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cf4b9211 LP |
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. */ | |
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 | ||
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 | ||
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 | ||
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 | ||
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 */ | |
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 */ | |
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 | */ | |
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, 0, MEDIA_NUM_DEVICES); | |
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(mdev->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 | */ | |
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 | */ | |
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 | ||
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"); |