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/spinlock.h>
  20 #include <linux/errno.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 DEFINE_SPINLOCK(minor_lock);
  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         spin_lock (&minor_lock);
  37         c = usb_minors[minor];
  38
  39         if (!c || !(new_fops = fops_get(c))) {
  40                 spin_unlock(&minor_lock);
  41                 return err;
  42         }
  43         spin_unlock(&minor_lock);
  44
  45         old_fops = file->f_op;
  46         file->f_op = new_fops;
  47         /* Curiouser and curiouser... NULL ->open() as "no device" ? */
  48         if (file->f_op->open)
  49                 err = file->f_op->open(inode,file);
  50         if (err) {
  51                 fops_put(file->f_op);
  52                 file->f_op = fops_get(old_fops);
  53         }
  54         fops_put(old_fops);
  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 int init_usb_class(void)
  69 {
  70         int result = 0;
  71
  72         if (usb_class != NULL) {
  73                 kref_get(&usb_class->kref);
  74                 goto exit;
  75         }
  76
  77         usb_class = kmalloc(sizeof(*usb_class), GFP_KERNEL);
  78         if (!usb_class) {
  79                 result = -ENOMEM;
  80                 goto exit;
  81         }
  82
  83         kref_init(&usb_class->kref);
  84         usb_class->class = class_create(THIS_MODULE, "usb");
  85         if (IS_ERR(usb_class->class)) {
  86                 result = IS_ERR(usb_class->class);
  87                 err("class_create failed for usb devices");
  88                 kfree(usb_class);
  89                 usb_class = NULL;
  90         }
  91
  92 exit:
  93         return result;
  94 }
  95
  96 static void release_usb_class(struct kref *kref)
  97 {
  98         /* Ok, we cheat as we know we only have one usb_class */
  99         class_destroy(usb_class->class);
 100         kfree(usb_class);
 101         usb_class = NULL;
 102 }
 103
 104 static void destroy_usb_class(void)
 105 {
 106         if (usb_class)
 107                 kref_put(&usb_class->kref, release_usb_class);
 108 }
 109
 110 int usb_major_init(void)
 111 {
 112         int error;
 113
 114         error = register_chrdev(USB_MAJOR, "usb", &usb_fops);
 115         if (error)
 116                 err("unable to get major %d for usb devices", USB_MAJOR);
 117
 118         return error;
 119 }
 120
 121 void usb_major_cleanup(void)
 122 {
 123         unregister_chrdev(USB_MAJOR, "usb");
 124 }
 125
 126 /**
 127  * usb_register_dev - register a USB device, and ask for a minor number
 128  * @intf: pointer to the usb_interface that is being registered
 129  * @class_driver: pointer to the usb_class_driver for this device
 130  *
 131  * This should be called by all USB drivers that use the USB major number.
 132  * If CONFIG_USB_DYNAMIC_MINORS is enabled, the minor number will be
 133  * dynamically allocated out of the list of available ones.  If it is not
 134  * enabled, the minor number will be based on the next available free minor,
 135  * starting at the class_driver->minor_base.
 136  *
 137  * This function also creates a usb class device in the sysfs tree.
 138  *
 139  * usb_deregister_dev() must be called when the driver is done with
 140  * the minor numbers given out by this function.
 141  *
 142  * Returns -EINVAL if something bad happens with trying to register a
 143  * device, and 0 on success.
 144  */
 145 int usb_register_dev(struct usb_interface *intf,
 146                      struct usb_class_driver *class_driver)
 147 {
 148         int retval = -EINVAL;
 149         int minor_base = class_driver->minor_base;
 150         int minor = 0;
 151         char name[BUS_ID_SIZE];
 152         char *temp;
 153
 154 #ifdef CONFIG_USB_DYNAMIC_MINORS
 155         /*
 156          * We don't care what the device tries to start at, we want to start
 157          * at zero to pack the devices into the smallest available space with
 158          * no holes in the minor range.
 159          */
 160         minor_base = 0;
 161 #endif
 162         intf->minor = -1;
 163
 164         dbg ("looking for a minor, starting at %d", minor_base);
 165
 166         if (class_driver->fops == NULL)
 167                 goto exit;
 168
 169         spin_lock (&minor_lock);
 170         for (minor = minor_base; minor < MAX_USB_MINORS; ++minor) {
 171                 if (usb_minors[minor])
 172                         continue;
 173
 174                 usb_minors[minor] = class_driver->fops;
 175
 176                 retval = 0;
 177                 break;
 178         }
 179         spin_unlock (&minor_lock);
 180
 181         if (retval)
 182                 goto exit;
 183
 184         retval = init_usb_class();
 185         if (retval)
 186                 goto exit;
 187
 188         intf->minor = minor;
 189
 190         /* create a usb class device for this usb interface */
 191         snprintf(name, BUS_ID_SIZE, class_driver->name, minor - minor_base);
 192         temp = strrchr(name, '/');
 193         if (temp && (temp[1] != 0x00))
 194                 ++temp;
 195         else
 196                 temp = name;
 197         intf->usb_dev = device_create(usb_class->class, &intf->dev,
 198                                       MKDEV(USB_MAJOR, minor), "%s", temp);
 199         if (IS_ERR(intf->usb_dev)) {
 200                 spin_lock (&minor_lock);
 201                 usb_minors[intf->minor] = NULL;
 202                 spin_unlock (&minor_lock);
 203                 retval = PTR_ERR(intf->usb_dev);
 204         }
 205 exit:
 206         return retval;
 207 }
 208 EXPORT_SYMBOL(usb_register_dev);
 209
 210 /**
 211  * usb_deregister_dev - deregister a USB device's dynamic minor.
 212  * @intf: pointer to the usb_interface that is being deregistered
 213  * @class_driver: pointer to the usb_class_driver for this device
 214  *
 215  * Used in conjunction with usb_register_dev().  This function is called
 216  * when the USB driver is finished with the minor numbers gotten from a
 217  * call to usb_register_dev() (usually when the device is disconnected
 218  * from the system.)
 219  *
 220  * This function also removes the usb class device from the sysfs tree.
 221  *
 222  * This should be called by all drivers that use the USB major number.
 223  */
 224 void usb_deregister_dev(struct usb_interface *intf,
 225                         struct usb_class_driver *class_driver)
 226 {
 227         int minor_base = class_driver->minor_base;
 228         char name[BUS_ID_SIZE];
 229
 230 #ifdef CONFIG_USB_DYNAMIC_MINORS
 231         minor_base = 0;
 232 #endif
 233
 234         if (intf->minor == -1)
 235                 return;
 236
 237         dbg ("removing %d minor", intf->minor);
 238
 239         spin_lock (&minor_lock);
 240         usb_minors[intf->minor] = NULL;
 241         spin_unlock (&minor_lock);
 242
 243         snprintf(name, BUS_ID_SIZE, class_driver->name, intf->minor - minor_base);
 244         device_destroy(usb_class->class, MKDEV(USB_MAJOR, intf->minor));
 245         intf->usb_dev = NULL;
 246         intf->minor = -1;
 247         destroy_usb_class();
 248 }
 249 EXPORT_SYMBOL(usb_deregister_dev);
 250
 251