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/smp_lock.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         lock_kernel();
  38         down_read(&minor_rwsem);
  39         c = usb_minors[minor];
  40
  41         if (!c || !(new_fops = fops_get(c)))
  42                 goto done;
  43
  44         old_fops = file->f_op;
  45         file->f_op = new_fops;
  46         /* Curiouser and curiouser... NULL ->open() as "no device" ? */
  47         if (file->f_op->open)
  48                 err = file->f_op->open(inode,file);
  49         if (err) {
  50                 fops_put(file->f_op);
  51                 file->f_op = fops_get(old_fops);
  52         }
  53         fops_put(old_fops);
  54  done:
  55         up_read(&minor_rwsem);
  56         unlock_kernel();
  57         return err;
  58 }
  59
  60 static const struct file_operations usb_fops = {
  61         .owner =        THIS_MODULE,
  62         .open =         usb_open,
  63 };
  64
  65 static struct usb_class {
  66         struct kref kref;
  67         struct class *class;
  68 } *usb_class;
  69
  70 static char *usb_nodename(struct device *dev)
  71 {
  72         struct usb_class_driver *drv;
  73
  74         drv = dev_get_drvdata(dev);
  75         if (!drv || !drv->nodename)
  76                 return NULL;
  77         return drv->nodename(dev);
  78 }
  79
  80 static int init_usb_class(void)
  81 {
  82         int result = 0;
  83
  84         if (usb_class != NULL) {
  85                 kref_get(&usb_class->kref);
  86                 goto exit;
  87         }
  88
  89         usb_class = kmalloc(sizeof(*usb_class), GFP_KERNEL);
  90         if (!usb_class) {
  91                 result = -ENOMEM;
  92                 goto exit;
  93         }
  94
  95         kref_init(&usb_class->kref);
  96         usb_class->class = class_create(THIS_MODULE, "usb");
  97         if (IS_ERR(usb_class->class)) {
  98                 result = IS_ERR(usb_class->class);
  99                 printk(KERN_ERR "class_create failed for usb devices\n");
 100                 kfree(usb_class);
 101                 usb_class = NULL;
 102         }
 103         usb_class->class->nodename = usb_nodename;
 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 = -EINVAL;
 163         int minor_base = class_driver->minor_base;
 164         int minor = 0;
 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         intf->minor = -1;
 177
 178         dbg ("looking for a minor, starting at %d", minor_base);
 179
 180         if (class_driver->fops == NULL)
 181                 goto exit;
 182
 183         down_write(&minor_rwsem);
 184         for (minor = minor_base; minor < MAX_USB_MINORS; ++minor) {
 185                 if (usb_minors[minor])
 186                         continue;
 187
 188                 usb_minors[minor] = class_driver->fops;
 189
 190                 retval = 0;
 191                 break;
 192         }
 193         up_write(&minor_rwsem);
 194
 195         if (retval)
 196                 goto exit;
 197
 198         retval = init_usb_class();
 199         if (retval)
 200                 goto exit;
 201
 202         intf->minor = minor;
 203
 204         /* create a usb class device for this usb interface */
 205         snprintf(name, sizeof(name), class_driver->name, minor - minor_base);
 206         temp = strrchr(name, '/');
 207         if (temp && (temp[1] != '\0'))
 208                 ++temp;
 209         else
 210                 temp = name;
 211         intf->usb_dev = device_create(usb_class->class, &intf->dev,
 212                                       MKDEV(USB_MAJOR, minor), class_driver,
 213                                       "%s", temp);
 214         if (IS_ERR(intf->usb_dev)) {
 215                 down_write(&minor_rwsem);
 216                 usb_minors[intf->minor] = NULL;
 217                 up_write(&minor_rwsem);
 218                 retval = PTR_ERR(intf->usb_dev);
 219         }
 220 exit:
 221         return retval;
 222 }
 223 EXPORT_SYMBOL_GPL(usb_register_dev);
 224
 225 /**
 226  * usb_deregister_dev - deregister a USB device's dynamic minor.
 227  * @intf: pointer to the usb_interface that is being deregistered
 228  * @class_driver: pointer to the usb_class_driver for this device
 229  *
 230  * Used in conjunction with usb_register_dev().  This function is called
 231  * when the USB driver is finished with the minor numbers gotten from a
 232  * call to usb_register_dev() (usually when the device is disconnected
 233  * from the system.)
 234  *
 235  * This function also removes the usb class device from the sysfs tree.
 236  *
 237  * This should be called by all drivers that use the USB major number.
 238  */
 239 void usb_deregister_dev(struct usb_interface *intf,
 240                         struct usb_class_driver *class_driver)
 241 {
 242         int minor_base = class_driver->minor_base;
 243         char name[20];
 244
 245 #ifdef CONFIG_USB_DYNAMIC_MINORS
 246         minor_base = 0;
 247 #endif
 248
 249         if (intf->minor == -1)
 250                 return;
 251
 252         dbg ("removing %d minor", intf->minor);
 253
 254         down_write(&minor_rwsem);
 255         usb_minors[intf->minor] = NULL;
 256         up_write(&minor_rwsem);
 257
 258         snprintf(name, sizeof(name), class_driver->name, intf->minor - minor_base);
 259         device_destroy(usb_class->class, MKDEV(USB_MAJOR, intf->minor));
 260         intf->usb_dev = NULL;
 261         intf->minor = -1;
 262         destroy_usb_class();
 263 }
 264 EXPORT_SYMBOL_GPL(usb_deregister_dev);