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1ccd7a2a DH |
1 | /* |
2 | * User-space I/O driver support for HID subsystem | |
3 | * Copyright (c) 2012 David Herrmann | |
4 | */ | |
5 | ||
6 | /* | |
7 | * This program is free software; you can redistribute it and/or modify it | |
8 | * under the terms of the GNU General Public License as published by the Free | |
9 | * Software Foundation; either version 2 of the License, or (at your option) | |
10 | * any later version. | |
11 | */ | |
12 | ||
13 | #include <linux/atomic.h> | |
14 | #include <linux/device.h> | |
15 | #include <linux/fs.h> | |
16 | #include <linux/hid.h> | |
17 | #include <linux/input.h> | |
18 | #include <linux/miscdevice.h> | |
19 | #include <linux/module.h> | |
20 | #include <linux/mutex.h> | |
21 | #include <linux/poll.h> | |
22 | #include <linux/sched.h> | |
23 | #include <linux/spinlock.h> | |
24 | #include <linux/uhid.h> | |
25 | #include <linux/wait.h> | |
26 | ||
27 | #define UHID_NAME "uhid" | |
ace3d861 DH |
28 | #define UHID_BUFSIZE 32 |
29 | ||
30 | struct uhid_device { | |
d937ae5f | 31 | struct mutex devlock; |
ace3d861 | 32 | struct hid_device *hid; |
6664ef72 | 33 | struct uhid_event input_buf; |
ace3d861 DH |
34 | |
35 | wait_queue_head_t waitq; | |
36 | spinlock_t qlock; | |
37 | __u8 head; | |
38 | __u8 tail; | |
39 | struct uhid_event *outq[UHID_BUFSIZE]; | |
40 | }; | |
1ccd7a2a DH |
41 | |
42 | static struct miscdevice uhid_misc; | |
43 | ||
ace3d861 DH |
44 | static void uhid_queue(struct uhid_device *uhid, struct uhid_event *ev) |
45 | { | |
46 | __u8 newhead; | |
47 | ||
48 | newhead = (uhid->head + 1) % UHID_BUFSIZE; | |
49 | ||
50 | if (newhead != uhid->tail) { | |
51 | uhid->outq[uhid->head] = ev; | |
52 | uhid->head = newhead; | |
53 | wake_up_interruptible(&uhid->waitq); | |
54 | } else { | |
55 | hid_warn(uhid->hid, "Output queue is full\n"); | |
56 | kfree(ev); | |
57 | } | |
58 | } | |
59 | ||
60 | static int uhid_queue_event(struct uhid_device *uhid, __u32 event) | |
61 | { | |
62 | unsigned long flags; | |
63 | struct uhid_event *ev; | |
64 | ||
65 | ev = kzalloc(sizeof(*ev), GFP_KERNEL); | |
66 | if (!ev) | |
67 | return -ENOMEM; | |
68 | ||
69 | ev->type = event; | |
70 | ||
71 | spin_lock_irqsave(&uhid->qlock, flags); | |
72 | uhid_queue(uhid, ev); | |
73 | spin_unlock_irqrestore(&uhid->qlock, flags); | |
74 | ||
75 | return 0; | |
76 | } | |
77 | ||
1ccd7a2a DH |
78 | static int uhid_char_open(struct inode *inode, struct file *file) |
79 | { | |
ace3d861 DH |
80 | struct uhid_device *uhid; |
81 | ||
82 | uhid = kzalloc(sizeof(*uhid), GFP_KERNEL); | |
83 | if (!uhid) | |
84 | return -ENOMEM; | |
85 | ||
d937ae5f | 86 | mutex_init(&uhid->devlock); |
ace3d861 DH |
87 | spin_lock_init(&uhid->qlock); |
88 | init_waitqueue_head(&uhid->waitq); | |
89 | ||
90 | file->private_data = uhid; | |
91 | nonseekable_open(inode, file); | |
92 | ||
1ccd7a2a DH |
93 | return 0; |
94 | } | |
95 | ||
96 | static int uhid_char_release(struct inode *inode, struct file *file) | |
97 | { | |
ace3d861 DH |
98 | struct uhid_device *uhid = file->private_data; |
99 | unsigned int i; | |
100 | ||
101 | for (i = 0; i < UHID_BUFSIZE; ++i) | |
102 | kfree(uhid->outq[i]); | |
103 | ||
104 | kfree(uhid); | |
105 | ||
1ccd7a2a DH |
106 | return 0; |
107 | } | |
108 | ||
109 | static ssize_t uhid_char_read(struct file *file, char __user *buffer, | |
110 | size_t count, loff_t *ppos) | |
111 | { | |
d937ae5f DH |
112 | struct uhid_device *uhid = file->private_data; |
113 | int ret; | |
114 | unsigned long flags; | |
115 | size_t len; | |
116 | ||
