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// SPDX-License-Identifier: GPL-2.0
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/*
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 * linux/drivers/char/misc.c
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 *
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 * Generic misc open routine by Johan Myreen
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 *
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 * Based on code from Linus
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 *
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 * Teemu Rantanen's Microsoft Busmouse support and Derrick Cole's
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 *   changes incorporated into 0.97pl4
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 *   by Peter Cervasio (pete%[email protected]) (08SEP92)
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 *   See busmouse.c for particulars.
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 *
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 * Made things a lot mode modular - easy to compile in just one or two
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 * of the misc drivers, as they are now completely independent. Linus.
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 *
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 * Support for loadable modules. 8-Sep-95 Philip Blundell <[email protected]>
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 *
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 * Fixed a failing symbol register to free the device registration
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 *		Alan Cox <[email protected]> 21-Jan-96
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 *
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 * Dynamic minors and /proc/mice by Alessandro Rubini. 26-Mar-96
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 *
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 * Renamed to misc and miscdevice to be more accurate. Alan Cox 26-Mar-96
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 *
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 * Handling of mouse minor numbers for kerneld:
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 *  Idea by Jacques Gelinas <[email protected]>,
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 *  adapted by Bjorn Ekwall <[email protected]>
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 *  corrected by Alan Cox <[email protected]>
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 *
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 * Changes for kmod (from kerneld):
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 *	Cyrus Durgin <[email protected]>
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 *
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 * Added devfs support. Richard Gooch <[email protected]>  10-Jan-1998
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 */
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#include <linux/module.h>
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#include <linux/fs.h>
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#include <linux/errno.h>
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#include <linux/miscdevice.h>
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#include <linux/kernel.h>
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#include <linux/major.h>
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#include <linux/mutex.h>
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#include <linux/proc_fs.h>
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#include <linux/seq_file.h>
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#include <linux/stat.h>
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#include <linux/init.h>
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#include <linux/device.h>
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#include <linux/tty.h>
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#include <linux/kmod.h>
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#include <linux/gfp.h>
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/*
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 * Head entry for the doubly linked miscdevice list
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 */
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static LIST_HEAD(misc_list);
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static DEFINE_MUTEX(misc_mtx);
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/*
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 * Assigned numbers.
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 */
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static DEFINE_IDA(misc_minors_ida);
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static int misc_minor_alloc(int minor)
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{
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	int ret = 0;
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	if (minor == MISC_DYNAMIC_MINOR) {
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		/* allocate free id */
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		ret = ida_alloc_range(&misc_minors_ida, MISC_DYNAMIC_MINOR + 1,
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				      MINORMASK, GFP_KERNEL);
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	} else {
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		ret = ida_alloc_range(&misc_minors_ida, minor, minor, GFP_KERNEL);
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	}
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	return ret;
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}
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static void misc_minor_free(int minor)
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{
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	ida_free(&misc_minors_ida, minor);
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}
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#ifdef CONFIG_PROC_FS
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static void *misc_seq_start(struct seq_file *seq, loff_t *pos)
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{
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	mutex_lock(&misc_mtx);
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	return seq_list_start(&misc_list, *pos);
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}
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static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
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{
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	return seq_list_next(v, &misc_list, pos);
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}
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static void misc_seq_stop(struct seq_file *seq, void *v)
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{
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	mutex_unlock(&misc_mtx);
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}
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static int misc_seq_show(struct seq_file *seq, void *v)
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{
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	const struct miscdevice *p = list_entry(v, struct miscdevice, list);
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	seq_printf(seq, "%3i %s\n", p->minor, p->name ? p->name : "");
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	return 0;
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}
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static const struct seq_operations misc_seq_ops = {
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	.start = misc_seq_start,
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	.next  = misc_seq_next,
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	.stop  = misc_seq_stop,
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	.show  = misc_seq_show,
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};
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#endif
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static int misc_open(struct inode *inode, struct file *file)
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{
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	int minor = iminor(inode);
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	struct miscdevice *c = NULL, *iter;
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	int err = -ENODEV;
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	const struct file_operations *new_fops = NULL;
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	mutex_lock(&misc_mtx);
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	list_for_each_entry(iter, &misc_list, list) {
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		if (iter->minor != minor)
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			continue;
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		c = iter;
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		new_fops = fops_get(iter->fops);
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		break;
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	}
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	/* Only request module for fixed minor code */
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	if (!new_fops && minor < MISC_DYNAMIC_MINOR) {
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		mutex_unlock(&misc_mtx);
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		request_module("char-major-%d-%d", MISC_MAJOR, minor);
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		mutex_lock(&misc_mtx);
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		list_for_each_entry(iter, &misc_list, list) {
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			if (iter->minor != minor)
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				continue;
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			c = iter;
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			new_fops = fops_get(iter->fops);
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			break;
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		}
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	}
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	if (!new_fops)
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		goto fail;
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	/*
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	 * Place the miscdevice in the file's
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	 * private_data so it can be used by the
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	 * file operations, including f_op->open below
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	 */
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	file->private_data = c;
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	err = 0;
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	replace_fops(file, new_fops);
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	if (file->f_op->open)
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		err = file->f_op->open(inode, file);
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fail:
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	mutex_unlock(&misc_mtx);
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	return err;
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}
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static char *misc_devnode(const struct device *dev, umode_t *mode)
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{
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	const struct miscdevice *c = dev_get_drvdata(dev);
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	if (mode && c->mode)
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		*mode = c->mode;
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	if (c->nodename)
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		return kstrdup(c->nodename, GFP_KERNEL);
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	return NULL;
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}
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static const struct class misc_class = {
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	.name		= "misc",
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	.devnode	= misc_devnode,
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};
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static const struct file_operations misc_fops = {
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	.owner		= THIS_MODULE,
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	.open		= misc_open,
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	.llseek		= noop_llseek,
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};
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/**
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 *	misc_register	-	register a miscellaneous device
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 *	@misc: device structure
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 *
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 *	Register a miscellaneous device with the kernel. If the minor
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 *	number is set to %MISC_DYNAMIC_MINOR a minor number is assigned
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 *	and placed in the minor field of the structure. For other cases
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 *	the minor number requested is used.
