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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
34
35 #include <linux/errno.h>
36 #include <linux/init.h>
37 #include <linux/module.h>
38 #include <linux/kernel.h>
39 #include <linux/kmod.h>
40 #include <linux/slab.h>
41 #include <linux/mm.h>
42 #include <linux/string.h>
43 #include <linux/types.h>
44 #include <linux/uaccess.h>
45
46 #include <media/media-devnode.h>
47
48 #define MEDIA_NUM_DEVICES 256
49 #define MEDIA_NAME "media"
50
51 static dev_t media_dev_t;
52
53 /*
54 * Active devices
55 */
56 static DEFINE_MUTEX(media_devnode_lock);
57 static DECLARE_BITMAP(media_devnode_nums, MEDIA_NUM_DEVICES);
58
59 /* Called when the last user of the media device exits. */
media_devnode_release(struct device * cd)60 static void media_devnode_release(struct device *cd)
61 {
62 struct media_devnode *mdev = to_media_devnode(cd);
63
64 mutex_lock(&media_devnode_lock);
65
66 /* Delete the cdev on this minor as well */
67 cdev_del(&mdev->cdev);
68
69 /* Mark device node number as free */
70 clear_bit(mdev->minor, media_devnode_nums);
71
72 mutex_unlock(&media_devnode_lock);
73
74 /* Release media_devnode and perform other cleanups as needed. */
75 if (mdev->release)
76 mdev->release(mdev);
77 }
78
79 static struct bus_type media_bus_type = {
80 .name = MEDIA_NAME,
81 };
82
media_read(struct file * filp,char __user * buf,size_t sz,loff_t * off)83 static ssize_t media_read(struct file *filp, char __user *buf,
84 size_t sz, loff_t *off)
85 {
86 struct media_devnode *mdev = media_devnode_data(filp);
87
88 if (!mdev->fops->read)
89 return -EINVAL;
90 if (!media_devnode_is_registered(mdev))
91 return -EIO;
92 return mdev->fops->read(filp, buf, sz, off);
93 }
94
media_write(struct file * filp,const char __user * buf,size_t sz,loff_t * off)95 static ssize_t media_write(struct file *filp, const char __user *buf,
96 size_t sz, loff_t *off)
97 {
98 struct media_devnode *mdev = media_devnode_data(filp);
99
100 if (!mdev->fops->write)
101 return -EINVAL;
102 if (!media_devnode_is_registered(mdev))
103 return -EIO;
104 return mdev->fops->write(filp, buf, sz, off);
105 }
106
media_poll(struct file * filp,struct poll_table_struct * poll)107 static unsigned int media_poll(struct file *filp,
108 struct poll_table_struct *poll)
109 {
110 struct media_devnode *mdev = media_devnode_data(filp);
111
112 if (!media_devnode_is_registered(mdev))
113 return POLLERR | POLLHUP;
114 if (!mdev->fops->poll)
115 return DEFAULT_POLLMASK;
116 return mdev->fops->poll(filp, poll);
117 }
118
119 static long
__media_ioctl(struct file * filp,unsigned int cmd,unsigned long arg,long (* ioctl_func)(struct file * filp,unsigned int cmd,unsigned long arg))120 __media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg,
121 long (*ioctl_func)(struct file *filp, unsigned int cmd,
122 unsigned long arg))
123 {
124 struct media_devnode *mdev = media_devnode_data(filp);
125
126 if (!ioctl_func)
127 return -ENOTTY;
128
129 if (!media_devnode_is_registered(mdev))
130 return -EIO;
131
132 return ioctl_func(filp, cmd, arg);
133 }
134
media_ioctl(struct file * filp,unsigned int cmd,unsigned long arg)135 static long media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
136 {
137 struct media_devnode *mdev = media_devnode_data(filp);
138
139 return __media_ioctl(filp, cmd, arg, mdev->fops->ioctl);
140 }
141
142 #ifdef CONFIG_COMPAT
143
media_compat_ioctl(struct file * filp,unsigned int cmd,unsigned long arg)144 static long media_compat_ioctl(struct file *filp, unsigned int cmd,
145 unsigned long arg)
146 {
147 struct media_devnode *mdev = media_devnode_data(filp);
148
149 return __media_ioctl(filp, cmd, arg, mdev->fops->compat_ioctl);
150 }
151
152 #endif /* CONFIG_COMPAT */
153
154 /* Override for the open function */
media_open(struct inode * inode,struct file * filp)155 static int media_open(struct inode *inode, struct file *filp)
156 {
157 struct media_devnode *mdev;
158 int ret;
159
160 /* Check if the media device is available. This needs to be done with
161 * the media_devnode_lock held to prevent an open/unregister race:
162 * without the lock, the device could be unregistered and freed between
163 * the media_devnode_is_registered() and get_device() calls, leading to
164 * a crash.
