HID: uhid: implement write() on uhid devices
[linux-2.6.git] / drivers / hid / uhid.c
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"
28 #define UHID_BUFSIZE    32
29
30 struct uhid_device {
31         struct mutex devlock;
32         struct hid_device *hid;
33         struct uhid_event input_buf;
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 };
41
42 static struct miscdevice uhid_misc;
43
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
78 static int uhid_char_open(struct inode *inode, struct file *file)
79 {
80         struct uhid_device *uhid;
81
82         uhid = kzalloc(sizeof(*uhid), GFP_KERNEL);
83         if (!uhid)
84                 return -ENOMEM;
85
86         mutex_init(&uhid->devlock);
87         spin_lock_init(&uhid->qlock);
88         init_waitqueue_head(&uhid->waitq);
89
90         file->private_data = uhid;
91         nonseekable_open(inode, file);
92
93         return 0;
94 }
95
96 static int uhid_char_release(struct inode *inode, struct file *file)
97 {
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
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 {
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;
155 }
156
157 static ssize_t uhid_char_write(struct file *file, const char __user *buffer,
158                                 size_t count, loff_t *ppos)
159 {
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;
189 }
190
191 static unsigned int uhid_char_poll(struct file *file, poll_table *wait)
192 {
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
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");