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 *
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 *	The structure passed is linked into the kernel and may not be
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 *	destroyed until it has been unregistered. By default, an open()
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 *	syscall to the device sets file->private_data to point to the
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 *	structure. Drivers don't need open in fops for this.
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 *
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 *	A zero is returned on success and a negative errno code for
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 *	failure.
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 */
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int misc_register(struct miscdevice *misc)
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{
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	dev_t dev;
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	int err = 0;
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	bool is_dynamic = (misc->minor == MISC_DYNAMIC_MINOR);
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	if (misc->minor > MISC_DYNAMIC_MINOR) {
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		pr_err("Invalid fixed minor %d for miscdevice '%s'\n",
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		       misc->minor, misc->name);
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		return -EINVAL;
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	}
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	INIT_LIST_HEAD(&misc->list);
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	mutex_lock(&misc_mtx);
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	if (is_dynamic) {
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		int i = misc_minor_alloc(misc->minor);
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228
		if (i < 0) {
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			err = -EBUSY;
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			goto out;
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		}
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		misc->minor = i;
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	} else {
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		struct miscdevice *c;
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		int i;
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		list_for_each_entry(c, &misc_list, list) {
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			if (c->minor == misc->minor) {
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				err = -EBUSY;
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				goto out;
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			}
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		}
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		i = misc_minor_alloc(misc->minor);
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		if (i < 0) {
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			err = -EBUSY;
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			goto out;
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		}
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	}
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	dev = MKDEV(MISC_MAJOR, misc->minor);
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	misc->this_device =
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		device_create_with_groups(&misc_class, misc->parent, dev,
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					  misc, misc->groups, "%s", misc->name);
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	if (IS_ERR(misc->this_device)) {
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		misc_minor_free(misc->minor);
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		if (is_dynamic) {
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			misc->minor = MISC_DYNAMIC_MINOR;
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		}
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		err = PTR_ERR(misc->this_device);
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		goto out;
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	}
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	/*
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	 * Add it to the front, so that later devices can "override"
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	 * earlier defaults
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	 */
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	list_add(&misc->list, &misc_list);
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 out:
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	mutex_unlock(&misc_mtx);
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	return err;
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}
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EXPORT_SYMBOL(misc_register);
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/**
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 *	misc_deregister - unregister a miscellaneous device
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 *	@misc: device to unregister
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 *
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 *	Unregister a miscellaneous device that was previously
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 *	successfully registered with misc_register().
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 */
283

284
void misc_deregister(struct miscdevice *misc)
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{
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	mutex_lock(&misc_mtx);
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	list_del_init(&misc->list);
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	device_destroy(&misc_class, MKDEV(MISC_MAJOR, misc->minor));
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	misc_minor_free(misc->minor);
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	if (misc->minor > MISC_DYNAMIC_MINOR)
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		misc->minor = MISC_DYNAMIC_MINOR;
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	mutex_unlock(&misc_mtx);
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}
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EXPORT_SYMBOL(misc_deregister);
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static int __init misc_init(void)
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{
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	int err;
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	struct proc_dir_entry *misc_proc_file;
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301
	misc_proc_file = proc_create_seq("misc", 0, NULL, &misc_seq_ops);
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	err = class_register(&misc_class);
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	if (err)
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		goto fail_remove;
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	err = __register_chrdev(MISC_MAJOR, 0, MINORMASK + 1, "misc", &misc_fops);
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	if (err < 0)
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		goto fail_printk;
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	return 0;
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fail_printk:
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	pr_err("unable to get major %d for misc devices\n", MISC_MAJOR);
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	class_unregister(&misc_class);
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fail_remove:
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	if (misc_proc_file)
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		remove_proc_entry("misc", NULL);
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	return err;
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}
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subsys_initcall(misc_init);
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