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#include <linux/errno.h>
 34#include <linux/init.h>
 35#include <linux/module.h>
 36#include <linux/kernel.h>
 37#include <linux/kmod.h>
 38#include <linux/slab.h>
 39#include <linux/mm.h>
 40#include <linux/string.h>
 41#include <linux/types.h>
 42#include <linux/uaccess.h>
 43
 44#include <media/media-devnode.h>
 45
 46#define MEDIA_NUM_DEVICES	256
 47#define MEDIA_NAME		"media"
 48
 49static dev_t media_dev_t;
 50
 51/*
 52 *	Active devices
 53 */
 54static DEFINE_MUTEX(media_devnode_lock);
 55static DECLARE_BITMAP(media_devnode_nums, MEDIA_NUM_DEVICES);
 56
 57/* Called when the last user of the media device exits. */
 58static void media_devnode_release(struct device *cd)
 59{
 60	struct media_devnode *mdev = to_media_devnode(cd);
 61
 62	mutex_lock(&media_devnode_lock);
 63
 64	/* Delete the cdev on this minor as well */
 65	cdev_del(&mdev->cdev);
 66
 67	/* Mark device node number as free */
 68	clear_bit(mdev->minor, media_devnode_nums);
 69
 70	mutex_unlock(&media_devnode_lock);
 71
 72	/* Release media_devnode and perform other cleanups as needed. */
 73	if (mdev->release)
 74		mdev->release(mdev);
 75}
 76
 77static struct bus_type media_bus_type = {
 78	.name = MEDIA_NAME,
 79};
 80
 81static ssize_t media_read(struct file *filp, char __user *buf,
 82		size_t sz, loff_t *off)
 83{
 84	struct media_devnode *mdev = media_devnode_data(filp);
 85
 86	if (!mdev->fops->read)
 87		return -EINVAL;
 88	if (!media_devnode_is_registered(mdev))
 89		return -EIO;
 90	return mdev->fops->read(filp, buf, sz, off);
 91}
 92
 93static ssize_t media_write(struct file *filp, const char __user *buf,
 94		size_t sz, loff_t *off)
 95{
 96	struct media_devnode *mdev = media_devnode_data(filp);
 97
 98	if (!mdev->fops->write)
 99		return -EINVAL;
100	if (!media_devnode_is_registered(mdev))
101		return -EIO;
102	return mdev->fops->write(filp, buf, sz, off);
103}
104
105static unsigned int media_poll(struct file *filp,
106			       struct poll_table_struct *poll)
107{
108	struct media_devnode *mdev = media_devnode_data(filp);
109
110	if (!media_devnode_is_registered(mdev))
111		return POLLERR | POLLHUP;
112	if (!mdev->fops->poll)
113		return DEFAULT_POLLMASK;
114	return mdev->fops->poll(filp, poll);
115}
116
117static long media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
118{
119	struct media_devnode *mdev = media_devnode_data(filp);
120
121	if (!mdev->fops->ioctl)
122		return -ENOTTY;
123
124	if (!media_devnode_is_registered(mdev))
125		return -EIO;
126
127	return mdev->fops->ioctl(filp, cmd, arg);
128}
129
130/* Override for the open function */
131static int media_open(struct inode *inode, struct file *filp)
132{
133	struct media_devnode *mdev;
134	int ret;
135
136	/* Check if the media device is available. This needs to be done with
137	 * the media_devnode_lock held to prevent an open/unregister race:
138	 * without the lock, the device could be unregistered and freed between
139	 * the media_devnode_is_registered() and get_device() calls, leading to
140	 * a crash.
141	 */
142	mutex_lock(&media_devnode_lock);
143	mdev = container_of(inode->i_cdev, struct media_devnode, cdev);
144	/* return ENXIO if the media device has been removed
145	   already or if it is not registered anymore. */
146	if (!media_devnode_is_registered(mdev)) {
147		mutex_unlock(&media_devnode_lock);
148		return -ENXIO;
149	}
150	/* and increase the device refcount */
151	get_device(&mdev->dev);
152	mutex_unlock(&media_devnode_lock);
153
154	filp->private_data = mdev;
155
156	if (mdev->fops->open) {
157		ret = mdev->fops->open(filp);
158		if (ret) {
159			put_device(&mdev->dev);
160			return ret;
161		}
162	}
163
164	return 0;
165}
166
167/* Override for the release function */
168static int media_release(struct inode *inode, struct file *filp)
169{
170	struct media_devnode *mdev = media_devnode_data(filp);
171	int ret = 0;
172
173	if (mdev->fops->release)
174		mdev->fops->release(filp);
175
176	/* decrease the refcount unconditionally since the release()
177	   return value is ignored. */
178	put_device(&mdev->dev);
179	filp->private_data = NULL;
180	return ret;
181}
182
183static const struct file_operations media_devnode_fops = {
184	.owner = THIS_MODULE,
185	.read = media_read,
186	.write = media_write,
187	.open = media_open,
188	.unlocked_ioctl = media_ioctl,
189	.release = media_release,
190	.poll = media_poll,
191	.llseek = no_llseek,
192};
193
194/**
195 * media_devnode_register - register a media device node
196 * @mdev: media device node structure we want to register
197 *
198 * The registration code assigns minor numbers and registers the new device node
199 * with the kernel. An error is returned if no free minor number can be found,
200 * or if the registration of the device node fails.
