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);
119 static long media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
121 struct media_devnode *mdev = media_devnode_data(filp);
123 if (!mdev->fops->ioctl)
126 if (!media_devnode_is_registered(mdev))
129 return mdev->fops->ioctl(filp, cmd, arg);
132 /* Override for the open function */
133 static int media_open(struct inode *inode, struct file *filp)
135 struct media_devnode *mdev;
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
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);
152 /* and increase the device refcount */
153 get_device(&mdev->dev);
154 mutex_unlock(&media_devnode_lock);
156 filp->private_data = mdev;
158 if (mdev->fops->open) {
159 ret = mdev->fops->open(filp);
161 put_device(&mdev->dev);
169 /* Override for the release function */
170 static int media_release(struct inode *inode, struct file *filp)
172 struct media_devnode *mdev = media_devnode_data(filp);
175 if (mdev->fops->release)
176 mdev->fops->release(filp);
178 /* decrease the refcount unconditionally since the release()
179 return value is ignored. */
180 put_device(&mdev->dev);
181 filp->private_data = NULL;
185 static const struct file_operations media_devnode_fops = {
186 .owner = THIS_MODULE,
188 .write = media_write,
190 .unlocked_ioctl = media_ioctl,
191 .release = media_release,
197 * media_devnode_register - register a media device node
198 * @mdev: media device node structure we want to register
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.
204 * Zero is returned on success.
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
210 int __must_check media_devnode_register(struct media_devnode *mdev)
215 /* Part 1: Find a free minor number */
216 mutex_lock(&media_devnode_lock);
217 minor = find_next_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES, 0);
218 if (minor == MEDIA_NUM_DEVICES) {
219 mutex_unlock(&media_devnode_lock);
220 pr_err("could not get a free minor\n");
224 set_bit(minor, media_devnode_nums);
225 mutex_unlock(&media_devnode_lock);
229 /* Part 2: Initialize and register the character device */
230 cdev_init(&mdev->cdev, &media_devnode_fops);
231 mdev->cdev.owner = mdev->fops->owner;
233 ret = cdev_add(&mdev->cdev, MKDEV(MAJOR(media_dev_t), mdev->minor), 1);
235 pr_err("%s: cdev_add failed\n", __func__);
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;
244 mdev->dev.parent = mdev->parent;
245 dev_set_name(&mdev->dev, "media%d", mdev->minor);
246 ret = device_register(&mdev->dev);
248 pr_err("%s: device_register failed\n", __func__);
252 /* Part 4: Activate this minor. The char device can now be used. */
253 set_bit(MEDIA_FLAG_REGISTERED, &mdev->flags);
258 cdev_del(&mdev->cdev);
259 clear_bit(mdev->minor, media_devnode_nums);
264 * media_devnode_unregister - unregister a media device node
265 * @mdev: the device node to unregister
267 * This unregisters the passed device. Future open calls will be met with
270 * This function can safely be called if the device node has never been
271 * registered or has already been unregistered.
273 void media_devnode_unregister(struct media_devnode *mdev)
275 /* Check if mdev was ever registered at all */
276 if (!media_devnode_is_registered(mdev))
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);
286 * Initialise media for linux
288 static int __init media_devnode_init(void)
292 pr_info("Linux media interface: v0.10\n");
293 ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES,
296 pr_warn("unable to allocate major\n");
300 ret = bus_register(&media_bus_type);
302 unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
303 pr_warn("bus_register failed\n");
310 static void __exit media_devnode_exit(void)
312 bus_unregister(&media_bus_type);
313 unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
316 subsys_initcall(media_devnode_init);
317 module_exit(media_devnode_exit)
319 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
320 MODULE_DESCRIPTION("Device node registration for media drivers");
321 MODULE_LICENSE("GPL");