1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Media device node
4 *
5 * Copyright (C) 2010 Nokia Corporation
6 *
7 * Based on drivers/media/video/v4l2_dev.c code authored by
8 * Mauro Carvalho Chehab <mchehab@kernel.org> (version 2)
9 * Alan Cox, <alan@lxorguk.ukuu.org.uk> (version 1)
10 *
11 * Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
12 * Sakari Ailus <sakari.ailus@iki.fi>
13 *
14 * --
15 *
16 * Generic media device node infrastructure to register and unregister
17 * character devices using a dynamic major number and proper reference
18 * counting.
19 */
20
21 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
22
23 #include <linux/errno.h>
24 #include <linux/init.h>
25 #include <linux/module.h>
26 #include <linux/kernel.h>
27 #include <linux/kmod.h>
28 #include <linux/slab.h>
29 #include <linux/mm.h>
30 #include <linux/string.h>
31 #include <linux/types.h>
32 #include <linux/uaccess.h>
33
34 #include <media/media-devnode.h>
35 #include <media/media-device.h>
36
37 #define MEDIA_NUM_DEVICES 256
38 #define MEDIA_NAME "media"
39
40 static dev_t media_dev_t;
41
42 /*
43 * Active devices
44 */
45 static DEFINE_MUTEX(media_devnode_lock);
46 static DECLARE_BITMAP(media_devnode_nums, MEDIA_NUM_DEVICES);
47
48 /* Called when the last user of the media device exits. */
media_devnode_release(struct device * cd)49 static void media_devnode_release(struct device *cd)
50 {
51 struct media_devnode *devnode = to_media_devnode(cd);
52
53 mutex_lock(&media_devnode_lock);
54 /* Mark device node number as free */
55 clear_bit(devnode->minor, media_devnode_nums);
56 mutex_unlock(&media_devnode_lock);
57
58 /* Release media_devnode and perform other cleanups as needed. */
59 if (devnode->release)
60 devnode->release(devnode);
61
62 kfree(devnode);
63 pr_debug("%s: Media Devnode Deallocated\n", __func__);
64 }
65
66 static const struct bus_type media_bus_type = {
67 .name = MEDIA_NAME,
68 };
69
media_read(struct file * filp,char __user * buf,size_t sz,loff_t * off)70 static ssize_t media_read(struct file *filp, char __user *buf,
71 size_t sz, loff_t *off)
72 {
73 struct media_devnode *devnode = media_devnode_data(filp);
74
75 if (!devnode->fops->read)
76 return -EINVAL;
77 if (!media_devnode_is_registered(devnode))
78 return -EIO;
79 return devnode->fops->read(filp, buf, sz, off);
80 }
81
media_write(struct file * filp,const char __user * buf,size_t sz,loff_t * off)82 static ssize_t media_write(struct file *filp, const char __user *buf,
83 size_t sz, loff_t *off)
84 {
85 struct media_devnode *devnode = media_devnode_data(filp);
86
87 if (!devnode->fops->write)
88 return -EINVAL;
89 if (!media_devnode_is_registered(devnode))
90 return -EIO;
91 return devnode->fops->write(filp, buf, sz, off);
92 }
93
media_poll(struct file * filp,struct poll_table_struct * poll)94 static __poll_t media_poll(struct file *filp,
95 struct poll_table_struct *poll)
96 {
97 struct media_devnode *devnode = media_devnode_data(filp);
98
99 if (!media_devnode_is_registered(devnode))
100 return EPOLLERR | EPOLLHUP;
101 if (!devnode->fops->poll)
102 return DEFAULT_POLLMASK;
103 return devnode->fops->poll(filp, poll);
104 }
105
106 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))107 __media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg,
108 long (*ioctl_func)(struct file *filp, unsigned int cmd,
109 unsigned long arg))
110 {
111 struct media_devnode *devnode = media_devnode_data(filp);
112
113 if (!ioctl_func)
114 return -ENOTTY;
115
116 if (!media_devnode_is_registered(devnode))
117 return -EIO;
118
119 return ioctl_func(filp, cmd, arg);
120 }
121
media_ioctl(struct file * filp,unsigned int cmd,unsigned long arg)122 static long media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
123 {
124 struct media_devnode *devnode = media_devnode_data(filp);
125
126 return __media_ioctl(filp, cmd, arg, devnode->fops->ioctl);
127 }
128
129 #ifdef CONFIG_COMPAT
130
media_compat_ioctl(struct file * filp,unsigned int cmd,unsigned long arg)131 static long media_compat_ioctl(struct file *filp, unsigned int cmd,
132 unsigned long arg)
133 {
134 struct media_devnode *devnode = media_devnode_data(filp);
135
136 return __media_ioctl(filp, cmd, arg, devnode->fops->compat_ioctl);
137 }
138
139 #endif /* CONFIG_COMPAT */
140
141 /* Override for the open function */
media_open(struct inode * inode,struct file * filp)142 static int media_open(struct inode *inode, struct file *filp)
143 {
144 struct media_devnode *devnode;
145 int ret;
146
147 /* Check if the media device is available. This needs to be done with
148 * the media_devnode_lock held to prevent an open/unregister race:
149 * without the lock, the device could be unregistered and freed between
150 * the media_devnode_is_registered() and get_device() calls, leading to
151 * a crash.
