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(data: 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(data: 3);
112 return;
113 }
114
115 parkbd_writelines(data: ((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(data: 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(serio: parkbd_port, data: (parkbd_buffer >> (2 - parkbd_mode)) & 0xff, flags: 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(port: pp, name: "parkbd",
149 par_dev_cb: &parkbd_parport_cb, cnt: 0);
150
151 if (!parkbd_dev)
152 return -ENODEV;
153
154 if (parport_claim(dev: parkbd_dev)) {
155 parport_unregister_device(dev: 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(*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(buf: serio->phys, size: sizeof(serio->phys), fmt: "%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(dev: parkbd_dev);
192 parport_unregister_device(dev: parkbd_dev);
193 return;
194 }
195
196 parkbd_writelines(data: 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(dev: parkbd_dev);
212 serio_unregister_port(serio: parkbd_port);
213 parport_unregister_device(dev: 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};
222module_parport_driver(parkbd_parport_driver);
223

source code of linux/drivers/input/serio/parkbd.c