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/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                 err("class_create failed for usb devices");
  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                 err("unable to get major %d for usb devices", USB_MAJOR);
 119
 120         return error;
 121 }
 122
 123 void usb_major_cleanup(void)
 124 {
 125         unregister_chrdev(USB_MAJOR, "usb");
 126 }
 127
 128 /**
 129  * usb_register_dev - register a USB device, and ask for a minor number
 130  * @intf: pointer to the usb_interface that is being registered
 131  * @class_driver: pointer to the usb_class_driver for this device
 132  *
 133  * This should be called by all USB drivers that use the USB major number.
 134  * If CONFIG_USB_DYNAMIC_MINORS is enabled, the minor number will be
 135  * dynamically allocated out of the list of available ones.  If it is not
 136  * enabled, the minor number will be based on the next available free minor,
 137  * starting at the class_driver->minor_base.
 138  *
 139  * This function also creates a usb class device in the sysfs tree.
 140  *
 141  * usb_deregister_dev() must be called when the driver is done with
 142  * the minor numbers given out by this function.
 143  *
 144  * Returns -EINVAL if something bad happens with trying to register a
 145  * device, and 0 on success.
 146  */
 147 int usb_register_dev(struct usb_interface *intf,
 148                      struct usb_class_driver *class_driver)
 149 {
 150         int retval = -EINVAL;
 151         int minor_base = class_driver->minor_base;
 152         int minor = 0;
 153         char name[BUS_ID_SIZE];
 154         char *temp;
 155
 156 #ifdef CONFIG_USB_DYNAMIC_MINORS
 157         /*
 158          * We don't care what the device tries to start at, we want to start
 159          * at zero to pack the devices into the smallest available space with
 160          * no holes in the minor range.
 161          */
 162         minor_base = 0;
 163 #endif
 164         intf->minor = -1;
 165
 166         dbg ("looking for a minor, starting at %d", minor_base);
 167
 168         if (class_driver->fops == NULL)
 169                 goto exit;
 170
 171         down_write(&minor_rwsem);
 172         for (minor = minor_base; minor < MAX_USB_MINORS; ++minor) {
 173                 if (usb_minors[minor])
 174                         continue;
 175
 176                 usb_minors[minor] = class_driver->fops;
 177
 178                 retval = 0;
 179                 break;
 180         }
 181         up_write(&minor_rwsem);
 182
 183         if (retval)
 184                 goto exit;
 185
 186         retval = init_usb_class();
 187         if (retval)
 188                 goto exit;
 189
 190         intf->minor = minor;
 191
 192         /* create a usb class device for this usb interface */
 193         snprintf(name, BUS_ID_SIZE, class_driver->name, minor - minor_base);
 194         temp = strrchr(name, '/');
 195         if (temp && (temp[1] != 0x00))
 196                 ++temp;
 197         else
 198                 temp = name;
 199         intf->usb_dev = device_create(usb_class->class, &intf->dev,
 200                                       MKDEV(USB_MAJOR, minor), "%s", temp);
 201         if (IS_ERR(intf->usb_dev)) {
 202                 down_write(&minor_rwsem);
 203                 usb_minors[intf->minor] = NULL;
 204                 up_write(&minor_rwsem);
 205                 retval = PTR_ERR(intf->usb_dev);
 206         }
 207 exit:
 208         return retval;
 209 }
 210 EXPORT_SYMBOL_GPL(usb_register_dev);
 211
 212 /**
 213  * usb_deregister_dev - deregister a USB device's dynamic minor.
 214  * @intf: pointer to the usb_interface that is being deregistered
 215  * @class_driver: pointer to the usb_class_driver for this device
 216  *
 217  * Used in conjunction with usb_register_dev().  This function is called
 218  * when the USB driver is finished with the minor numbers gotten from a
 219  * call to usb_register_dev() (usually when the device is disconnected
 220  * from the system.)
 221  *
 222  * This function also removes the usb class device from the sysfs tree.
 223  *
 224  * This should be called by all drivers that use the USB major number.
 225  */
 226 void usb_deregister_dev(struct usb_interface *intf,
 227                         struct usb_class_driver *class_driver)
 228 {
 229         int minor_base = class_driver->minor_base;
 230         char name[BUS_ID_SIZE];
 231
 232 #ifdef CONFIG_USB_DYNAMIC_MINORS
 233         minor_base = 0;
 234 #endif
 235
 236         if (intf->minor == -1)
 237                 return;
 238
 239         dbg ("removing %d minor", intf->minor);
 240
 241         down_write(&minor_rwsem);
 242         usb_minors[intf->minor] = NULL;
 243         up_write(&minor_rwsem);
 244
 245         snprintf(name, BUS_ID_SIZE, class_driver->name, intf->minor - minor_base);
 246         device_destroy(usb_class->class, MKDEV(USB_MAJOR, intf->minor));
 247         intf->usb_dev = NULL;
 248         intf->minor = -1;
 249         destroy_usb_class();
 250 }
 251 EXPORT_SYMBOL_GPL(usb_deregister_dev);