// SPDX-License-Identifier: GPL-2.0/* * linux/drivers/char/misc.c * * Generic misc open routine by Johan Myreen * * Based on code from Linus * * Teemu Rantanen's Microsoft Busmouse support and Derrick Cole's *   changes incorporated into 0.97pl4 *   by Peter Cervasio (pete%q106fm.uucp@wupost.wustl.edu) (08SEP92) *   See busmouse.c for particulars. * * Made things a lot mode modular - easy to compile in just one or two * of the misc drivers, as they are now completely independent. Linus. * * Support for loadable modules. 8-Sep-95 Philip Blundell <pjb27@cam.ac.uk> * * Fixed a failing symbol register to free the device registration *		Alan Cox <alan@lxorguk.ukuu.org.uk> 21-Jan-96 * * Dynamic minors and /proc/mice by Alessandro Rubini. 26-Mar-96 * * Renamed to misc and miscdevice to be more accurate. Alan Cox 26-Mar-96 * * Handling of mouse minor numbers for kerneld: *  Idea by Jacques Gelinas <jack@solucorp.qc.ca>, *  adapted by Bjorn Ekwall <bj0rn@blox.se> *  corrected by Alan Cox <alan@lxorguk.ukuu.org.uk> * * Changes for kmod (from kerneld): *	Cyrus Durgin <cider@speakeasy.org> * * Added devfs support. Richard Gooch <rgooch@atnf.csiro.au>  10-Jan-1998 */ #include <linux/module.h> #include <linux/fs.h>#include <linux/errno.h>#include <linux/miscdevice.h>#include <linux/kernel.h>#include <linux/major.h>#include <linux/mutex.h>#include <linux/proc_fs.h>#include <linux/seq_file.h>#include <linux/stat.h>#include <linux/init.h>#include <linux/device.h>#include <linux/tty.h>#include <linux/kmod.h>#include <linux/gfp.h> /* * Head entry for the doubly linked miscdevice list */static LIST_HEAD(misc_list);static DEFINE_MUTEX(misc_mtx); /* * Assigned numbers, used for dynamic minors */#define DYNAMIC_MINORS 128 /* like dynamic majors */static DEFINE_IDA(misc_minors_ida); static int misc_minor_alloc(void){	int ret; 	ret = ida_alloc_max(&misc_minors_ida, DYNAMIC_MINORS - 1, GFP_KERNEL);	if (ret >= 0) {		ret = DYNAMIC_MINORS - ret - 1;	} else {		ret = ida_alloc_range(&misc_minors_ida, MISC_DYNAMIC_MINOR + 1,				      MINORMASK, GFP_KERNEL);	}	return ret;} static void misc_minor_free(int minor){	if (minor < DYNAMIC_MINORS)		ida_free(&misc_minors_ida, DYNAMIC_MINORS - minor - 1);	else if (minor > MISC_DYNAMIC_MINOR)		ida_free(&misc_minors_ida, minor);} #ifdef CONFIG_PROC_FSstatic void *misc_seq_start(struct seq_file *seq, loff_t *pos){	mutex_lock(&misc_mtx);	return seq_list_start(&misc_list, *pos);} static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos){	return seq_list_next(v, &misc_list, pos);} static void misc_seq_stop(struct seq_file *seq, void *v){	mutex_unlock(&misc_mtx);} static int misc_seq_show(struct seq_file *seq, void *v){	const struct miscdevice *p = list_entry(v, struct miscdevice, list); 	seq_printf(seq, "%3i %s\n", p->minor, p->name ? p->name : "");	return 0;}  static const struct seq_operations misc_seq_ops = {	.start = misc_seq_start,	.next  = misc_seq_next,	.stop  = misc_seq_stop,	.show  = misc_seq_show,};#endif static int misc_open(struct inode *inode, struct file *file){	int minor = iminor(inode);	struct miscdevice *c = NULL, *iter;	int err = -ENODEV;	const struct file_operations *new_fops = NULL; 	mutex_lock(&misc_mtx); 	list_for_each_entry(iter, &misc_list, list) {		if (iter->minor != minor)			continue;		c = iter;		new_fops = fops_get(iter->fops);		break;	} 	if (!new_fops) {		mutex_unlock(&misc_mtx);		request_module("char-major-%d-%d", MISC_MAJOR, minor);		mutex_lock(&misc_mtx); 		