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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
34
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>
45
46#include <media/media-devnode.h>
47
48#define MEDIA_NUM_DEVICES	256
49#define MEDIA_NAME		"media"
50
51static dev_t media_dev_t;
52
53/*
54 *	Active devices
55 */
56static DEFINE_MUTEX(media_devnode_lock);
57static DECLARE_BITMAP(media_devnode_nums, MEDIA_NUM_DEVICES);
58
59/* Called when the last user of the media device exits. */
60static 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
79static struct bus_type media_bus_type = {
80	.name = MEDIA_NAME,
81};
82
83static 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
95static 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
107static 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
119static long
120__media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg,
121	      long (*ioctl_func)(struct file *filp, unsigned int cmd,
122				 unsigned long arg))
123{
124	struct media_devnode *mdev = media_devnode_data(filp);
125
126	if (!ioctl_func)
127		return -ENOTTY;
128
129	if (!media_devnode_is_registered(mdev))
130		return -EIO;
131
132	return ioctl_func(filp, cmd, arg);
133}
134
135static long media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
136{
137	struct media_devnode *mdev = media_devnode_data(filp);
138
139	return __media_ioctl(filp, cmd, arg, mdev->fops->ioctl);
140}
141
142#ifdef CONFIG_COMPAT
143
144static long media_compat_ioctl(struct file *filp, unsigned int cmd,
145			       unsigned long arg)
146{
147	struct media_devnode *mdev = media_devnode_data(filp);
148
149	return __media_ioctl(filp, cmd, arg, mdev->fops->compat_ioctl);
150}
151
152#endif /* CONFIG_COMPAT */
153
154/* Override for the open function */
155static int media_open(struct inode *inode, struct file *filp)
156{
157	struct media_devnode *mdev;
158	int ret;
159
160	/* Check if the media device is available. This needs to be done with
161	 * the media_devnode_lock held to prevent an open/unregister race:
162	 * without the lock, the device could be unregistered and freed between
163	 * the media_devnode_is_registered() and get_device() calls, leading to
164	 * a crash.
165	 */
166	mutex_lock(&media_devnode_lock);
167	mdev = container_of(inode->i_cdev, struct media_devnode, cdev);
168	/* return ENXIO if the media device has been removed
169	   already or if it is not registered anymore. */
170	if (!media_devnode_is_registered(mdev)) {
171		mutex_unlock(&media_devnode_lock);
172		return -ENXIO;
173	}
174	/* and increase the device refcount */
175	get_device(&mdev->dev);
176	mutex_unlock(&media_devnode_lock);
177
178	filp->private_data = mdev;
179
180	if (mdev->fops->open) {
181		ret = mdev->fops->open(filp);
182		if (ret) {
183			put_device(&mdev->dev);
184			return ret;
185		}
186	}
187
188	return 0;
189}
190
191/* Override for the release function */
192static int media_release(struct inode *inode, struct file *filp)
193{
194	struct media_devnode *mdev = media_devnode_data(filp);
195
196	if (mdev->fops->release)
197		mdev->fops->release(filp);
198
199	/* decrease the refcount unconditionally since the release()
200	   return value is ignored. */
201	put_device(&mdev->dev);
202	filp->private_data = NULL;
203	return 0;
204}
205
206static const struct file_operations media_devnode_fops = {
207	.owner = THIS_MODULE,
208	.read = media_read,
209	.write = media_write,
210	.open = media_open,
211	.unlocked_ioctl = media_ioctl,
212#ifdef CONFIG_COMPAT
213	.compat_ioctl = media_compat_ioctl,
214#endif /* CONFIG_COMPAT */
215	.release = media_release,
216	.poll = media_poll,
217	.llseek = no_llseek,
218};
219
220/**
221 * media_devnode_register - register a media device node
222 * @mdev: media device node structure we want to register
223 *
224 * The registration code assigns minor numbers and registers the new device node
225 * with the kernel. An error is returned if no free minor number can be found,
226 * or if the registration of the device node fails.
