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 <mchehab@infradead.org> (version 2)
8 * Alan Cox, <alan@lxorguk.ukuu.org.uk> (version 1)
9 *
10 * Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
11 * Sakari Ailus <sakari.ailus@iki.fi>
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 * You should have received a copy of the GNU General Public License
23 * along with this program; if not, write to the Free Software
24 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
25 *
26 * --
27 *
28 * Generic media device node infrastructure to register and unregister
29 * character devices using a dynamic major number and proper reference
30 * counting.
31 */
32
33 #include <linux/errno.h>
34 #include <linux/init.h>
35 #include <linux/module.h>
36 #include <linux/kernel.h>
37 #include <linux/kmod.h>
38 #include <linux/slab.h>
39 #include <linux/mm.h>
40 #include <linux/string.h>
41 #include <linux/types.h>
42 #include <linux/uaccess.h>
43
44 #include <media/media-devnode.h>
45
46 #define MEDIA_NUM_DEVICES 256
47 #define MEDIA_NAME "media"
48
49 static dev_t media_dev_t;
50
51 /*
52 * Active devices
53 */
54 static DEFINE_MUTEX(media_devnode_lock);
55 static DECLARE_BITMAP(media_devnode_nums, MEDIA_NUM_DEVICES);
56
57 /* Called when the last user of the media device exits. */
media_devnode_release(struct device * cd)58 static void media_devnode_release(struct device *cd)
59 {
60 struct media_devnode *mdev = to_media_devnode(cd);
61
62 mutex_lock(&media_devnode_lock);
63
64 /* Delete the cdev on this minor as well */
65 cdev_del(&mdev->cdev);
66
67 /* Mark device node number as free */
68 clear_bit(mdev->minor, media_devnode_nums);
69
70 mutex_unlock(&media_devnode_lock);
71
72 /* Release media_devnode and perform other cleanups as needed. */
73 if (mdev->release)
74 mdev->release(mdev);
75 }
76
77 static struct bus_type media_bus_type = {
78 .name = MEDIA_NAME,
79 };
80
media_read(struct file * filp,char __user * buf,size_t sz,loff_t * off)81 static ssize_t media_read(struct file *filp, char __user *buf,
82 size_t sz, loff_t *off)
83 {
84 struct media_devnode *mdev = media_devnode_data(filp);
85
86 if (!mdev->fops->read)
87 return -EINVAL;
88 if (!media_devnode_is_registered(mdev))
89 return -EIO;
90 return mdev->fops->read(filp, buf, sz, off);
91 }
92
media_write(struct file * filp,const char __user * buf,size_t sz,loff_t * off)93 static ssize_t media_write(struct file *filp, const char __user *buf,
94 size_t sz, loff_t *off)
95 {
96 struct media_devnode *mdev = media_devnode_data(filp);
97
98 if (!mdev->fops->write)
99 return -EINVAL;
100 if (!media_devnode_is_registered(mdev))
101 return -EIO;
102 return mdev->fops->write(filp, buf, sz, off);
103 }
104
media_poll(struct file * filp,struct poll_table_struct * poll)105 static unsigned int media_poll(struct file *filp,
106 struct poll_table_struct *poll)
107 {
108 struct media_devnode *mdev = media_devnode_data(filp);
109
110 if (!media_devnode_is_registered(mdev))
111 return POLLERR | POLLHUP;
112 if (!mdev->fops->poll)
113 return DEFAULT_POLLMASK;
114 return mdev->fops->poll(filp, poll);
115 }
116
media_ioctl(struct file * filp,unsigned int cmd,unsigned long arg)117 static long media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
118 {
119 struct media_devnode *mdev = media_devnode_data(filp);
120
121 if (!mdev->fops->ioctl)
122 return -ENOTTY;
123
124 if (!media_devnode_is_registered(mdev))
125 return -EIO;
126
127 return mdev->fops->ioctl(filp, cmd, arg);
128 }
129
130 /* Override for the open function */
media_open(struct inode * inode,struct file * filp)131 static int media_open(struct inode *inode, struct file *filp)
132 {
133 struct media_devnode *mdev;
134 int ret;
135
136 /* Check if the media device is available. This needs to be done with
137 * the media_devnode_lock held to prevent an open/unregister race:
138 * without the lock, the device could be unregistered and freed between
139 * the media_devnode_is_registered() and get_device() calls, leading to
140 * a crash.
