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
30 static const struct file_operations *usb_minors[MAX_USB_MINORS];
31 static DECLARE_RWSEM(minor_rwsem);
32 static DEFINE_MUTEX(init_usb_class_mutex);
33
usb_open(struct inode * inode,struct file * file)34 static int usb_open(struct inode *inode, struct file *file)
35 {
36 int err = -ENODEV;
37 const struct file_operations *new_fops;
38
39 down_read(&minor_rwsem);
40 new_fops = fops_get(usb_minors[iminor(inode)]);
41
42 if (!new_fops)
43 goto done;
44
45 replace_fops(file, new_fops);
46 /* Curiouser and curiouser... NULL ->open() as "no device" ? */
47 if (file->f_op->open)
48 err = file->f_op->open(inode, file);
49 done:
50 up_read(&minor_rwsem);
51 return err;
52 }
53
54 static const struct file_operations usb_fops = {
55 .owner = THIS_MODULE,
56 .open = usb_open,
57 .llseek = noop_llseek,
58 };
59
60 static struct usb_class {
61 struct kref kref;
62 struct class *class;
63 } *usb_class;
64
usb_devnode(struct device * dev,umode_t * mode)65 static char *usb_devnode(struct device *dev, umode_t *mode)
66 {
67 struct usb_class_driver *drv;
68
69 drv = dev_get_drvdata(dev);
70 if (!drv || !drv->devnode)
71 return NULL;
72 return drv->devnode(dev, mode);
73 }
74
init_usb_class(void)75 static int init_usb_class(void)
76 {
77 int result = 0;
78
79 if (usb_class != NULL) {
80 kref_get(&usb_class->kref);
81 goto exit;
82 }
83
84 usb_class = kmalloc(sizeof(*usb_class), GFP_KERNEL);
85 if (!usb_class) {
86 result = -ENOMEM;
87 goto exit;
88 }
89
90 kref_init(&usb_class->kref);
91 usb_class->class = class_create(THIS_MODULE, "usbmisc");
92 if (IS_ERR(usb_class->class)) {
93 result = PTR_ERR(usb_class->class);
94 printk(KERN_ERR "class_create failed for usb devices\n");
95 kfree(usb_class);
96 usb_class = NULL;
97 goto exit;
98 }
99 usb_class->class->devnode = usb_devnode;
100
101 exit:
102 return result;
103 }
104
release_usb_class(struct kref * kref)105 static void release_usb_class(struct kref *kref)
106 {
107 /* Ok, we cheat as we know we only have one usb_class */
108 class_destroy(usb_class->class);
109 kfree(usb_class);
110 usb_class = NULL;
111 }
112
destroy_usb_class(void)113 static void destroy_usb_class(void)
114 {
115 mutex_lock(&init_usb_class_mutex);
116 kref_put(&usb_class->kref, release_usb_class);
117 mutex_unlock(&init_usb_class_mutex);
118 }
119
usb_major_init(void)120 int usb_major_init(void)
121 {
122 int error;
123
124 error = register_chrdev(USB_MAJOR, "usb", &usb_fops);
125 if (error)
126 printk(KERN_ERR "Unable to get major %d for usb devices\n",
127 USB_MAJOR);
128
129 return error;
130 }
131
usb_major_cleanup(void)132 void usb_major_cleanup(void)
133 {
134 unregister_chrdev(USB_MAJOR, "usb");
135 }
136
137 /**
138 * usb_register_dev - register a USB device, and ask for a minor number
139 * @intf: pointer to the usb_interface that is being registered
140 * @class_driver: pointer to the usb_class_driver for this device
141 *
142 * This should be called by all USB drivers that use the USB major number.
143 * If CONFIG_USB_DYNAMIC_MINORS is enabled, the minor number will be
144 * dynamically allocated out of the list of available ones. If it is not
145 * enabled, the minor number will be based on the next available free minor,
146 * starting at the class_driver->minor_base.
147 *
148 * This function also creates a usb class device in the sysfs tree.
149 *
150 * usb_deregister_dev() must be called when the driver is done with
151 * the minor numbers given out by this function.
152 *
153 * Return: -EINVAL if something bad happens with trying to register a
154 * device, and 0 on success.
155 */
usb_register_dev(struct usb_interface * intf,struct usb_class_driver * class_driver)156 int usb_register_dev(struct usb_interface *intf,
157 struct usb_class_driver *class_driver)
158 {
159 int retval;
160 int minor_base = class_driver->minor_base;
161 int minor;
162 char name[20];
163
164 #ifdef CONFIG_USB_DYNAMIC_MINORS
165 /*
166 * We don't care what the device tries to start at, we want to start
167 * at zero to pack the devices into the smallest available space with
168 * no holes in the minor range.
169 */
170 minor_base = 0;
171 #endif
172
173 if (class_driver->fops == NULL)
174 return -EINVAL;
175 if (intf->minor >= 0)
176 return -EADDRINUSE;
177
178 mutex_lock(&init_usb_class_mutex);
179 retval = init_usb_class();
180 mutex_unlock(&init_usb_class_mutex);
181
182 if (retval)
183 return retval;
184
185 dev_dbg(&intf->dev, "looking for a minor, starting at %d\n", minor_base);
186
187 down_write(&minor_rwsem);
188 for (minor = minor_base; minor < MAX_USB_MINORS; ++minor) {
189 if (usb_minors[minor])
190 continue;
191
192 usb_minors[minor] = class_driver->fops;
193 intf->minor = minor;
194 break;
195 }
196 if (intf->minor < 0) {
197 up_write(&minor_rwsem);
198 return -EXFULL;
199 }
200
201 /* create a usb class device for this usb interface */
202 snprintf(name, sizeof(name), class_driver->name, minor - minor_base);
203 intf->usb_dev = device_create(usb_class->class, &intf->dev,
204 MKDEV(USB_MAJOR, minor), class_driver,
205 "%s", kbasename(name));
206 if (IS_ERR(intf->usb_dev)) {
207 usb_minors[minor] = NULL;
208 intf->minor = -1;
209 retval = PTR_ERR(intf->usb_dev);
210 }
211 up_write(&minor_rwsem);
212 return retval;
213 }
214 EXPORT_SYMBOL_GPL(usb_register_dev);
215
216 /**
217 * usb_deregister_dev - deregister a USB device's dynamic minor.
218 * @intf: pointer to the usb_interface that is being deregistered
219 * @class_driver: pointer to the usb_class_driver for this device
220 *
221 * Used in conjunction with usb_register_dev(). This function is called
222 * when the USB driver is finished with the minor numbers gotten from a
223 * call to usb_register_dev() (usually when the device is disconnected
224 * from the system.)
225 *
226 * This function also removes the usb class device from the sysfs tree.
227 *
228 * This should be called by all drivers that use the USB major number.
229 */
usb_deregister_dev(struct usb_interface * intf,struct usb_class_driver * class_driver)230 void usb_deregister_dev(struct usb_interface *intf,
231 struct usb_class_driver *class_driver)
232 {
233 if (intf->minor == -1)
234 return;
235
236 dev_dbg(&intf->dev, "removing %d minor\n", intf->minor);
237 device_destroy(usb_class->class, MKDEV(USB_MAJOR, intf->minor));
238
239 down_write(&minor_rwsem);
240 usb_minors[intf->minor] = NULL;
241 up_write(&minor_rwsem);
242
243 intf->usb_dev = NULL;
244 intf->minor = -1;
245 destroy_usb_class();
246 }
247 EXPORT_SYMBOL_GPL(usb_deregister_dev);
248