drivers/usb/core/file.c

   1 /*
   2  * drivers/usb/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/config.h>
  19 #include <linux/module.h>
  20 #include <linux/spinlock.h>
  21 #include <linux/errno.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 DEFINE_SPINLOCK(minor_lock);
  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         spin_lock (&minor_lock);
  38         c = usb_minors[minor];
  39
  40         if (!c || !(new_fops = fops_get(c))) {
  41                 spin_unlock(&minor_lock);
  42                 return err;
  43         }
  44         spin_unlock(&minor_lock);
  45
  46         old_fops = file->f_op;
  47         file->f_op = new_fops;
  48         /* Curiouser and curiouser... NULL ->open() as "no device" ? */
  49         if (file->f_op->open)
  50                 err = file->f_op->open(inode,file);
  51         if (err) {
  52                 fops_put(file->f_op);
  53                 file->f_op = fops_get(old_fops);
  54         }
  55         fops_put(old_fops);
  56         return err;
  57 }
  58
  59 static struct file_operations usb_fops = {
  60         .owner =        THIS_MODULE,
  61         .open =         usb_open,
  62 };
  63
  64 static struct class *usb_class;
  65
  66 int usb_major_init(void)
  67 {
  68         int error;
  69
  70         error = register_chrdev(USB_MAJOR, "usb", &usb_fops);
  71         if (error) {
  72                 err("unable to get major %d for usb devices", USB_MAJOR);
  73                 goto out;
  74         }
  75
  76         usb_class = class_create(THIS_MODULE, "usb");
  77         if (IS_ERR(usb_class)) {
  78                 error = PTR_ERR(usb_class);
  79                 err("class_create failed for usb devices");
  80                 unregister_chrdev(USB_MAJOR, "usb");
  81                 goto out;
  82         }
  83
  84 out:
  85         return error;
  86 }
  87
  88 void usb_major_cleanup(void)
  89 {
  90         class_destroy(usb_class);
  91         unregister_chrdev(USB_MAJOR, "usb");
  92 }
  93
  94 /**
  95  * usb_register_dev - register a USB device, and ask for a minor number
  96  * @intf: pointer to the usb_interface that is being registered
  97  * @class_driver: pointer to the usb_class_driver for this device
  98  *
  99  * This should be called by all USB drivers that use the USB major number.
 100  * If CONFIG_USB_DYNAMIC_MINORS is enabled, the minor number will be
 101  * dynamically allocated out of the list of available ones.  If it is not
 102  * enabled, the minor number will be based on the next available free minor,
 103  * starting at the class_driver->minor_base.
 104  *
 105  * This function also creates a usb class device in the sysfs tree.
 106  *
 107  * usb_deregister_dev() must be called when the driver is done with
 108  * the minor numbers given out by this function.
 109  *
 110  * Returns -EINVAL if something bad happens with trying to register a
 111  * device, and 0 on success.
 112  */
 113 int usb_register_dev(struct usb_interface *intf,
 114                      struct usb_class_driver *class_driver)
 115 {
 116         int retval = -EINVAL;
 117         int minor_base = class_driver->minor_base;
 118         int minor = 0;
 119         char name[BUS_ID_SIZE];
 120         char *temp;
 121
 122 #ifdef CONFIG_USB_DYNAMIC_MINORS
 123         /*
 124          * We don't care what the device tries to start at, we want to start
 125          * at zero to pack the devices into the smallest available space with
 126          * no holes in the minor range.
 127          */
 128         minor_base = 0;
 129 #endif
 130         intf->minor = -1;
 131
 132         dbg ("looking for a minor, starting at %d", minor_base);
 133
 134         if (class_driver->fops == NULL)
 135                 goto exit;
 136
 137         spin_lock (&minor_lock);
 138         for (minor = minor_base; minor < MAX_USB_MINORS; ++minor) {
 139                 if (usb_minors[minor])
 140                         continue;
 141
 142                 usb_minors[minor] = class_driver->fops;
 143
 144                 retval = 0;
 145                 break;
 146         }
 147         spin_unlock (&minor_lock);
 148
 149         if (retval)
 150                 goto exit;
 151
 152         intf->minor = minor;
 153
 154         /* create a usb class device for this usb interface */
 155         snprintf(name, BUS_ID_SIZE, class_driver->name, minor - minor_base);
 156         temp = strrchr(name, '/');
 157         if (temp && (temp[1] != 0x00))
 158                 ++temp;
 159         else
 160                 temp = name;
 161         intf->class_dev = class_device_create(usb_class, NULL,
 162                                               MKDEV(USB_MAJOR, minor),
 163                                               &intf->dev, "%s", temp);
 164         if (IS_ERR(intf->class_dev)) {
 165                 spin_lock (&minor_lock);
 166                 usb_minors[intf->minor] = NULL;
 167                 spin_unlock (&minor_lock);
 168                 retval = PTR_ERR(intf->class_dev);
 169         }
 170 exit:
 171         return retval;
 172 }
 173 EXPORT_SYMBOL(usb_register_dev);
 174
 175 /**
 176  * usb_deregister_dev - deregister a USB device's dynamic minor.
 177  * @intf: pointer to the usb_interface that is being deregistered
 178  * @class_driver: pointer to the usb_class_driver for this device
 179  *
 180  * Used in conjunction with usb_register_dev().  This function is called
 181  * when the USB driver is finished with the minor numbers gotten from a
 182  * call to usb_register_dev() (usually when the device is disconnected
 183  * from the system.)
 184  *
 185  * This function also removes the usb class device from the sysfs tree.
 186  *
 187  * This should be called by all drivers that use the USB major number.
 188  */
 189 void usb_deregister_dev(struct usb_interface *intf,
 190                         struct usb_class_driver *class_driver)
 191 {
 192         int minor_base = class_driver->minor_base;
 193         char name[BUS_ID_SIZE];
 194
 195 #ifdef CONFIG_USB_DYNAMIC_MINORS
 196         minor_base = 0;
 197 #endif
 198
 199         if (intf->minor == -1)
 200                 return;
 201
 202         dbg ("removing %d minor", intf->minor);
 203
 204         spin_lock (&minor_lock);
 205         usb_minors[intf->minor] = NULL;
 206         spin_unlock (&minor_lock);
 207
 208         snprintf(name, BUS_ID_SIZE, class_driver->name, intf->minor - minor_base);
 209         class_device_destroy(usb_class, MKDEV(USB_MAJOR, intf->minor));
 210         intf->class_dev = NULL;
 211         intf->minor = -1;
 212 }
 213 EXPORT_SYMBOL(usb_deregister_dev);
 214
 215