1 /* 2 * drivers/usb/core/file.c 3 * 4 * (C) Copyright Linus Torvalds 1999 5 * (C) Copyright Johannes Erdfelt 1999-2001 6 * (C) Copyright Andreas Gal 1999 7 * (C) Copyright Gregory P. Smith 1999 8 * (C) Copyright Deti Fliegl 1999 (new USB architecture) 9 * (C) Copyright Randy Dunlap 2000 10 * (C) Copyright David Brownell 2000-2001 (kernel hotplug, usb_device_id, 11 * more docs, etc) 12 * (C) Copyright Yggdrasil Computing, Inc. 2000 13 * (usb_device_id matching changes by Adam J. Richter) 14 * (C) Copyright Greg Kroah-Hartman 2002-2003 15 * 16 * Released under the GPLv2 only. 17 * SPDX-License-Identifier: GPL-2.0 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 struct usb_class { 60 struct kref kref; 61 struct class *class; 62 } *usb_class; 63 64 static char *usb_devnode(struct device *dev, umode_t *mode) 65 { 66 struct usb_class_driver *drv; 67 68 drv = dev_get_drvdata(dev); 69 if (!drv || !drv->devnode) 70 return NULL; 71 return drv->devnode(dev, mode); 72 } 73 74 static int init_usb_class(void) 75 { 76 int result = 0; 77 78 if (usb_class != NULL) { 79 kref_get(&usb_class->kref); 80 goto exit; 81 } 82 83 usb_class = kmalloc(sizeof(*usb_class), GFP_KERNEL); 84 if (!usb_class) { 85 result = -ENOMEM; 86 goto exit; 87 } 88 89 kref_init(&usb_class->kref); 90 usb_class->class = class_create(THIS_MODULE, "usbmisc"); 91 if (IS_ERR(usb_class->class)) { 92 result = PTR_ERR(usb_class->class); 93 printk(KERN_ERR "class_create failed for usb devices\n"); 94 kfree(usb_class); 95 usb_class = NULL; 96 goto exit; 97 } 98 usb_class->class->devnode = usb_devnode; 99 100 exit: 101 return result; 102 } 103 104 static void release_usb_class(struct kref *kref) 105 { 106 /* Ok, we cheat as we know we only have one usb_class */ 107 class_destroy(usb_class->class); 108 kfree(usb_class); 109 usb_class = NULL; 110 } 111 112 static void destroy_usb_class(void) 113 { 114 if (usb_class) 115 kref_put(&usb_class->kref, release_usb_class); 116 } 117 118 int usb_major_init(void) 119 { 120 int error; 121 122 error = register_chrdev(USB_MAJOR, "usb", &usb_fops); 123 if (error) 124 printk(KERN_ERR "Unable to get major %d for usb devices\n", 125 USB_MAJOR); 126 127 return error; 128 } 129 130 void usb_major_cleanup(void) 131 { 132 unregister_chrdev(USB_MAJOR, "usb"); 133 } 134 135 /** 136 * usb_register_dev - register a USB device, and ask for a minor number 137 * @intf: pointer to the usb_interface that is being registered 138 * @class_driver: pointer to the usb_class_driver for this device 139 * 140 * This should be called by all USB drivers that use the USB major number. 141 * If CONFIG_USB_DYNAMIC_MINORS is enabled, the minor number will be 142 * dynamically allocated out of the list of available ones. If it is not 143 * enabled, the minor number will be based on the next available free minor, 144 * starting at the class_driver->minor_base. 145 * 146 * This function also creates a usb class device in the sysfs tree. 147 * 148 * usb_deregister_dev() must be called when the driver is done with 149 * the minor numbers given out by this function. 150 * 151 * Return: -EINVAL if something bad happens with trying to register a 152 * device, and 0 on success. 153 */ 154 int usb_register_dev(struct usb_interface *intf, 155 struct usb_class_driver *class_driver) 156 { 157 int retval; 158 int minor_base = class_driver->minor_base; 159 int minor; 160 char name[20]; 161 162 #ifdef CONFIG_USB_DYNAMIC_MINORS 163 /* 164 * We don't care what the device tries to start at, we want to start 165 * at zero to pack the devices into the smallest available space with 166 * no holes in the minor range. 167 */ 168 minor_base = 0; 169 #endif 170 171 if (class_driver->fops == NULL) 172 return -EINVAL; 173 if (intf->minor >= 0) 174 return -EADDRINUSE; 175 176 retval = init_usb_class(); 177 if (retval) 178 return retval; 179 180 dev_dbg(&intf->dev, "looking for a minor, starting at %d\n", minor_base); 181 182 down_write(&minor_rwsem); 183 for (minor = minor_base; minor < MAX_USB_MINORS; ++minor) { 184 if (usb_minors[minor]) 185 continue; 186 187 usb_minors[minor] = class_driver->fops; 188 intf->minor = minor; 189 break; 190 } 191 up_write(&minor_rwsem); 192 if (intf->minor < 0) 193 return -EXFULL; 194 195 /* create a usb class device for this usb interface */ 196 snprintf(name, sizeof(name), class_driver->name, minor - minor_base); 197 intf->usb_dev = device_create(usb_class->class, &intf->dev, 198 MKDEV(USB_MAJOR, minor), class_driver, 199 "%s", kbasename(name)); 200 if (IS_ERR(intf->usb_dev)) { 201 down_write(&minor_rwsem); 202 usb_minors[minor] = NULL; 203 intf->minor = -1; 204 up_write(&minor_rwsem); 205 retval = PTR_ERR(intf->usb_dev); 206 } 207 return retval; 208 } 209 EXPORT_SYMBOL_GPL(usb_register_dev); 210 211 /** 212 * usb_deregister_dev - deregister a USB device's dynamic minor. 213 * @intf: pointer to the usb_interface that is being deregistered 214 * @class_driver: pointer to the usb_class_driver for this device 215 * 216 * Used in conjunction with usb_register_dev(). This function is called 217 * when the USB driver is finished with the minor numbers gotten from a 218 * call to usb_register_dev() (usually when the device is disconnected 219 * from the system.) 220 * 221 * This function also removes the usb class device from the sysfs tree. 222 * 223 * This should be called by all drivers that use the USB major number. 224 */ 225 void usb_deregister_dev(struct usb_interface *intf, 226 struct usb_class_driver *class_driver) 227 { 228 if (intf->minor == -1) 229 return; 230 231 dev_dbg(&intf->dev, "removing %d minor\n", intf->minor); 232 233 down_write(&minor_rwsem); 234 usb_minors[intf->minor] = NULL; 235 up_write(&minor_rwsem); 236 237 device_destroy(usb_class->class, MKDEV(USB_MAJOR, intf->minor)); 238 intf->usb_dev = NULL; 239 intf->minor = -1; 240 destroy_usb_class(); 241 } 242 EXPORT_SYMBOL_GPL(usb_deregister_dev); 243