1// SPDX-License-Identifier: GPL-2.0
2/*
3 * drivers/usb/core/file.c
4 *
5 * (C) Copyright Linus Torvalds 1999
6 * (C) Copyright Johannes Erdfelt 1999-2001
7 * (C) Copyright Andreas Gal 1999
8 * (C) Copyright Gregory P. Smith 1999
9 * (C) Copyright Deti Fliegl 1999 (new USB architecture)
10 * (C) Copyright Randy Dunlap 2000
11 * (C) Copyright David Brownell 2000-2001 (kernel hotplug, usb_device_id,
12 *	more docs, etc)
13 * (C) Copyright Yggdrasil Computing, Inc. 2000
14 *     (usb_device_id matching changes by Adam J. Richter)
15 * (C) Copyright Greg Kroah-Hartman 2002-2003
16 *
17 * Released under the GPLv2 only.
18 */
19
20#include <linux/module.h>
21#include <linux/errno.h>
22#include <linux/rwsem.h>
23#include <linux/slab.h>
24#include <linux/string.h>
25#include <linux/usb.h>
26
27#include "usb.h"
28
29#define MAX_USB_MINORS	256
30static const struct file_operations *usb_minors[MAX_USB_MINORS];
31static DECLARE_RWSEM(minor_rwsem);
32
33static int usb_open(struct inode *inode, struct file *file)
34{
35	int err = -ENODEV;
36	const struct file_operations *new_fops;
37
38	down_read(&minor_rwsem);
39	new_fops = fops_get(usb_minors[iminor(inode)]);
40
41	if (!new_fops)
42		goto done;
43
44	replace_fops(file, new_fops);
45	/* Curiouser and curiouser... NULL ->open() as "no device" ? */
46	if (file->f_op->open)
47		err = file->f_op->open(inode, file);
48 done:
49	up_read(&minor_rwsem);
50	return err;
51}
52
53static const struct file_operations usb_fops = {
54	.owner =	THIS_MODULE,
55	.open =		usb_open,
56	.llseek =	noop_llseek,
57};
58
59static char *usb_devnode(const struct device *dev, umode_t *mode)
60{
61	struct usb_class_driver *drv;
62
63	drv = dev_get_drvdata(dev);
64	if (!drv || !drv->devnode)
65		return NULL;
66	return drv->devnode(dev, mode);
67}
68
69const struct class usbmisc_class = {
70	.name		= "usbmisc",
71	.devnode	= usb_devnode,
72};
73
74int usb_major_init(void)
75{
76	int error;
77
78	error = register_chrdev(USB_MAJOR, "usb", &usb_fops);
79	if (error)
80		printk(KERN_ERR "Unable to get major %d for usb devices\n",
81		       USB_MAJOR);
82
83	return error;
84}
85
86void usb_major_cleanup(void)
87{
88	unregister_chrdev(USB_MAJOR, "usb");
89}
90
91/**
92 * usb_register_dev - register a USB device, and ask for a minor number
93 * @intf: pointer to the usb_interface that is being registered
94 * @class_driver: pointer to the usb_class_driver for this device
95 *
96 * This should be called by all USB drivers that use the USB major number.
97 * If CONFIG_USB_DYNAMIC_MINORS is enabled, the minor number will be
98 * dynamically allocated out of the list of available ones.  If it is not
99 * enabled, the minor number will be based on the next available free minor,
100 * starting at the class_driver->minor_base.
101 *
102 * This function also creates a usb class device in the sysfs tree.
103 *
104 * usb_deregister_dev() must be called when the driver is done with
105 * the minor numbers given out by this function.
106 *
107 * Return: -EINVAL if something bad happens with trying to register a
108 * device, and 0 on success.
109 */
110int usb_register_dev(struct usb_interface *intf,
111		     struct usb_class_driver *class_driver)
112{
113	int retval = 0;
114	int minor_base = class_driver->minor_base;
115	int minor;
116	char name[20];
117
118#ifdef CONFIG_USB_DYNAMIC_MINORS
119	/*
120	 * We don't care what the device tries to start at, we want to start
121	 * at zero to pack the devices into the smallest available space with
122	 * no holes in the minor range.
123	 */
124	minor_base = 0;
125#endif
126
127	if (class_driver->fops == NULL)
128		return -EINVAL;
129	if (intf->minor >= 0)
130		return -EADDRINUSE;
131
132	dev_dbg(&intf->dev, "looking for a minor, starting at %d\n", minor_base);
133
134	down_write(&minor_rwsem);
135	for (minor = minor_base; minor < MAX_USB_MINORS; ++minor) {
136		if (usb_minors[minor])
137			continue;
138
139		usb_minors[minor] = class_driver->fops;
140		intf->minor = minor;
141		break;
142	}
143	if (intf->minor < 0) {
144		up_write(&minor_rwsem);
145		return -EXFULL;
146	}
147
148	/* create a usb class device for this usb interface */
149	snprintf(name, sizeof(name), class_driver->name, minor - minor_base);
150	intf->usb_dev = device_create(&usbmisc_class, &intf->dev,
151				      MKDEV(USB_MAJOR, minor), class_driver,
152				      "%s", kbasename(name));
153	if (IS_ERR(intf->usb_dev)) {
154		usb_minors[minor] = NULL;
155		intf->minor = -1;
156		retval = PTR_ERR(intf->usb_dev);
157	}
158	up_write(&minor_rwsem);
159	return retval;
160}
161EXPORT_SYMBOL_GPL(usb_register_dev);
162
163/**
164 * usb_deregister_dev - deregister a USB device's dynamic minor.
165 * @intf: pointer to the usb_interface that is being deregistered
166 * @class_driver: pointer to the usb_class_driver for this device
167 *
168 * Used in conjunction with usb_register_dev().  This function is called
169 * when the USB driver is finished with the minor numbers gotten from a
170 * call to usb_register_dev() (usually when the device is disconnected
171 * from the system.)
172 *
173 * This function also removes the usb class device from the sysfs tree.
174 *
175 * This should be called by all drivers that use the USB major number.
176 */
177void usb_deregister_dev(struct usb_interface *intf,
178			struct usb_class_driver *class_driver)
179{
180	if (intf->minor == -1)
181		return;
182
183	dev_dbg(&intf->dev, "removing %d minor\n", intf->minor);
184	device_destroy(&usbmisc_class, MKDEV(USB_MAJOR, intf->minor));
185
186	down_write(&minor_rwsem);
187	usb_minors[intf->minor] = NULL;
188	up_write(&minor_rwsem);
189
190	intf->usb_dev = NULL;
191	intf->minor = -1;
192}
193EXPORT_SYMBOL_GPL(usb_deregister_dev);
194