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 */ 17 18 #include <linux/module.h> 19 #include <linux/errno.h> 20 #include <linux/rwsem.h> 21 #include <linux/slab.h> 22 #include <linux/usb.h> 23 24 #include "usb.h" 25 26 #define MAX_USB_MINORS 256 27 static const struct file_operations *usb_minors[MAX_USB_MINORS]; 28 static DECLARE_RWSEM(minor_rwsem); 29 30 static int usb_open(struct inode * inode, struct file * file) 31 { 32 int minor = iminor(inode); 33 const struct file_operations *c; 34 int err = -ENODEV; 35 const struct file_operations *old_fops, *new_fops = NULL; 36 37 down_read(&minor_rwsem); 38 c = usb_minors[minor]; 39 40 if (!c || !(new_fops = fops_get(c))) 41 goto done; 42 43 old_fops = file->f_op; 44 file->f_op = 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 if (err) { 49 fops_put(file->f_op); 50 file->f_op = fops_get(old_fops); 51 } 52 fops_put(old_fops); 53 done: 54 up_read(&minor_rwsem); 55 return err; 56 } 57 58 static const struct file_operations usb_fops = { 59 .owner = THIS_MODULE, 60 .open = usb_open, 61 .llseek = noop_llseek, 62 }; 63 64 static struct usb_class { 65 struct kref kref; 66 struct class *class; 67 } *usb_class; 68 69 static char *usb_devnode(struct device *dev, umode_t *mode) 70 { 71 struct usb_class_driver *drv; 72 73 drv = dev_get_drvdata(dev); 74 if (!drv || !drv->devnode) 75 return NULL; 76 return drv->devnode(dev, mode); 77 } 78 79 static int init_usb_class(void) 80 { 81 int result = 0; 82 83 if (usb_class != NULL) { 84 kref_get(&usb_class->kref); 85 goto exit; 86 } 87 88 usb_class = kmalloc(sizeof(*usb_class), GFP_KERNEL); 89 if (!usb_class) { 90 result = -ENOMEM; 91 goto exit; 92 } 93 94 kref_init(&usb_class->kref); 95 usb_class->class = class_create(THIS_MODULE, "usbmisc"); 96 if (IS_ERR(usb_class->class)) { 97 result = PTR_ERR(usb_class->class); 98 printk(KERN_ERR "class_create failed for usb devices\n"); 99 kfree(usb_class); 100 usb_class = NULL; 101 goto exit; 102 } 103 usb_class->class->devnode = usb_devnode; 104 105 exit: 106 return result; 107 } 108 109 static void release_usb_class(struct kref *kref) 110 { 111 /* Ok, we cheat as we know we only have one usb_class */ 112 class_destroy(usb_class->class); 113 kfree(usb_class); 114 usb_class = NULL; 115 } 116 117 static void destroy_usb_class(void) 118 { 119 if (usb_class) 120 kref_put(&usb_class->kref, release_usb_class); 121 } 122 123 int usb_major_init(void) 124 { 125 int error; 126 127 error = register_chrdev(USB_MAJOR, "usb", &usb_fops); 128 if (error) 129 printk(KERN_ERR "Unable to get major %d for usb devices\n", 130 USB_MAJOR); 131 132 return error; 133 } 134 135 void usb_major_cleanup(void) 136 { 137 unregister_chrdev(USB_MAJOR, "usb"); 138 } 139 140 /** 141 * usb_register_dev - register a USB device, and ask for a minor number 142 * @intf: pointer to the usb_interface that is being registered 143 * @class_driver: pointer to the usb_class_driver for this device 144 * 145 * This should be called by all USB drivers that use the USB major number. 146 * If CONFIG_USB_DYNAMIC_MINORS is enabled, the minor number will be 147 * dynamically allocated out of the list of available ones. If it is not 148 * enabled, the minor number will be based on the next available free minor, 149 * starting at the class_driver->minor_base. 150 * 151 * This function also creates a usb class device in the sysfs tree. 152 * 153 * usb_deregister_dev() must be called when the driver is done with 154 * the minor numbers given out by this function. 155 * 156 * Return: -EINVAL if something bad happens with trying to register a 157 * device, and 0 on success. 158 */ 159 int usb_register_dev(struct usb_interface *intf, 160 struct usb_class_driver *class_driver) 161 { 162 int retval; 163 int minor_base = class_driver->minor_base; 164 int minor; 165 char name[20]; 166 char *temp; 167 168 #ifdef CONFIG_USB_DYNAMIC_MINORS 169 /* 170 * We don't care what the device tries to start at, we want to start 171 * at zero to pack the devices into the smallest available space with 172 * no holes in the minor range. 173 */ 174 minor_base = 0; 175 #endif 176 177 if (class_driver->fops == NULL) 178 return -EINVAL; 179 if (intf->minor >= 0) 180 return -EADDRINUSE; 181 182 retval = init_usb_class(); 183 if (retval) 184 return retval; 185 186 dev_dbg(&intf->dev, "looking for a minor, starting at %d\n", minor_base); 187 188 down_write(&minor_rwsem); 189 for (minor = minor_base; minor < MAX_USB_MINORS; ++minor) { 190 if (usb_minors[minor]) 191 continue; 192 193 usb_minors[minor] = class_driver->fops; 194 intf->minor = minor; 195 break; 196 } 197 up_write(&minor_rwsem); 198 if (intf->minor < 0) 199 return -EXFULL; 200 201 /* create a usb class device for this usb interface */ 202 snprintf(name, sizeof(name), class_driver->name, minor - minor_base); 203 temp = strrchr(name, '/'); 204 if (temp && (temp[1] != '\0')) 205 ++temp; 206 else 207 temp = name; 208 intf->usb_dev = device_create(usb_class->class, &intf->dev, 209 MKDEV(USB_MAJOR, minor), class_driver, 210 "%s", temp); 211 if (IS_ERR(intf->usb_dev)) { 212 down_write(&minor_rwsem); 213 usb_minors[minor] = NULL; 214 intf->minor = -1; 215 up_write(&minor_rwsem); 216 retval = PTR_ERR(intf->usb_dev); 217 } 218 return retval; 219 } 220 EXPORT_SYMBOL_GPL(usb_register_dev); 221 222 /** 223 * usb_deregister_dev - deregister a USB device's dynamic minor. 224 * @intf: pointer to the usb_interface that is being deregistered 225 * @class_driver: pointer to the usb_class_driver for this device 226 * 227 * Used in conjunction with usb_register_dev(). This function is called 228 * when the USB driver is finished with the minor numbers gotten from a 229 * call to usb_register_dev() (usually when the device is disconnected 230 * from the system.) 231 * 232 * This function also removes the usb class device from the sysfs tree. 233 * 234 * This should be called by all drivers that use the USB major number. 235 */ 236 void usb_deregister_dev(struct usb_interface *intf, 237 struct usb_class_driver *class_driver) 238 { 239 if (intf->minor == -1) 240 return; 241 242 dev_dbg(&intf->dev, "removing %d minor\n", intf->minor); 243 244 down_write(&minor_rwsem); 245 usb_minors[intf->minor] = NULL; 246 up_write(&minor_rwsem); 247 248 device_destroy(usb_class->class, MKDEV(USB_MAJOR, intf->minor)); 249 intf->usb_dev = NULL; 250 intf->minor = -1; 251 destroy_usb_class(); 252 } 253 EXPORT_SYMBOL_GPL(usb_deregister_dev); 254