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 #include <asm/system.h>
44
45 #include <media/media-devnode.h>
46
47 #define MEDIA_NUM_DEVICES 256
48 #define MEDIA_NAME "media"
49
50 static dev_t media_dev_t;
51
52 /*
53 * Active devices
54 */
55 static DEFINE_MUTEX(media_devnode_lock);
56 static DECLARE_BITMAP(media_devnode_nums, MEDIA_NUM_DEVICES);
57
58 /* Called when the last user of the media device exits. */
media_devnode_release(struct device * cd)59 static void media_devnode_release(struct device *cd)
60 {
61 struct media_devnode *mdev = to_media_devnode(cd);
62
63 mutex_lock(&media_devnode_lock);
64
65 /* Delete the cdev on this minor as well */
66 cdev_del(&mdev->cdev);
67
68 /* Mark device node number as free */
69 clear_bit(mdev->minor, media_devnode_nums);
70
71 mutex_unlock(&media_devnode_lock);
72
73 /* Release media_devnode and perform other cleanups as needed. */
74 if (mdev->release)
75 mdev->release(mdev);
76 }
77
78 static struct bus_type media_bus_type = {
79 .name = MEDIA_NAME,
80 };
81
media_read(struct file * filp,char __user * buf,size_t sz,loff_t * off)82 static ssize_t media_read(struct file *filp, char __user *buf,
83 size_t sz, loff_t *off)
84 {
85 struct media_devnode *mdev = media_devnode_data(filp);
86
87 if (!mdev->fops->read)
88 return -EINVAL;
89 if (!media_devnode_is_registered(mdev))
90 return -EIO;
91 return mdev->fops->read(filp, buf, sz, off);
92 }
93
media_write(struct file * filp,const char __user * buf,size_t sz,loff_t * off)94 static ssize_t media_write(struct file *filp, const char __user *buf,
95 size_t sz, loff_t *off)
96 {
97 struct media_devnode *mdev = media_devnode_data(filp);
98
99 if (!mdev->fops->write)
100 return -EINVAL;
101 if (!media_devnode_is_registered(mdev))
102 return -EIO;
103 return mdev->fops->write(filp, buf, sz, off);
104 }
105
media_poll(struct file * filp,struct poll_table_struct * poll)106 static unsigned int media_poll(struct file *filp,
107 struct poll_table_struct *poll)
108 {
109 struct media_devnode *mdev = media_devnode_data(filp);
110
111 if (!media_devnode_is_registered(mdev))
112 return POLLERR | POLLHUP;
113 if (!mdev->fops->poll)
114 return DEFAULT_POLLMASK;
115 return mdev->fops->poll(filp, poll);
116 }
117
media_ioctl(struct file * filp,unsigned int cmd,unsigned long arg)118 static long media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
119 {
120 struct media_devnode *mdev = media_devnode_data(filp);
121
122 if (!mdev->fops->ioctl)
123 return -ENOTTY;
124
125 if (!media_devnode_is_registered(mdev))
126 return -EIO;
127
128 return mdev->fops->ioctl(filp, cmd, arg);
129 }
130
131 /* Override for the open function */
media_open(struct inode * inode,struct file * filp)132 static int media_open(struct inode *inode, struct file *filp)
133 {
134 struct media_devnode *mdev;
135 int ret;
136
137 /* Check if the media device is available. This needs to be done with
138 * the media_devnode_lock held to prevent an open/unregister race:
139 * without the lock, the device could be unregistered and freed between
140 * the media_devnode_is_registered() and get_device() calls, leading to
141 * a crash.
142 */
143 mutex_lock(&media_devnode_lock);
144 mdev = container_of(inode->i_cdev, struct media_devnode, cdev);
145 /* return ENXIO if the media device has been removed
146 already or if it is not registered anymore. */
147 if (!media_devnode_is_registered(mdev)) {
148 mutex_unlock(&media_devnode_lock);
149 return -ENXIO;
150 }
151 /* and increase the device refcount */
152 get_device(&mdev->dev);
153 mutex_unlock(&media_devnode_lock);
154
155 filp->private_data = mdev;
156
157 if (mdev->fops->open) {
158 ret = mdev->fops->open(filp);
159 if (ret) {
160 put_device(&mdev->dev);
161 return ret;
162 }
163 }
164
165 return 0;
166 }
167
168 /* Override for the release function */
media_release(struct inode * inode,struct file * filp)169 static int media_release(struct inode *inode, struct file *filp)
170 {
171 struct media_devnode *mdev = media_devnode_data(filp);
172 int ret = 0;
173
174 if (mdev->fops->release)
175 mdev->fops->release(filp);
176
177 /* decrease the refcount unconditionally since the release()
178 return value is ignored. */
179 put_device(&mdev->dev);
180 filp->private_data = NULL;
181 return ret;
182 }
183
184 static const struct file_operations media_devnode_fops = {
185 .owner = THIS_MODULE,
186 .read = media_read,
187 .write = media_write,
188 .open = media_open,
189 .unlocked_ioctl = media_ioctl,
190 .release = media_release,
191 .poll = media_poll,
192 .llseek = no_llseek,
193 };
194
195 /**
196 * media_devnode_register - register a media device node
197 * @mdev: media device node structure we want to register
198 *
199 * The registration code assigns minor numbers and registers the new device node
200 * with the kernel. An error is returned if no free minor number can be found,
201 * or if the registration of the device node fails.