141 */
142 mutex_lock(&media_devnode_lock);
143 mdev = container_of(inode->i_cdev, struct media_devnode, cdev);
144 /* return ENXIO if the media device has been removed
145 already or if it is not registered anymore. */
146 if (!media_devnode_is_registered(mdev)) {
147 mutex_unlock(&media_devnode_lock);
148 return -ENXIO;
149 }
150 /* and increase the device refcount */
151 get_device(&mdev->dev);
152 mutex_unlock(&media_devnode_lock);
153
154 filp->private_data = mdev;
155
156 if (mdev->fops->open) {
157 ret = mdev->fops->open(filp);
158 if (ret) {
159 put_device(&mdev->dev);
160 return ret;
161 }
162 }
163
164 return 0;
165 }
166
167 /* Override for the release function */
media_release(struct inode * inode,struct file * filp)168 static int media_release(struct inode *inode, struct file *filp)
169 {
170 struct media_devnode *mdev = media_devnode_data(filp);
171 int ret = 0;
172
173 if (mdev->fops->release)
174 mdev->fops->release(filp);
175
176 /* decrease the refcount unconditionally since the release()
177 return value is ignored. */
178 put_device(&mdev->dev);
179 filp->private_data = NULL;
180 return ret;
181 }
182
183 static const struct file_operations media_devnode_fops = {
184 .owner = THIS_MODULE,
185 .read = media_read,
186 .write = media_write,
187 .open = media_open,
188 .unlocked_ioctl = media_ioctl,
189 .release = media_release,
190 .poll = media_poll,
191 .llseek = no_llseek,
192 };
193
194 /**
195 * media_devnode_register - register a media device node
196 * @mdev: media device node structure we want to register
197 *
198 * The registration code assigns minor numbers and registers the new device node
199 * with the kernel. An error is returned if no free minor number can be found,
200 * or if the registration of the device node fails.
201 *
202 * Zero is returned on success.
203 *
204 * Note that if the media_devnode_register call fails, the release() callback of
205 * the media_devnode structure is *not* called, so the caller is responsible for
206 * freeing any data.
207 */
media_devnode_register(struct media_devnode * mdev)208 int __must_check media_devnode_register(struct media_devnode *mdev)
209 {
210 int minor;
211 int ret;
212
213 /* Part 1: Find a free minor number */
214 mutex_lock(&media_devnode_lock);
215 minor = find_next_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES, 0);
216 if (minor == MEDIA_NUM_DEVICES) {
217 mutex_unlock(&media_devnode_lock);
218 printk(KERN_ERR "could not get a free minor\n");
219 return -ENFILE;
220 }
221
222 set_bit(minor, media_devnode_nums);
223 mutex_unlock(&media_devnode_lock);
224
225 mdev->minor = minor;
226
227 /* Part 2: Initialize and register the character device */
228 cdev_init(&mdev->cdev, &media_devnode_fops);
229 mdev->cdev.owner = mdev->fops->owner;
230
231 ret = cdev_add(&mdev->cdev, MKDEV(MAJOR(media_dev_t), mdev->minor), 1);
232 if (ret < 0) {
233 printk(KERN_ERR "%s: cdev_add failed\n", __func__);
234 goto error;
235 }
236
237 /* Part 3: Register the media device */
238 mdev->dev.bus = &media_bus_type;
239 mdev->dev.devt = MKDEV(MAJOR(media_dev_t), mdev->minor);
240 mdev->dev.release = media_devnode_release;
241 if (mdev->parent)
242 mdev->dev.parent = mdev->parent;
243 dev_set_name(&mdev->dev, "media%d", mdev->minor);
244 ret = device_register(&mdev->dev);
245 if (ret < 0) {
246 printk(KERN_ERR "%s: device_register failed\n", __func__);
247 goto error;
248 }
249
250 /* Part 4: Activate this minor. The char device can now be used. */
251 set_bit(MEDIA_FLAG_REGISTERED, &mdev->flags);
252
253 return 0;
254
255 error:
256 cdev_del(&mdev->cdev);
257 clear_bit(mdev->minor, media_devnode_nums);
258 return ret;
259 }
260
261 /**
262 * media_devnode_unregister - unregister a media device node
263 * @mdev: the device node to unregister
264 *
265 * This unregisters the passed device. Future open calls will be met with
266 * errors.
267 *
268 * This function can safely be called if the device node has never been
269 * registered or has already been unregistered.
270 */
media_devnode_unregister(struct media_devnode * mdev)271 void media_devnode_unregister(struct media_devnode *mdev)
272 {
273 /* Check if mdev was ever registered at all */
274 if (!media_devnode_is_registered(mdev))
275 return;
276
277 mutex_lock(&media_devnode_lock);
278 clear_bit(MEDIA_FLAG_REGISTERED, &mdev->flags);
279 mutex_unlock(&media_devnode_lock);
280 device_unregister(&mdev->dev);
281 }
282
283 /*
284 * Initialise media for linux
285 */
media_devnode_init(void)286 static int __init media_devnode_init(void)
287 {
288 int ret;
289
290 printk(KERN_INFO "Linux media interface: v0.10\n");
291 ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES,
292 MEDIA_NAME);
293 if (ret < 0) {
294 printk(KERN_WARNING "media: unable to allocate major\n");
295 return ret;
296 }
297
298 ret = bus_register(&media_bus_type);
299 if (ret < 0) {
300 unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
301 printk(KERN_WARNING "media: bus_register failed\n");
302 return -EIO;
303 }
304
305 return 0;
306 }
307
media_devnode_exit(void)308 static void __exit media_devnode_exit(void)
309 {
310 bus_unregister(&media_bus_type);
311 unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
312 }
313
314 subsys_initcall(media_devnode_init);
315 module_exit(media_devnode_exit)
316
317 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
318 MODULE_DESCRIPTION("Device node registration for media drivers");
319 MODULE_LICENSE("GPL");
320