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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> | |
cf4b9211 LP |
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. */ | |
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 | ||
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 | ||
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 | ||
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 | ||
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 */ | |
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 */ | |
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 | */ | |
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); | |
8c89ddd5 | 215 | minor = find_next_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES, 0); |
cf4b9211 LP |
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 | ||
8c89ddd5 | 222 | set_bit(minor, media_devnode_nums); |
cf4b9211 LP |
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 | */ | |
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 | */ | |
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 | ||
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 | ||
ff732d28 | 314 | subsys_initcall(media_devnode_init); |
cf4b9211 LP |
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"); |