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@kernel.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 * --
 23 *
 24 * Generic media device node infrastructure to register and unregister
 25 * character devices using a dynamic major number and proper reference
 26 * counting.
 27 */
 28
 29#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 30
 31#include <linux/errno.h>
 32#include <linux/init.h>
 33#include <linux/module.h>
 34#include <linux/kernel.h>
 35#include <linux/kmod.h>
 36#include <linux/slab.h>
 37#include <linux/mm.h>
 38#include <linux/string.h>
 39#include <linux/types.h>
 40#include <linux/uaccess.h>
 41
 42#include <media/media-devnode.h>
 43#include <media/media-device.h>
 44
 45#define MEDIA_NUM_DEVICES	256
 46#define MEDIA_NAME		"media"
 47
 48static dev_t media_dev_t;
 49
 50/*
 51 *	Active devices
 52 */
 53static DEFINE_MUTEX(media_devnode_lock);
 54static DECLARE_BITMAP(media_devnode_nums, MEDIA_NUM_DEVICES);
 55
 56/* Called when the last user of the media device exits. */
 57static void media_devnode_release(struct device *cd)
 58{
 59	struct media_devnode *devnode = to_media_devnode(cd);
 60
 61	mutex_lock(&media_devnode_lock);
 62	/* Mark device node number as free */
 63	clear_bit(devnode->minor, media_devnode_nums);
 64	mutex_unlock(&media_devnode_lock);
 65
 66	/* Release media_devnode and perform other cleanups as needed. */
 67	if (devnode->release)
 68		devnode->release(devnode);
 69
 70	kfree(devnode);
 71	pr_debug("%s: Media Devnode Deallocated\n", __func__);
 72}
 73
 74static struct bus_type media_bus_type = {
 75	.name = MEDIA_NAME,
 76};
 77
 78static ssize_t media_read(struct file *filp, char __user *buf,
 79		size_t sz, loff_t *off)
 80{
 81	struct media_devnode *devnode = media_devnode_data(filp);
 82
 83	if (!devnode->fops->read)
 84		return -EINVAL;
 85	if (!media_devnode_is_registered(devnode))
 86		return -EIO;
 87	return devnode->fops->read(filp, buf, sz, off);
 88}
 89
 90static ssize_t media_write(struct file *filp, const char __user *buf,
 91		size_t sz, loff_t *off)
 92{
 93	struct media_devnode *devnode = media_devnode_data(filp);
 94
 95	if (!devnode->fops->write)
 96		return -EINVAL;
 97	if (!media_devnode_is_registered(devnode))
 98		return -EIO;
 99	return devnode->fops->write(filp, buf, sz, off);
100}
101
102static __poll_t media_poll(struct file *filp,
103			       struct poll_table_struct *poll)
104{
105	struct media_devnode *devnode = media_devnode_data(filp);
106
107	if (!media_devnode_is_registered(devnode))
108		return EPOLLERR | EPOLLHUP;
109	if (!devnode->fops->poll)
110		return DEFAULT_POLLMASK;
111	return devnode->fops->poll(filp, poll);
112}
113
114static long
115__media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg,
116	      long (*ioctl_func)(struct file *filp, unsigned int cmd,
117				 unsigned long arg))
118{
119	struct media_devnode *devnode = media_devnode_data(filp);
120
121	if (!ioctl_func)
122		return -ENOTTY;
123
124	if (!media_devnode_is_registered(devnode))
125		return -EIO;
126
127	return ioctl_func(filp, cmd, arg);
128}
129
130static long media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
131{
132	struct media_devnode *devnode = media_devnode_data(filp);
133
134	return __media_ioctl(filp, cmd, arg, devnode->fops->ioctl);
135}
136
137#ifdef CONFIG_COMPAT
138
139static long media_compat_ioctl(struct file *filp, unsigned int cmd,
140			       unsigned long arg)
141{
142	struct media_devnode *devnode = media_devnode_data(filp);
143
144	return __media_ioctl(filp, cmd, arg, devnode->fops->compat_ioctl);
145}
146
147#endif /* CONFIG_COMPAT */
148
149/* Override for the open function */
150static int media_open(struct inode *inode, struct file *filp)
151{
152	struct media_devnode *devnode;
153	int ret;
154
155	/* Check if the media device is available. This needs to be done with
156	 * the media_devnode_lock held to prevent an open/unregister race:
157	 * without the lock, the device could be unregistered and freed between
158	 * the media_devnode_is_registered() and get_device() calls, leading to
159	 * a crash.
