aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/media/media-devnode.c
blob: 7acd19c881debe4de5e98e9658108489d4c98c10 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
/*
 * Media device node
 *
 * Copyright (C) 2010 Nokia Corporation
 *
 * Based on drivers/media/video/v4l2_dev.c code authored by
 *	Mauro Carvalho Chehab <mchehab@infradead.org> (version 2)
 *	Alan Cox, <alan@lxorguk.ukuu.org.uk> (version 1)
 *
 * Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
 *	     Sakari Ailus <sakari.ailus@iki.fi>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * --
 *
 * Generic media device node infrastructure to register and unregister
 * character devices using a dynamic major number and proper reference
 * counting.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/errno.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/kmod.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/uaccess.h>

#include <media/media-devnode.h>

#define MEDIA_NUM_DEVICES	256
#define MEDIA_NAME		"media"

static dev_t media_dev_t;

/*
 *	Active devices
 */
static DEFINE_MUTEX(media_devnode_lock);
static DECLARE_BITMAP(media_devnode_nums, MEDIA_NUM_DEVICES);

/* Called when the last user of the media device exits. */
static void media_devnode_release(struct device *cd)
{
	struct media_devnode *mdev = to_media_devnode(cd);

	mutex_lock(&media_devnode_lock);

	/* Delete the cdev on this minor as well */
	cdev_del(&mdev->cdev);

	/* Mark device node number as free */
	clear_bit(mdev->minor, media_devnode_nums);

	mutex_unlock(&media_devnode_lock);

	/* Release media_devnode and perform other cleanups as needed. */
	if (mdev->release)
		mdev->release(mdev);
}

static struct bus_type media_bus_type = {
	.name = MEDIA_NAME,
};

static ssize_t media_read(struct file *filp, char __user *buf,
		size_t sz, loff_t *off)
{
	struct media_devnode *mdev = media_devnode_data(filp);

	if (!mdev->fops->read)
		return -EINVAL;
	if (!media_devnode_is_registered(mdev))
		return -EIO;
	return mdev->fops->read(filp, buf, sz, off);
}

static ssize_t media_write(struct file *filp, const char __user *buf,
		size_t sz, loff_t *off)
{
	struct media_devnode *mdev = media_devnode_data(filp);

	if (!mdev->fops->write)
		return -EINVAL;
	if (!media_devnode_is_registered(mdev))
		return -EIO;
	return mdev->fops->write(filp, buf, sz, off);
}

static unsigned int media_poll(struct file *filp,
			       struct poll_table_struct *poll)
{
	struct media_devnode *mdev = media_devnode_data(filp);

	if (!media_devnode_is_registered(mdev))
		return POLLERR | POLLHUP;
	if (!mdev->fops->poll)
		return DEFAULT_POLLMASK;
	return mdev->fops->poll(filp, poll);
}

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))
{
	struct media_devnode *mdev = media_devnode_data(filp);

	if (!ioctl_func)
		return -ENOTTY;

	if (!media_devnode_is_registered(mdev))
		return -EIO;

	return ioctl_func(filp, cmd, arg);
}

static long media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
	struct media_devnode *mdev = media_devnode_data(filp);

	return __media_ioctl(filp, cmd, arg, mdev->fops->ioctl);
}

#ifdef CONFIG_COMPAT

static long media_compat_ioctl(struct file *filp, unsigned int cmd,
			       unsigned long arg)
{
	struct media_devnode *mdev = media_devnode_data(filp);

	return __media_ioctl(filp, cmd, arg, mdev->fops->compat_ioctl);
}

#endif /* CONFIG_COMPAT */

/* Override for the open function */
static int media_open(struct inode *inode, struct file *filp)
{
	struct media_devnode *mdev;
	int ret;

	/* Check if the media device is available. This needs to be done with
	 * the media_devnode_lock held to prevent an open/unregister race:
	 * without the lock, the device could be unregistered and freed between
	 * the media_devnode_is_registered() and get_device() calls, leading to
	 * a crash.
	 */
	mutex_lock(&media_devnode_lock);
	mdev = container_of(inode->i_cdev, struct media_devnode, cdev);
	/* return ENXIO if the media device has been removed
	   already or if it is not registered anymore. */
	if (!media_devnode_is_registered(mdev)) {
		mutex_unlock(&media_devnode_lock);
		return -ENXIO;
	}
	/* and increase the device refcount */
	get_device(&mdev->dev);
	mutex_unlock(&media_devnode_lock);

	filp->private_data = mdev;

	if (mdev->fops->open) {
		ret = mdev->fops->open(filp);
		if (ret) {
			put_device(&mdev->dev);
			return ret;
		}
	}

	return 0;
}

/* Override for the release function */
static int media_release(struct inode *inode, struct file *filp)
{
	struct media_devnode *mdev = media_devnode_data(filp);
	int ret = 0;

	if (mdev->fops->release)
		mdev->fops->release(filp);