165 */
166 mutex_lock(&media_devnode_lock);
167 mdev = container_of(inode->i_cdev, struct media_devnode, cdev);
168 /* return ENXIO if the media device has been removed
169 already or if it is not registered anymore. */
170 if (!media_devnode_is_registered(mdev)) {
171 mutex_unlock(&media_devnode_lock);
172 return -ENXIO;
173 }
174 /* and increase the device refcount */
175 get_device(&mdev->dev);
176 mutex_unlock(&media_devnode_lock);
177
178 filp->private_data = mdev;
179
180 if (mdev->fops->open) {
181 ret = mdev->fops->open(filp);
182 if (ret) {
183 put_device(&mdev->dev);
184 return ret;
185 }
186 }
187
188 return 0;
189 }
190
191 /* Override for the release function */
media_release(struct inode * inode,struct file * filp)192 static int media_release(struct inode *inode, struct file *filp)
193 {
194 struct media_devnode *mdev = media_devnode_data(filp);
195 int ret = 0;
196
197 if (mdev->fops->release)
198 mdev->fops->release(filp);
199
200 /* decrease the refcount unconditionally since the release()
201 return value is ignored. */
202 put_device(&mdev->dev);
203 filp->private_data = NULL;
204 return ret;
205 }
206
207 static const struct file_operations media_devnode_fops = {
208 .owner = THIS_MODULE,
209 .read = media_read,
210 .write = media_write,
211 .open = media_open,
212 .unlocked_ioctl = media_ioctl,
213 #ifdef CONFIG_COMPAT
214 .compat_ioctl = media_compat_ioctl,
215 #endif /* CONFIG_COMPAT */
216 .release = media_release,
217 .poll = media_poll,
218 .llseek = no_llseek,
219 };
220
221 /**
222 * media_devnode_register - register a media device node
223 * @mdev: media device node structure we want to register
224 *
225 * The registration code assigns minor numbers and registers the new device node
226 * with the kernel. An error is returned if no free minor number can be found,
227 * or if the registration of the device node fails.
228 *
229 * Zero is returned on success.
230 *
231 * Note that if the media_devnode_register call fails, the release() callback of
232 * the media_devnode structure is *not* called, so the caller is responsible for
233 * freeing any data.
234 */
media_devnode_register(struct media_devnode * mdev)235 int __must_check media_devnode_register(struct media_devnode *mdev)
236 {
237 int minor;
238 int ret;
239
240 /* Part 1: Find a free minor number */
241 mutex_lock(&media_devnode_lock);
242 minor = find_next_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES, 0);
243 if (minor == MEDIA_NUM_DEVICES) {
244 mutex_unlock(&media_devnode_lock);
245 pr_err("could not get a free minor\n");
246 return -ENFILE;
247 }
248
249 set_bit(minor, media_devnode_nums);
250 mutex_unlock(&media_devnode_lock);
251
252 mdev->minor = minor;
253
254 /* Part 2: Initialize and register the character device */
255 cdev_init(&mdev->cdev, &media_devnode_fops);
256 mdev->cdev.owner = mdev->fops->owner;
257
258 ret = cdev_add(&mdev->cdev, MKDEV(MAJOR(media_dev_t), mdev->minor), 1);
259 if (ret < 0) {
260 pr_err("%s: cdev_add failed\n", __func__);
261 goto error;
262 }
263
264 /* Part 3: Register the media device */
265 mdev->dev.bus = &media_bus_type;
266 mdev->dev.devt = MKDEV(MAJOR(media_dev_t), mdev->minor);
267 mdev->dev.release = media_devnode_release;
268 if (mdev->parent)
269 mdev->dev.parent = mdev->parent;
270 dev_set_name(&mdev->dev, "media%d", mdev->minor);
271 ret = device_register(&mdev->dev);
272 if (ret < 0) {
273 pr_err("%s: device_register failed\n", __func__);
274 goto error;
275 }
276
277 /* Part 4: Activate this minor. The char device can now be used. */
278 set_bit(MEDIA_FLAG_REGISTERED, &mdev->flags);
279
280 return 0;
281
282 error:
283 cdev_del(&mdev->cdev);
284 clear_bit(mdev->minor, media_devnode_nums);
285 return ret;
286 }
287
288 /**
289 * media_devnode_unregister - unregister a media device node
290 * @mdev: the device node to unregister
291 *
292 * This unregisters the passed device. Future open calls will be met with
293 * errors.
294 *
295 * This function can safely be called if the device node has never been
296 * registered or has already been unregistered.
297 */
media_devnode_unregister(struct media_devnode * mdev)298 void media_devnode_unregister(struct media_devnode *mdev)
299 {
300 /* Check if mdev was ever registered at all */
301 if (!media_devnode_is_registered(mdev))
302 return;
303
304 mutex_lock(&media_devnode_lock);
305 clear_bit(MEDIA_FLAG_REGISTERED, &mdev->flags);
306 mutex_unlock(&media_devnode_lock);
307 device_unregister(&mdev->dev);
308 }
309
310 /*
311 * Initialise media for linux
312 */
media_devnode_init(void)313 static int __init media_devnode_init(void)
314 {
315 int ret;
316
317 pr_info("Linux media interface: v0.10\n");
318 ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES,
319 MEDIA_NAME);
320 if (ret < 0) {
321 pr_warn("unable to allocate major\n");
322 return ret;
323 }
324
325 ret = bus_register(&media_bus_type);
326 if (ret < 0) {
327 unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
328 pr_warn("bus_register failed\n");
329 return -EIO;
330 }
331
332 return 0;
333 }
334
media_devnode_exit(void)335 static void __exit media_devnode_exit(void)
336 {
337 bus_unregister(&media_bus_type);
338 unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
339 }
340
341 subsys_initcall(media_devnode_init);
342 module_exit(media_devnode_exit)
343
344 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
345 MODULE_DESCRIPTION("Device node registration for media drivers");
346 MODULE_LICENSE("GPL");
347