1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Input device TTY line discipline
4 *
5 * Copyright (c) 1999-2002 Vojtech Pavlik
6 *
7 * This is a module that converts a tty line into a much simpler
8 * 'serial io port' abstraction that the input device drivers use.
9 */
10
11
12#include <linux/uaccess.h>
13#include <linux/kernel.h>
14#include <linux/sched.h>
15#include <linux/slab.h>
16#include <linux/module.h>
17#include <linux/init.h>
18#include <linux/serio.h>
19#include <linux/tty.h>
20#include <linux/compat.h>
21
22MODULE_AUTHOR("Vojtech Pavlik <vojtech@ucw.cz>");
23MODULE_DESCRIPTION("Input device TTY line discipline");
24MODULE_LICENSE("GPL");
25MODULE_ALIAS_LDISC(N_MOUSE);
26
27#define SERPORT_BUSY 1
28#define SERPORT_ACTIVE 2
29#define SERPORT_DEAD 3
30
31struct serport {
32 struct tty_struct *tty;
33 wait_queue_head_t wait;
34 struct serio *serio;
35 struct serio_device_id id;
36 spinlock_t lock;
37 unsigned long flags;
38};
39
40/*
41 * Callback functions from the serio code.
42 */
43
44static int serport_serio_write(struct serio *serio, unsigned char data)
45{
46 struct serport *serport = serio->port_data;
47 return -(serport->tty->ops->write(serport->tty, &data, 1) != 1);
48}
49
50static int serport_serio_open(struct serio *serio)
51{
52 struct serport *serport = serio->port_data;
53
54 guard(spinlock_irqsave)(l: &serport->lock);
55 set_bit(SERPORT_ACTIVE, addr: &serport->flags);
56
57 return 0;
58}
59
60
61static void serport_serio_close(struct serio *serio)
62{
63 struct serport *serport = serio->port_data;
64
65 guard(spinlock_irqsave)(l: &serport->lock);
66 clear_bit(SERPORT_ACTIVE, addr: &serport->flags);
67}
68
69/*
70 * serport_ldisc_open() is the routine that is called upon setting our line
71 * discipline on a tty. It prepares the serio struct.
72 */
73
74static int serport_ldisc_open(struct tty_struct *tty)
75{
76 struct serport *serport;
77
78 if (!capable(CAP_SYS_ADMIN))
79 return -EPERM;
80
81 serport = kzalloc(sizeof(*serport), GFP_KERNEL);
82 if (!serport)
83 return -ENOMEM;
84
85 serport->tty = tty;
86 spin_lock_init(&serport->lock);
87 init_waitqueue_head(&serport->wait);
88
89 tty->disc_data = serport;
90 tty->receive_room = 256;
91 set_bit(nr: TTY_DO_WRITE_WAKEUP, addr: &tty->flags);
92
93 return 0;
94}
95
96/*
97 * serport_ldisc_close() is the opposite of serport_ldisc_open()
98 */
99
100static void serport_ldisc_close(struct tty_struct *tty)
101{
102 struct serport *serport = tty->disc_data;
103
104 kfree(objp: serport);
105}
106
107/*
108 * serport_ldisc_receive() is called by the low level tty driver when characters
109 * are ready for us. We forward the characters and flags, one by one to the
110 * 'interrupt' routine.
111 */
112
113static void serport_ldisc_receive(struct tty_struct *tty, const u8 *cp,
114 const u8 *fp, size_t count)
115{
116 struct serport *serport = tty->disc_data;
117 unsigned int ch_flags = 0;
118 int i;
119
120 guard(spinlock_irqsave)(l: &serport->lock);
121
122 if (!test_bit(SERPORT_ACTIVE, &serport->flags))
123 return;
124
125 for (i = 0; i < count; i++) {
126 if (fp) {
127 switch (fp[i]) {
128 case TTY_FRAME:
129 ch_flags = SERIO_FRAME;
130 break;
131
132 case TTY_PARITY:
133 ch_flags = SERIO_PARITY;
134 break;
135
136 default:
137 ch_flags = 0;
138 break;
139 }
140 }
141
142 serio_interrupt(serio: serport->serio, data: cp[i], flags: ch_flags);
143 }
144}
145
146/*
147 * serport_ldisc_read() just waits indefinitely if everything goes well.
148 * However, when the serio driver closes the serio port, it finishes,
149 * returning 0 characters.