201 *
202 * Zero is returned on success.
203 *
204 * Note that if the media_devnode_register call fails, the release() callback of
205 * the media_devnode structure is *not* called, so the caller is responsible for
206 * freeing any data.
207 */
208int __must_check media_devnode_register(struct media_devnode *mdev)
209{
210	int minor;
211	int ret;
212
213	/* Part 1: Find a free minor number */
214	mutex_lock(&media_devnode_lock);
215	minor = find_next_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES, 0);
216	if (minor == MEDIA_NUM_DEVICES) {
217		mutex_unlock(&media_devnode_lock);
218		printk(KERN_ERR "could not get a free minor\n");
219		return -ENFILE;
220	}
221
222	set_bit(minor, media_devnode_nums);
223	mutex_unlock(&media_devnode_lock);
224
225	mdev->minor = minor;
226
227	/* Part 2: Initialize and register the character device */
228	cdev_init(&mdev->cdev, &media_devnode_fops);
229	mdev->cdev.owner = mdev->fops->owner;
230
231	ret = cdev_add(&mdev->cdev, MKDEV(MAJOR(media_dev_t), mdev->minor), 1);
232	if (ret < 0) {
233		printk(KERN_ERR "%s: cdev_add failed\n", __func__);
234		goto error;
235	}
236
237	/* Part 3: Register the media device */
238	mdev->dev.bus = &media_bus_type;
239	mdev->dev.devt = MKDEV(MAJOR(media_dev_t), mdev->minor);
240	mdev->dev.release = media_devnode_release;
241	if (mdev->parent)
242		mdev->dev.parent = mdev->parent;
243	dev_set_name(&mdev->dev, "media%d", mdev->minor);
244	ret = device_register(&mdev->dev);
245	if (ret < 0) {
246		printk(KERN_ERR "%s: device_register failed\n", __func__);
247		goto error;
248	}
249
250	/* Part 4: Activate this minor. The char device can now be used. */
251	set_bit(MEDIA_FLAG_REGISTERED, &mdev->flags);
252
253	return 0;
254
255error:
256	cdev_del(&mdev->cdev);
257	clear_bit(mdev->minor, media_devnode_nums);
258	return ret;
259}
260
261/**
262 * media_devnode_unregister - unregister a media device node
263 * @mdev: the device node to unregister
264 *
265 * This unregisters the passed device. Future open calls will be met with
266 * errors.
267 *
268 * This function can safely be called if the device node has never been
269 * registered or has already been unregistered.
270 */
271void media_devnode_unregister(struct media_devnode *mdev)
272{
273	/* Check if mdev was ever registered at all */
274	if (!media_devnode_is_registered(mdev))
275		return;
276
277	mutex_lock(&media_devnode_lock);
278	clear_bit(MEDIA_FLAG_REGISTERED, &mdev->flags);
279	mutex_unlock(&media_devnode_lock);
280	device_unregister(&mdev->dev);
281}
282
283/*
284 *	Initialise media for linux
285 */
286static int __init media_devnode_init(void)
287{
288	int ret;
289
290	printk(KERN_INFO "Linux media interface: v0.10\n");
291	ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES,
292				  MEDIA_NAME);
293	if (ret < 0) {
294		printk(KERN_WARNING "media: unable to allocate major\n");
295		return ret;
296	}
297
298	ret = bus_register(&media_bus_type);
299	if (ret < 0) {
300		unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
301		printk(KERN_WARNING "media: bus_register failed\n");
302		return -EIO;
303	}
304
305	return 0;
306}
307
308static void __exit media_devnode_exit(void)
309{
310	bus_unregister(&media_bus_type);
311	unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
312}
313
314subsys_initcall(media_devnode_init);
315module_exit(media_devnode_exit)
316
317MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
318MODULE_DESCRIPTION("Device node registration for media drivers");
319MODULE_LICENSE("GPL");