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 err = -ENODEV;
  33         const struct file_operations *new_fops;
  34
  35         down_read(&minor_rwsem);
  36         new_fops = fops_get(usb_minors[iminor(inode)]);
  37
  38         if (!new_fops)
  39                 goto done;
  40
  41         replace_fops(file, new_fops);
  42         /* Curiouser and curiouser... NULL ->open() as "no device" ? */
  43         if (file->f_op->open)
  44                 err = file->f_op->open(inode, file);
  45  done:
  46         up_read(&minor_rwsem);
  47         return err;
  48 }
  49
  50 static const struct file_operations usb_fops = {
  51         .owner =        THIS_MODULE,
  52         .open =         usb_open,
  53         .llseek =       noop_llseek,
  54 };
  55
  56 static struct usb_class {
  57         struct kref kref;
  58         struct class *class;
  59 } *usb_class;
  60
  61 static char *usb_devnode(struct device *dev, umode_t *mode)
  62 {
  63         struct usb_class_driver *drv;
  64
  65         drv = dev_get_drvdata(dev);
  66         if (!drv || !drv->devnode)
  67                 return NULL;
  68         return drv->devnode(dev, mode);
  69 }
  70
  71 static int init_usb_class(void)
  72 {
  73         int result = 0;
  74
  75         if (usb_class != NULL) {
  76                 kref_get(&usb_class->kref);
  77                 goto exit;
  78         }
  79
  80         usb_class = kmalloc(sizeof(*usb_class), GFP_KERNEL);
  81         if (!usb_class) {
  82                 result = -ENOMEM;
  83                 goto exit;
  84         }
  85
  86         kref_init(&usb_class->kref);
  87         usb_class->class = class_create(THIS_MODULE, "usbmisc");
  88         if (IS_ERR(usb_class->class)) {
  89                 result = PTR_ERR(usb_class->class);
  90                 printk(KERN_ERR "class_create failed for usb devices\n");
  91                 kfree(usb_class);
  92                 usb_class = NULL;
  93                 goto exit;
  94         }
  95         usb_class->class->devnode = usb_devnode;
  96
  97 exit:
  98         return result;
  99 }
 100
 101 static void release_usb_class(struct kref *kref)
 102 {
 103         /* Ok, we cheat as we know we only have one usb_class */
 104         class_destroy(usb_class->class);
 105         kfree(usb_class);
 106         usb_class = NULL;
 107 }
 108
 109 static void destroy_usb_class(void)
 110 {
 111         if (usb_class)
 112                 kref_put(&usb_class->kref, release_usb_class);
 113 }
 114
 115 int usb_major_init(void)
 116 {
 117         int error;
 118
 119         error = register_chrdev(USB_MAJOR, "usb", &usb_fops);
 120         if (error)
 121                 printk(KERN_ERR "Unable to get major %d for usb devices\n",
 122                        USB_MAJOR);
 123
 124         return error;
 125 }
 126
 127 void usb_major_cleanup(void)
 128 {
 129         unregister_chrdev(USB_MAJOR, "usb");
 130 }
 131
 132 /**
 133  * usb_register_dev - register a USB device, and ask for a minor number
 134  * @intf: pointer to the usb_interface that is being registered
 135  * @class_driver: pointer to the usb_class_driver for this device
 136  *
 137  * This should be called by all USB drivers that use the USB major number.
 138  * If CONFIG_USB_DYNAMIC_MINORS is enabled, the minor number will be
 139  * dynamically allocated out of the list of available ones.  If it is not
 140  * enabled, the minor number will be based on the next available free minor,
 141  * starting at the class_driver->minor_base.
 142  *
 143  * This function also creates a usb class device in the sysfs tree.
 144  *
 145  * usb_deregister_dev() must be called when the driver is done with
 146  * the minor numbers given out by this function.
 147  *
 148  * Return: -EINVAL if something bad happens with trying to register a
 149  * device, and 0 on success.
 150  */
 151 int usb_register_dev(struct usb_interface *intf,
 152                      struct usb_class_driver *class_driver)
 153 {
 154         int retval;
 155         int minor_base = class_driver->minor_base;
 156         int minor;
 157         char name[20];
 158         char *temp;
 159
 160 #ifdef CONFIG_USB_DYNAMIC_MINORS
 161         /*
 162          * We don't care what the device tries to start at, we want to start
 163          * at zero to pack the devices into the smallest available space with
 164          * no holes in the minor range.
 165          */
 166         minor_base = 0;
 167 #endif
 168
 169         if (class_driver->fops == NULL)
 170                 return -EINVAL;
 171         if (intf->minor >= 0)
 172                 return -EADDRINUSE;
 173
 174         retval = init_usb_class();
 175         if (retval)
 176                 return retval;
 177
 178         dev_dbg(&intf->dev, "looking for a minor, starting at %d\n", minor_base);
 179
 180         down_write(&minor_rwsem);
 181         for (minor = minor_base; minor < MAX_USB_MINORS; ++minor) {
 182                 if (usb_minors[minor])
 183                         continue;
 184
 185                 usb_minors[minor] = class_driver->fops;
 186                 intf->minor = minor;
 187                 break;
 188         }
 189         up_write(&minor_rwsem);
 190         if (intf->minor < 0)
 191                 return -EXFULL;
 192
 193         /* create a usb class device for this usb interface */
 194         snprintf(name, sizeof(name), class_driver->name, minor - minor_base);
 195         temp = strrchr(name, '/');
 196         if (temp && (temp[1] != '\0'))
 197                 ++temp;
 198         else
 199                 temp = name;
 200         intf->usb_dev = device_create(usb_class->class, &intf->dev,
 201                                       MKDEV(USB_MAJOR, minor), class_driver,
 202                                       "%s", temp);
 203         if (IS_ERR(intf->usb_dev)) {
 204                 down_write(&minor_rwsem);
 205                 usb_minors[minor] = NULL;
 206                 intf->minor = -1;
 207                 up_write(&minor_rwsem);
 208                 retval = PTR_ERR(intf->usb_dev);
 209         }
 210         return retval;
 211 }
 212 EXPORT_SYMBOL_GPL(usb_register_dev);
 213
 214 /**
 215  * usb_deregister_dev - deregister a USB device's dynamic minor.
 216  * @intf: pointer to the usb_interface that is being deregistered
 217  * @class_driver: pointer to the usb_class_driver for this device
 218  *
 219  * Used in conjunction with usb_register_dev().  This function is called
 220  * when the USB driver is finished with the minor numbers gotten from a
 221  * call to usb_register_dev() (usually when the device is disconnected
 222  * from the system.)
 223  *
 224  * This function also removes the usb class device from the sysfs tree.
 225  *
 226  * This should be called by all drivers that use the USB major number.
 227  */
 228 void usb_deregister_dev(struct usb_interface *intf,
 229                         struct usb_class_driver *class_driver)
 230 {
 231         if (intf->minor == -1)
 232                 return;
 233
 234         dev_dbg(&intf->dev, "removing %d minor\n", intf->minor);
 235
 236         down_write(&minor_rwsem);
 237         usb_minors[intf->minor] = NULL;
 238         up_write(&minor_rwsem);
 239
 240         device_destroy(usb_class->class, MKDEV(USB_MAJOR, intf->minor));
 241         intf->usb_dev = NULL;
 242         intf->minor = -1;
 243         destroy_usb_class();
 244 }
 245 EXPORT_SYMBOL_GPL(usb_deregister_dev);