4 * Copyright (C) 2010 Nokia Corporation
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)
10 * Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
11 * Sakari Ailus <sakari.ailus@iki.fi>
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.
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.
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
28 * Generic media device node infrastructure to register and unregister
29 * character devices using a dynamic major number and proper reference
33 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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>
42 #include <linux/string.h>
43 #include <linux/types.h>
44 #include <linux/uaccess.h>
46 #include <media/media-devnode.h>
48 #define MEDIA_NUM_DEVICES 256
49 #define MEDIA_NAME "media"
51 static dev_t media_dev_t
;
56 static DEFINE_MUTEX(media_devnode_lock
);
57 static DECLARE_BITMAP(media_devnode_nums
, MEDIA_NUM_DEVICES
);
59 /* Called when the last user of the media device exits. */
60 static void media_devnode_release(struct device
*cd
)
62 struct media_devnode
*mdev
= to_media_devnode(cd
);
64 mutex_lock(&media_devnode_lock
);
66 /* Delete the cdev on this minor as well */
67 cdev_del(&mdev
->cdev
);
69 /* Mark device node number as free */
70 clear_bit(mdev
->minor
, media_devnode_nums
);
72 mutex_unlock(&media_devnode_lock
);
74 /* Release media_devnode and perform other cleanups as needed. */
79 static struct bus_type media_bus_type
= {
83 static ssize_t
media_read(struct file
*filp
, char __user
*buf
,
84 size_t sz
, loff_t
*off
)
86 struct media_devnode
*mdev
= media_devnode_data(filp
);
88 if (!mdev
->fops
->read
)
90 if (!media_devnode_is_registered(mdev
))
92 return mdev
->fops
->read(filp
, buf
, sz
, off
);
95 static ssize_t
media_write(struct file
*filp
, const char __user
*buf
,
96 size_t sz
, loff_t
*off
)
98 struct media_devnode
*mdev
= media_devnode_data(filp
);
100 if (!mdev
->fops
->write
)
102 if (!media_devnode_is_registered(mdev
))
104 return mdev
->fops
->write(filp
, buf
, sz
, off
);
107 static unsigned int media_poll(struct file
*filp
,
108 struct poll_table_struct
*poll
)
110 struct media_devnode
*mdev
= media_devnode_data(filp
);
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
);
120 __media_ioctl(struct file
*filp
, unsigned int cmd
, unsigned long arg
,
121 long (*ioctl_func
)(struct file
*filp
, unsigned int cmd
,
124 struct media_devnode
*mdev
= media_devnode_data(filp
);
129 if (!media_devnode_is_registered(mdev
))
132 return ioctl_func(filp
, cmd
, arg
);
135 static long media_ioctl(struct file
*filp
, unsigned int cmd
, unsigned long arg
)
137 struct media_devnode
*mdev
= media_devnode_data(filp
);
139 return __media_ioctl(filp
, cmd
, arg
, mdev
->fops
->ioctl
);
144 static long media_compat_ioctl(struct file
*filp
, unsigned int cmd
,
147 struct media_devnode
*mdev
= media_devnode_data(filp
);
149 return __media_ioctl(filp
, cmd
, arg
, mdev
->fops
->compat_ioctl
);
152 #endif /* CONFIG_COMPAT */
154 /* Override for the open function */
155 static int media_open(struct inode
*inode
, struct file
*filp
)
157 struct media_devnode
*mdev
;
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
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
);
174 /* and increase the device refcount */
175 get_device(&mdev
->dev
);
176 mutex_unlock(&media_devnode_lock
);
178 filp
->private_data
= mdev
;
180 if (mdev
->fops
->open
) {
181 ret
= mdev
->fops
->open(filp
);
183 put_device(&mdev
->dev
);
191 /* Override for the release function */
192 static int media_release(struct inode
*inode
, struct file
*filp
)
194 struct media_devnode
*mdev
= media_devnode_data(filp
);
197 if (mdev
->fops
->release
)
198 mdev
->fops
->release(filp
);
200 /* decrease the refcount unconditionally since the release()
201 return value is ignored. */
202 put_device(&mdev
->dev
);
203 filp
->private_data
= NULL
;
207 static const struct file_operations media_devnode_fops
= {
208 .owner
= THIS_MODULE
,
210 .write
= media_write
,
212 .unlocked_ioctl
= media_ioctl
,
214 .compat_ioctl
= media_compat_ioctl
,
215 #endif /* CONFIG_COMPAT */
216 .release
= media_release
,
222 * media_devnode_register - register a media device node
223 * @mdev: media device node structure we want to register
225 * The registration code assigns minor numbers and registers the new device node
226 * with the kernel. An error is returned if no free minor number can be found,
227 * or if the registration of the device node fails.
