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/string.h>
  23 #include <linux/usb.h>
  24
  25 #include "usb.h"
  26
  27 #define MAX_USB_MINORS  256
  28 static const struct file_operations *usb_minors[MAX_USB_MINORS];
  29 static DECLARE_RWSEM(minor_rwsem);
  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         if (usb_class)
 113                 kref_put(&usb_class->kref, release_usb_class);
 114 }
 115
 116 int usb_major_init(void)
 117 {
 118         int error;
 119
 120         error = register_chrdev(USB_MAJOR, "usb", &usb_fops);
 121         if (error)
 122                 printk(KERN_ERR "Unable to get major %d for usb devices\n",
 123                        USB_MAJOR);
 124
 125         return error;
 126 }
 127
 128 void usb_major_cleanup(void)
 129 {
 130         unregister_chrdev(USB_MAJOR, "usb");
 131 }
 132
 133 /**
 134  * usb_register_dev - register a USB device, and ask for a minor number
 135  * @intf: pointer to the usb_interface that is being registered
 136  * @class_driver: pointer to the usb_class_driver for this device
 137  *
 138  * This should be called by all USB drivers that use the USB major number.
 139  * If CONFIG_USB_DYNAMIC_MINORS is enabled, the minor number will be
 140  * dynamically allocated out of the list of available ones.  If it is not
 141  * enabled, the minor number will be based on the next available free minor,
 142  * starting at the class_driver->minor_base.
 143  *
 144  * This function also creates a usb class device in the sysfs tree.
 145  *
 146  * usb_deregister_dev() must be called when the driver is done with
 147  * the minor numbers given out by this function.
 148  *
 149  * Return: -EINVAL if something bad happens with trying to register a
 150  * device, and 0 on success.
 151  */
 152 int usb_register_dev(struct usb_interface *intf,
 153                      struct usb_class_driver *class_driver)
 154 {
 155         int retval;
 156         int minor_base = class_driver->minor_base;
 157         int minor;
 158         char name[20];
 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         intf->usb_dev = device_create(usb_class->class, &intf->dev,
 196                                       MKDEV(USB_MAJOR, minor), class_driver,
 197                                       "%s", kbasename(name));
 198         if (IS_ERR(intf->usb_dev)) {
 199                 down_write(&minor_rwsem);
 200                 usb_minors[minor] = NULL;
 201                 intf->minor = -1;
 202                 up_write(&minor_rwsem);
 203                 retval = PTR_ERR(intf->usb_dev);
 204         }
 205         return retval;
 206 }
 207 EXPORT_SYMBOL_GPL(usb_register_dev);
 208
 209 /**
 210  * usb_deregister_dev - deregister a USB device's dynamic minor.
 211  * @intf: pointer to the usb_interface that is being deregistered
 212  * @class_driver: pointer to the usb_class_driver for this device
 213  *
 214  * Used in conjunction with usb_register_dev().  This function is called
 215  * when the USB driver is finished with the minor numbers gotten from a
 216  * call to usb_register_dev() (usually when the device is disconnected
 217  * from the system.)
 218  *
 219  * This function also removes the usb class device from the sysfs tree.
 220  *
 221  * This should be called by all drivers that use the USB major number.
 222  */
 223 void usb_deregister_dev(struct usb_interface *intf,
 224                         struct usb_class_driver *class_driver)
 225 {
 226         if (intf->minor == -1)
 227                 return;
 228
 229         dev_dbg(&intf->dev, "removing %d minor\n", intf->minor);
 230
 231         down_write(&minor_rwsem);
 232         usb_minors[intf->minor] = NULL;
 233         up_write(&minor_rwsem);
 234
 235         device_destroy(usb_class->class, MKDEV(USB_MAJOR, intf->minor));
 236         intf->usb_dev = NULL;
 237         intf->minor = -1;
 238         destroy_usb_class();
 239 }
 240 EXPORT_SYMBOL_GPL(usb_deregister_dev);