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 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 65 static char *usb_devnode(const 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 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("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 } 104 105 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 } 112 113 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 } 119 120 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 } 131 132 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 */ 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 */ 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