list_for_each_entry(iter, &misc_list, list) {			if (iter->minor != minor)				continue;			c = iter;			new_fops = fops_get(iter->fops);			break;		}		if (!new_fops)			goto fail;	} 	/*	 * Place the miscdevice in the file's	 * private_data so it can be used by the	 * file operations, including f_op->open below	 */	file->private_data = c; 	err = 0;	replace_fops(file, new_fops);	if (file->f_op->open)		err = file->f_op->open(inode, file);fail:	mutex_unlock(&misc_mtx);	return err;} static char *misc_devnode(const struct device *dev, umode_t *mode){	const struct miscdevice *c = dev_get_drvdata(dev); 	if (mode && c->mode)		*mode = c->mode;	if (c->nodename)		return kstrdup(c->nodename, GFP_KERNEL);	return NULL;} static const struct class misc_class = {	.name		= "misc",	.devnode	= misc_devnode,}; static const struct file_operations misc_fops = {	.owner		= THIS_MODULE,	.open		= misc_open,	.llseek		= noop_llseek,}; /** *	misc_register	-	register a miscellaneous device *	@misc: device structure * *	Register a miscellaneous device with the kernel. If the minor *	number is set to %MISC_DYNAMIC_MINOR a minor number is assigned *	and placed in the minor field of the structure. For other cases *	the minor number requested is used. * *	The structure passed is linked into the kernel and may not be *	destroyed until it has been unregistered. By default, an open() *	syscall to the device sets file->private_data to point to the *	structure. Drivers don't need open in fops for this. * *	A zero is returned on success and a negative errno code for *	failure. */ int misc_register(struct miscdevice *misc){	dev_t dev;	int err = 0;	bool is_dynamic = (misc->minor == MISC_DYNAMIC_MINOR); 	INIT_LIST_HEAD(&misc->list); 	mutex_lock(&misc_mtx); 	if (is_dynamic) {		int i = misc_minor_alloc(); 		if (i < 0) {			err = -EBUSY;			goto out;		}		misc->minor = i;	} else {		struct miscdevice *c; 		list_for_each_entry(c, &misc_list, list) {			if (c->minor == misc->minor) {				err = -EBUSY;				goto out;			}		}	} 	dev = MKDEV(MISC_MAJOR, misc->minor); 	misc->this_device =		device_create_with_groups(&misc_class, misc->parent, dev,					  misc, misc->groups, "%s", misc->name);	if (IS_ERR(misc->this_device)) {		if (is_dynamic) {			misc_minor_free(misc->minor);			misc->minor = MISC_DYNAMIC_MINOR;		}		err = PTR_ERR(misc->this_device);		goto out;	} 	/*	 * Add it to the front, so that later devices can "override"	 * earlier defaults	 */	list_add(&misc->list, &misc_list); out:	mutex_unlock(&misc_mtx);	return err;}EXPORT_SYMBOL(misc_register); /** *	misc_deregister - unregister a miscellaneous device *	@misc: device to unregister * *	Unregister a miscellaneous device that was previously *	successfully registered with misc_register(). */ void misc_deregister(struct miscdevice *misc){	if (WARN_ON(list_empty(&misc->list)))		return; 	mutex_lock(&misc_mtx);	list_del(&misc->list);	device_destroy(&misc_class, MKDEV(MISC_MAJOR, misc->minor));	misc_minor_free(misc->minor);	mutex_unlock(&misc_mtx);}EXPORT_SYMBOL(misc_deregister); static int __init misc_init(void){	int err;	struct proc_dir_entry *ret; 	ret = proc_create_seq("misc", 0, NULL, &misc_seq_ops);	err = class_register(&misc_class);	if (err)		goto fail_remove; 	err = -EIO;	if (register_chrdev(MISC_MAJOR, "misc", &misc_fops))		goto fail_printk;	return 0; fail_printk:	pr_err("unable to get major %d for misc devices\n", MISC_MAJOR);	class_unregister(&misc_class);fail_remove:	if (ret)		remove_proc_entry("misc", NULL);	return err;}subsys_initcall(misc_init);