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 33 static 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 53 static const struct file_operations usb_fops = { 54 .owner = THIS_MODULE, 55 .open = usb_open, 56 .llseek = noop_llseek, 57 }; 58 59 static 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 69 const struct class usbmisc_class = { 70 .name = "usbmisc", 71 .devnode = usb_devnode, 72 }; 73 74 int 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 86 void 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 */ 110 int 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 } 161 EXPORT_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 */ 177 void 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 } 193 EXPORT_SYMBOL_GPL(usb_deregister_dev); 194