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* drivers/usb/core/file.c
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* (C) Copyright Linus Torvalds 1999
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* (C) Copyright Johannes Erdfelt 1999-2001
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* (C) Copyright Andreas Gal 1999
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* (C) Copyright Gregory P. Smith 1999
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* (C) Copyright Deti Fliegl 1999 (new USB architecture)
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* (C) Copyright Randy Dunlap 2000
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* (C) Copyright David Brownell 2000-2001 (kernel hotplug, usb_device_id,
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* (C) Copyright Yggdrasil Computing, Inc. 2000
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* (usb_device_id matching changes by Adam J. Richter)
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* (C) Copyright Greg Kroah-Hartman 2002-2003
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#include <linux/module.h>
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#include <linux/errno.h>
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#include <linux/rwsem.h>
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#include <linux/slab.h>
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#include <linux/usb.h>
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#define MAX_USB_MINORS 256
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static const struct file_operations *usb_minors[MAX_USB_MINORS];
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static DECLARE_RWSEM(minor_rwsem);
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static int usb_open(struct inode * inode, struct file * file)
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int minor = iminor(inode);
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const struct file_operations *c;
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const struct file_operations *old_fops, *new_fops = NULL;
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down_read(&minor_rwsem);
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c = usb_minors[minor];
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if (!c || !(new_fops = fops_get(c)))
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old_fops = file->f_op;
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file->f_op = new_fops;
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/* Curiouser and curiouser... NULL ->open() as "no device" ? */
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err = file->f_op->open(inode,file);
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file->f_op = fops_get(old_fops);
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up_read(&minor_rwsem);
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static const struct file_operations usb_fops = {
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.llseek = noop_llseek,
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static struct usb_class {
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static char *usb_devnode(struct device *dev, mode_t *mode)
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struct usb_class_driver *drv;
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drv = dev_get_drvdata(dev);
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if (!drv || !drv->devnode)
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return drv->devnode(dev, mode);
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static int init_usb_class(void)
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if (usb_class != NULL) {
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kref_get(&usb_class->kref);
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usb_class = kmalloc(sizeof(*usb_class), GFP_KERNEL);
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kref_init(&usb_class->kref);
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usb_class->class = class_create(THIS_MODULE, "usb");
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if (IS_ERR(usb_class->class)) {
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result = IS_ERR(usb_class->class);
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printk(KERN_ERR "class_create failed for usb devices\n");
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usb_class->class->devnode = usb_devnode;
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static void release_usb_class(struct kref *kref)
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/* Ok, we cheat as we know we only have one usb_class */
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class_destroy(usb_class->class);
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static void destroy_usb_class(void)
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kref_put(&usb_class->kref, release_usb_class);
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int usb_major_init(void)
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error = register_chrdev(USB_MAJOR, "usb", &usb_fops);
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printk(KERN_ERR "Unable to get major %d for usb devices\n",
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void usb_major_cleanup(void)
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unregister_chrdev(USB_MAJOR, "usb");
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* usb_register_dev - register a USB device, and ask for a minor number
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* @intf: pointer to the usb_interface that is being registered
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* @class_driver: pointer to the usb_class_driver for this device
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* This should be called by all USB drivers that use the USB major number.
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* If CONFIG_USB_DYNAMIC_MINORS is enabled, the minor number will be
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* dynamically allocated out of the list of available ones. If it is not
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* enabled, the minor number will be based on the next available free minor,
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* starting at the class_driver->minor_base.
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* This function also creates a usb class device in the sysfs tree.
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* usb_deregister_dev() must be called when the driver is done with
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* the minor numbers given out by this function.
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* Returns -EINVAL if something bad happens with trying to register a
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* device, and 0 on success.
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int usb_register_dev(struct usb_interface *intf,
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struct usb_class_driver *class_driver)
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int minor_base = class_driver->minor_base;
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#ifdef CONFIG_USB_DYNAMIC_MINORS
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* We don't care what the device tries to start at, we want to start
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* at zero to pack the devices into the smallest available space with
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* no holes in the minor range.
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if (class_driver->fops == NULL)
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if (intf->minor >= 0)
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retval = init_usb_class();
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dev_dbg(&intf->dev, "looking for a minor, starting at %d", minor_base);
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down_write(&minor_rwsem);
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for (minor = minor_base; minor < MAX_USB_MINORS; ++minor) {
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if (usb_minors[minor])
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usb_minors[minor] = class_driver->fops;
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up_write(&minor_rwsem);
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/* create a usb class device for this usb interface */
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snprintf(name, sizeof(name), class_driver->name, minor - minor_base);
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temp = strrchr(name, '/');
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if (temp && (temp[1] != '\0'))
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intf->usb_dev = device_create(usb_class->class, &intf->dev,
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MKDEV(USB_MAJOR, minor), class_driver,
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if (IS_ERR(intf->usb_dev)) {
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down_write(&minor_rwsem);
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usb_minors[minor] = NULL;
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up_write(&minor_rwsem);
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retval = PTR_ERR(intf->usb_dev);
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EXPORT_SYMBOL_GPL(usb_register_dev);
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* usb_deregister_dev - deregister a USB device's dynamic minor.
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* @intf: pointer to the usb_interface that is being deregistered
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* @class_driver: pointer to the usb_class_driver for this device
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* Used in conjunction with usb_register_dev(). This function is called
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* when the USB driver is finished with the minor numbers gotten from a
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* call to usb_register_dev() (usually when the device is disconnected
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* This function also removes the usb class device from the sysfs tree.
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* This should be called by all drivers that use the USB major number.
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void usb_deregister_dev(struct usb_interface *intf,
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struct usb_class_driver *class_driver)
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if (intf->minor == -1)
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dbg ("removing %d minor", intf->minor);
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down_write(&minor_rwsem);
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usb_minors[intf->minor] = NULL;
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up_write(&minor_rwsem);
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device_destroy(usb_class->class, MKDEV(USB_MAJOR, intf->minor));
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intf->usb_dev = NULL;
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EXPORT_SYMBOL_GPL(usb_deregister_dev);