229 * Zero is returned on success.
231 * Note that if the media_devnode_register call fails, the release() callback of
232 * the media_devnode structure is *not* called, so the caller is responsible for
235 int __must_check
media_devnode_register(struct media_devnode
*mdev
,
236 struct module
*owner
)
241 /* Part 1: Find a free minor number */
242 mutex_lock(&media_devnode_lock
);
243 minor
= find_next_zero_bit(media_devnode_nums
, MEDIA_NUM_DEVICES
, 0);
244 if (minor
== MEDIA_NUM_DEVICES
) {
245 mutex_unlock(&media_devnode_lock
);
246 pr_err("could not get a free minor\n");
250 set_bit(minor
, media_devnode_nums
);
251 mutex_unlock(&media_devnode_lock
);
255 /* Part 2: Initialize and register the character device */
256 cdev_init(&mdev
->cdev
, &media_devnode_fops
);
257 mdev
->cdev
.owner
= owner
;
259 ret
= cdev_add(&mdev
->cdev
, MKDEV(MAJOR(media_dev_t
), mdev
->minor
), 1);
261 pr_err("%s: cdev_add failed\n", __func__
);
265 /* Part 3: Register the media device */
266 mdev
->dev
.bus
= &media_bus_type
;
267 mdev
->dev
.devt
= MKDEV(MAJOR(media_dev_t
), mdev
->minor
);
268 mdev
->dev
.release
= media_devnode_release
;
270 mdev
->dev
.parent
= mdev
->parent
;
271 dev_set_name(&mdev
->dev
, "media%d", mdev
->minor
);
272 ret
= device_register(&mdev
->dev
);
274 pr_err("%s: device_register failed\n", __func__
);
278 /* Part 4: Activate this minor. The char device can now be used. */
279 set_bit(MEDIA_FLAG_REGISTERED
, &mdev
->flags
);
284 cdev_del(&mdev
->cdev
);
285 clear_bit(mdev
->minor
, media_devnode_nums
);
290 * media_devnode_unregister - unregister a media device node
291 * @mdev: the device node to unregister
293 * This unregisters the passed device. Future open calls will be met with
296 * This function can safely be called if the device node has never been
297 * registered or has already been unregistered.
299 void media_devnode_unregister(struct media_devnode
*mdev
)
301 /* Check if mdev was ever registered at all */
302 if (!media_devnode_is_registered(mdev
))
305 mutex_lock(&media_devnode_lock
);
306 clear_bit(MEDIA_FLAG_REGISTERED
, &mdev
->flags
);
307 mutex_unlock(&media_devnode_lock
);
308 device_unregister(&mdev
->dev
);
312 * Initialise media for linux
314 static int __init
media_devnode_init(void)
318 pr_info("Linux media interface: v0.10\n");
319 ret
= alloc_chrdev_region(&media_dev_t
, 0, MEDIA_NUM_DEVICES
,
322 pr_warn("unable to allocate major\n");
326 ret
= bus_register(&media_bus_type
);
328 unregister_chrdev_region(media_dev_t
, MEDIA_NUM_DEVICES
);
329 pr_warn("bus_register failed\n");
336 static void __exit
media_devnode_exit(void)
338 bus_unregister(&media_bus_type
);
339 unregister_chrdev_region(media_dev_t
, MEDIA_NUM_DEVICES
);
342 subsys_initcall(media_devnode_init
);
343 module_exit(media_devnode_exit
)
345 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
346 MODULE_DESCRIPTION("Device node registration for media drivers");
347 MODULE_LICENSE("GPL");