xref: /openbmc/linux/drivers/input/serio/parkbd.c (revision a9f08ad7)
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 
49 MODULE_AUTHOR("Vojtech Pavlik <vojtech@ucw.cz>");
50 MODULE_DESCRIPTION("Parallel port to Keyboard port adapter driver");
51 MODULE_LICENSE("GPL");
52 
53 static unsigned int parkbd_pp_no;
54 module_param_named(port, parkbd_pp_no, int, 0);
55 MODULE_PARM_DESC(port, "Parallel port the adapter is connected to (default is 0)");
56 
57 static unsigned int parkbd_mode = SERIO_8042;
58 module_param_named(mode, parkbd_mode, uint, 0);
59 MODULE_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 
64 static int parkbd_buffer;
65 static int parkbd_counter;
66 static unsigned long parkbd_last;
67 static int parkbd_writing;
68 static unsigned long parkbd_start;
69 
70 static struct pardevice *parkbd_dev;
71 static struct serio *parkbd_port;
72 
parkbd_readlines(void)73 static int parkbd_readlines(void)
74 {
75 	return (parport_read_status(parkbd_dev->port) >> 6) ^ 2;
76 }
77 
parkbd_writelines(int data)78 static void parkbd_writelines(int data)
79 {
80 	parport_write_control(parkbd_dev->port, (~data & 3) | 0x10);
81 }
82 
parkbd_write(struct serio * port,unsigned char c)83 static 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 
parkbd_interrupt(void * dev_id)102 static 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 
parkbd_getport(struct parport * pp)140 static 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 
parkbd_allocate_serio(void)164 static 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 
parkbd_attach(struct parport * pp)179 static 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 
parkbd_detach(struct parport * port)206 static 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 
217 static struct parport_driver parkbd_parport_driver = {
218 	.name = "parkbd",
219 	.match_port = parkbd_attach,
220 	.detach = parkbd_detach,
221 	.devmodel = true,
222 };
223 module_parport_driver(parkbd_parport_driver);
224