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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 | ||
3c16b2b3 SK |
33 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
34 | ||
cf4b9211 LP |
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> | |
cf4b9211 LP |
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. */ | |
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 | ||
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 | ||
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 | ||
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) | |
120 | { | |
121 | struct media_devnode *mdev = media_devnode_data(filp); | |
122 | ||
123 | if (!mdev->fops->ioctl) | |
124 | return -ENOTTY; | |
125 | ||
126 | if (!media_devnode_is_registered(mdev)) | |
127 | return -EIO; | |
128 | ||
129 | return mdev->fops->ioctl(filp, cmd, arg); | |
130 | } | |
131 | ||
132 | /* Override for the open function */ | |
133 | static int media_open(struct inode *inode, struct file *filp) | |
134 | { | |
135 | struct media_devnode *mdev; | |
136 | int ret; | |
137 | ||
138 | /* Check if the media device is available. This needs to be done with | |
139 | * the media_devnode_lock held to prevent an open/unregister race: | |
140 | * without the lock, the device could be unregistered and freed between | |
141 | * the media_devnode_is_registered() and get_device() calls, leading to | |
142 | * a crash. | |
143 | */ | |
144 | mutex_lock(&media_devnode_lock); | |
145 | mdev = container_of(inode->i_cdev, struct media_devnode, cdev); | |
146 | /* return ENXIO if the media device has been removed | |
147 | already or if it is not registered anymore. */ | |
148 | if (!media_devnode_is_registered(mdev)) { | |
149 | mutex_unlock(&media_devnode_lock); | |
150 | return -ENXIO; | |
151 | } | |
152 | /* and increase the device refcount */ | |
153 | get_device(&mdev->dev); | |
154 | mutex_unlock(&media_devnode_lock); | |
155 | ||
156 | filp->private_data = mdev; | |
157 | ||
158 | if (mdev->fops->open) { | |
159 | ret = mdev->fops->open(filp); | |
160 | if (ret) { | |
161 | put_device(&mdev->dev); | |
162 | return ret; | |
163 | } | |
164 | } | |
165 | ||
166 | return 0; | |
167 | } | |
168 | ||
169 | /* Override for the release function */ | |
170 | static int media_release(struct inode *inode, struct file *filp) | |
171 | { | |
172 | struct media_devnode *mdev = media_devnode_data(filp); | |
173 | int ret = 0; | |
174 | ||
175 | if (mdev->fops->release) | |
176 | mdev->fops->release(filp); | |
177 | ||
178 | /* decrease the refcount unconditionally since the release() | |
179 | return value is ignored. */ | |
180 | put_device(&mdev->dev); | |
181 | filp->private_data = NULL; | |
182 | return ret; | |
183 | } | |
184 | ||
185 | static const struct file_operations media_devnode_fops = { | |
186 | .owner = THIS_MODULE, | |
187 | .read = media_read, | |
188 | .write = media_write, | |
189 | .open = media_open, | |
190 | .unlocked_ioctl = media_ioctl, | |
191 | .release = media_release, | |
192 | .poll = media_poll, | |
193 | .llseek = no_llseek, | |
194 | }; | |
195 | ||
196 | /** | |
197 | * media_devnode_register - register a media device node | |
198 | * @mdev: media device node structure we want to register | |
199 | * | |
200 | * The registration code assigns minor numbers and registers the new device node | |
201 | * with the kernel. An error is returned if no free minor number can be found, | |
202 | * or if the registration of the device node fails. | |
203 | * | |
204 | * Zero is returned on success. | |
205 | * | |
206 | * Note that if the media_devnode_register call fails, the release() callback of | |
207 | * the media_devnode structure is *not* called, so the caller is responsible for | |
208 | * freeing any data. | |
209 | */ | |
210 | int __must_check media_devnode_register(struct media_devnode *mdev) | |
211 | { | |
212 | int minor; | |
213 | int ret; | |