160	 */
161	mutex_lock(&media_devnode_lock);
162	devnode = container_of(inode->i_cdev, struct media_devnode, cdev);
163	/* return ENXIO if the media device has been removed
164	   already or if it is not registered anymore. */
165	if (!media_devnode_is_registered(devnode)) {
166		mutex_unlock(&media_devnode_lock);
167		return -ENXIO;
168	}
169	/* and increase the device refcount */
170	get_device(&devnode->dev);
171	mutex_unlock(&media_devnode_lock);
172
173	filp->private_data = devnode;
174
175	if (devnode->fops->open) {
176		ret = devnode->fops->open(filp);
177		if (ret) {
178			put_device(&devnode->dev);
179			filp->private_data = NULL;
180			return ret;
181		}
182	}
183
184	return 0;
185}
186
187/* Override for the release function */
188static int media_release(struct inode *inode, struct file *filp)
189{
190	struct media_devnode *devnode = media_devnode_data(filp);
191
192	if (devnode->fops->release)
193		devnode->fops->release(filp);
194
195	filp->private_data = NULL;
196
197	/* decrease the refcount unconditionally since the release()
198	   return value is ignored. */
199	put_device(&devnode->dev);
200
201	pr_debug("%s: Media Release\n", __func__);
202	return 0;
203}
204
205static const struct file_operations media_devnode_fops = {
206	.owner = THIS_MODULE,
207	.read = media_read,
208	.write = media_write,
209	.open = media_open,
210	.unlocked_ioctl = media_ioctl,
211#ifdef CONFIG_COMPAT
212	.compat_ioctl = media_compat_ioctl,
213#endif /* CONFIG_COMPAT */
214	.release = media_release,
215	.poll = media_poll,
216	.llseek = no_llseek,
217};
218
219int __must_check media_devnode_register(struct media_device *mdev,
220					struct media_devnode *devnode,
221					struct module *owner)
222{
223	int minor;
224	int ret;
225
226	/* Part 1: Find a free minor number */
227	mutex_lock(&media_devnode_lock);
228	minor = find_next_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES, 0);
229	if (minor == MEDIA_NUM_DEVICES) {
230		mutex_unlock(&media_devnode_lock);
231		pr_err("could not get a free minor\n");
232		kfree(devnode);
233		return -ENFILE;
234	}
235
236	set_bit(minor, media_devnode_nums);
237	mutex_unlock(&media_devnode_lock);
238
239	devnode->minor = minor;
240	devnode->media_dev = mdev;
241
242	/* Part 1: Initialize dev now to use dev.kobj for cdev.kobj.parent */
243	devnode->dev.bus = &media_bus_type;
244	devnode->dev.devt = MKDEV(MAJOR(media_dev_t), devnode->minor);
245	devnode->dev.release = media_devnode_release;
246	if (devnode->parent)
247		devnode->dev.parent = devnode->parent;
248	dev_set_name(&devnode->dev, "media%d", devnode->minor);
249	device_initialize(&devnode->dev);
250
251	/* Part 2: Initialize the character device */
252	cdev_init(&devnode->cdev, &media_devnode_fops);
253	devnode->cdev.owner = owner;
254
255	/* Part 3: Add the media and char device */
256	ret = cdev_device_add(&devnode->cdev, &devnode->dev);
257	if (ret < 0) {
258		pr_err("%s: cdev_device_add failed\n", __func__);
259		goto cdev_add_error;
260	}
261
262	/* Part 4: Activate this minor. The char device can now be used. */
263	set_bit(MEDIA_FLAG_REGISTERED, &devnode->flags);
264
265	return 0;
266
267cdev_add_error:
268	mutex_lock(&media_devnode_lock);
269	clear_bit(devnode->minor, media_devnode_nums);
270	devnode->media_dev = NULL;
271	mutex_unlock(&media_devnode_lock);
272
273	put_device(&devnode->dev);
274	return ret;
275}
276
277void media_devnode_unregister_prepare(struct media_devnode *devnode)
278{
279	/* Check if devnode was ever registered at all */
280	if (!media_devnode_is_registered(devnode))
281		return;
282
283	mutex_lock(&media_devnode_lock);
284	clear_bit(MEDIA_FLAG_REGISTERED, &devnode->flags);
285	mutex_unlock(&media_devnode_lock);
286}
287
288void media_devnode_unregister(struct media_devnode *devnode)
289{
290	mutex_lock(&media_devnode_lock);
291	/* Delete the cdev on this minor as well */
292	cdev_device_del(&devnode->cdev, &devnode->dev);
293	mutex_unlock(&media_devnode_lock);
294	devnode->media_dev = NULL;
295	put_device(&devnode->dev);
296}
297
298/*
299 *	Initialise media for linux
300 */
301static int __init media_devnode_init(void)
302{
303	int ret;
304
305	pr_info("Linux media interface: v0.10\n");
306	ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES,
307				  MEDIA_NAME);
308	if (ret < 0) {
309		pr_warn("unable to allocate major\n");
310		return ret;
311	}
312
313	ret = bus_register(&media_bus_type);
314	if (ret < 0) {
315		unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
316		pr_warn("bus_register failed\n");
317		return -EIO;
318	}
319
320	return 0;
321}
322
323static void __exit media_devnode_exit(void)
324{
325	bus_unregister(&media_bus_type);
326	unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
327}
328
329subsys_initcall(media_devnode_init);
330module_exit(media_devnode_exit)
331
332MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
333MODULE_DESCRIPTION("Device node registration for media drivers");
334MODULE_LICENSE("GPL");