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 lock_kernel(); 38 down_read(&minor_rwsem); 39 c = usb_minors[minor]; 40 41 if (!c || !(new_fops = fops_get(c))) 42 goto done; 43 44 old_fops = file->f_op; 45 file->f_op = 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 if (err) { 50 fops_put(file->f_op); 51 file->f_op = fops_get(old_fops); 52 } 53 fops_put(old_fops); 54 done: 55 up_read(&minor_rwsem); 56 unlock_kernel(); 57 return err; 58 } 59 60 static const struct file_operations usb_fops = { 61 .owner = THIS_MODULE, 62 .open = usb_open, 63 }; 64 65 static struct usb_class { 66 struct kref kref; 67 struct class *class; 68 } *usb_class; 69 70 static int init_usb_class(void) 71 { 72 int result = 0; 73 74 if (usb_class != NULL) { 75 kref_get(&usb_class->kref); 76 goto exit; 77 } 78 79 usb_class = kmalloc(sizeof(*usb_class), GFP_KERNEL); 80 if (!usb_class) { 81 result = -ENOMEM; 82 goto exit; 83 } 84 85 kref_init(&usb_class->kref); 86 usb_class->class = class_create(THIS_MODULE, "usb"); 87 if (IS_ERR(usb_class->class)) { 88 result = IS_ERR(usb_class->class); 89 printk(KERN_ERR "class_create failed for usb devices\n"); 90 kfree(usb_class); 91 usb_class = NULL; 92 } 93 94 exit: 95 return result; 96 } 97 98 static void release_usb_class(struct kref *kref) 99 { 100 /* Ok, we cheat as we know we only have one usb_class */ 101 class_destroy(usb_class->class); 102 kfree(usb_class); 103 usb_class = NULL; 104 } 105 106 static void destroy_usb_class(void) 107 { 108 if (usb_class) 109 kref_put(&usb_class->kref, release_usb_class); 110 } 111 112 int usb_major_init(void) 113 { 114 int error; 115 116 error = register_chrdev(USB_MAJOR, "usb", &usb_fops); 117 if (error) 118 printk(KERN_ERR "Unable to get major %d for usb devices\n", 119 USB_MAJOR); 120 121 return error; 122 } 123 124 void usb_major_cleanup(void) 125 { 126 unregister_chrdev(USB_MAJOR, "usb"); 127 } 128 129 /** 130 * usb_register_dev - register a USB device, and ask for a minor number 131 * @intf: pointer to the usb_interface that is being registered 132 * @class_driver: pointer to the usb_class_driver for this device 133 * 134 * This should be called by all USB drivers that use the USB major number. 135 * If CONFIG_USB_DYNAMIC_MINORS is enabled, the minor number will be 136 * dynamically allocated out of the list of available ones. If it is not 137 * enabled, the minor number will be based on the next available free minor, 138 * starting at the class_driver->minor_base. 139 * 140 * This function also creates a usb class device in the sysfs tree. 141 * 142 * usb_deregister_dev() must be called when the driver is done with 143 * the minor numbers given out by this function. 144 * 145 * Returns -EINVAL if something bad happens with trying to register a 146 * device, and 0 on success. 147 */ 148 int usb_register_dev(struct usb_interface *intf, 149 struct usb_class_driver *class_driver) 150 { 151 int retval = -EINVAL; 152 int minor_base = class_driver->minor_base; 153 int minor = 0; 154 char name[20]; 155 char *temp; 156 157 #ifdef CONFIG_USB_DYNAMIC_MINORS 158 /* 159 * We don't care what the device tries to start at, we want to start 160 * at zero to pack the devices into the smallest available space with 161 * no holes in the minor range. 162 */ 163 minor_base = 0; 164 #endif 165 intf->minor = -1; 166 167 dbg ("looking for a minor, starting at %d", minor_base); 168 169 if (class_driver->fops == NULL) 170 goto exit; 171 172 down_write(&minor_rwsem); 173 for (minor = minor_base; minor < MAX_USB_MINORS; ++minor) { 174 if (usb_minors[minor]) 175 continue; 176 177 usb_minors[minor] = class_driver->fops; 178 179 retval = 0; 180 break; 181 } 182 up_write(&minor_rwsem); 183 184 if (retval) 185 goto exit; 186 187 retval = init_usb_class(); 188 if (retval) 189 goto exit; 190 191 intf->minor = minor; 192 193 /* create a usb class device for this usb interface */ 194 snprintf(name, sizeof(name), class_driver->name, minor - minor_base); 195 temp = strrchr(name, '/'); 196 if (temp && (temp[1] != '\0')) 197 ++temp; 198 else 199 temp = name; 200 intf->usb_dev = device_create(usb_class->class, &intf->dev, 201 MKDEV(USB_MAJOR, minor), NULL, 202 "%s", temp); 203 if (IS_ERR(intf->usb_dev)) { 204 down_write(&minor_rwsem); 205 usb_minors[intf->minor] = NULL; 206 up_write(&minor_rwsem); 207 retval = PTR_ERR(intf->usb_dev); 208 } 209 exit: 210 return retval; 211 } 212 EXPORT_SYMBOL_GPL(usb_register_dev); 213 214 /** 215 * usb_deregister_dev - deregister a USB device's dynamic minor. 216 * @intf: pointer to the usb_interface that is being deregistered 217 * @class_driver: pointer to the usb_class_driver for this device 218 * 219 * Used in conjunction with usb_register_dev(). This function is called 220 * when the USB driver is finished with the minor numbers gotten from a 221 * call to usb_register_dev() (usually when the device is disconnected 222 * from the system.) 223 * 224 * This function also removes the usb class device from the sysfs tree. 225 * 226 * This should be called by all drivers that use the USB major number. 227 */ 228 void usb_deregister_dev(struct usb_interface *intf, 229 struct usb_class_driver *class_driver) 230 { 231 int minor_base = class_driver->minor_base; 232 char name[20]; 233 234 #ifdef CONFIG_USB_DYNAMIC_MINORS 235 minor_base = 0; 236 #endif 237 238 if (intf->minor == -1) 239 return; 240 241 dbg ("removing %d minor", intf->minor); 242 243 down_write(&minor_rwsem); 244 usb_minors[intf->minor] = NULL; 245 up_write(&minor_rwsem); 246 247 snprintf(name, sizeof(name), class_driver->name, intf->minor - minor_base); 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