214 | ||
215 | /* Part 1: Find a free minor number */ | |
216 | mutex_lock(&media_devnode_lock); | |
8c89ddd5 | 217 | minor = find_next_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES, 0); |
cf4b9211 LP |
218 | if (minor == MEDIA_NUM_DEVICES) { |
219 | mutex_unlock(&media_devnode_lock); | |
3c16b2b3 | 220 | pr_err("could not get a free minor\n"); |
cf4b9211 LP |
221 | return -ENFILE; |
222 | } | |
223 | ||
8c89ddd5 | 224 | set_bit(minor, media_devnode_nums); |
cf4b9211 LP |
225 | mutex_unlock(&media_devnode_lock); |
226 | ||
227 | mdev->minor = minor; | |
228 | ||
229 | /* Part 2: Initialize and register the character device */ | |
230 | cdev_init(&mdev->cdev, &media_devnode_fops); | |
231 | mdev->cdev.owner = mdev->fops->owner; | |
232 | ||
233 | ret = cdev_add(&mdev->cdev, MKDEV(MAJOR(media_dev_t), mdev->minor), 1); | |
234 | if (ret < 0) { | |
3c16b2b3 | 235 | pr_err("%s: cdev_add failed\n", __func__); |
cf4b9211 LP |
236 | goto error; |
237 | } | |
238 | ||
239 | /* Part 3: Register the media device */ | |
240 | mdev->dev.bus = &media_bus_type; | |
241 | mdev->dev.devt = MKDEV(MAJOR(media_dev_t), mdev->minor); | |
242 | mdev->dev.release = media_devnode_release; | |
243 | if (mdev->parent) | |
244 | mdev->dev.parent = mdev->parent; | |
245 | dev_set_name(&mdev->dev, "media%d", mdev->minor); | |
246 | ret = device_register(&mdev->dev); | |
247 | if (ret < 0) { | |
3c16b2b3 | 248 | pr_err("%s: device_register failed\n", __func__); |
cf4b9211 LP |
249 | goto error; |
250 | } | |
251 | ||
252 | /* Part 4: Activate this minor. The char device can now be used. */ | |
253 | set_bit(MEDIA_FLAG_REGISTERED, &mdev->flags); | |
254 | ||
255 | return 0; | |
256 | ||
257 | error: | |
258 | cdev_del(&mdev->cdev); | |
259 | clear_bit(mdev->minor, media_devnode_nums); | |
260 | return ret; | |
261 | } | |
262 | ||
263 | /** | |
264 | * media_devnode_unregister - unregister a media device node | |
265 | * @mdev: the device node to unregister | |
266 | * | |
267 | * This unregisters the passed device. Future open calls will be met with | |
268 | * errors. | |
269 | * | |
270 | * This function can safely be called if the device node has never been | |
271 | * registered or has already been unregistered. | |
272 | */ | |
273 | void media_devnode_unregister(struct media_devnode *mdev) | |
274 | { | |
275 | /* Check if mdev was ever registered at all */ | |
276 | if (!media_devnode_is_registered(mdev)) | |
277 | return; | |
278 | ||
279 | mutex_lock(&media_devnode_lock); | |
280 | clear_bit(MEDIA_FLAG_REGISTERED, &mdev->flags); | |
281 | mutex_unlock(&media_devnode_lock); | |
282 | device_unregister(&mdev->dev); | |
283 | } | |
284 | ||
285 | /* | |
286 | * Initialise media for linux | |
287 | */ | |
288 | static int __init media_devnode_init(void) | |
289 | { | |
290 | int ret; | |
291 | ||
3c16b2b3 | 292 | pr_info("Linux media interface: v0.10\n"); |
cf4b9211 LP |
293 | ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES, |
294 | MEDIA_NAME); | |
295 | if (ret < 0) { | |
3c16b2b3 | 296 | pr_warn("unable to allocate major\n"); |
cf4b9211 LP |
297 | return ret; |
298 | } | |
299 | ||
300 | ret = bus_register(&media_bus_type); | |
301 | if (ret < 0) { | |
302 | unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES); | |
3c16b2b3 | 303 | pr_warn("bus_register failed\n"); |
cf4b9211 LP |
304 | return -EIO; |
305 | } | |
306 | ||
307 | return 0; | |
308 | } | |
309 | ||
310 | static void __exit media_devnode_exit(void) | |
311 | { | |
312 | bus_unregister(&media_bus_type); | |
313 | unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES); | |
314 | } | |
315 | ||
ff732d28 | 316 | subsys_initcall(media_devnode_init); |
cf4b9211 LP |
317 | module_exit(media_devnode_exit) |
318 | ||
319 | MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>"); | |
320 | MODULE_DESCRIPTION("Device node registration for media drivers"); | |
321 | MODULE_LICENSE("GPL"); |