117 | /* they need at least the "type" member of uhid_event */ | |
118 | if (count < sizeof(__u32)) | |
119 | return -EINVAL; | |
120 | ||
121 | try_again: | |
122 | if (file->f_flags & O_NONBLOCK) { | |
123 | if (uhid->head == uhid->tail) | |
124 | return -EAGAIN; | |
125 | } else { | |
126 | ret = wait_event_interruptible(uhid->waitq, | |
127 | uhid->head != uhid->tail); | |
128 | if (ret) | |
129 | return ret; | |
130 | } | |
131 | ||
132 | ret = mutex_lock_interruptible(&uhid->devlock); | |
133 | if (ret) | |
134 | return ret; | |
135 | ||
136 | if (uhid->head == uhid->tail) { | |
137 | mutex_unlock(&uhid->devlock); | |
138 | goto try_again; | |
139 | } else { | |
140 | len = min(count, sizeof(**uhid->outq)); | |
141 | if (copy_to_user(buffer, &uhid->outq[uhid->tail], len)) { | |
142 | ret = -EFAULT; | |
143 | } else { | |
144 | kfree(uhid->outq[uhid->tail]); | |
145 | uhid->outq[uhid->tail] = NULL; | |
146 | ||
147 | spin_lock_irqsave(&uhid->qlock, flags); | |
148 | uhid->tail = (uhid->tail + 1) % UHID_BUFSIZE; | |
149 | spin_unlock_irqrestore(&uhid->qlock, flags); | |
150 | } | |
151 | } | |
152 | ||
153 | mutex_unlock(&uhid->devlock); | |
154 | return ret ? ret : len; | |
1ccd7a2a DH |
155 | } |
156 | ||
157 | static ssize_t uhid_char_write(struct file *file, const char __user *buffer, | |
158 | size_t count, loff_t *ppos) | |
159 | { | |
6664ef72 DH |
160 | struct uhid_device *uhid = file->private_data; |
161 | int ret; | |
162 | size_t len; | |
163 | ||
164 | /* we need at least the "type" member of uhid_event */ | |
165 | if (count < sizeof(__u32)) | |
166 | return -EINVAL; | |
167 | ||
168 | ret = mutex_lock_interruptible(&uhid->devlock); | |
169 | if (ret) | |
170 | return ret; | |
171 | ||
172 | memset(&uhid->input_buf, 0, sizeof(uhid->input_buf)); | |
173 | len = min(count, sizeof(uhid->input_buf)); | |
174 | if (copy_from_user(&uhid->input_buf, buffer, len)) { | |
175 | ret = -EFAULT; | |
176 | goto unlock; | |
177 | } | |
178 | ||
179 | switch (uhid->input_buf.type) { | |
180 | default: | |
181 | ret = -EOPNOTSUPP; | |
182 | } | |
183 | ||
184 | unlock: | |
185 | mutex_unlock(&uhid->devlock); | |
186 | ||
187 | /* return "count" not "len" to not confuse the caller */ | |
188 | return ret ? ret : count; | |
1ccd7a2a DH |
189 | } |
190 | ||
191 | static unsigned int uhid_char_poll(struct file *file, poll_table *wait) | |
192 | { | |
1f9dec1e DH |
193 | struct uhid_device *uhid = file->private_data; |
194 | ||
195 | poll_wait(file, &uhid->waitq, wait); | |
196 | ||
197 | if (uhid->head != uhid->tail) | |
198 | return POLLIN | POLLRDNORM; | |
199 | ||
1ccd7a2a DH |
200 | return 0; |
201 | } | |
202 | ||
203 | static const struct file_operations uhid_fops = { | |
204 | .owner = THIS_MODULE, | |
205 | .open = uhid_char_open, | |
206 | .release = uhid_char_release, | |
207 | .read = uhid_char_read, | |
208 | .write = uhid_char_write, | |
209 | .poll = uhid_char_poll, | |
210 | .llseek = no_llseek, | |
211 | }; | |
212 | ||
213 | static struct miscdevice uhid_misc = { | |
214 | .fops = &uhid_fops, | |
215 | .minor = MISC_DYNAMIC_MINOR, | |
216 | .name = UHID_NAME, | |
217 | }; | |
218 | ||
219 | static int __init uhid_init(void) | |
220 | { | |
221 | return misc_register(&uhid_misc); | |
222 | } | |
223 | ||
224 | static void __exit uhid_exit(void) | |
225 | { | |
226 | misc_deregister(&uhid_misc); | |
227 | } | |
228 | ||
229 | module_init(uhid_init); | |
230 | module_exit(uhid_exit); | |
231 | MODULE_LICENSE("GPL"); | |
232 | MODULE_AUTHOR("David Herrmann <dh.herrmann@gmail.com>"); | |
233 | MODULE_DESCRIPTION("User-space I/O driver support for HID subsystem"); |