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5523662e SCP |
1 | /* |
2 | * userio kernel serio device emulation module | |
3 | * Copyright (C) 2015 Red Hat | |
4 | * Copyright (C) 2015 Stephen Chandler Paul <thatslyude@gmail.com> | |
5 | * | |
6 | * This program is free software; you can redistribute it and/or modify it | |
7 | * under the terms of the GNU Lesser General Public License as published by | |
8 | * the Free Software Foundation; either version 2 of the License, or (at | |
9 | * your option) any later version. | |
10 | * | |
11 | * This program is distributed in the hope that it will be useful, but | |
12 | * WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser | |
14 | * General Public License for more details. | |
15 | */ | |
16 | ||
17 | #include <linux/circ_buf.h> | |
18 | #include <linux/mutex.h> | |
19 | #include <linux/module.h> | |
20 | #include <linux/init.h> | |
21 | #include <linux/kernel.h> | |
22 | #include <linux/serio.h> | |
23 | #include <linux/slab.h> | |
24 | #include <linux/fs.h> | |
25 | #include <linux/miscdevice.h> | |
26 | #include <linux/sched.h> | |
27 | #include <linux/poll.h> | |
28 | #include <uapi/linux/userio.h> | |
29 | ||
30 | #define USERIO_NAME "userio" | |
31 | #define USERIO_BUFSIZE 16 | |
32 | ||
33 | static struct miscdevice userio_misc; | |
34 | ||
35 | struct userio_device { | |
36 | struct serio *serio; | |
37 | struct mutex mutex; | |
38 | ||
39 | bool running; | |
40 | ||
41 | u8 head; | |
42 | u8 tail; | |
43 | ||
44 | spinlock_t buf_lock; | |
45 | unsigned char buf[USERIO_BUFSIZE]; | |
46 | ||
47 | wait_queue_head_t waitq; | |
48 | }; | |
49 | ||
50 | /** | |
51 | * userio_device_write - Write data from serio to a userio device in userspace | |
52 | * @id: The serio port for the userio device | |
53 | * @val: The data to write to the device | |
54 | */ | |
55 | static int userio_device_write(struct serio *id, unsigned char val) | |
56 | { | |
57 | struct userio_device *userio = id->port_data; | |
58 | unsigned long flags; | |
59 | ||
60 | spin_lock_irqsave(&userio->buf_lock, flags); | |
61 | ||
62 | userio->buf[userio->head] = val; | |
63 | userio->head = (userio->head + 1) % USERIO_BUFSIZE; | |
64 | ||
65 | if (userio->head == userio->tail) | |
66 | dev_warn(userio_misc.this_device, | |
67 | "Buffer overflowed, userio client isn't keeping up"); | |
68 | ||
69 | spin_unlock_irqrestore(&userio->buf_lock, flags); | |
70 | ||
71 | wake_up_interruptible(&userio->waitq); | |
72 | ||
73 | return 0; | |
74 | } | |
75 | ||
76 | static int userio_char_open(struct inode *inode, struct file *file) | |
77 | { | |
78 | struct userio_device *userio; | |
79 | ||
80 | userio = kzalloc(sizeof(struct userio_device), GFP_KERNEL); | |
81 | if (!userio) | |
82 | return -ENOMEM; | |
83 | ||
84 | mutex_init(&userio->mutex); | |
85 | spin_lock_init(&userio->buf_lock); | |
86 | init_waitqueue_head(&userio->waitq); | |
87 | ||
88 | userio->serio = kzalloc(sizeof(struct serio), GFP_KERNEL); | |
89 | if (!userio->serio) { | |
90 | kfree(userio); | |
91 | return -ENOMEM; | |
92 | } | |
93 | ||
94 | userio->serio->write = userio_device_write; | |
95 | userio->serio->port_data = userio; | |
96 | ||
97 | file->private_data = userio; | |
98 | ||
99 | return 0; | |
100 | } | |
101 | ||
102 | static int userio_char_release(struct inode *inode, struct file *file) | |
103 | { | |
104 | struct userio_device *userio = file->private_data; | |
105 | ||
106 | if (userio->running) { | |
107 | /* | |
108 | * Don't free the serio port here, serio_unregister_port() | |
109 | * does it for us. | |
110 | */ | |
111 | serio_unregister_port(userio->serio); | |
112 | } else { | |
113 | kfree(userio->serio); | |
114 | } | |
115 | ||
116 | kfree(userio); | |
117 | ||
118 | return 0; | |
119 | } | |
120 | ||
121 | static ssize_t userio_char_read(struct file *file, char __user *user_buffer, | |
122 | size_t count, loff_t *ppos) | |
123 | { | |
124 | struct userio_device *userio = file->private_data; | |
125 | int error; | |
126 | size_t nonwrap_len, copylen; | |
127 | unsigned char buf[USERIO_BUFSIZE]; | |
128 | unsigned long flags; | |
129 | ||
130 | /* | |
131 | * By the time we get here, the data that was waiting might have | |
132 | * been taken by another thread. Grab the buffer lock and check if | |
133 | * there's still any data waiting, otherwise repeat this process | |
134 | * until we have data (unless the file descriptor is non-blocking | |
135 | * of course). | |
136 | */ | |
