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#include <asm/system.h>
 44
 45#include <media/media-devnode.h>
 46
 47#define MEDIA_NUM_DEVICES	256
 48#define MEDIA_NAME		"media"
 49
 50static dev_t media_dev_t;
 51
 52/*
 53 *	Active devices
 54 */
 55static DEFINE_MUTEX(media_devnode_lock);
 56static DECLARE_BITMAP(media_devnode_nums, MEDIA_NUM_DEVICES);
 57
 58/* Called when the last user of the media device exits. */
 59static void media_devnode_release(struct device *cd)
 60{
 61	struct media_devnode *mdev = to_media_devnode(cd);
 62
 63	mutex_lock(&media_devnode_lock);
 64
 65	/* Delete the cdev on this minor as well */
 66	cdev_del(&mdev->cdev);
 67
 68	/* Mark device node number as free */
 69	clear_bit(mdev->minor, media_devnode_nums);
 70
 71	mutex_unlock(&media_devnode_lock);
 72
 73	/* Release media_devnode and perform other cleanups as needed. */
 74	if (mdev->release)
 75		mdev->release(mdev);
 76}
 77
 78static struct bus_type media_bus_type = {
 79	.name = MEDIA_NAME,
 80};
 81
 82static ssize_t media_read(struct file *filp, char __user *buf,
 83		size_t sz, loff_t *off)
 84{
 85	struct media_devnode *mdev = media_devnode_data(filp);
 86
 87	if (!mdev->fops->read)
 88		return -EINVAL;
 89	if (!media_devnode_is_registered(mdev))
 90		return -EIO;
 91	return mdev->fops->read(filp, buf, sz, off);
 92}
 93
 94static ssize_t media_write(struct file *filp, const char __user *buf,
 95		size_t sz, loff_t *off)
 96{
 97	struct media_devnode *mdev = media_devnode_data(filp);
 98
 99	if (!mdev->fops->write)
100		return -EINVAL;
101	if (!media_devnode_is_registered(mdev))
102		return -EIO;
103	return mdev->fops->write(filp, buf, sz, off);
104}
105
106static unsigned int media_poll(struct file *filp,
107			       struct poll_table_struct *poll)
108{
109	struct media_devnode *mdev = media_devnode_data(filp);
110
111	if (!media_devnode_is_registered(mdev))
112		return POLLERR | POLLHUP;
113	if (!mdev->fops->poll)
114		return DEFAULT_POLLMASK;
115	return mdev->fops->poll(filp, poll);
116}
117
118static long media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
119{
120	struct media_devnode *mdev = media_devnode_data(filp);
121
122	if (!mdev->fops->ioctl)
123		return -ENOTTY;
124
125	if (!media_devnode_is_registered(mdev))
126		return -EIO;
127
128	return mdev->fops->ioctl(filp, cmd, arg);
129}
130
131/* Override for the open function */
132static int media_open(struct inode *inode, struct file *filp)
133{
134	struct media_devnode *mdev;
135	int ret;
136
137	/* Check if the media device is available. This needs to be done with
138	 * the media_devnode_lock held to prevent an open/unregister race:
139	 * without the lock, the device could be unregistered and freed between
140	 * the media_devnode_is_registered() and get_device() calls, leading to
141	 * a crash.
142	 */
143	mutex_lock(&media_devnode_lock);
144	mdev = container_of(inode->i_cdev, struct media_devnode, cdev);
145	/* return ENXIO if the media device has been removed
146	   already or if it is not registered anymore. */
147	if (!media_devnode_is_registered(mdev)) {
148		mutex_unlock(&media_devnode_lock);
149		return -ENXIO;
150	}
151	/* and increase the device refcount */
152	get_device(&mdev->dev);
153	mutex_unlock(&media_devnode_lock);
154
155	filp->private_data = mdev;
156
157	if (mdev->fops->open) {
158		ret = mdev->fops->open(filp);
159		if (ret) {
160			put_device(&mdev->dev);
161			return ret;
162		}
163	}
164
165	return 0;
166}
167
168/* Override for the release function */
169static int media_release(struct inode *inode, struct file *filp)
170{
171	struct media_devnode *mdev = media_devnode_data(filp);
172	int ret = 0;
173
174	if (mdev->fops->release)
175		mdev->fops->release(filp);
176
177	/* decrease the refcount unconditionally since the release()
178	   return value is ignored. */
179	put_device(&mdev->dev);
180	filp->private_data = NULL;
181	return ret;
182}
183
184static const struct file_operations media_devnode_fops = {
185	.owner = THIS_MODULE,
186	.read = media_read,
187	.write = media_write,
188	.open = media_open,
189	.unlocked_ioctl = media_ioctl,
190	.release = media_release,
191	.poll = media_poll,
192	.llseek = no_llseek,
193};
194
195/**
196 * media_devnode_register - register a media device node
197 * @mdev: media device node structure we want to register
198 *
199 * The registration code assigns minor numbers and registers the new device node
200 * with the kernel. An error is returned if no free minor number can be found,
201 * or if the registration of the device node fails.