202 *
203 * Zero is returned on success.
204 *
205 * Note that if the media_devnode_register call fails, the release() callback of
206 * the media_devnode structure is *not* called, so the caller is responsible for
207 * freeing any data.
208 */
media_devnode_register(struct media_devnode * mdev)209 int __must_check media_devnode_register(struct media_devnode *mdev)
210 {
211 int minor;
212 int ret;
213
214 /* Part 1: Find a free minor number */
215 mutex_lock(&media_devnode_lock);
216 minor = find_next_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES, 0);
217 if (minor == MEDIA_NUM_DEVICES) {
218 mutex_unlock(&media_devnode_lock);
219 printk(KERN_ERR "could not get a free minor\n");
220 return -ENFILE;
221 }
222
223 set_bit(minor, media_devnode_nums);
224 mutex_unlock(&media_devnode_lock);
225
226 mdev->minor = minor;
227
228 /* Part 2: Initialize and register the character device */
229 cdev_init(&mdev->cdev, &media_devnode_fops);
230 mdev->cdev.owner = mdev->fops->owner;
231
232 ret = cdev_add(&mdev->cdev, MKDEV(MAJOR(media_dev_t), mdev->minor), 1);
233 if (ret < 0) {
234 printk(KERN_ERR "%s: cdev_add failed\n", __func__);
235 goto error;
236 }
237
238 /* Part 3: Register the media device */
239 mdev->dev.bus = &media_bus_type;
240 mdev->dev.devt = MKDEV(MAJOR(media_dev_t), mdev->minor);
241 mdev->dev.release = media_devnode_release;
242 if (mdev->parent)
243 mdev->dev.parent = mdev->parent;
244 dev_set_name(&mdev->dev, "media%d", mdev->minor);
245 ret = device_register(&mdev->dev);
246 if (ret < 0) {
247 printk(KERN_ERR "%s: device_register failed\n", __func__);
248 goto error;
249 }
250
251 /* Part 4: Activate this minor. The char device can now be used. */
252 set_bit(MEDIA_FLAG_REGISTERED, &mdev->flags);
253
254 return 0;
255
256 error:
257 cdev_del(&mdev->cdev);
258 clear_bit(mdev->minor, media_devnode_nums);
259 return ret;
260 }
261
262 /**
263 * media_devnode_unregister - unregister a media device node
264 * @mdev: the device node to unregister
265 *
266 * This unregisters the passed device. Future open calls will be met with
267 * errors.
268 *
269 * This function can safely be called if the device node has never been
270 * registered or has already been unregistered.
271 */
media_devnode_unregister(struct media_devnode * mdev)272 void media_devnode_unregister(struct media_devnode *mdev)
273 {
274 /* Check if mdev was ever registered at all */
275 if (!media_devnode_is_registered(mdev))
276 return;
277
278 mutex_lock(&media_devnode_lock);
279 clear_bit(MEDIA_FLAG_REGISTERED, &mdev->flags);
280 mutex_unlock(&media_devnode_lock);
281 device_unregister(&mdev->dev);
282 }
283
284 /*
285 * Initialise media for linux
286 */
media_devnode_init(void)287 static int __init media_devnode_init(void)
288 {
289 int ret;
290
291 printk(KERN_INFO "Linux media interface: v0.10\n");
292 ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES,
293 MEDIA_NAME);
294 if (ret < 0) {
295 printk(KERN_WARNING "media: unable to allocate major\n");
296 return ret;
297 }
298
299 ret = bus_register(&media_bus_type);
300 if (ret < 0) {
301 unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
302 printk(KERN_WARNING "media: bus_register failed\n");
303 return -EIO;
304 }
305
306 return 0;
307 }
308
media_devnode_exit(void)309 static void __exit media_devnode_exit(void)
310 {
311 bus_unregister(&media_bus_type);
312 unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
313 }
314
315 module_init(media_devnode_init)
316 module_exit(media_devnode_exit)
317
318 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
319 MODULE_DESCRIPTION("Device node registration for media drivers");
320 MODULE_LICENSE("GPL");
321