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 static DEFINE_MUTEX(init_usb_class_mutex);
  30
  31 static int usb_open(struct inode *inode, struct file *file)
  32 {
  33         int err = -ENODEV;
  34         const struct file_operations *new_fops;
  35
  36         down_read(&minor_rwsem);
  37         new_fops = fops_get(usb_minors[iminor(inode)]);
  38
  39         if (!new_fops)
  40                 goto done;
  41
  42         replace_fops(file, new_fops);
  43         /* Curiouser and curiouser... NULL ->open() as "no device" ? */
  44         if (file->f_op->open)
  45                 err = file->f_op->open(inode, file);
  46  done:
  47         up_read(&minor_rwsem);
  48         return err;
  49 }
  50
  51 static const struct file_operations usb_fops = {
  52         .owner =        THIS_MODULE,
  53         .open =         usb_open,
  54         .llseek =       noop_llseek,
  55 };
  56
  57 static struct usb_class {
  58         struct kref kref;
  59         struct class *class;
  60 } *usb_class;
  61
  62 static char *usb_devnode(struct device *dev, umode_t *mode)
  63 {
  64         struct usb_class_driver *drv;
  65
  66         drv = dev_get_drvdata(dev);
  67         if (!drv || !drv->devnode)
  68                 return NULL;
  69         return drv->devnode(dev, mode);
  70 }
  71
  72 static int init_usb_class(void)
  73 {
  74         int result = 0;
  75
  76         if (usb_class != NULL) {
  77                 kref_get(&usb_class->kref);
  78                 goto exit;
  79         }
  80
  81         usb_class = kmalloc(sizeof(*usb_class), GFP_KERNEL);
  82         if (!usb_class) {
  83                 result = -ENOMEM;
  84                 goto exit;
  85         }
  86
  87         kref_init(&usb_class->kref);
  88         usb_class->class = class_create(THIS_MODULE, "usbmisc");
  89         if (IS_ERR(usb_class->class)) {
  90                 result = PTR_ERR(usb_class->class);
  91                 printk(KERN_ERR "class_create failed for usb devices\n");
  92                 kfree(usb_class);
  93                 usb_class = NULL;
  94                 goto exit;
  95         }
  96         usb_class->class->devnode = usb_devnode;
  97
  98 exit:
  99         return result;
 100 }
 101
 102 static void release_usb_class(struct kref *kref)
 103 {
 104         /* Ok, we cheat as we know we only have one usb_class */
 105         class_destroy(usb_class->class);
 106         kfree(usb_class);
 107         usb_class = NULL;
 108 }
 109
 110 static void destroy_usb_class(void)
 111 {
 112         mutex_lock(&init_usb_class_mutex);
 113         kref_put(&usb_class->kref, release_usb_class);
 114         mutex_unlock(&init_usb_class_mutex);
 115 }
 116
 117 int usb_major_init(void)
 118 {
 119         int error;
 120
 121         error = register_chrdev(USB_MAJOR, "usb", &usb_fops);
 122         if (error)
 123                 printk(KERN_ERR "Unable to get major %d for usb devices\n",
 124                        USB_MAJOR);
 125
 126         return error;
 127 }
 128
 129 void usb_major_cleanup(void)
 130 {
 131         unregister_chrdev(USB_MAJOR, "usb");
 132 }
 133
 134 /**
 135  * usb_register_dev - register a USB device, and ask for a minor number
 136  * @intf: pointer to the usb_interface that is being registered
 137  * @class_driver: pointer to the usb_class_driver for this device
 138  *
 139  * This should be called by all USB drivers that use the USB major number.
 140  * If CONFIG_USB_DYNAMIC_MINORS is enabled, the minor number will be
 141  * dynamically allocated out of the list of available ones.  If it is not
 142  * enabled, the minor number will be based on the next available free minor,
 143  * starting at the class_driver->minor_base.
 144  *
 145  * This function also creates a usb class device in the sysfs tree.
