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Laurent Pinchartcf4b9212009-12-09 08:39:56 -03001/*
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
Sachin Kamat3c16b2b2012-09-24 08:26:24 -030033#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
34
Laurent Pinchartcf4b9212009-12-09 08:39:56 -030035#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>
Laurent Pinchartcf4b9212009-12-09 08:39:56 -030045
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 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 */
133static 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 */
170static 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
185static 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 */
210int __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);
Laurent Pinchart8c89ddd2011-05-30 15:45:47 -0300217 minor = find_next_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES, 0);
Laurent Pinchartcf4b9212009-12-09 08:39:56 -0300218 if (minor == MEDIA_NUM_DEVICES) {
219 mutex_unlock(&media_devnode_lock);
Sachin Kamat3c16b2b2012-09-24 08:26:24 -0300220 pr_err("could not get a free minor\n");
Laurent Pinchartcf4b9212009-12-09 08:39:56 -0300221 return -ENFILE;
222 }
223
Laurent Pinchart8c89ddd2011-05-30 15:45:47 -0300224 set_bit(minor, media_devnode_nums);
Laurent Pinchartcf4b9212009-12-09 08:39:56 -0300225 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) {
Sachin Kamat3c16b2b2012-09-24 08:26:24 -0300235 pr_err("%s: cdev_add failed\n", __func__);
Laurent Pinchartcf4b9212009-12-09 08:39:56 -0300236 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) {
Sachin Kamat3c16b2b2012-09-24 08:26:24 -0300248 pr_err("%s: device_register failed\n", __func__);
Laurent Pinchartcf4b9212009-12-09 08:39:56 -0300249 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
257error:
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 */
273void 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 */
288static int __init media_devnode_init(void)
289{
290 int ret;
291
Sachin Kamat3c16b2b2012-09-24 08:26:24 -0300292 pr_info("Linux media interface: v0.10\n");
Laurent Pinchartcf4b9212009-12-09 08:39:56 -0300293 ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES,
294 MEDIA_NAME);
295 if (ret < 0) {
Sachin Kamat3c16b2b2012-09-24 08:26:24 -0300296 pr_warn("unable to allocate major\n");
Laurent Pinchartcf4b9212009-12-09 08:39:56 -0300297 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);
Sachin Kamat3c16b2b2012-09-24 08:26:24 -0300303 pr_warn("bus_register failed\n");
Laurent Pinchartcf4b9212009-12-09 08:39:56 -0300304 return -EIO;
305 }
306
307 return 0;
308}
309
310static 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
Laurent Pinchartff732d22012-03-12 10:02:47 -0300316subsys_initcall(media_devnode_init);
Laurent Pinchartcf4b9212009-12-09 08:39:56 -0300317module_exit(media_devnode_exit)
318
319MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
320MODULE_DESCRIPTION("Device node registration for media drivers");
321MODULE_LICENSE("GPL");