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/smp_lock.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 }; 62 63 static struct usb_class { 64 struct kref kref; 65 struct class *class; 66 } *usb_class; 67 68 static char *usb_devnode(struct device *dev, mode_t *mode) 69 { 70 struct usb_class_driver *drv; 71 72 drv = dev_get_drvdata(dev); 73 if (!drv || !drv->devnode) 74 return NULL; 75 return drv->devnode(dev, mode); 76 } 77 78 static int init_usb_class(void) 79 { 80 int result = 0; 81 82 if (usb_class != NULL) { 83 kref_get(&usb_class->kref); 84 goto exit; 85 } 86 87 usb_class = kmalloc(sizeof(*usb_class), GFP_KERNEL); 88 if (!usb_class) { 89 result = -ENOMEM; 90 goto exit; 91 } 92 93 kref_init(&usb_class->kref); 94 usb_class->class = class_create(THIS_MODULE, "usb"); 95 if (IS_ERR(usb_class->class)) { 96 result = IS_ERR(usb_class->class); 97 printk(KERN_ERR "class_create failed for usb devices\n"); 98 kfree(usb_class); 99 usb_class = NULL; 100 goto exit; 101 } 102 usb_class->class->devnode = usb_devnode; 103 104 exit: 105 return result; 106 } 107 108 static void release_usb_class(struct kref *kref) 109 { 110 /* Ok, we cheat as we know we only have one usb_class */ 111 class_destroy(usb_class->class); 112 kfree(usb_class); 113 usb_class = NULL; 114 } 115 116 static void destroy_usb_class(void) 117 { 118 if (usb_class) 119 kref_put(&usb_class->kref, release_usb_class); 120 } 121 122 int usb_major_init(void) 123 { 124 int error; 125 126 error = register_chrdev(USB_MAJOR, "usb", &usb_fops); 127 if (error) 128 printk(KERN_ERR "Unable to get major %d for usb devices\n", 129 USB_MAJOR); 130 131 return error; 132 } 133 134 void usb_major_cleanup(void) 135 { 136 unregister_chrdev(USB_MAJOR, "usb"); 137 } 138 139 /** 140 * usb_register_dev - register a USB device, and ask for a minor number 141 * @intf: pointer to the usb_interface that is being registered 142 * @class_driver: pointer to the usb_class_driver for this device 143 * 144 * This should be called by all USB drivers that use the USB major number. 145 * If CONFIG_USB_DYNAMIC_MINORS is enabled, the minor number will be 146 * dynamically allocated out of the list of available ones. If it is not 147 * enabled, the minor number will be based on the next available free minor, 148 * starting at the class_driver->minor_base. 149 * 150 * This function also creates a usb class device in the sysfs tree. 151 * 152 * usb_deregister_dev() must be called when the driver is done with 153 * the minor numbers given out by this function. 154 * 155 * Returns -EINVAL if something bad happens with trying to register a 156 * device, and 0 on success. 157 */ 158 int usb_register_dev(struct usb_interface *intf, 159 struct usb_class_driver *class_driver) 160 { 161 int retval = -EINVAL; 162 int minor_base = class_driver->minor_base; 163 int minor = 0; 164 char name[20]; 165 char *temp; 166 167 #ifdef CONFIG_USB_DYNAMIC_MINORS 168 /* 169 * We don't care what the device tries to start at, we want to start 170 * at zero to pack the devices into the smallest available space with 171 * no holes in the minor range. 172 */ 173 minor_base = 0; 174 #endif 175 intf->minor = -1; 176 177 dbg ("looking for a minor, starting at %d", minor_base); 178 179 if (class_driver->fops == NULL) 180 goto exit; 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; 188 189 retval = 0; 190 break; 191 } 192 up_write(&minor_rwsem); 193 194 if (retval) 195 goto exit; 196 197 retval = init_usb_class(); 198 if (retval) 199 goto exit; 200 201 intf->minor = minor; 202 203 /* create a usb class device for this usb interface */ 204 snprintf(name, sizeof(name), class_driver->name, minor - minor_base); 205 temp = strrchr(name, '/'); 206 if (temp && (temp[1] != '\0')) 207 ++temp; 208 else 209 temp = name; 210 intf->usb_dev = device_create(usb_class->class, &intf->dev, 211 MKDEV(USB_MAJOR, minor), class_driver, 212 "%s", temp); 213 if (IS_ERR(intf->usb_dev)) { 214 down_write(&minor_rwsem); 215 usb_minors[intf->minor] = NULL; 216 up_write(&minor_rwsem); 217 retval = PTR_ERR(intf->usb_dev); 218 } 219 exit: 220 return retval; 221 } 222 EXPORT_SYMBOL_GPL(usb_register_dev); 223 224 /** 225 * usb_deregister_dev - deregister a USB device's dynamic minor. 226 * @intf: pointer to the usb_interface that is being deregistered 227 * @class_driver: pointer to the usb_class_driver for this device 228 * 229 * Used in conjunction with usb_register_dev(). This function is called 230 * when the USB driver is finished with the minor numbers gotten from a 231 * call to usb_register_dev() (usually when the device is disconnected 232 * from the system.) 233 * 234 * This function also removes the usb class device from the sysfs tree. 235 * 236 * This should be called by all drivers that use the USB major number. 237 */ 238 void usb_deregister_dev(struct usb_interface *intf, 239 struct usb_class_driver *class_driver) 240 { 241 int minor_base = class_driver->minor_base; 242 char name[20]; 243 244 #ifdef CONFIG_USB_DYNAMIC_MINORS 245 minor_base = 0; 246 #endif 247 248 if (intf->minor == -1) 249 return; 250 251 dbg ("removing %d minor", intf->minor); 252 253 down_write(&minor_rwsem); 254 usb_minors[intf->minor] = NULL; 255 up_write(&minor_rwsem); 256 257 snprintf(name, sizeof(name), class_driver->name, intf->minor - minor_base); 258 device_destroy(usb_class->class, MKDEV(USB_MAJOR, intf->minor)); 259 intf->usb_dev = NULL; 260 intf->minor = -1; 261 destroy_usb_class(); 262 } 263 EXPORT_SYMBOL_GPL(usb_deregister_dev); 264