152 */
153 mutex_lock(&media_devnode_lock);
154 devnode = container_of(inode->i_cdev, struct media_devnode, cdev);
155 /* return ENXIO if the media device has been removed
156 already or if it is not registered anymore. */
157 if (!media_devnode_is_registered(devnode)) {
158 mutex_unlock(&media_devnode_lock);
159 return -ENXIO;
160 }
161 /* and increase the device refcount */
162 get_device(&devnode->dev);
163 mutex_unlock(&media_devnode_lock);
164
165 filp->private_data = devnode;
166
167 if (devnode->fops->open) {
168 ret = devnode->fops->open(filp);
169 if (ret) {
170 put_device(&devnode->dev);
171 filp->private_data = NULL;
172 return ret;
173 }
174 }
175
176 return 0;
177 }
178
179 /* Override for the release function */
media_release(struct inode * inode,struct file * filp)180 static int media_release(struct inode *inode, struct file *filp)
181 {
182 struct media_devnode *devnode = media_devnode_data(filp);
183
184 if (devnode->fops->release)
185 devnode->fops->release(filp);
186
187 filp->private_data = NULL;
188
189 /* decrease the refcount unconditionally since the release()
190 return value is ignored. */
191 put_device(&devnode->dev);
192
193 return 0;
194 }
195
196 static const struct file_operations media_devnode_fops = {
197 .owner = THIS_MODULE,
198 .read = media_read,
199 .write = media_write,
200 .open = media_open,
201 .unlocked_ioctl = media_ioctl,
202 #ifdef CONFIG_COMPAT
203 .compat_ioctl = media_compat_ioctl,
204 #endif /* CONFIG_COMPAT */
205 .release = media_release,
206 .poll = media_poll,
207 };
208
media_devnode_register(struct media_device * mdev,struct media_devnode * devnode,struct module * owner)209 int __must_check media_devnode_register(struct media_device *mdev,
210 struct media_devnode *devnode,
211 struct module *owner)
212 {
213 int minor;
214 int ret;
215
216 /* Part 1: Find a free minor number */
217 mutex_lock(&media_devnode_lock);
218 minor = find_first_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES);
219 if (minor == MEDIA_NUM_DEVICES) {
220 mutex_unlock(&media_devnode_lock);
221 pr_err("could not get a free minor\n");
222 kfree(devnode);
223 return -ENFILE;
224 }
225
226 set_bit(minor, media_devnode_nums);
227 mutex_unlock(&media_devnode_lock);
228
229 devnode->minor = minor;
230 devnode->media_dev = mdev;
231
232 /* Part 1: Initialize dev now to use dev.kobj for cdev.kobj.parent */
233 devnode->dev.bus = &media_bus_type;
234 devnode->dev.devt = MKDEV(MAJOR(media_dev_t), devnode->minor);
235 devnode->dev.release = media_devnode_release;
236 if (devnode->parent)
237 devnode->dev.parent = devnode->parent;
238 dev_set_name(&devnode->dev, "media%d", devnode->minor);
239 device_initialize(&devnode->dev);
240
241 /* Part 2: Initialize the character device */
242 cdev_init(&devnode->cdev, &media_devnode_fops);
243 devnode->cdev.owner = owner;
244 kobject_set_name(&devnode->cdev.kobj, "media%d", devnode->minor);
245
246 /* Part 3: Add the media and char device */
247 set_bit(MEDIA_FLAG_REGISTERED, &devnode->flags);
248 ret = cdev_device_add(&devnode->cdev, &devnode->dev);
249 if (ret < 0) {
250 clear_bit(MEDIA_FLAG_REGISTERED, &devnode->flags);
251 pr_err("%s: cdev_device_add failed\n", __func__);
252 goto cdev_add_error;
253 }
254
255 return 0;
256
257 cdev_add_error:
258 mutex_lock(&media_devnode_lock);
259 clear_bit(devnode->minor, media_devnode_nums);
260 devnode->media_dev = NULL;
261 mutex_unlock(&media_devnode_lock);
262
263 put_device(&devnode->dev);
264 return ret;
265 }
266
media_devnode_unregister_prepare(struct media_devnode * devnode)267 void media_devnode_unregister_prepare(struct media_devnode *devnode)
268 {
269 /* Check if devnode was ever registered at all */
270 if (!media_devnode_is_registered(devnode))
271 return;
272
273 mutex_lock(&media_devnode_lock);
274 clear_bit(MEDIA_FLAG_REGISTERED, &devnode->flags);
275 mutex_unlock(&media_devnode_lock);
276 }
277
media_devnode_unregister(struct media_devnode * devnode)278 void media_devnode_unregister(struct media_devnode *devnode)
279 {
280 mutex_lock(&media_devnode_lock);
281 /* Delete the cdev on this minor as well */
282 cdev_device_del(&devnode->cdev, &devnode->dev);
283 devnode->media_dev = NULL;
284 mutex_unlock(&media_devnode_lock);
285
286 put_device(&devnode->dev);
287 }
288
289 /*
290 * Initialise media for linux
291 */
media_devnode_init(void)292 static int __init media_devnode_init(void)
293 {
294 int ret;
295
296 pr_info("Linux media interface: v0.10\n");
297 ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES,
298 MEDIA_NAME);
299 if (ret < 0) {
300 pr_warn("unable to allocate major\n");
301 return ret;
302 }
303
304 ret = bus_register(&media_bus_type);
305 if (ret < 0) {
306 unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
307 pr_warn("bus_register failed\n");
308 return -EIO;
309 }
310
311 return 0;
312 }
313
media_devnode_exit(void)314 static void __exit media_devnode_exit(void)
315 {
316 bus_unregister(&media_bus_type);
317 unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
318 }
319
320 subsys_initcall(media_devnode_init);
321 module_exit(media_devnode_exit)
322
323 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
324 MODULE_DESCRIPTION("Device node registration for media drivers");
325 MODULE_LICENSE("GPL");
326