usb/core/file.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * drivers/usb/core/file.c
0004  *
0005  * (C) Copyright Linus Torvalds 1999
0006  * (C) Copyright Johannes Erdfelt 1999-2001
0007  * (C) Copyright Andreas Gal 1999
0008  * (C) Copyright Gregory P. Smith 1999
0009  * (C) Copyright Deti Fliegl 1999 (new USB architecture)
0010  * (C) Copyright Randy Dunlap 2000
0011  * (C) Copyright David Brownell 2000-2001 (kernel hotplug, usb_device_id,
0012  *  more docs, etc)
0013  * (C) Copyright Yggdrasil Computing, Inc. 2000
0014  *     (usb_device_id matching changes by Adam J. Richter)
0015  * (C) Copyright Greg Kroah-Hartman 2002-2003
0016  *
0017  * Released under the GPLv2 only.
0018  */
0019
0020 #include <linux/module.h>
0021 #include <linux/errno.h>
0022 #include <linux/rwsem.h>
0023 #include <linux/slab.h>
0024 #include <linux/string.h>
0025 #include <linux/usb.h>
0026
0027 #include "usb.h"
0028
0029 #define MAX_USB_MINORS  256
0030 static const struct file_operations *usb_minors[MAX_USB_MINORS];
0031 static DECLARE_RWSEM(minor_rwsem);
0032 static DEFINE_MUTEX(init_usb_class_mutex);
0033
0034 static int usb_open(struct inode *inode, struct file *file)
0035 {
0036     int err = -ENODEV;
0037     const struct file_operations *new_fops;
0038
0039     down_read(&minor_rwsem);
0040     new_fops = fops_get(usb_minors[iminor(inode)]);
0041
0042     if (!new_fops)
0043         goto done;
0044
0045     replace_fops(file, new_fops);
0046     /* Curiouser and curiouser... NULL ->open() as "no device" ? */
0047     if (file->f_op->open)
0048         err = file->f_op->open(inode, file);
0049  done:
0050     up_read(&minor_rwsem);
0051     return err;
0052 }
0053
0054 static const struct file_operations usb_fops = {
0055     .owner =    THIS_MODULE,
0056     .open =     usb_open,
0057     .llseek =   noop_llseek,
0058 };
0059
0060 static struct usb_class {
0061     struct kref kref;
0062     struct class *class;
0063 } *usb_class;
0064
0065 static char *usb_devnode(struct device *dev, umode_t *mode)
0066 {
0067     struct usb_class_driver *drv;
0068
0069     drv = dev_get_drvdata(dev);
0070     if (!drv || !drv->devnode)
0071         return NULL;
0072     return drv->devnode(dev, mode);
0073 }
0074
0075 static int init_usb_class(void)
0076 {
0077     int result = 0;
0078
0079     if (usb_class != NULL) {
0080         kref_get(&usb_class->kref);
0081         goto exit;
0082     }
0083
0084     usb_class = kmalloc(sizeof(*usb_class), GFP_KERNEL);
0085     if (!usb_class) {
0086         result = -ENOMEM;
0087         goto exit;
0088     }
0089
0090     kref_init(&usb_class->kref);
0091     usb_class->class = class_create(THIS_MODULE, "usbmisc");
0092     if (IS_ERR(usb_class->class)) {
0093         result = PTR_ERR(usb_class->class);
0094         printk(KERN_ERR "class_create failed for usb devices\n");
0095         kfree(usb_class);
0096         usb_class = NULL;
0097         goto exit;
0098     }
0099     usb_class->class->devnode = usb_devnode;
0100
0101 exit:
0102     return result;
0103 }
0104
0105 static void release_usb_class(struct kref *kref)
0106 {
0107     /* Ok, we cheat as we know we only have one usb_class */
0108     class_destroy(usb_class->class);
0109     kfree(usb_class);
0110     usb_class = NULL;
0111 }
0112
0113 static void destroy_usb_class(void)
0114 {
0115     mutex_lock(&init_usb_class_mutex);
0116     kref_put(&usb_class->kref, release_usb_class);
0117     mutex_unlock(&init_usb_class_mutex);
0118 }
0119
0120 int usb_major_init(void)
0121 {
0122     int error;
0123
0124     error = register_chrdev(USB_MAJOR, "usb", &usb_fops);
0125     if (error)
0126         printk(KERN_ERR "Unable to get major %d for usb devices\n",
0127                USB_MAJOR);
0128
0129     return error;
0130 }
0131
0132 void usb_major_cleanup(void)
0133 {
0134     unregister_chrdev(USB_MAJOR, "usb");
0135 }
0136
0137 /**
0138  * usb_register_dev - register a USB device, and ask for a minor number
0139  * @intf: pointer to the usb_interface that is being registered
0140  * @class_driver: pointer to the usb_class_driver for this device
0141  *
0142  * This should be called by all USB drivers that use the USB major number.
