summaryrefslogtreecommitdiffstats
path: root/drivers/input/serio/userio.c
blob: df1fd41860ac90591a6927b927ef2638c7491861 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
/*
 * userio kernel serio device emulation module
 * Copyright (C) 2015 Red Hat
 * Copyright (C) 2015 Stephen Chandler Paul <thatslyude@gmail.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or (at
 * your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
 * General Public License for more details.
 */

#include <linux/circ_buf.h>
#include <linux/mutex.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/serio.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <linux/sched.h>
#include <linux/poll.h>
#include <uapi/linux/userio.h>

#define USERIO_NAME		"userio"
#define USERIO_BUFSIZE		16

static struct miscdevice userio_misc;

struct userio_device {
	struct serio *serio;
	struct mutex mutex;

	bool running;

	u8 head;
	u8 tail;

	spinlock_t buf_lock;
	unsigned char buf[USERIO_BUFSIZE];

	wait_queue_head_t waitq;
};

/**
 * userio_device_write - Write data from serio to a userio device in userspace
 * @id: The serio port for the userio device
 * @val: The data to write to the device
 */
static int userio_device_write(struct serio *id, unsigned char val)
{
	struct userio_device *userio = id->port_data;
	unsigned long flags;

	spin_lock_irqsave(&userio->buf_lock, flags);

	userio->buf[userio->head] = val;
	userio->head = (userio->head + 1) % USERIO_BUFSIZE;

	if (userio->head == userio->tail)
		dev_warn(userio_misc.this_device,
			 "Buffer overflowed, userio client isn't keeping up");

	spin_unlock_irqrestore(&userio->buf_lock, flags);

	wake_up_interruptible(&userio->waitq);

	return 0;
}

static int userio_char_open(struct inode *inode, struct file *file)
{
	struct userio_device *userio;

	userio = kzalloc(sizeof(struct userio_device), GFP_KERNEL);
	if (!userio)
		return -ENOMEM;

	mutex_init(&userio->mutex);
	spin_lock_init(&userio->buf_lock);
	init_waitqueue_head(&userio->waitq);

	userio->serio = kzalloc(sizeof(struct serio), GFP_KERNEL);
	if (!userio->serio) {
		kfree(userio);
		return -ENOMEM;
	}

	userio->serio->write = userio_device_write;
	userio->serio->port_data = userio;

	file->private_data = userio;

	return 0;
}

static int userio_char_release(struct inode *inode, struct file *file)
{
	struct userio_device *userio = file->private_data;

	if (userio->running) {
		/*
		 * Don't free the serio port here, serio_unregister_port()
		 * does it for us.
		 */
		serio_unregister_port(userio->serio);
	} else {
		kfree(userio->serio);
	}

	kfree(userio);

	return 0;
}

static ssize_t userio_char_read(struct file *file, char __user *user_buffer,
				size_t count, loff_t *ppos)
{
	struct userio_device *userio = file->private_data;
	int error;
	size_t nonwrap_len, copylen;
	unsigned char buf[USERIO_BUFSIZE];
	unsigned long flags;

	/*
	 * By the time we get here, the data that was waiting might have
	 * been taken by another thread. Grab the buffer lock and check if
	 * there's still any data waiting, otherwise repeat this process
	 * until we have data (unless the file descriptor is non-blocking
	 * of course).
	 */
	for (;;) {
		spin_lock_irqsave(&userio->buf_lock, flags);

		nonwrap_len = CIRC_CNT_TO_END(userio->head,
					      userio->tail,
					      USERIO_BUFSIZE);
		copylen = min(nonwrap_len, count);
		if (copylen) {
			memcpy(buf, &userio->buf[userio->tail], copylen);
			userio->tail = (userio->tail + copylen) %
							USERIO_BUFSIZE;
		}

		spin_unlock_irqrestore(&userio->buf_lock, flags);

		if (nonwrap_len)
			break;

		/* buffer was/is empty */
		if (file->f_flags & O_NONBLOCK)
			return -EAGAIN;

		/*
		 * count == 0 is special - no IO is done but we check
		 * for error conditions (see above).
		 */
		if (count == 0)
			return 0;

		error = wait_event_interruptible(userio->waitq,
						 userio->head != userio->tail);
		if (error)
			return error;
	}

	if (copylen)
		if (copy_to_user(user_buffer, buf, copylen))
			return -EFAULT;

	return copylen;
}

static ssize_t userio_char_write(struct file *file, const char __user *buffer,
				 size_t count, loff_t *ppos)
{
	struct userio_device *userio = file->private_data;
	struct userio_cmd cmd;
	int error;

	if (count != sizeof(cmd)) {
		dev_warn(userio_misc.this_device, "Invalid payload size\n");
		return -EINVAL;
	}

	if (copy_from_user(&cmd, buffer, sizeof(cmd)))
		return -EFAULT;

	error = mutex_lock_interruptible(&userio->mutex);
	if (error)
		return error;

	switch (cmd.type) {
	case USERIO_CMD_REGISTER:
		if (!userio->serio->id.type) {
			dev_warn(userio_misc.this_device,
				 "No port type given on /dev/userio\n");

			error = -EINVAL;
			goto out;
		}

		if (userio->running) {
			dev_warn(userio_misc.this_device,
				 "Begin command sent, but we're already running\n");
			error = -EBUSY;
			goto out;
		}

		userio->running = true;
		serio_register_port(userio->serio);
		break;

	case USERIO_CMD_SET_PORT_TYPE:
		if (userio->running) {
			dev_warn(userio_misc.this_device,
				 "Can't change port type on an already running userio instance\n");
			error = -EBUSY;
			goto out;
		}

		userio->serio->id.type = cmd.data;
		break;

	case USERIO_CMD_SEND_INTERRUPT:
		if (!userio->running) {
			dev_warn(userio_misc.this_device,
				 "The device must be registered before sending interrupts\n");
			error = -ENODEV;
			goto out;
		}

		serio_interrupt(userio->serio, cmd.data, 0);
		break;

	default:
		error = -EOPNOTSUPP;
		goto out;
	}

out:
	mutex_unlock(&userio->mutex);
	return error ?: count;
}

static unsigned int userio_char_poll(struct file *file, poll_table *wait)
{
	struct userio_device *userio = file->private_data;

	poll_wait(file, &userio->waitq, wait);

	if (userio->head != userio->tail)
		return POLLIN | POLLRDNORM;

	return 0;
}

static const struct file_operations userio_fops = {
	.owner		= THIS_MODULE,
	.open		= userio_char_open,
	.release	= userio_char_release,
	.read		= userio_char_read,
	.write		= userio_char_write,
	.poll		= userio_char_poll,
	.llseek		= no_llseek,
};

static struct miscdevice userio_misc = {
	.fops	= &userio_fops,
	.minor	= USERIO_MINOR,
	.name	= USERIO_NAME,
};
module_driver(userio_misc, misc_register, misc_deregister);

MODULE_ALIAS_MISCDEV(USERIO_MINOR);
MODULE_ALIAS("devname:" USERIO_NAME);

MODULE_AUTHOR("Stephen Chandler Paul <thatslyude@gmail.com>");
MODULE_DESCRIPTION("Virtual Serio Device Support");
MODULE_LICENSE("GPL");
OpenPOWER on IntegriCloud