projects/linux·blob v4.13 · refs

334 lines · 8.6 KiB

1/*
2 * Media device node
3 *
4 * Copyright (C) 2010 Nokia Corporation
5 *
6 * Based on drivers/media/video/v4l2_dev.c code authored by
7 * Mauro Carvalho Chehab <[email protected]> (version 2)
8 * Alan Cox, <[email protected]> (version 1)
9 *
10 * Contacts: Laurent Pinchart <[email protected]>
11 * Sakari Ailus <[email protected]>
12 *
13 * This program is free software; you can redistribute it and/or modify
14 * it under the terms of the GNU General Public License version 2 as
15 * published by the Free Software Foundation.
16 *
17 * This program is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 * GNU General Public License for more details.
21 *
22 * --
23 *
24 * Generic media device node infrastructure to register and unregister
25 * character devices using a dynamic major number and proper reference
26 * counting.
27 */
28
29#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
30
31#include <linux/errno.h>
32#include <linux/init.h>
33#include <linux/module.h>
34#include <linux/kernel.h>
35#include <linux/kmod.h>
36#include <linux/slab.h>
37#include <linux/mm.h>
38#include <linux/string.h>
39#include <linux/types.h>
40#include <linux/uaccess.h>
41
42#include <media/media-devnode.h>
43#include <media/media-device.h>
44
45#define MEDIA_NUM_DEVICES 256
46#define MEDIA_NAME "media"
47
48static dev_t media_dev_t;
49
50/*
51 * Active devices
52 */
53static DEFINE_MUTEX(media_devnode_lock);
54static DECLARE_BITMAP(media_devnode_nums, MEDIA_NUM_DEVICES);
55
56/* Called when the last user of the media device exits. */
57static void media_devnode_release(struct device *cd)
58{
59 struct media_devnode *devnode = to_media_devnode(cd);
60
61 mutex_lock(&media_devnode_lock);
62 /* Mark device node number as free */
63 clear_bit(devnode->minor, media_devnode_nums);
64 mutex_unlock(&media_devnode_lock);
65
66 /* Release media_devnode and perform other cleanups as needed. */
67 if (devnode->release)
68 devnode->release(devnode);
69
70 kfree(devnode);
71 pr_debug("%s: Media Devnode Deallocated\n", __func__);
72}
73
74static struct bus_type media_bus_type = {
75 .name = MEDIA_NAME,
76};
77
78static ssize_t media_read(struct file *filp, char __user *buf,
79 size_t sz, loff_t *off)
80{
81 struct media_devnode *devnode = media_devnode_data(filp);
82
83 if (!devnode->fops->read)
84 return -EINVAL;
85 if (!media_devnode_is_registered(devnode))
86 return -EIO;
87 return devnode->fops->read(filp, buf, sz, off);
88}
89
90static ssize_t media_write(struct file *filp, const char __user *buf,
91 size_t sz, loff_t *off)
92{
93 struct media_devnode *devnode = media_devnode_data(filp);
94
95 if (!devnode->fops->write)
96 return -EINVAL;
97 if (!media_devnode_is_registered(devnode))
98 return -EIO;
99 return devnode->fops->write(filp, buf, sz, off);
100}
101
102static unsigned int media_poll(struct file *filp,
103 struct poll_table_struct *poll)
104{
105 struct media_devnode *devnode = media_devnode_data(filp);
106
107 if (!media_devnode_is_registered(devnode))
108 return POLLERR | POLLHUP;
109 if (!devnode->fops->poll)
110 return DEFAULT_POLLMASK;
111 return devnode->fops->poll(filp, poll);
112}
113
114static long
115__media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg,
116 long (*ioctl_func)(struct file *filp, unsigned int cmd,
117 unsigned long arg))
118{
119 struct media_devnode *devnode = media_devnode_data(filp);
120
121 if (!ioctl_func)
122 return -ENOTTY;
123
124 if (!media_devnode_is_registered(devnode))
125 return -EIO;
126
127 return ioctl_func(filp, cmd, arg);
128}
129
130static long media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
131{
132 struct media_devnode *devnode = media_devnode_data(filp);
133
134 return __media_ioctl(filp, cmd, arg, devnode->fops->ioctl);
135}
136
137#ifdef CONFIG_COMPAT
138
139static long media_compat_ioctl(struct file *filp, unsigned int cmd,
140 unsigned long arg)
141{
142 struct media_devnode *devnode = media_devnode_data(filp);
143
144 return __media_ioctl(filp, cmd, arg, devnode->fops->compat_ioctl);
145}
146
147#endif /* CONFIG_COMPAT */
148
149/* Override for the open function */
150static int media_open(struct inode *inode, struct file *filp)
151{
152 struct media_devnode *devnode;
153 int ret;
154
155 /* Check if the media device is available. This needs to be done with
156 * the media_devnode_lock held to prevent an open/unregister race:
157 * without the lock, the device could be unregistered and freed between
158 * the media_devnode_is_registered() and get_device() calls, leading to
159 * a crash.