137 | for (;;) { | |
138 | spin_lock_irqsave(&userio->buf_lock, flags); | |
139 | ||
140 | nonwrap_len = CIRC_CNT_TO_END(userio->head, | |
141 | userio->tail, | |
142 | USERIO_BUFSIZE); | |
143 | copylen = min(nonwrap_len, count); | |
144 | if (copylen) { | |
145 | memcpy(buf, &userio->buf[userio->tail], copylen); | |
146 | userio->tail = (userio->tail + copylen) % | |
147 | USERIO_BUFSIZE; | |
148 | } | |
149 | ||
150 | spin_unlock_irqrestore(&userio->buf_lock, flags); | |
151 | ||
152 | if (nonwrap_len) | |
153 | break; | |
154 | ||
155 | /* buffer was/is empty */ | |
156 | if (file->f_flags & O_NONBLOCK) | |
157 | return -EAGAIN; | |
158 | ||
159 | /* | |
160 | * count == 0 is special - no IO is done but we check | |
161 | * for error conditions (see above). | |
162 | */ | |
163 | if (count == 0) | |
164 | return 0; | |
165 | ||
166 | error = wait_event_interruptible(userio->waitq, | |
167 | userio->head != userio->tail); | |
168 | if (error) | |
169 | return error; | |
170 | } | |
171 | ||
172 | if (copylen) | |
173 | if (copy_to_user(user_buffer, buf, copylen)) | |
174 | return -EFAULT; | |
175 | ||
176 | return copylen; | |
177 | } | |
178 | ||
179 | static ssize_t userio_char_write(struct file *file, const char __user *buffer, | |
180 | size_t count, loff_t *ppos) | |
181 | { | |
182 | struct userio_device *userio = file->private_data; | |
183 | struct userio_cmd cmd; | |
184 | int error; | |
185 | ||
186 | if (count != sizeof(cmd)) { | |
187 | dev_warn(userio_misc.this_device, "Invalid payload size\n"); | |
188 | return -EINVAL; | |
189 | } | |
190 | ||
191 | if (copy_from_user(&cmd, buffer, sizeof(cmd))) | |
192 | return -EFAULT; | |
193 | ||
194 | error = mutex_lock_interruptible(&userio->mutex); | |
195 | if (error) | |
196 | return error; | |
197 | ||
198 | switch (cmd.type) { | |
199 | case USERIO_CMD_REGISTER: | |
200 | if (!userio->serio->id.type) { | |
201 | dev_warn(userio_misc.this_device, | |
202 | "No port type given on /dev/userio\n"); | |
203 | ||
204 | error = -EINVAL; | |
205 | goto out; | |
206 | } | |
207 | ||
208 | if (userio->running) { | |
209 | dev_warn(userio_misc.this_device, | |
210 | "Begin command sent, but we're already running\n"); | |
211 | error = -EBUSY; | |
212 | goto out; | |
213 | } | |
214 | ||
215 | userio->running = true; | |
216 | serio_register_port(userio->serio); | |
217 | break; | |
218 | ||
219 | case USERIO_CMD_SET_PORT_TYPE: | |
220 | if (userio->running) { | |
221 | dev_warn(userio_misc.this_device, | |
222 | "Can't change port type on an already running userio instance\n"); | |
223 | error = -EBUSY; | |
224 | goto out; | |
225 | } | |
226 | ||
227 | userio->serio->id.type = cmd.data; | |
228 | break; | |
229 | ||
230 | case USERIO_CMD_SEND_INTERRUPT: | |
231 | if (!userio->running) { | |
232 | dev_warn(userio_misc.this_device, | |
233 | "The device must be registered before sending interrupts\n"); | |
234 | error = -ENODEV; | |
235 | goto out; | |
236 | } | |
237 | ||
238 | serio_interrupt(userio->serio, cmd.data, 0); | |
239 | break; | |
240 | ||
241 | default: | |
242 | error = -EOPNOTSUPP; | |
243 | goto out; | |
244 | } | |
245 | ||
246 | out: | |
247 | mutex_unlock(&userio->mutex); | |
248 | return error ?: count; | |
249 | } | |
250 | ||
afc9a42b | 251 | static __poll_t userio_char_poll(struct file *file, poll_table *wait) |
5523662e SCP |
252 | { |
253 | struct userio_device *userio = file->private_data; | |
254 | ||
255 | poll_wait(file, &userio->waitq, wait); | |
256 | ||
257 | if (userio->head != userio->tail) | |
a9a08845 | 258 | return EPOLLIN | EPOLLRDNORM; |
5523662e SCP |
259 | |
260 | return 0; | |
261 | } | |
262 | ||
263 | static const struct file_operations userio_fops = { | |
264 | .owner = THIS_MODULE, | |
265 | .open = userio_char_open, | |
266 | .release = userio_char_release, | |
267 | .read = userio_char_read, | |
268 | .write = userio_char_write, | |
269 | .poll = userio_char_poll, | |
270 | .llseek = no_llseek, | |
271 | }; | |
272 | ||
273 | static struct miscdevice userio_misc = { | |
274 | .fops = &userio_fops, | |
275 | .minor = USERIO_MINOR, | |
276 | .name = USERIO_NAME, | |
277 | }; | |
278 | module_driver(userio_misc, misc_register, misc_deregister); | |
279 | ||
280 | MODULE_ALIAS_MISCDEV(USERIO_MINOR); | |
281 | MODULE_ALIAS("devname:" USERIO_NAME); | |
282 | ||
283 | MODULE_AUTHOR("Stephen Chandler Paul <thatslyude@gmail.com>"); | |
284 | MODULE_DESCRIPTION("Virtual Serio Device Support"); | |
285 | MODULE_LICENSE("GPL"); |