drivers/usb/core/file.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * drivers/usb/core/file.c
   4  *
   5  * (C) Copyright Linus Torvalds 1999
   6  * (C) Copyright Johannes Erdfelt 1999-2001
   7  * (C) Copyright Andreas Gal 1999
   8  * (C) Copyright Gregory P. Smith 1999
   9  * (C) Copyright Deti Fliegl 1999 (new USB architecture)
  10  * (C) Copyright Randy Dunlap 2000
  11  * (C) Copyright David Brownell 2000-2001 (kernel hotplug, usb_device_id,
  12  *      more docs, etc)
  13  * (C) Copyright Yggdrasil Computing, Inc. 2000
  14  *     (usb_device_id matching changes by Adam J. Richter)
  15  * (C) Copyright Greg Kroah-Hartman 2002-2003
  16  *
  17  * Released under the GPLv2 only.
  18  */
  19
  20 #include <linux/module.h>
  21 #include <linux/errno.h>
  22 #include <linux/rwsem.h>
  23 #include <linux/slab.h>
  24 #include <linux/string.h>
  25 #include <linux/usb.h>
  26
  27 #include "usb.h"
  28
  29 #define MAX_USB_MINORS  256
  30 static const struct file_operations *usb_minors[MAX_USB_MINORS];
  31 static DECLARE_RWSEM(minor_rwsem);
  32 static DEFINE_MUTEX(init_usb_class_mutex);
  33
  34 static int usb_open(struct inode *inode, struct file *file)
  35 {
  36         int err = -ENODEV;
  37         const struct file_operations *new_fops;
  38
  39         down_read(&minor_rwsem);
  40         new_fops = fops_get(usb_minors[iminor(inode)]);
  41
  42         if (!new_fops)
  43                 goto done;
  44
  45         replace_fops(file, 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  done:
  50         up_read(&minor_rwsem);
  51         return err;
  52 }
  53
  54 static const struct file_operations usb_fops = {
  55         .owner =        THIS_MODULE,
  56         .open =         usb_open,
  57         .llseek =       noop_llseek,
  58 };
  59
  60 static struct usb_class {
  61         struct kref kref;
  62         struct class *class;
  63 } *usb_class;
  64
  65 static char *usb_devnode(struct device *dev, umode_t *mode)
  66 {
  67         struct usb_class_driver *drv;
  68
  69         drv = dev_get_drvdata(dev);
  70         if (!drv || !drv->devnode)
  71                 return NULL;
  72         return drv->devnode(dev, mode);
  73 }
  74
  75 static int init_usb_class(void)
  76 {
  77         int result = 0;
  78
  79         if (usb_class != NULL) {
  80                 kref_get(&usb_class->kref);
  81                 goto exit;
  82         }
  83
  84         usb_class = kmalloc(sizeof(*usb_class), GFP_KERNEL);
  85         if (!usb_class) {
  86                 result = -ENOMEM;
  87                 goto exit;
  88         }
  89
  90         kref_init(&usb_class->kref);
  91         usb_class->class = class_create(THIS_MODULE, "usbmisc");
  92         if (IS_ERR(usb_class->class)) {
  93                 result = PTR_ERR(usb_class->class);
  94                 printk(KERN_ERR "class_create failed for usb devices\n");
  95                 kfree(usb_class);
  96                 usb_class = NULL;
  97                 goto exit;
  98         }
  99         usb_class->class->devnode = usb_devnode;
 100
 101 exit:
 102         return result;
 103 }
 104
 105 static void release_usb_class(struct kref *kref)
 106 {
 107         /* Ok, we cheat as we know we only have one usb_class */
 108         class_destroy(usb_class->class);
 109         kfree(usb_class);
 110         usb_class = NULL;
 111 }
 112
 113 static void destroy_usb_class(void)
 114 {
 115         mutex_lock(&init_usb_class_mutex);
 116         kref_put(&usb_class->kref, release_usb_class);
 117         mutex_unlock(&init_usb_class_mutex);
 118 }
 119
 120 int usb_major_init(void)
 121 {
 122         int error;
 123
 124         error = register_chrdev(USB_MAJOR, "usb", &usb_fops);
 125         if (error)
 126                 printk(KERN_ERR "Unable to get major %d for usb devices\n",
 127                        USB_MAJOR);
 128
 129         return error;
 130 }
 131
 132 void usb_major_cleanup(void)
 133 {
 134         unregister_chrdev(USB_MAJOR, "usb");
 135 }
 136
 137 /**
 138  * usb_register_dev - register a USB device, and ask for a minor number
 139  * @intf: pointer to the usb_interface that is being registered
 140  * @class_driver: pointer to the usb_class_driver for this device
 141  *
 142  * This should be called by all USB drivers that use the USB major number.