160 */
161 mutex_lock(&media_devnode_lock);
162 devnode = container_of(inode->i_cdev, struct media_devnode, cdev);
163 /* return ENXIO if the media device has been removed
164 already or if it is not registered anymore. */
165 if (!media_devnode_is_registered(devnode)) {
166 mutex_unlock(&media_devnode_lock);
167 return -ENXIO;
168 }
169 /* and increase the device refcount */
170 get_device(&devnode->dev);
171 mutex_unlock(&media_devnode_lock);
172
173 filp->private_data = devnode;
174
175 if (devnode->fops->open) {
176 ret = devnode->fops->open(filp);
177 if (ret) {
178 put_device(&devnode->dev);
179 filp->private_data = NULL;
180 return ret;
181 }
182 }
183
184 return 0;
185}
186
187/* Override for the release function */
188static int media_release(struct inode *inode, struct file *filp)
189{
190 struct media_devnode *devnode = media_devnode_data(filp);
191
192 if (devnode->fops->release)
193 devnode->fops->release(filp);
194
195 filp->private_data = NULL;
196
197 /* decrease the refcount unconditionally since the release()
198 return value is ignored. */
199 put_device(&devnode->dev);
200
201 pr_debug("%s: Media Release\n", __func__);
202 return 0;
203}
204
205static const struct file_operations media_devnode_fops = {
206 .owner = THIS_MODULE,
207 .read = media_read,
208 .write = media_write,
209 .open = media_open,
210 .unlocked_ioctl = media_ioctl,
211#ifdef CONFIG_COMPAT
212 .compat_ioctl = media_compat_ioctl,
213#endif /* CONFIG_COMPAT */
214 .release = media_release,
215 .poll = media_poll,
216 .llseek = no_llseek,
217};
218
219int __must_check media_devnode_register(struct media_device *mdev,
220 struct media_devnode *devnode,
221 struct module *owner)
222{
223 int minor;
224 int ret;
225
226 /* Part 1: Find a free minor number */
227 mutex_lock(&media_devnode_lock);
228 minor = find_next_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES, 0);
229 if (minor == MEDIA_NUM_DEVICES) {
230 mutex_unlock(&media_devnode_lock);
231 pr_err("could not get a free minor\n");
232 kfree(devnode);
233 return -ENFILE;
234 }
235
236 set_bit(minor, media_devnode_nums);
237 mutex_unlock(&media_devnode_lock);
238
239 devnode->minor = minor;
240 devnode->media_dev = mdev;
241
242 /* Part 1: Initialize dev now to use dev.kobj for cdev.kobj.parent */
243 devnode->dev.bus = &media_bus_type;
244 devnode->dev.devt = MKDEV(MAJOR(media_dev_t), devnode->minor);
245 devnode->dev.release = media_devnode_release;
246 if (devnode->parent)
247 devnode->dev.parent = devnode->parent;
248 dev_set_name(&devnode->dev, "media%d", devnode->minor);
249 device_initialize(&devnode->dev);
250
251 /* Part 2: Initialize the character device */
252 cdev_init(&devnode->cdev, &media_devnode_fops);
253 devnode->cdev.owner = owner;
254
255 /* Part 3: Add the media and char device */
256 ret = cdev_device_add(&devnode->cdev, &devnode->dev);
257 if (ret < 0) {
258 pr_err("%s: cdev_device_add failed\n", __func__);
259 goto cdev_add_error;
260 }
261
262 /* Part 4: Activate this minor. The char device can now be used. */
263 set_bit(MEDIA_FLAG_REGISTERED, &devnode->flags);
264
265 return 0;
266
267cdev_add_error:
268 mutex_lock(&media_devnode_lock);
269 clear_bit(devnode->minor, media_devnode_nums);
270 devnode->media_dev = NULL;
271 mutex_unlock(&media_devnode_lock);
272
273 put_device(&devnode->dev);
274 return ret;
275}
276
277void media_devnode_unregister_prepare(struct media_devnode *devnode)
278{
279 /* Check if devnode was ever registered at all */
280 if (!media_devnode_is_registered(devnode))
281 return;
282
283 mutex_lock(&media_devnode_lock);
284 clear_bit(MEDIA_FLAG_REGISTERED, &devnode->flags);
285 mutex_unlock(&media_devnode_lock);
286}
287
288void media_devnode_unregister(struct media_devnode *devnode)
289{
290 mutex_lock(&media_devnode_lock);
291 /* Delete the cdev on this minor as well */
292 cdev_device_del(&devnode->cdev, &devnode->dev);
293 mutex_unlock(&media_devnode_lock);
294 devnode->media_dev = NULL;
295 put_device(&devnode->dev);
296}
297
298/*
299 * Initialise media for linux
300 */
301static int __init media_devnode_init(void)
302{
303 int ret;
304
305 pr_info("Linux media interface: v0.10\n");
306 ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES,
307 MEDIA_NAME);
308 if (ret < 0) {
309 pr_warn("unable to allocate major\n");
310 return ret;
311 }
312
313 ret = bus_register(&media_bus_type);
314 if (ret < 0) {
315 unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
316 pr_warn("bus_register failed\n");
317 return -EIO;
318 }
319
320 return 0;
321}
322
323static void __exit media_devnode_exit(void)
324{
325 bus_unregister(&media_bus_type);
326 unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
327}
328
329subsys_initcall(media_devnode_init);
330module_exit(media_devnode_exit)
331
332MODULE_AUTHOR("Laurent Pinchart <[email protected]>");
333MODULE_DESCRIPTION("Device node registration for media drivers");
334MODULE_LICENSE("GPL");