linux-imx

// SPDX-License-Identifier: GPL-2.0

/*

 *  linux/fs/char_dev.c

 *

 *  Copyright (C) 1991, 1992  Linus Torvalds

 */

​

#include <linux/init.h>

#include <linux/fs.h>

#include <linux/kdev_t.h>

#include <linux/slab.h>

#include <linux/string.h>

​

#include <linux/major.h>

#include <linux/errno.h>

#include <linux/module.h>

#include <linux/seq_file.h>

​

#include <linux/kobject.h>

#include <linux/kobj_map.h>

#include <linux/cdev.h>

#include <linux/mutex.h>

#include <linux/backing-dev.h>

#include <linux/tty.h>

​

#include "internal.h"

​

static struct kobj_map *cdev_map;

​

static DEFINE_MUTEX(chrdevs_lock);

​

#define CHRDEV_MAJOR_HASH_SIZE 255

​

static struct char_device_struct {

    struct char_device_struct *next;

    unsigned int major;

    unsigned int baseminor;

    int minorct;

    char name[64];

    struct cdev *cdev;      /* will die */

} *chrdevs[CHRDEV_MAJOR_HASH_SIZE];

​

/* index in the above */

static inline int major_to_index(unsigned major)

{

    return major % CHRDEV_MAJOR_HASH_SIZE;

}

​

#ifdef CONFIG_PROC_FS

​

void chrdev_show(struct seq_file *f, off_t offset)

{

    struct char_device_struct *cd;

​

    mutex_lock(&chrdevs_lock);

    for (cd = chrdevs[major_to_index(offset)]; cd; cd = cd->next) {

        if (cd->major == offset)

            seq_printf(f, "%3d %s\n", cd->major, cd->name);

    }

    mutex_unlock(&chrdevs_lock);

}

​

#endif /* CONFIG_PROC_FS */

​

static int find_dynamic_major(void)

{

    int i;

    struct char_device_struct *cd;

​

    for (i = ARRAY_SIZE(chrdevs)-1; i >= CHRDEV_MAJOR_DYN_END; i--) {

        if (chrdevs[i] == NULL)

            return i;

    }

​

    for (i = CHRDEV_MAJOR_DYN_EXT_START;

         i >= CHRDEV_MAJOR_DYN_EXT_END; i--) {

        for (cd = chrdevs[major_to_index(i)]; cd; cd = cd->next)

            if (cd->major == i)

                break;

​

        if (cd == NULL)

            return i;

    }

​

    return -EBUSY;

}

​

/*

 * Register a single major with a specified minor range.

 *

 * If major == 0 this functions will dynamically allocate a major and return

 * its number.