 143  * If CONFIG_USB_DYNAMIC_MINORS is enabled, the minor number will be
 144  * dynamically allocated out of the list of available ones.  If it is not
 145  * enabled, the minor number will be based on the next available free minor,
 146  * starting at the class_driver->minor_base.
 147  *
 148  * This function also creates a usb class device in the sysfs tree.
 149  *
 150  * usb_deregister_dev() must be called when the driver is done with
 151  * the minor numbers given out by this function.
 152  *
 153  * Return: -EINVAL if something bad happens with trying to register a
 154  * device, and 0 on success.
 155  */
 156 int usb_register_dev(struct usb_interface *intf,
 157                      struct usb_class_driver *class_driver)
 158 {
 159         int retval;
 160         int minor_base = class_driver->minor_base;
 161         int minor;
 162         char name[20];
 163
 164 #ifdef CONFIG_USB_DYNAMIC_MINORS
 165         /*
 166          * We don't care what the device tries to start at, we want to start
 167          * at zero to pack the devices into the smallest available space with
 168          * no holes in the minor range.
 169          */
 170         minor_base = 0;
 171 #endif
 172
 173         if (class_driver->fops == NULL)
 174                 return -EINVAL;
 175         if (intf->minor >= 0)
 176                 return -EADDRINUSE;
 177
 178         mutex_lock(&init_usb_class_mutex);
 179         retval = init_usb_class();
 180         mutex_unlock(&init_usb_class_mutex);
 181
 182         if (retval)
 183                 return retval;
 184
 185         dev_dbg(&intf->dev, "looking for a minor, starting at %d\n", minor_base);
 186
 187         down_write(&minor_rwsem);
 188         for (minor = minor_base; minor < MAX_USB_MINORS; ++minor) {
 189                 if (usb_minors[minor])
 190                         continue;
 191
 192                 usb_minors[minor] = class_driver->fops;
 193                 intf->minor = minor;
 194                 break;
 195         }
 196         if (intf->minor < 0) {
 197                 up_write(&minor_rwsem);
 198                 return -EXFULL;
 199         }
 200
 201         /* create a usb class device for this usb interface */
 202         snprintf(name, sizeof(name), class_driver->name, minor - minor_base);
 203         intf->usb_dev = device_create(usb_class->class, &intf->dev,
 204                                       MKDEV(USB_MAJOR, minor), class_driver,
 205                                       "%s", kbasename(name));
 206         if (IS_ERR(intf->usb_dev)) {
 207                 usb_minors[minor] = NULL;
 208                 intf->minor = -1;
 209                 retval = PTR_ERR(intf->usb_dev);
 210         }
 211         up_write(&minor_rwsem);
 212         return retval;
 213 }
 214 EXPORT_SYMBOL_GPL(usb_register_dev);
 215
 216 /**
 217  * usb_deregister_dev - deregister a USB device's dynamic minor.
 218  * @intf: pointer to the usb_interface that is being deregistered
 219  * @class_driver: pointer to the usb_class_driver for this device
 220  *
 221  * Used in conjunction with usb_register_dev().  This function is called
 222  * when the USB driver is finished with the minor numbers gotten from a
 223  * call to usb_register_dev() (usually when the device is disconnected
 224  * from the system.)
 225  *
 226  * This function also removes the usb class device from the sysfs tree.
 227  *
 228  * This should be called by all drivers that use the USB major number.
 229  */
 230 void usb_deregister_dev(struct usb_interface *intf,
 231                         struct usb_class_driver *class_driver)
 232 {
 233         if (intf->minor == -1)
 234                 return;
 235
 236         dev_dbg(&intf->dev, "removing %d minor\n", intf->minor);
 237         device_destroy(usb_class->class, MKDEV(USB_MAJOR, intf->minor));
 238
 239         down_write(&minor_rwsem);
 240         usb_minors[intf->minor] = NULL;
 241         up_write(&minor_rwsem);
 242
 243         intf->usb_dev = NULL;
 244         intf->minor = -1;
 245         destroy_usb_class();
 246 }
 247 EXPORT_SYMBOL_GPL(usb_deregister_dev);