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/usb.h> 22 23 #include "usb.h" 24 25 #define MAX_USB_MINORS 256 26 static const struct file_operations *usb_minors[MAX_USB_MINORS]; 27 static DECLARE_RWSEM(minor_rwsem); 28 29 static int usb_open(struct inode * inode, struct file * file) 30 { 31 int minor = iminor(inode); 32 const struct file_operations *c; 33 int err = -ENODEV; 34 const struct file_operations *old_fops, *new_fops = NULL; 35 36 down_read(&minor_rwsem); 37 c = usb_minors[minor]; 38 39 if (!c || !(new_fops = fops_get(c))) 40 goto done; 41 42 old_fops = file->f_op; 43 file->f_op = new_fops; 44 /* Curiouser and curiouser... NULL ->open() as "no device" ? */ 45 if (file->f_op->open) 46 err = file->f_op->open(inode,file); 47 if (err) { 48 fops_put(file->f_op); 49 file->f_op = fops_get(old_fops); 50 } 51 fops_put(old_fops); 52 done: 53 up_read(&minor_rwsem); 54 return err; 55 } 56 57 static const struct file_operations usb_fops = { 58 .owner = THIS_MODULE, 59 .open = usb_open, 60 }; 61 62 static struct usb_class { 63 struct kref kref; 64 struct class *class; 65 } *usb_class; 66 67 static int init_usb_class(void) 68 { 69 int result = 0; 70 71 if (usb_class != NULL) { 72 kref_get(&usb_class->kref); 73 goto exit; 74 } 75 76 usb_class = kmalloc(sizeof(*usb_class), GFP_KERNEL); 77 if (!usb_class) { 78 result = -ENOMEM; 79 goto exit; 80 } 81 82 kref_init(&usb_class->kref); 83 usb_class->class = class_create(THIS_MODULE, "usb"); 84 if (IS_ERR(usb_class->class)) { 85 result = IS_ERR(usb_class->class); 86 err("class_create failed for usb devices"); 87 kfree(usb_class); 88 usb_class = NULL; 89 } 90 91 exit: 92 return result; 93 } 94 95 static void release_usb_class(struct kref *kref) 96 { 97 /* Ok, we cheat as we know we only have one usb_class */ 98 class_destroy(usb_class->class); 99 kfree(usb_class); 100 usb_class = NULL; 101 } 102 103 static void destroy_usb_class(void) 104 { 105 if (usb_class) 106 kref_put(&usb_class->kref, release_usb_class); 107 } 108 109 int usb_major_init(void) 110 { 111 int error; 112 113 error = register_chrdev(USB_MAJOR, "usb", &usb_fops); 114 if (error) 115 err("unable to get major %d for usb devices", USB_MAJOR); 116 117 return error; 118 } 119 120 void usb_major_cleanup(void) 121 { 122 unregister_chrdev(USB_MAJOR, "usb"); 123 } 124 125 /** 126 * usb_register_dev - register a USB device, and ask for a minor number 127 * @intf: pointer to the usb_interface that is being registered 128 * @class_driver: pointer to the usb_class_driver for this device 129 * 130 * This should be called by all USB drivers that use the USB major number. 131 * If CONFIG_USB_DYNAMIC_MINORS is enabled, the minor number will be 132 * dynamically allocated out of the list of available ones. If it is not 133 * enabled, the minor number will be based on the next available free minor, 134 * starting at the class_driver->minor_base. 135 * 136 * This function also creates a usb class device in the sysfs tree. 137 * 138 * usb_deregister_dev() must be called when the driver is done with 139 * the minor numbers given out by this function. 140 * 141 * Returns -EINVAL if something bad happens with trying to register a 142 * device, and 0 on success. 143 */ 144 int usb_register_dev(struct usb_interface *intf, 145 struct usb_class_driver *class_driver) 146 { 147 int retval = -EINVAL; 148 int minor_base = class_driver->minor_base; 149 int minor = 0; 150 char name[BUS_ID_SIZE]; 151 char *temp; 152 153 #ifdef CONFIG_USB_DYNAMIC_MINORS 154 /* 155 * We don't care what the device tries to start at, we want to start 156 * at zero to pack the devices into the smallest available space with 157 * no holes in the minor range. 158 */ 159 minor_base = 0; 160 #endif 161 intf->minor = -1; 162 163 dbg ("looking for a minor, starting at %d", minor_base); 164 165 if (class_driver->fops == NULL) 166 goto exit; 167 168 down_write(&minor_rwsem); 169 for (minor = minor_base; minor < MAX_USB_MINORS; ++minor) { 170 if (usb_minors[minor]) 171 continue; 172 173 usb_minors[minor] = class_driver->fops; 174 175 retval = 0; 176 break; 177 } 178 up_write(&minor_rwsem); 179 180 if (retval) 181 goto exit; 182 183 retval = init_usb_class(); 184 if (retval) 185 goto exit; 186 187 intf->minor = minor; 188 189 /* create a usb class device for this usb interface */ 190 snprintf(name, BUS_ID_SIZE, class_driver->name, minor - minor_base); 191 temp = strrchr(name, '/'); 192 if (temp && (temp[1] != 0x00)) 193 ++temp; 194 else 195 temp = name; 196 intf->usb_dev = device_create(usb_class->class, &intf->dev, 197 MKDEV(USB_MAJOR, minor), "%s", temp); 198 if (IS_ERR(intf->usb_dev)) { 199 down_write(&minor_rwsem); 200 usb_minors[intf->minor] = NULL; 201 up_write(&minor_rwsem); 202 retval = PTR_ERR(intf->usb_dev); 203 } 204 exit: 205 return retval; 206 } 207 EXPORT_SYMBOL(usb_register_dev); 208 209 /** 210 * usb_deregister_dev - deregister a USB device's dynamic minor. 211 * @intf: pointer to the usb_interface that is being deregistered 212 * @class_driver: pointer to the usb_class_driver for this device 213 * 214 * Used in conjunction with usb_register_dev(). This function is called 215 * when the USB driver is finished with the minor numbers gotten from a 216 * call to usb_register_dev() (usually when the device is disconnected 217 * from the system.) 218 * 219 * This function also removes the usb class device from the sysfs tree. 220 * 221 * This should be called by all drivers that use the USB major number. 222 */ 223 void usb_deregister_dev(struct usb_interface *intf, 224 struct usb_class_driver *class_driver) 225 { 226 int minor_base = class_driver->minor_base; 227 char name[BUS_ID_SIZE]; 228 229 #ifdef CONFIG_USB_DYNAMIC_MINORS 230 minor_base = 0; 231 #endif 232 233 if (intf->minor == -1) 234 return; 235 236 dbg ("removing %d minor", intf->minor); 237 238 down_write(&minor_rwsem); 239 usb_minors[intf->minor] = NULL; 240 up_write(&minor_rwsem); 241 242 snprintf(name, BUS_ID_SIZE, class_driver->name, intf->minor - minor_base); 243 device_destroy(usb_class->class, MKDEV(USB_MAJOR, intf->minor)); 244 intf->usb_dev = NULL; 245 intf->minor = -1; 246 destroy_usb_class(); 247 } 248 EXPORT_SYMBOL(usb_deregister_dev); 249