1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Media device node
  4 *
  5 * Copyright (C) 2010 Nokia Corporation
  6 *
  7 * Based on drivers/media/video/v4l2_dev.c code authored by
  8 *	Mauro Carvalho Chehab <mchehab@kernel.org> (version 2)
  9 *	Alan Cox, <alan@lxorguk.ukuu.org.uk> (version 1)
 10 *
 11 * Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
 12 *	     Sakari Ailus <sakari.ailus@iki.fi>
 13 *
 14 * --
 15 *
 16 * Generic media device node infrastructure to register and unregister
 17 * character devices using a dynamic major number and proper reference
 18 * counting.
 19 */
 20
 21#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 22
 23#include <linux/errno.h>
 24#include <linux/init.h>
 25#include <linux/module.h>
 26#include <linux/kernel.h>
 27#include <linux/kmod.h>
 28#include <linux/slab.h>
 29#include <linux/mm.h>
 30#include <linux/string.h>
 31#include <linux/types.h>
 32#include <linux/uaccess.h>
 33
 34#include <media/media-devnode.h>
 35#include <media/media-device.h>
 36
 37#define MEDIA_NUM_DEVICES	256
 38#define MEDIA_NAME		"media"
 39
 40static dev_t media_dev_t;
 41
 42/*
 43 *	Active devices
 44 */
 45static DEFINE_MUTEX(media_devnode_lock);
 46static DECLARE_BITMAP(media_devnode_nums, MEDIA_NUM_DEVICES);
 47
 48/* Called when the last user of the media device exits. */
 49static void media_devnode_release(struct device *cd)
 50{
 51	struct media_devnode *devnode = to_media_devnode(cd);
 52
 53	mutex_lock(&media_devnode_lock);
 54	/* Mark device node number as free */
 55	clear_bit(devnode->minor, media_devnode_nums);
 56	mutex_unlock(&media_devnode_lock);
 57
 58	/* Release media_devnode and perform other cleanups as needed. */
 59	if (devnode->release)
 60		devnode->release(devnode);
 61
 62	kfree(devnode);
 63	pr_debug("%s: Media Devnode Deallocated\n", __func__);
 64}
 65
 66static struct bus_type media_bus_type = {
 67	.name = MEDIA_NAME,
 68};
 69
 70static ssize_t media_read(struct file *filp, char __user *buf,
 71		size_t sz, loff_t *off)
 72{
 73	struct media_devnode *devnode = media_devnode_data(filp);
 74
 75	if (!devnode->fops->read)
 76		return -EINVAL;
 77	if (!media_devnode_is_registered(devnode))
 78		return -EIO;
 79	return devnode->fops->read(filp, buf, sz, off);
 80}
 81
 82static ssize_t media_write(struct file *filp, const char __user *buf,
 83		size_t sz, loff_t *off)
 84{
 85	struct media_devnode *devnode = media_devnode_data(filp);
 86
 87	if (!devnode->fops->write)
 88		return -EINVAL;
 89	if (!media_devnode_is_registered(devnode))
 90		return -EIO;
 91	return devnode->fops->write(filp, buf, sz, off);
 92}
 93
 94static __poll_t media_poll(struct file *filp,
 95			       struct poll_table_struct *poll)
 96{
 97	struct media_devnode *devnode = media_devnode_data(filp);
 98
 99	if (!media_devnode_is_registered(devnode))
100		return EPOLLERR | EPOLLHUP;
101	if (!devnode->fops->poll)
102		return DEFAULT_POLLMASK;
103	return devnode->fops->poll(filp, poll);
104}
105
106static long
107__media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg,
108	      long (*ioctl_func)(struct file *filp, unsigned int cmd,
109				 unsigned long arg))
110{
111	struct media_devnode *devnode = media_devnode_data(filp);
112
113	if (!ioctl_func)
114		return -ENOTTY;
115
116	if (!media_devnode_is_registered(devnode))
117		return -EIO;
118
119	return ioctl_func(filp, cmd, arg);
120}
121
122static long media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
123{
124	struct media_devnode *devnode = media_devnode_data(filp);
125
126	return __media_ioctl(filp, cmd, arg, devnode->fops->ioctl);
127}
128
129#ifdef CONFIG_COMPAT
130
131static long media_compat_ioctl(struct file *filp, unsigned int cmd,
132			       unsigned long arg)
133{
134	struct media_devnode *devnode = media_devnode_data(filp);
135
136	return __media_ioctl(filp, cmd, arg, devnode->fops->compat_ioctl);
137}
138
139#endif /* CONFIG_COMPAT */
140
141/* Override for the open function */
142static int media_open(struct inode *inode, struct file *filp)
143{
144	struct media_devnode *devnode;
145	int ret;
146
147	/* Check if the media device is available. This needs to be done with
148	 * the media_devnode_lock held to prevent an open/unregister race:
149	 * without the lock, the device could be unregistered and freed between
150	 * the media_devnode_is_registered() and get_device() calls, leading to
151	 * a crash.
