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