drivers/usb/core/file.c

   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);