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
40static dev_t media_dev_t;
41
42/*
43 *	Active devices
44 */
45static DEFINE_MUTEX(media_devnode_lock);
46static DECLARE_BITMAP(media_devnode_nums, MEDIA_NUM_DEVICES);
47
48/* Called when the last user of the media device exits. */
49static 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
66static const struct bus_type media_bus_type = {
67	.name = MEDIA_NAME,
68};
69
70static 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
82static 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
94static __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
106static long
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
122static 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
131static 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 */
142static 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 */
180static 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
196static 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	.llseek = no_llseek,
208};
209
210int __must_check media_devnode_register(struct media_device *mdev,
211					struct media_devnode *devnode,
212					struct module *owner)
213{
214	int minor;
215	int ret;
216
217	/* Part 1: Find a free minor number */
218	mutex_lock(&media_devnode_lock);
219	minor = find_first_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES);
220	if (minor == MEDIA_NUM_DEVICES) {
221		mutex_unlock(&media_devnode_lock);
222		pr_err("could not get a free minor\n");
223		kfree(devnode);
224		return -ENFILE;
225	}
226
227	set_bit(minor, media_devnode_nums);
228	mutex_unlock(&media_devnode_lock);
229
230	devnode->minor = minor;
231	devnode->media_dev = mdev;
232
233	/* Part 1: Initialize dev now to use dev.kobj for cdev.kobj.parent */
234	devnode->dev.bus = &media_bus_type;
235	devnode->dev.devt = MKDEV(MAJOR(media_dev_t), devnode->minor);
236	devnode->dev.release = media_devnode_release;
237	if (devnode->parent)
238		devnode->dev.parent = devnode->parent;
239	dev_set_name(&devnode->dev, "media%d", devnode->minor);
240	device_initialize(&devnode->dev);
241
242	/* Part 2: Initialize the character device */
243	cdev_init(&devnode->cdev, &media_devnode_fops);
244	devnode->cdev.owner = owner;
245	kobject_set_name(&devnode->cdev.kobj, "media%d", devnode->minor);
246
247	/* Part 3: Add the media and char device */
248	ret = cdev_device_add(&devnode->cdev, &devnode->dev);
249	if (ret < 0) {
250		pr_err("%s: cdev_device_add failed\n", __func__);
251		goto cdev_add_error;
252	}
253
254	/* Part 4: Activate this minor. The char device can now be used. */
255	set_bit(MEDIA_FLAG_REGISTERED, &devnode->flags);
256
257	return 0;
258
259cdev_add_error:
260	mutex_lock(&media_devnode_lock);
261	clear_bit(devnode->minor, media_devnode_nums);
262	devnode->media_dev = NULL;
263	mutex_unlock(&media_devnode_lock);
264
265	put_device(&devnode->dev);
266	return ret;
267}
268
269void media_devnode_unregister_prepare(struct media_devnode *devnode)
270{
271	/* Check if devnode was ever registered at all */
272	if (!media_devnode_is_registered(devnode))
273		return;
274
275	mutex_lock(&media_devnode_lock);
276	clear_bit(MEDIA_FLAG_REGISTERED, &devnode->flags);
277	mutex_unlock(&media_devnode_lock);
278}
279
280void media_devnode_unregister(struct media_devnode *devnode)
281{
282	mutex_lock(&media_devnode_lock);
283	/* Delete the cdev on this minor as well */
284	cdev_device_del(&devnode->cdev, &devnode->dev);
285	devnode->media_dev = NULL;
286	mutex_unlock(&media_devnode_lock);
287
288	put_device(&devnode->dev);
289}
290
291/*
292 *	Initialise media for linux
293 */
294static int __init media_devnode_init(void)
295{
296	int ret;
297
298	pr_info("Linux media interface: v0.10\n");
299	ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES,
300				  MEDIA_NAME);
301	if (ret < 0) {
302		pr_warn("unable to allocate major\n");
303		return ret;
304	}
305
306	ret = bus_register(&media_bus_type);
307	if (ret < 0) {
308		unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
309		pr_warn("bus_register failed\n");
310		return -EIO;
311	}
312
313	return 0;
314}
315
316static void __exit media_devnode_exit(void)
317{
318	bus_unregister(&media_bus_type);
319	unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
320}
321
322subsys_initcall(media_devnode_init);
323module_exit(media_devnode_exit)
324
325MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
326MODULE_DESCRIPTION("Device node registration for media drivers");
327MODULE_LICENSE("GPL");
328