 146  *
 147  * usb_deregister_dev() must be called when the driver is done with
 148  * the minor numbers given out by this function.
 149  *
 150  * Return: -EINVAL if something bad happens with trying to register a
 151  * device, and 0 on success.
 152  */
 153 int usb_register_dev(struct usb_interface *intf,
 154                      struct usb_class_driver *class_driver)
 155 {
 156         int retval;
 157         int minor_base = class_driver->minor_base;
 158         int minor;
 159         char name[20];
 160         char *temp;
 161
 162 #ifdef CONFIG_USB_DYNAMIC_MINORS
 163         /*
 164          * We don't care what the device tries to start at, we want to start
 165          * at zero to pack the devices into the smallest available space with
 166          * no holes in the minor range.
 167          */
 168         minor_base = 0;
 169 #endif
 170
 171         if (class_driver->fops == NULL)
 172                 return -EINVAL;
 173         if (intf->minor >= 0)
 174                 return -EADDRINUSE;
 175
 176         mutex_lock(&init_usb_class_mutex);
 177         retval = init_usb_class();
 178         mutex_unlock(&init_usb_class_mutex);
 179
 180         if (retval)
 181                 return retval;
 182
 183         dev_dbg(&intf->dev, "looking for a minor, starting at %d\n", minor_base);
 184
 185         down_write(&minor_rwsem);
 186         for (minor = minor_base; minor < MAX_USB_MINORS; ++minor) {
 187                 if (usb_minors[minor])
 188                         continue;
 189
 190                 usb_minors[minor] = class_driver->fops;
 191                 intf->minor = minor;
 192                 break;
 193         }
 194         up_write(&minor_rwsem);
 195         if (intf->minor < 0)
 196                 return -EXFULL;
 197
 198         /* create a usb class device for this usb interface */
 199         snprintf(name, sizeof(name), class_driver->name, minor - minor_base);
 200         temp = strrchr(name, '/');
 201         if (temp && (temp[1] != '\0'))
 202                 ++temp;
 203         else
 204                 temp = name;
 205         intf->usb_dev = device_create(usb_class->class, &intf->dev,
 206                                       MKDEV(USB_MAJOR, minor), class_driver,
 207                                       "%s", temp);
 208         if (IS_ERR(intf->usb_dev)) {
 209                 down_write(&minor_rwsem);
 210                 usb_minors[minor] = NULL;
 211                 intf->minor = -1;
 212                 up_write(&minor_rwsem);
 213                 retval = PTR_ERR(intf->usb_dev);
 214         }
 215         return retval;
 216 }
 217 EXPORT_SYMBOL_GPL(usb_register_dev);
 218
 219 /**
 220  * usb_deregister_dev - deregister a USB device's dynamic minor.
 221  * @intf: pointer to the usb_interface that is being deregistered
 222  * @class_driver: pointer to the usb_class_driver for this device
 223  *
 224  * Used in conjunction with usb_register_dev().  This function is called
 225  * when the USB driver is finished with the minor numbers gotten from a
 226  * call to usb_register_dev() (usually when the device is disconnected
 227  * from the system.)
 228  *
 229  * This function also removes the usb class device from the sysfs tree.
 230  *
 231  * This should be called by all drivers that use the USB major number.
 232  */
 233 void usb_deregister_dev(struct usb_interface *intf,
 234                         struct usb_class_driver *class_driver)
 235 {
 236         if (intf->minor == -1)
 237                 return;
 238
 239         dev_dbg(&intf->dev, "removing %d minor\n", intf->minor);
 240
 241         down_write(&minor_rwsem);
 242         usb_minors[intf->minor] = NULL;
 243         up_write(&minor_rwsem);
 244
 245         device_destroy(usb_class->class, MKDEV(USB_MAJOR, intf->minor));
 246         intf->usb_dev = NULL;
 247         intf->minor = -1;
 248         destroy_usb_class();
 249 }
 250 EXPORT_SYMBOL_GPL(usb_deregister_dev);