	/* decrease the refcount unconditionally since the release()
	   return value is ignored. */
	put_device(&mdev->dev);
	filp->private_data = NULL;
	return ret;
}

static const struct file_operations media_devnode_fops = {
	.owner = THIS_MODULE,
	.read = media_read,
	.write = media_write,
	.open = media_open,
	.unlocked_ioctl = media_ioctl,
#ifdef CONFIG_COMPAT
	.compat_ioctl = media_compat_ioctl,
#endif /* CONFIG_COMPAT */
	.release = media_release,
	.poll = media_poll,
	.llseek = no_llseek,
};

/**
 * media_devnode_register - register a media device node
 * @mdev: media device node structure we want to register
 *
 * The registration code assigns minor numbers and registers the new device node
 * with the kernel. An error is returned if no free minor number can be found,
 * or if the registration of the device node fails.
 *
 * Zero is returned on success.
 *
 * Note that if the media_devnode_register call fails, the release() callback of
 * the media_devnode structure is *not* called, so the caller is responsible for
 * freeing any data.
 */
int __must_check media_devnode_register(struct media_devnode *mdev,
					struct module *owner)
{
	int minor;
	int ret;

	/* Part 1: Find a free minor number */
	mutex_lock(&media_devnode_lock);
	minor = find_next_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES, 0);
	if (minor == MEDIA_NUM_DEVICES) {
		mutex_unlock(&media_devnode_lock);
		pr_err("could not get a free minor\n");
		return -ENFILE;
	}

	set_bit(minor, media_devnode_nums);
	mutex_unlock(&media_devnode_lock);

	mdev->minor = minor;

	/* Part 2: Initialize and register the character device */
	cdev_init(&mdev->cdev, &media_devnode_fops);
	mdev->cdev.owner = owner;

	ret = cdev_add(&mdev->cdev, MKDEV(MAJOR(media_dev_t), mdev->minor), 1);
	if (ret < 0) {
		pr_err("%s: cdev_add failed\n", __func__);
		goto error;
	}

	/* Part 3: Register the media device */
	mdev->dev.bus = &media_bus_type;
	mdev->dev.devt = MKDEV(MAJOR(media_dev_t), mdev->minor);
	mdev->dev.release = media_devnode_release;
	if (mdev->parent)
		mdev->dev.parent = mdev->parent;
	dev_set_name(&mdev->dev, "media%d", mdev->minor);
	ret = device_register(&mdev->dev);
	if (ret < 0) {
		pr_err("%s: device_register failed\n", __func__);
		goto error;
	}

	/* Part 4: Activate this minor. The char device can now be used. */
	set_bit(MEDIA_FLAG_REGISTERED, &mdev->flags);

	return 0;

error:
	cdev_del(&mdev->cdev);
	clear_bit(mdev->minor, media_devnode_nums);
	return ret;
}

/**
 * media_devnode_unregister - unregister a media device node
 * @mdev: the device node to unregister
 *
 * This unregisters the passed device. Future open calls will be met with
 * errors.
 *
 * This function can safely be called if the device node has never been
 * registered or has already been unregistered.
 */
void media_devnode_unregister(struct media_devnode *mdev)
{
	/* Check if mdev was ever registered at all */
	if (!media_devnode_is_registered(mdev))
		return;

	mutex_lock(&media_devnode_lock);
	clear_bit(MEDIA_FLAG_REGISTERED, &mdev->flags);
	mutex_unlock(&media_devnode_lock);
	device_unregister(&mdev->dev);
}

/*
 *	Initialise media for linux
 */
static int __init media_devnode_init(void)
{
	int ret;

	pr_info("Linux media interface: v0.10\n");
	ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES,
				  MEDIA_NAME);
	if (ret < 0) {
		pr_warn("unable to allocate major\n");
		return ret;
	}

	ret = bus_register(&media_bus_type);
	if (ret < 0) {
		unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
		pr_warn("bus_register failed\n");
		return -EIO;
	}

	return 0;
}

static void __exit media_devnode_exit(void)
{
	bus_unregister(&media_bus_type);
	unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
}

subsys_initcall(media_devnode_init);
module_exit(media_devnode_exit)

MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
MODULE_DESCRIPTION("Device node registration for media drivers");
MODULE_LICENSE("GPL");

Privacy Policy