0143  * If CONFIG_USB_DYNAMIC_MINORS is enabled, the minor number will be
0144  * dynamically allocated out of the list of available ones.  If it is not
0145  * enabled, the minor number will be based on the next available free minor,
0146  * starting at the class_driver->minor_base.
0147  *
0148  * This function also creates a usb class device in the sysfs tree.
0149  *
0150  * usb_deregister_dev() must be called when the driver is done with
0151  * the minor numbers given out by this function.
0152  *
0153  * Return: -EINVAL if something bad happens with trying to register a
0154  * device, and 0 on success.
0155  */
0156 int usb_register_dev(struct usb_interface *intf,
0157              struct usb_class_driver *class_driver)
0158 {
0159     int retval;
0160     int minor_base = class_driver->minor_base;
0161     int minor;
0162     char name[20];
0163
0164 #ifdef CONFIG_USB_DYNAMIC_MINORS
0165     /*
0166      * We don't care what the device tries to start at, we want to start
0167      * at zero to pack the devices into the smallest available space with
0168      * no holes in the minor range.
0169      */
0170     minor_base = 0;
0171 #endif
0172
0173     if (class_driver->fops == NULL)
0174         return -EINVAL;
0175     if (intf->minor >= 0)
0176         return -EADDRINUSE;
0177
0178     mutex_lock(&init_usb_class_mutex);
0179     retval = init_usb_class();
0180     mutex_unlock(&init_usb_class_mutex);
0181
0182     if (retval)
0183         return retval;
0184
0185     dev_dbg(&intf->dev, "looking for a minor, starting at %d\n", minor_base);
0186
0187     down_write(&minor_rwsem);
0188     for (minor = minor_base; minor < MAX_USB_MINORS; ++minor) {
0189         if (usb_minors[minor])
0190             continue;
0191
0192         usb_minors[minor] = class_driver->fops;
0193         intf->minor = minor;
0194         break;
0195     }
0196     if (intf->minor < 0) {
0197         up_write(&minor_rwsem);
0198         return -EXFULL;
0199     }
0200
0201     /* create a usb class device for this usb interface */
0202     snprintf(name, sizeof(name), class_driver->name, minor - minor_base);
0203     intf->usb_dev = device_create(usb_class->class, &intf->dev,
0204                       MKDEV(USB_MAJOR, minor), class_driver,
0205                       "%s", kbasename(name));
0206     if (IS_ERR(intf->usb_dev)) {
0207         usb_minors[minor] = NULL;
0208         intf->minor = -1;
0209         retval = PTR_ERR(intf->usb_dev);
0210     }
0211     up_write(&minor_rwsem);
0212     return retval;
0213 }
0214 EXPORT_SYMBOL_GPL(usb_register_dev);
0215
0216 /**
0217  * usb_deregister_dev - deregister a USB device's dynamic minor.
0218  * @intf: pointer to the usb_interface that is being deregistered
0219  * @class_driver: pointer to the usb_class_driver for this device
0220  *
0221  * Used in conjunction with usb_register_dev().  This function is called
0222  * when the USB driver is finished with the minor numbers gotten from a
0223  * call to usb_register_dev() (usually when the device is disconnected
0224  * from the system.)
0225  *
0226  * This function also removes the usb class device from the sysfs tree.
0227  *
0228  * This should be called by all drivers that use the USB major number.
0229  */
0230 void usb_deregister_dev(struct usb_interface *intf,
0231             struct usb_class_driver *class_driver)
0232 {
0233     if (intf->minor == -1)
0234         return;
0235
0236     dev_dbg(&intf->dev, "removing %d minor\n", intf->minor);
0237     device_destroy(usb_class->class, MKDEV(USB_MAJOR, intf->minor));
0238
0239     down_write(&minor_rwsem);
0240     usb_minors[intf->minor] = NULL;
0241     up_write(&minor_rwsem);
0242
0243     intf->usb_dev = NULL;
0244     intf->minor = -1;
0245     destroy_usb_class();
0246 }
0247 EXPORT_SYMBOL_GPL(usb_deregister_dev);