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/slab.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         down_read(&minor_rwsem);
  38         c = usb_minors[minor];
  39
  40         if (!c || !(new_fops = fops_get(c)))
  41                 goto done;
  42
  43         old_fops = file->f_op;
  44         file->f_op = new_fops;
  45         /* Curiouser and curiouser... NULL ->open() as "no device" ? */
  46         if (file->f_op->open)
  47                 err = file->f_op->open(inode,file);
  48         if (err) {
  49                 fops_put(file->f_op);
  50                 file->f_op = fops_get(old_fops);
  51         }
  52         fops_put(old_fops);
  53  done:
  54         up_read(&minor_rwsem);
  55         return err;
  56 }
  57
  58 static const struct file_operations usb_fops = {
  59         .owner =        THIS_MODULE,
  60         .open =         usb_open,
  61         .llseek =       noop_llseek,
  62 };
  63
  64 static struct usb_class {
  65         struct kref kref;
  66         struct class *class;
  67 } *usb_class;
  68
  69 static char *usb_devnode(struct device *dev, mode_t *mode)
  70 {
  71         struct usb_class_driver *drv;
  72
  73         drv = dev_get_drvdata(dev);
  74         if (!drv || !drv->devnode)
  75                 return NULL;
  76         return drv->devnode(dev, mode);
  77 }
  78
  79 static int init_usb_class(void)
  80 {
  81         int result = 0;
  82
  83         if (usb_class != NULL) {
  84                 kref_get(&usb_class->kref);
  85                 goto exit;
  86         }
  87
  88         usb_class = kmalloc(sizeof(*usb_class), GFP_KERNEL);
  89         if (!usb_class) {
  90                 result = -ENOMEM;
  91                 goto exit;
  92         }
  93
  94         kref_init(&usb_class->kref);
  95         usb_class->class = class_create(THIS_MODULE, "usb");
  96         if (IS_ERR(usb_class->class)) {
  97                 result = IS_ERR(usb_class->class);
  98                 printk(KERN_ERR "class_create failed for usb devices\n");
  99                 kfree(usb_class);
 100                 usb_class = NULL;
 101                 goto exit;
 102         }
 103         usb_class->class->devnode = usb_devnode;
 104
 105 exit:
 106         return result;
 107 }
 108
 109 static void release_usb_class(struct kref *kref)
 110 {
 111         /* Ok, we cheat as we know we only have one usb_class */
 112         class_destroy(usb_class->class);
 113         kfree(usb_class);
 114         usb_class = NULL;
 115 }
 116
 117 static void destroy_usb_class(void)
 118 {
 119         if (usb_class)
 120                 kref_put(&usb_class->kref, release_usb_class);
 121 }
 122
 123 int usb_major_init(void)
 124 {
 125         int error;
 126
 127         error = register_chrdev(USB_MAJOR, "usb", &usb_fops);
 128         if (error)
 129                 printk(KERN_ERR "Unable to get major %d for usb devices\n",
 130                        USB_MAJOR);
 131
 132         return error;
 133 }
 134
 135 void usb_major_cleanup(void)
 136 {
 137         unregister_chrdev(USB_MAJOR, "usb");
 138 }
 139
 140 /**
 141  * usb_register_dev - register a USB device, and ask for a minor number
 142  * @intf: pointer to the usb_interface that is being registered
 143  * @class_driver: pointer to the usb_class_driver for this device
 144  *
 145  * This should be called by all USB drivers that use the USB major number.
 146  * If CONFIG_USB_DYNAMIC_MINORS is enabled, the minor number will be
 147  * dynamically allocated out of the list of available ones.  If it is not
 148  * enabled, the minor number will be based on the next available free minor,
 149  * starting at the class_driver->minor_base.
 150  *
 151  * This function also creates a usb class device in the sysfs tree.
 152  *
 153  * usb_deregister_dev() must be called when the driver is done with
 154  * the minor numbers given out by this function.
 155  *
 156  * Returns -EINVAL if something bad happens with trying to register a
 157  * device, and 0 on success.
 158  */
 159 int usb_register_dev(struct usb_interface *intf,
 160                      struct usb_class_driver *class_driver)
 161 {
 162         int retval;
 163         int minor_base = class_driver->minor_base;
 164         int minor;
 165         char name[20];
 166         char *temp;
 167
 168 #ifdef CONFIG_USB_DYNAMIC_MINORS
 169         /*
 170          * We don't care what the device tries to start at, we want to start
 171          * at zero to pack the devices into the smallest available space with
 172          * no holes in the minor range.
 173          */
 174         minor_base = 0;
 175 #endif
 176
 177         if (class_driver->fops == NULL)
 178                 return -EINVAL;
 179         if (intf->minor >= 0)
 180                 return -EADDRINUSE;
 181
 182         retval = init_usb_class();
 183         if (retval)
 184                 return retval;
 185
 186         dev_dbg(&intf->dev, "looking for a minor, starting at %d", minor_base);
 187
 188         down_write(&minor_rwsem);
 189         for (minor = minor_base; minor < MAX_USB_MINORS; ++minor) {
 190                 if (usb_minors[minor])
 191                         continue;
 192
 193                 usb_minors[minor] = class_driver->fops;
 194                 intf->minor = minor;
 195                 break;
 196         }
 197         up_write(&minor_rwsem);
 198         if (intf->minor < 0)
 199                 return -EXFULL;
 200
 201         /* create a usb class device for this usb interface */
 202         snprintf(name, sizeof(name), class_driver->name, minor - minor_base);
 203         temp = strrchr(name, '/');
 204         if (temp && (temp[1] != '\0'))
 205                 ++temp;
 206         else
 207                 temp = name;
 208         intf->usb_dev = device_create(usb_class->class, &intf->dev,
 209                                       MKDEV(USB_MAJOR, minor), class_driver,
 210                                       "%s", temp);
 211         if (IS_ERR(intf->usb_dev)) {
 212                 down_write(&minor_rwsem);
 213                 usb_minors[minor] = NULL;
 214                 intf->minor = -1;
 215                 up_write(&minor_rwsem);
 216                 retval = PTR_ERR(intf->usb_dev);
 217         }
 218         return retval;
 219 }
 220 EXPORT_SYMBOL_GPL(usb_register_dev);
 221
 222 /**
 223  * usb_deregister_dev - deregister a USB device's dynamic minor.
 224  * @intf: pointer to the usb_interface that is being deregistered
 225  * @class_driver: pointer to the usb_class_driver for this device
 226  *
 227  * Used in conjunction with usb_register_dev().  This function is called
 228  * when the USB driver is finished with the minor numbers gotten from a
 229  * call to usb_register_dev() (usually when the device is disconnected
 230  * from the system.)
 231  *
 232  * This function also removes the usb class device from the sysfs tree.
 233  *
 234  * This should be called by all drivers that use the USB major number.
 235  */
 236 void usb_deregister_dev(struct usb_interface *intf,
 237                         struct usb_class_driver *class_driver)
 238 {
 239         if (intf->minor == -1)
 240                 return;
 241
 242         dbg ("removing %d minor", intf->minor);
 243
 244         down_write(&minor_rwsem);
 245         usb_minors[intf->minor] = NULL;
 246         up_write(&minor_rwsem);
 247
 248         device_destroy(usb_class->class, MKDEV(USB_MAJOR, intf->minor));
 249         intf->usb_dev = NULL;
 250         intf->minor = -1;
 251         destroy_usb_class();
 252 }
 253 EXPORT_SYMBOL_GPL(usb_deregister_dev);