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(lock: &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(size: 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(size: sizeof(struct serio), GFP_KERNEL); |
89 | if (!userio->serio) { |
90 | kfree(objp: 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(serio: userio->serio); |
112 | } else { |
113 | kfree(objp: userio->serio); |
114 | } |
115 | |
116 | kfree(objp: 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(lock: &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(to: user_buffer, from: buf, n: 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(to: &cmd, from: buffer, n: 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(serio: userio->serio, data: cmd.data, flags: 0); |
239 | break; |
240 | |
241 | default: |
242 | error = -EOPNOTSUPP; |
243 | goto out; |
244 | } |
245 | |
246 | out: |
247 | mutex_unlock(lock: &userio->mutex); |
248 | return error ?: count; |
249 | } |
250 | |
251 | static __poll_t userio_char_poll(struct file *file, poll_table *wait) |
252 | { |
253 | struct userio_device *userio = file->private_data; |
254 | |
255 | poll_wait(filp: file, wait_address: &userio->waitq, p: wait); |
256 | |
257 | if (userio->head != userio->tail) |
258 | return EPOLLIN | EPOLLRDNORM; |
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" ); |
286 | |