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(sem: &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(sem: &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, name: "usb", fops: &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, name: "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(sem: &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(sem: &minor_rwsem);
145 return -EXFULL;
146 }
147
148 /* create a usb class device for this usb interface */
149 snprintf(buf: name, size: sizeof(name), fmt: class_driver->name, minor - minor_base);
150 intf->usb_dev = device_create(cls: &usbmisc_class, parent: &intf->dev,
151 MKDEV(USB_MAJOR, minor), drvdata: class_driver,
152 fmt: "%s", kbasename(path: name));
153 if (IS_ERR(ptr: intf->usb_dev)) {
154 usb_minors[minor] = NULL;
155 intf->minor = -1;
156 retval = PTR_ERR(ptr: intf->usb_dev);
157 }
158 up_write(sem: &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(cls: &usbmisc_class, MKDEV(USB_MAJOR, intf->minor));
185
186 down_write(sem: &minor_rwsem);
187 usb_minors[intf->minor] = NULL;
188 up_write(sem: &minor_rwsem);
189
190 intf->usb_dev = NULL;
191 intf->minor = -1;
192}
193EXPORT_SYMBOL_GPL(usb_deregister_dev);
194