227 *
228 * Zero is returned on success.
229 *
230 * Note that if the media_devnode_register call fails, the release() callback of
231 * the media_devnode structure is *not* called, so the caller is responsible for
232 * freeing any data.
233 */
234int __must_check media_devnode_register(struct media_devnode *mdev,
235					struct module *owner)
236{
237	int minor;
238	int ret;
239
240	/* Part 1: Find a free minor number */
241	mutex_lock(&media_devnode_lock);
242	minor = find_next_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES, 0);
243	if (minor == MEDIA_NUM_DEVICES) {
244		mutex_unlock(&media_devnode_lock);
245		pr_err("could not get a free minor\n");
246		return -ENFILE;
247	}
248
249	set_bit(minor, media_devnode_nums);
250	mutex_unlock(&media_devnode_lock);
251
252	mdev->minor = minor;
253
254	/* Part 2: Initialize and register the character device */
255	cdev_init(&mdev->cdev, &media_devnode_fops);
256	mdev->cdev.owner = owner;
257
258	ret = cdev_add(&mdev->cdev, MKDEV(MAJOR(media_dev_t), mdev->minor), 1);
259	if (ret < 0) {
260		pr_err("%s: cdev_add failed\n", __func__);
261		goto error;
262	}
263
264	/* Part 3: Register the media device */
265	mdev->dev.bus = &media_bus_type;
266	mdev->dev.devt = MKDEV(MAJOR(media_dev_t), mdev->minor);
267	mdev->dev.release = media_devnode_release;
268	if (mdev->parent)
269		mdev->dev.parent = mdev->parent;
270	dev_set_name(&mdev->dev, "media%d", mdev->minor);
271	ret = device_register(&mdev->dev);
272	if (ret < 0) {
273		pr_err("%s: device_register failed\n", __func__);
274		goto error;
275	}
276
277	/* Part 4: Activate this minor. The char device can now be used. */
278	set_bit(MEDIA_FLAG_REGISTERED, &mdev->flags);
279
280	return 0;
281
282error:
283	cdev_del(&mdev->cdev);
284	clear_bit(mdev->minor, media_devnode_nums);
285	return ret;
286}
287
288/**
289 * media_devnode_unregister - unregister a media device node
290 * @mdev: the device node to unregister
291 *
292 * This unregisters the passed device. Future open calls will be met with
293 * errors.
294 *
295 * This function can safely be called if the device node has never been
296 * registered or has already been unregistered.
297 */
298void media_devnode_unregister(struct media_devnode *mdev)
299{
300	/* Check if mdev was ever registered at all */
301	if (!media_devnode_is_registered(mdev))
302		return;
303
304	mutex_lock(&media_devnode_lock);
305	clear_bit(MEDIA_FLAG_REGISTERED, &mdev->flags);
306	mutex_unlock(&media_devnode_lock);
307	device_unregister(&mdev->dev);
308}
309
310/*
311 *	Initialise media for linux
312 */
313static int __init media_devnode_init(void)
314{
315	int ret;
316
317	pr_info("Linux media interface: v0.10\n");
318	ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES,
319				  MEDIA_NAME);
320	if (ret < 0) {
321		pr_warn("unable to allocate major\n");
322		return ret;
323	}
324
325	ret = bus_register(&media_bus_type);
326	if (ret < 0) {
327		unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
328		pr_warn("bus_register failed\n");
329		return -EIO;
330	}
331
332	return 0;
333}
334
335static void __exit media_devnode_exit(void)
336{
337	bus_unregister(&media_bus_type);
338	unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
339}
340
341subsys_initcall(media_devnode_init);
342module_exit(media_devnode_exit)
343
344MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
345MODULE_DESCRIPTION("Device node registration for media drivers");
346MODULE_LICENSE("GPL");
347