the resistors should be somewhere
34 * around 5 kOhm, but the adapter will likely work without the resistors,
35 * too.
36 *
37 * The +5V source can be taken either from USB, from mouse or keyboard ports,
38 * or from a joystick port. Unfortunately, the parallel port of a PC doesn't
39 * have a +5V pin, and feeding the keyboard from signal pins is out of question
40 * with 300 mA power reqirement of a typical AT keyboard.
41 */
42
43#include <linux/module.h>
44#include <linux/parport.h>
45#include <linux/slab.h>
46#include <linux/init.h>
47#include <linux/serio.h>
48
49MODULE_AUTHOR("Vojtech Pavlik <vojtech@ucw.cz>");
50MODULE_DESCRIPTION("Parallel port to Keyboard port adapter driver");
51MODULE_LICENSE("GPL");
52
53static unsigned int parkbd_pp_no;
54module_param_named(port, parkbd_pp_no, int, 0);
55MODULE_PARM_DESC(port, "Parallel port the adapter is connected to (default is 0)");
56
57static unsigned int parkbd_mode = SERIO_8042;
58module_param_named(mode, parkbd_mode, uint, 0);
59MODULE_PARM_DESC(mode, "Mode of operation: XT = 0/AT = 1 (default)");
60
61#define PARKBD_CLOCK	0x01	/* Strobe & Ack */
62#define PARKBD_DATA	0x02	/* AutoFd & Busy */
63
64static int parkbd_buffer;
65static int parkbd_counter;
66static unsigned long parkbd_last;
67static int parkbd_writing;
68static unsigned long parkbd_start;
69
70static struct pardevice *parkbd_dev;
71static struct serio *parkbd_port;
72
73static int parkbd_readlines(void)
74{
75	return (parport_read_status(parkbd_dev->port) >> 6) ^ 2;
76}
77
78static void parkbd_writelines(int data)
79{
80	parport_write_control(parkbd_dev->port, (~data & 3) | 0x10);
81}
82
83static int parkbd_write(struct serio *port, unsigned char c)
84{
85	unsigned char p;
86
87	if (!parkbd_mode) return -1;
88
89        p = c ^ (c >> 4);
90	p = p ^ (p >> 2);
91	p = p ^ (p >> 1);
92
93	parkbd_counter = 0;
94	parkbd_writing = 1;
95	parkbd_buffer = c | (((int) (~p & 1)) << 8) | 0x600;
96
97	parkbd_writelines(2);
98
99	return 0;
100}
101
102static void parkbd_interrupt(void *dev_id)
103{
104
105	if (parkbd_writing) {
106
107		if (parkbd_counter && ((parkbd_counter == 11) || time_after(jiffies, parkbd_last + HZ/100))) {
108			parkbd_counter = 0;
109			parkbd_buffer = 0;
110			parkbd_writing = 0;
111			parkbd_writelines(3);
112			return;
113		}
114
115		parkbd_writelines(((parkbd_buffer >> parkbd_counter++) & 1) | 2);
116
117		if (parkbd_counter == 11) {
118			parkbd_counter = 0;
119			parkbd_buffer = 0;
120			parkbd_writing = 0;
121			parkbd_writelines(3);
122		}
123
124	} else {
125
126		if ((parkbd_counter == parkbd_mode + 10) || time_after(jiffies, parkbd_last + HZ/100)) {
127			parkbd_counter = 0;
128			parkbd_buffer = 0;
129		}
130
131		parkbd_buffer |= (parkbd_readlines() >> 1) << parkbd_counter++;
132
133		if (parkbd_counter == parkbd_mode + 10)
134			serio_interrupt(parkbd_port, (parkbd_buffer >> (2 - parkbd_mode)) & 0xff, 0);
135	}
136
137	parkbd_last = jiffies;
138}
139
140static int parkbd_getport(struct parport *pp)
141{
142	struct pardev_cb parkbd_parport_cb;
143
144	memset(&parkbd_parport_cb, 0, sizeof(parkbd_parport_cb));
145	parkbd_parport_cb.irq_func = parkbd_interrupt;
146	parkbd_parport_cb.flags = PARPORT_FLAG_EXCL;
147
148	parkbd_dev = parport_register_dev_model(pp, "parkbd",
149						&parkbd_parport_cb, 0);
150
151	if (!parkbd_dev)
152		return -ENODEV;
153
154	if (parport_claim(parkbd_dev)) {
155		parport_unregister_device(parkbd_dev);
156		return -EBUSY;
157	}
158
159	parkbd_start = jiffies;
160
161	return 0;
162}
163
164static struct serio *parkbd_allocate_serio(void)
165{
166	struct serio *serio;
167
168	serio = kzalloc(sizeof(struct serio), GFP_KERNEL);
169	if (serio) {
170		serio->id.type = parkbd_mode;
171		serio->write = parkbd_write;
172		strscpy(serio->name, "PARKBD AT/XT keyboard adapter", sizeof(serio->name));
173		snprintf(serio->phys, sizeof(serio->phys), "%s/serio0", parkbd_dev->port->name);
174	}
175
176	return serio;
177}
178
179static void parkbd_attach(struct parport *pp)
180{
181	if (pp->number != parkbd_pp_no) {
182		pr_debug("Not using parport%d.\n", pp->number);
183		return;
184	}
185
186	if (parkbd_getport(pp))
187		return;
188
189	parkbd_port = parkbd_allocate_serio();
190	if (!parkbd_port) {
191		parport_release(parkbd_dev);
192		parport_unregister_device(parkbd_dev);
193		return;
194	}
195
196	parkbd_writelines(3);
197
198	serio_register_port(parkbd_port);
199
200	printk(KERN_INFO "serio: PARKBD %s adapter on %s\n",
201                        parkbd_mode ? "AT" : "XT", parkbd_dev->port->name);
202
203	return;
204}
205
206static void parkbd_detach(struct parport *port)
207{
208	if (!parkbd_port || port->number != parkbd_pp_no)
209		return;
210
211	parport_release(parkbd_dev);
212	serio_unregister_port(parkbd_port);
213	parport_unregister_device(parkbd_dev);
214	parkbd_port = NULL;
215}
216
217static struct parport_driver parkbd_parport_driver = {
218	.name = "parkbd",
219	.match_port = parkbd_attach,
220	.detach = parkbd_detach,
221	.devmodel = true,
222};
223module_parport_driver(parkbd_parport_driver);
224