152	 */
153	mutex_lock(&media_devnode_lock);
154	devnode = container_of(inode->i_cdev, struct media_devnode, cdev);
155	/* return ENXIO if the media device has been removed
156	   already or if it is not registered anymore. */
157	if (!media_devnode_is_registered(devnode)) {
158		mutex_unlock(&media_devnode_lock);
159		return -ENXIO;
160	}
161	/* and increase the device refcount */
162	get_device(&devnode->dev);
163	mutex_unlock(&media_devnode_lock);
164
165	filp->private_data = devnode;
166
167	if (devnode->fops->open) {
168		ret = devnode->fops->open(filp);
169		if (ret) {
170			put_device(&devnode->dev);
171			filp->private_data = NULL;
172			return ret;
173		}
174	}
175
176	return 0;
177}
178
179/* Override for the release function */
180static int media_release(struct inode *inode, struct file *filp)
181{
182	struct media_devnode *devnode = media_devnode_data(filp);
183
184	if (devnode->fops->release)
185		devnode->fops->release(filp);
186
187	filp->private_data = NULL;
188
189	/* decrease the refcount unconditionally since the release()
190	   return value is ignored. */
191	put_device(&devnode->dev);
192
193	pr_debug("%s: Media Release\n", __func__);
194	return 0;
195}
196
197static const struct file_operations media_devnode_fops = {
198	.owner = THIS_MODULE,
199	.read = media_read,
200	.write = media_write,
201	.open = media_open,
202	.unlocked_ioctl = media_ioctl,
203#ifdef CONFIG_COMPAT
204	.compat_ioctl = media_compat_ioctl,
205#endif /* CONFIG_COMPAT */
206	.release = media_release,
207	.poll = media_poll,
208	.llseek = no_llseek,
209};
210
211int __must_check media_devnode_register(struct media_device *mdev,
212					struct media_devnode *devnode,
213					struct module *owner)
214{
215	int minor;
216	int ret;
217
218	/* Part 1: Find a free minor number */
219	mutex_lock(&media_devnode_lock);
220	minor = find_first_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES);
221	if (minor == MEDIA_NUM_DEVICES) {
222		mutex_unlock(&media_devnode_lock);
223		pr_err("could not get a free minor\n");
224		kfree(devnode);
225		return -ENFILE;
226	}
227
228	set_bit(minor, media_devnode_nums);
229	mutex_unlock(&media_devnode_lock);
230
231	devnode->minor = minor;
232	devnode->media_dev = mdev;
233
234	/* Part 1: Initialize dev now to use dev.kobj for cdev.kobj.parent */
235	devnode->dev.bus = &media_bus_type;
236	devnode->dev.devt = MKDEV(MAJOR(media_dev_t), devnode->minor);
237	devnode->dev.release = media_devnode_release;
238	if (devnode->parent)
239		devnode->dev.parent = devnode->parent;
240	dev_set_name(&devnode->dev, "media%d", devnode->minor);
241	device_initialize(&devnode->dev);
242
243	/* Part 2: Initialize the character device */
244	cdev_init(&devnode->cdev, &media_devnode_fops);
245	devnode->cdev.owner = owner;
246	kobject_set_name(&devnode->cdev.kobj, "media%d", devnode->minor);
247
248	/* Part 3: Add the media and char device */
249	ret = cdev_device_add(&devnode->cdev, &devnode->dev);
250	if (ret < 0) {
251		pr_err("%s: cdev_device_add failed\n", __func__);
252		goto cdev_add_error;
253	}
254
255	/* Part 4: Activate this minor. The char device can now be used. */
256	set_bit(MEDIA_FLAG_REGISTERED, &devnode->flags);
257
258	return 0;
259
260cdev_add_error:
261	mutex_lock(&media_devnode_lock);
262	clear_bit(devnode->minor, media_devnode_nums);
263	devnode->media_dev = NULL;
264	mutex_unlock(&media_devnode_lock);
265
266	put_device(&devnode->dev);
267	return ret;
268}
269
270void media_devnode_unregister_prepare(struct media_devnode *devnode)
271{
272	/* Check if devnode was ever registered at all */
273	if (!media_devnode_is_registered(devnode))
274		return;
275
276	mutex_lock(&media_devnode_lock);
277	clear_bit(MEDIA_FLAG_REGISTERED, &devnode->flags);
278	mutex_unlock(&media_devnode_lock);
279}
280
281void media_devnode_unregister(struct media_devnode *devnode)
282{
283	mutex_lock(&media_devnode_lock);
284	/* Delete the cdev on this minor as well */
285	cdev_device_del(&devnode->cdev, &devnode->dev);
286	devnode->media_dev = NULL;
287	mutex_unlock(&media_devnode_lock);
288
289	put_device(&devnode->dev);
290}
291
292/*
293 *	Initialise media for linux
294 */
295static int __init media_devnode_init(void)
296{
297	int ret;
298
299	pr_info("Linux media interface: v0.10\n");
300	ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES,
301				  MEDIA_NAME);
302	if (ret < 0) {
303		pr_warn("unable to allocate major\n");
304		return ret;
305	}
306
307	ret = bus_register(&media_bus_type);
308	if (ret < 0) {
309		unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
310		pr_warn("bus_register failed\n");
311		return -EIO;
312	}
313
314	return 0;
315}
316
317static void __exit media_devnode_exit(void)
318{
319	bus_unregister(&media_bus_type);
320	unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
321}
322
323subsys_initcall(media_devnode_init);
324module_exit(media_devnode_exit)
325
326MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
327MODULE_DESCRIPTION("Device node registration for media drivers");
328MODULE_LICENSE("GPL");