Release 4.14 drivers/char/misc.c

// 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 64 
/* like dynamic majors */
static DECLARE_BITMAP(misc_minors, DYNAMIC_MINORS);

#ifdef CONFIG_PROC_FS


static void *misc_seq_start(struct seq_file *seq, loff_t *pos)
{
	mutex_lock(&misc_mtx);
	return seq_list_start(&misc_list, *pos);
}

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8
25.00%
2
33.33%
Pavel Emelyanov
5
15.62%
1
16.67%
Matthias Kaehlcke
2
6.25%
1
16.67%
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32
100.00%
6
100.00%



static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
	return seq_list_next(v, &misc_list, pos);
}

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5
16.13%
1
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31
100.00%
2
100.00%



static void misc_seq_stop(struct seq_file *seq, void *v)
{
	mutex_unlock(&misc_mtx);
}

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21
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2
100.00%



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;
}


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18
32.73%
2
50.00%
Pavel Emelyanov
8
14.55%
1
25.00%
Total
55
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4
100.00%


static const struct seq_operations misc_seq_ops = {
	.start = misc_seq_start,
	.next  = misc_seq_next,
	.stop  = misc_seq_stop,
	.show  = misc_seq_show,
};



static int misc_seq_open(struct inode *inode, struct file *file)
{
	return seq_open(file, &misc_seq_ops);
}

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2
66.67%
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25
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3
100.00%


static const struct file_operations misc_proc_fops = {
	.owner	 = THIS_MODULE,
	.open    = misc_seq_open,
	.read    = seq_read,
	.llseek  = seq_lseek,
	.release = seq_release,
};
#endif



static int misc_open(struct inode *inode, struct file *file)
{
	int minor = iminor(inode);
	struct miscdevice *c;
	int err = -ENODEV;
	const struct file_operations *new_fops = NULL;

	mutex_lock(&misc_mtx);

	list_for_each_entry(c, &misc_list, list) {
		if (c->minor == minor) {
			new_fops = fops_get(c->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(c, &misc_list, list) {
			if (c->minor == minor) {
				new_fops = fops_get(c->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;
}

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Linus Torvalds (pre-git)
138
70.77%
11
57.89%
Stephen Hemminger
32
16.41%
1
5.26%
Matthias Kaehlcke
8
4.10%
1
5.26%
Tom Van Braeckel
7
3.59%
1
5.26%
Al Viro
5
2.56%
2
10.53%
Mikael Pettersson
3
1.54%
1
5.26%
Linus Torvalds
1
0.51%
1
5.26%
Arjan van de Ven
1
0.51%
1
5.26%
Total
195
100.00%
19
100.00%


static struct class *misc_class;


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 = find_first_zero_bit(misc_minors, DYNAMIC_MINORS);

		if (i >= DYNAMIC_MINORS) {
			err = -EBUSY;
			goto out;
		}
		misc->minor = DYNAMIC_MINORS - i - 1;
		set_bit(i, misc_minors);
	} 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) {
			int i = DYNAMIC_MINORS - misc->minor - 1;

			if (i < DYNAMIC_MINORS && i >= 0)
				clear_bit(i, misc_minors);
			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;
}

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8.70%
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2
8.70%
Dae S. Kim
32
12.60%
1
4.35%
Greg Kroah-Hartman
27
10.63%
5
21.74%
Vladimir Zapolskiy
24
9.45%
1
4.35%
Elad Wexler
12
4.72%
1
4.35%
Neil Horman
8
3.15%
1
4.35%
Robert Love
6
2.36%
1
4.35%
Takashi Iwai
5
1.97%
1
4.35%
Matthias Kaehlcke
4
1.57%
1
4.35%
Andrew Morton
2
0.79%
1
4.35%
Kay Sievers
1
0.39%
1
4.35%
Total
254
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23
100.00%

/**
 *      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)
{
	int i = DYNAMIC_MINORS - misc->minor - 1;

	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));
	if (i < DYNAMIC_MINORS && i >= 0)
		clear_bit(i, misc_minors);
	mutex_unlock(&misc_mtx);
}

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18.60%
4
30.77%
Thadeu Lima de Souza Cascardo
11
12.79%
2
15.38%
Stephen Hemminger
10
11.63%
1
7.69%
Matthias Kaehlcke
4
4.65%
1
7.69%
Akinobu Mita
3
3.49%
1
7.69%
Rafael J. Wysocki
1
1.16%
1
7.69%
Total
86
100.00%
13
100.00%


EXPORT_SYMBOL(misc_register);

EXPORT_SYMBOL(misc_deregister);



static char *misc_devnode(struct device *dev, umode_t *mode)
{
	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;
}

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3
100.00%



static int __init misc_init(void)
{
	int err;
	struct proc_dir_entry *ret;

	ret = proc_create("misc", 0, NULL, &misc_proc_fops);
	misc_class = class_create(THIS_MODULE, "misc");
	err = PTR_ERR(misc_class);
	if (IS_ERR(misc_class))
		goto fail_remove;

	err = -EIO;
	if (register_chrdev(MISC_MAJOR, "misc", &misc_fops))
		goto fail_printk;
	misc_class->devnode = misc_devnode;
	return 0;

fail_printk:
	pr_err("unable to get major %d for misc devices\n", MISC_MAJOR);
	class_destroy(misc_class);
fail_remove:
	if (ret)
		remove_proc_entry("misc", NULL);
	return err;
}
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28.45%
9
45.00%
Greg Kroah-Hartman
18
15.52%
3
15.00%
Sudip Mukherjee
11
9.48%
1
5.00%
Kay Sievers
6
5.17%
2
10.00%
Chris Wright
4
3.45%
1
5.00%
Stephen Hemminger
3
2.59%
1
5.00%
Andrew Morton
1
0.86%
1
5.00%
Varsha Rao
1
0.86%
1
5.00%
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116
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20
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subsys_initcall(misc_init);
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369
34.78%
27
38.03%
Stephen Hemminger
261
24.60%
3
4.23%
Greg Kroah-Hartman
73
6.88%
8
11.27%
Kay Sievers
66
6.22%
2
2.82%
Thadeu Lima de Souza Cascardo
61
5.75%
2
2.82%
Denis V. Lunev
39
3.68%
1
1.41%
Dae S. Kim
32
3.02%
1
1.41%
Matthias Kaehlcke
25
2.36%
1
1.41%
Vladimir Zapolskiy
24
2.26%
1
1.41%
Pavel Emelyanov
18
1.70%
1
1.41%
Elad Wexler
12
1.13%
1
1.41%
Sudip Mukherjee
11
1.04%
1
1.41%
Neil Horman
8
0.75%
1
1.41%
Tom Van Braeckel
7
0.66%
1
1.41%
Andrew Morton
7
0.66%
2
2.82%
Al Viro
6
0.57%
3
4.23%
Robert Love
6
0.57%
1
1.41%
Takashi Iwai
5
0.47%
1
1.41%
Arnd Bergmann
5
0.47%
1
1.41%
Art Haas
4
0.38%
1
1.41%
Chris Wright
4
0.38%
1
1.41%
Akinobu Mita
3
0.28%
1
1.41%
Tejun Heo
3
0.28%
1
1.41%
Mikael Pettersson
3
0.28%
1
1.41%
Arjan van de Ven
3
0.28%
2
2.82%
Rafael J. Wysocki
2
0.19%
1
1.41%
James Morris
1
0.09%
1
1.41%
Varsha Rao
1
0.09%
1
1.41%
Tal Shorer
1
0.09%
1
1.41%
Linus Torvalds
1
0.09%
1
1.41%
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71
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Directory: drivers/char

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