1 // SPDX-License-Identifier: GPL-2.0
3 * drivers/usb/core/file.c
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,
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
17 * Released under the GPLv2 only.
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>
29 #define MAX_USB_MINORS 256
30 static const struct file_operations *usb_minors[MAX_USB_MINORS];
31 static DECLARE_RWSEM(minor_rwsem);
33 static int usb_open(struct inode *inode, struct file *file)
36 const struct file_operations *new_fops;
38 down_read(&minor_rwsem);
39 new_fops = fops_get(usb_minors[iminor(inode)]);
44 replace_fops(file, new_fops);
45 /* Curiouser and curiouser... NULL ->open() as "no device" ? */
47 err = file->f_op->open(inode, file);
49 up_read(&minor_rwsem);
53 static const struct file_operations usb_fops = {
56 .llseek = noop_llseek,
59 static char *usb_devnode(const struct device *dev, umode_t *mode)
61 struct usb_class_driver *drv;
63 drv = dev_get_drvdata(dev);
64 if (!drv || !drv->devnode)
66 return drv->devnode(dev, mode);
69 const struct class usbmisc_class = {
71 .devnode = usb_devnode,
74 int usb_major_init(void)
78 error = register_chrdev(USB_MAJOR, "usb", &usb_fops);
80 printk(KERN_ERR "Unable to get major %d for usb devices\n",
86 void usb_major_cleanup(void)
88 unregister_chrdev(USB_MAJOR, "usb");
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
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.
102 * This function also creates a usb class device in the sysfs tree.
104 * usb_deregister_dev() must be called when the driver is done with
105 * the minor numbers given out by this function.
107 * Return: -EINVAL if something bad happens with trying to register a
108 * device, and 0 on success.
110 int usb_register_dev(struct usb_interface *intf,
111 struct usb_class_driver *class_driver)
114 int minor_base = class_driver->minor_base;
118 #ifdef CONFIG_USB_DYNAMIC_MINORS
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.
127 if (class_driver->fops == NULL)
129 if (intf->minor >= 0)
132 dev_dbg(&intf->dev, "looking for a minor, starting at %d\n", minor_base);
134 down_write(&minor_rwsem);
135 for (minor = minor_base; minor < MAX_USB_MINORS; ++minor) {
136 if (usb_minors[minor])
139 usb_minors[minor] = class_driver->fops;
143 if (intf->minor < 0) {
144 up_write(&minor_rwsem);
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;
156 retval = PTR_ERR(intf->usb_dev);
158 up_write(&minor_rwsem);
161 EXPORT_SYMBOL_GPL(usb_register_dev);
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
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
173 * This function also removes the usb class device from the sysfs tree.
175 * This should be called by all drivers that use the USB major number.
177 void usb_deregister_dev(struct usb_interface *intf,
178 struct usb_class_driver *class_driver)
180 if (intf->minor == -1)
183 dev_dbg(&intf->dev, "removing %d minor\n", intf->minor);
184 device_destroy(&usbmisc_class, MKDEV(USB_MAJOR, intf->minor));
186 down_write(&minor_rwsem);
187 usb_minors[intf->minor] = NULL;
188 up_write(&minor_rwsem);
190 intf->usb_dev = NULL;
193 EXPORT_SYMBOL_GPL(usb_deregister_dev);