150 */
151
152static ssize_t serport_ldisc_read(struct tty_struct * tty, struct file * file,
153 u8 *kbuf, size_t nr, void **cookie,
154 unsigned long offset)
155{
156 struct serport *serport = tty->disc_data;
157 struct serio *serio;
158
159 if (test_and_set_bit(SERPORT_BUSY, addr: &serport->flags))
160 return -EBUSY;
161
162 serport->serio = serio = kzalloc(sizeof(*serio), GFP_KERNEL);
163 if (!serio)
164 return -ENOMEM;
165
166 strscpy(serio->name, "Serial port", sizeof(serio->name));
167 snprintf(buf: serio->phys, size: sizeof(serio->phys), fmt: "%s/serio0", tty_name(tty));
168 serio->id = serport->id;
169 serio->id.type = SERIO_RS232;
170 serio->write = serport_serio_write;
171 serio->open = serport_serio_open;
172 serio->close = serport_serio_close;
173 serio->port_data = serport;
174 serio->dev.parent = tty->dev;
175
176 serio_register_port(serport->serio);
177 printk(KERN_INFO "serio: Serial port %s\n", tty_name(tty));
178
179 wait_event_interruptible(serport->wait, test_bit(SERPORT_DEAD, &serport->flags));
180 serio_unregister_port(serio: serport->serio);
181 serport->serio = NULL;
182
183 clear_bit(SERPORT_DEAD, addr: &serport->flags);
184 clear_bit(SERPORT_BUSY, addr: &serport->flags);
185
186 return 0;
187}
188
189static void serport_set_type(struct tty_struct *tty, unsigned long type)
190{
191 struct serport *serport = tty->disc_data;
192
193 serport->id.proto = type & 0x000000ff;
194 serport->id.id = (type & 0x0000ff00) >> 8;
195 serport->id.extra = (type & 0x00ff0000) >> 16;
196}
197
198/*
199 * serport_ldisc_ioctl() allows to set the port protocol, and device ID
200 */
201
202static int serport_ldisc_ioctl(struct tty_struct *tty, unsigned int cmd,
203 unsigned long arg)
204{
205 if (cmd == SPIOCSTYPE) {
206 unsigned long type;
207
208 if (get_user(type, (unsigned long __user *) arg))
209 return -EFAULT;
210
211 serport_set_type(tty, type);
212 return 0;
213 }
214
215 return -EINVAL;
216}
217
218#ifdef CONFIG_COMPAT
219#define COMPAT_SPIOCSTYPE _IOW('q', 0x01, compat_ulong_t)
220static int serport_ldisc_compat_ioctl(struct tty_struct *tty,
221 unsigned int cmd, unsigned long arg)
222{
223 if (cmd == COMPAT_SPIOCSTYPE) {
224 void __user *uarg = compat_ptr(uptr: arg);
225 compat_ulong_t compat_type;
226
227 if (get_user(compat_type, (compat_ulong_t __user *)uarg))
228 return -EFAULT;
229
230 serport_set_type(tty, type: compat_type);
231 return 0;
232 }
233
234 return -EINVAL;
235}
236#endif
237
238static void serport_ldisc_hangup(struct tty_struct *tty)
239{
240 struct serport *serport = tty->disc_data;
241
242 scoped_guard(spinlock_irqsave, &serport->lock)
243 set_bit(SERPORT_DEAD, addr: &serport->flags);
244
245 wake_up_interruptible(&serport->wait);
246}
247
248static void serport_ldisc_write_wakeup(struct tty_struct * tty)
249{
250 struct serport *serport = tty->disc_data;
251
252 guard(spinlock_irqsave)(l: &serport->lock);
253
254 if (test_bit(SERPORT_ACTIVE, &serport->flags))
255 serio_drv_write_wakeup(serio: serport->serio);
256}
257
258/*
259 * The line discipline structure.
260 */
261
262static struct tty_ldisc_ops serport_ldisc = {
263 .owner = THIS_MODULE,
264 .num = N_MOUSE,
265 .name = "input",
266 .open = serport_ldisc_open,
267 .close = serport_ldisc_close,
268 .read = serport_ldisc_read,
269 .ioctl = serport_ldisc_ioctl,
270#ifdef CONFIG_COMPAT
271 .compat_ioctl = serport_ldisc_compat_ioctl,
272#endif
273 .receive_buf = serport_ldisc_receive,
274 .hangup = serport_ldisc_hangup,
275 .write_wakeup = serport_ldisc_write_wakeup
276};
277
278/*
279 * The functions for insering/removing us as a module.
280 */
281
282static int __init serport_init(void)
283{
284 int retval;
285 retval = tty_register_ldisc(new_ldisc: &serport_ldisc);
286 if (retval)
287 printk(KERN_ERR "serport.c: Error registering line discipline.\n");
288
289 return retval;
290}
291
292static void __exit serport_exit(void)
293{
294 tty_unregister_ldisc(ldisc: &serport_ldisc);
295}
296
297module_init(serport_init);
298module_exit(serport_exit);
299