linux/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%[email protected]) (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 <[email protected]>
 *
 * Fixed a failing symbol register to free the device registration
 *		Alan Cox <[email protected]> 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 <[email protected]>,
 *  adapted by Bjorn Ekwall <[email protected]>
 *  corrected by Alan Cox <[email protected]>
 *
 * Changes for kmod (from kerneld):
 *	Cyrus Durgin <[email protected]>
 *
 * Added devfs support. Richard Gooch <[email protected]>  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 …
static DEFINE_IDA(misc_minors_ida);

static int misc_minor_alloc(void)
{ … }

static void misc_minor_free(int minor)
{ … }

#ifdef CONFIG_PROC_FS
static void *misc_seq_start(struct seq_file *seq, loff_t *pos)
{ … }

static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{ … }

static void misc_seq_stop(struct seq_file *seq, void *v)
{ … }

static int misc_seq_show(struct seq_file *seq, void *v)
{ … }


static const struct seq_operations misc_seq_ops = …;
#endif

static int misc_open(struct inode *inode, struct file *file)
{ … }

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

static const struct class misc_class = …;

static const struct file_operations misc_fops = …;

/**
 *	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)
{ … }
EXPORT_SYMBOL(…);

/**
 *	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)
{ … }
EXPORT_SYMBOL(…);

static int __init misc_init(void)
{ … }
subsys_initcall(misc_init);