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/smp_lock.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 minor = iminor(inode);
  34         const struct file_operations *c;
  35         int err = -ENODEV;
  36         const struct file_operations *old_fops, *new_fops = NULL;
  37
  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         return err;
  57 }
  58
  59 static const struct file_operations usb_fops = {
  60         .owner =        THIS_MODULE,
  61         .open =         usb_open,
  62         .llseek =       noop_llseek,
  63 };
  64
  65 static struct usb_class {
  66         struct kref kref;
  67         struct class *class;
  68 } *usb_class;
  69
  70 static char *usb_devnode(struct device *dev, mode_t *mode)
  71 {
  72         struct usb_class_driver *drv;
  73
  74         drv = dev_get_drvdata(dev);
  75         if (!drv || !drv->devnode)
  76                 return NULL;
  77         return drv->devnode(dev, mode);
  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                 goto exit;
 103         }
 104         usb_class->class->devnode = usb_devnode;
 105
 106 exit:
 107         return result;
 108 }
 109
 110 static void release_usb_class(struct kref *kref)
 111 {
 112         /* Ok, we cheat as we know we only have one usb_class */
 113         class_destroy(usb_class->class);
 114         kfree(usb_class);
 115         usb_class = NULL;
 116 }
 117
 118 static void destroy_usb_class(void)
 119 {
 120         if (usb_class)
 121                 kref_put(&usb_class->kref, release_usb_class);
 122 }
 123
 124 int usb_major_init(void)
 125 {
 126         int error;
 127
 128         error = register_chrdev(USB_MAJOR, "usb", &usb_fops);
 129         if (error)
 130                 printk(KERN_ERR "Unable to get major %d for usb devices\n",
 131                        USB_MAJOR);
 132
 133         return error;
 134 }
 135
 136 void usb_major_cleanup(void)
 137 {
 138         unregister_chrdev(USB_MAJOR, "usb");
 139 }
 140
 141 /**
 142  * usb_register_dev - register a USB device, and ask for a minor number
 143  * @intf: pointer to the usb_interface that is being registered
 144  * @class_driver: pointer to the usb_class_driver for this device
 145  *
 146  * This should be called by all USB drivers that use the USB major number.
 147  * If CONFIG_USB_DYNAMIC_MINORS is enabled, the minor number will be
 148  * dynamically allocated out of the list of available ones.  If it is not
 149  * enabled, the minor number will be based on the next available free minor,
 150  * starting at the class_driver->minor_base.
 151  *
 152  * This function also creates a usb class device in the sysfs tree.
 153  *
 154  * usb_deregister_dev() must be called when the driver is done with
 155  * the minor numbers given out by this function.
 156  *
 157  * Returns -EINVAL if something bad happens with trying to register a
 158  * device, and 0 on success.
 159  */
 160 int usb_register_dev(struct usb_interface *intf,
 161                      struct usb_class_driver *class_driver)
 162 {
 163         int retval = -EINVAL;
 164         int minor_base = class_driver->minor_base;
 165         int minor = 0;
 166         char name[20];
 167         char *temp;
 168
 169 #ifdef CONFIG_USB_DYNAMIC_MINORS
 170         /*
 171          * We don't care what the device tries to start at, we want to start
 172          * at zero to pack the devices into the smallest available space with
 173          * no holes in the minor range.
 174          */
 175         minor_base = 0;
 176 #endif
 177         intf->minor = -1;
 178
 179         dbg ("looking for a minor, starting at %d", minor_base);
 180
 181         if (class_driver->fops == NULL)
 182                 goto exit;
 183
 184         down_write(&minor_rwsem);
 185         for (minor = minor_base; minor < MAX_USB_MINORS; ++minor) {
 186                 if (usb_minors[minor])
 187                         continue;
 188
 189                 usb_minors[minor] = class_driver->fops;
 190
 191                 retval = 0;
 192                 break;
 193         }
 194         up_write(&minor_rwsem);
 195
 196         if (retval)
 197                 goto exit;
 198
 199         retval = init_usb_class();
 200         if (retval)
 201                 goto exit;
 202
 203         intf->minor = minor;
 204
 205         /* create a usb class device for this usb interface */
 206         snprintf(name, sizeof(name), class_driver->name, minor - minor_base);
 207         temp = strrchr(name, '/');
 208         if (temp && (temp[1] != '\0'))
 209                 ++temp;
 210         else
 211                 temp = name;
 212         intf->usb_dev = device_create(usb_class->class, &intf->dev,
 213                                       MKDEV(USB_MAJOR, minor), class_driver,
 214                                       "%s", temp);
 215         if (IS_ERR(intf->usb_dev)) {
 216                 down_write(&minor_rwsem);
 217                 usb_minors[intf->minor] = NULL;
 218                 up_write(&minor_rwsem);
 219                 retval = PTR_ERR(intf->usb_dev);
 220         }
 221 exit:
 222         return retval;
 223 }
 224 EXPORT_SYMBOL_GPL(usb_register_dev);
 225
 226 /**
 227  * usb_deregister_dev - deregister a USB device's dynamic minor.
 228  * @intf: pointer to the usb_interface that is being deregistered
 229  * @class_driver: pointer to the usb_class_driver for this device
 230  *
 231  * Used in conjunction with usb_register_dev().  This function is called
 232  * when the USB driver is finished with the minor numbers gotten from a
 233  * call to usb_register_dev() (usually when the device is disconnected
 234  * from the system.)
 235  *
 236  * This function also removes the usb class device from the sysfs tree.
 237  *
 238  * This should be called by all drivers that use the USB major number.
 239  */
 240 void usb_deregister_dev(struct usb_interface *intf,
 241                         struct usb_class_driver *class_driver)
 242 {
 243         int minor_base = class_driver->minor_base;
 244         char name[20];
 245
 246 #ifdef CONFIG_USB_DYNAMIC_MINORS
 247         minor_base = 0;
 248 #endif
 249
 250         if (intf->minor == -1)
 251                 return;
 252
 253         dbg ("removing %d minor", intf->minor);
 254
 255         down_write(&minor_rwsem);
 256         usb_minors[intf->minor] = NULL;
 257         up_write(&minor_rwsem);
 258
 259         snprintf(name, sizeof(name), class_driver->name, intf->minor - minor_base);
 260         device_destroy(usb_class->class, MKDEV(USB_MAJOR, intf->minor));
 261         intf->usb_dev = NULL;
 262         intf->minor = -1;
 263         destroy_usb_class();
 264 }
 265 EXPORT_SYMBOL_GPL(usb_deregister_dev);