202 *
203 * Zero is returned on success.
204 *
205 * Note that if the media_devnode_register call fails, the release() callback of
206 * the media_devnode structure is *not* called, so the caller is responsible for
207 * freeing any data.
208 */
209int __must_check media_devnode_register(struct media_devnode *mdev)
210{
211	int minor;
212	int ret;
213
214	/* Part 1: Find a free minor number */
215	mutex_lock(&media_devnode_lock);
216	minor = find_next_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES, 0);
217	if (minor == MEDIA_NUM_DEVICES) {
218		mutex_unlock(&media_devnode_lock);
219		printk(KERN_ERR "could not get a free minor\n");
220		return -ENFILE;
221	}
222
223	set_bit(minor, media_devnode_nums);
224	mutex_unlock(&media_devnode_lock);
225
226	mdev->minor = minor;
227
228	/* Part 2: Initialize and register the character device */
229	cdev_init(&mdev->cdev, &media_devnode_fops);
230	mdev->cdev.owner = mdev->fops->owner;
231
232	ret = cdev_add(&mdev->cdev, MKDEV(MAJOR(media_dev_t), mdev->minor), 1);
233	if (ret < 0) {
234		printk(KERN_ERR "%s: cdev_add failed\n", __func__);
235		goto error;
236	}
237
238	/* Part 3: Register the media device */
239	mdev->dev.bus = &media_bus_type;
240	mdev->dev.devt = MKDEV(MAJOR(media_dev_t), mdev->minor);
241	mdev->dev.release = media_devnode_release;
242	if (mdev->parent)
243		mdev->dev.parent = mdev->parent;
244	dev_set_name(&mdev->dev, "media%d", mdev->minor);
245	ret = device_register(&mdev->dev);
246	if (ret < 0) {
247		printk(KERN_ERR "%s: device_register failed\n", __func__);
248		goto error;
249	}
250
251	/* Part 4: Activate this minor. The char device can now be used. */
252	set_bit(MEDIA_FLAG_REGISTERED, &mdev->flags);
253
254	return 0;
255
256error:
257	cdev_del(&mdev->cdev);
258	clear_bit(mdev->minor, media_devnode_nums);
259	return ret;
260}
261
262/**
263 * media_devnode_unregister - unregister a media device node
264 * @mdev: the device node to unregister
265 *
266 * This unregisters the passed device. Future open calls will be met with
267 * errors.
268 *
269 * This function can safely be called if the device node has never been
270 * registered or has already been unregistered.
271 */
272void media_devnode_unregister(struct media_devnode *mdev)
273{
274	/* Check if mdev was ever registered at all */
275	if (!media_devnode_is_registered(mdev))
276		return;
277
278	mutex_lock(&media_devnode_lock);
279	clear_bit(MEDIA_FLAG_REGISTERED, &mdev->flags);
280	mutex_unlock(&media_devnode_lock);
281	device_unregister(&mdev->dev);
282}
283
284/*
285 *	Initialise media for linux
286 */
287static int __init media_devnode_init(void)
288{
289	int ret;
290
291	printk(KERN_INFO "Linux media interface: v0.10\n");
292	ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES,
293				  MEDIA_NAME);
294	if (ret < 0) {
295		printk(KERN_WARNING "media: unable to allocate major\n");
296		return ret;
297	}
298
299	ret = bus_register(&media_bus_type);
300	if (ret < 0) {
301		unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
302		printk(KERN_WARNING "media: bus_register failed\n");
303		return -EIO;
304	}
305
306	return 0;
307}
308
309static void __exit media_devnode_exit(void)
310{
311	bus_unregister(&media_bus_type);
312	unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
313}
314
315module_init(media_devnode_init)
316module_exit(media_devnode_exit)
317
318MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
319MODULE_DESCRIPTION("Device node registration for media drivers");
320MODULE_LICENSE("GPL");