devices.c

linux1.1源代码

/*
 *  linux/fs/devices.c
 *
 * (C) 1993 Matthias Urlichs -- collected common code and tables.
 * 
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

#include <linux/fs.h>
#include <linux/major.h>
#include <linux/string.h>
#include <linux/sched.h>
#include <linux/ext_fs.h>
#include <linux/stat.h>
#include <linux/fcntl.h>
#include <linux/errno.h>

struct device_struct {
	const char * name;
	struct file_operations * fops;
};

static struct device_struct chrdevs[MAX_CHRDEV] = {
	{ NULL, NULL },
};

static struct device_struct blkdevs[MAX_BLKDEV] = {
	{ NULL, NULL },
};

struct file_operations * get_blkfops(unsigned int major)
{
	if (major >= MAX_BLKDEV)
		return NULL;
	return blkdevs[major].fops;
}

struct file_operations * get_chrfops(unsigned int major)
{
	if (major >= MAX_CHRDEV)
		return NULL;
	return chrdevs[major].fops;
}

int register_chrdev(unsigned int major, const char * name, struct file_operations *fops)
{
	if (major >= MAX_CHRDEV)
		return -EINVAL;
	if (chrdevs[major].fops)
		return -EBUSY;
	chrdevs[major].name = name;
	chrdevs[major].fops = fops;
	return 0;
}

int register_blkdev(unsigned int major, const char * name, struct file_operations *fops)
{
	if (major >= MAX_BLKDEV)
		return -EINVAL;
	if (blkdevs[major].fops)
		return -EBUSY;
	blkdevs[major].name = name;
	blkdevs[major].fops = fops;
	return 0;
}

int unregister_chrdev(unsigned int major, const char * name)
{
	if (major >= MAX_CHRDEV)
		return -EINVAL;
	if (!chrdevs[major].fops)
		return -EINVAL;
	if (strcmp(chrdevs[major].name, name))
		return -EINVAL;
	chrdevs[major].name = NULL;
	chrdevs[major].fops = NULL;
	return 0;
}

int unregister_blkdev(unsigned int major, const char * name)
{
	if (major >= MAX_BLKDEV)
		return -EINVAL;
	if (!blkdevs[major].fops)
		return -EINVAL;
	if (strcmp(blkdevs[major].name, name))
		return -EINVAL;
	blkdevs[major].name = NULL;
	blkdevs[major].fops = NULL;
	return 0;
}

/*
 * Called every time a block special file is opened
 */
int blkdev_open(struct inode * inode, struct file * filp)
{
	int i;

	i = MAJOR(inode->i_rdev);
	if (i >= MAX_BLKDEV || !blkdevs[i].fops)
		return -ENODEV;
	filp->f_op = blkdevs[i].fops;
	if (filp->f_op->open)
		return filp->f_op->open(inode,filp);
	return 0;
}	

/*
 * Dummy default file-operations: the only thing this does
 * is contain the open that then fills in the correct operations
 * depending on the special file...
 */
struct file_operations def_blk_fops = {
	NULL,		/* lseek */
	NULL,		/* read */
	NULL,		/* write */
	NULL,		/* readdir */
	NULL,		/* select */
	NULL,		/* ioctl */
	NULL,		/* mmap */
	blkdev_open,	/* open */
	NULL,		/* release */
};

struct inode_operations blkdev_inode_operations = {
	&def_blk_fops,		/* default file operations */
	NULL,			/* create */
	NULL,			/* lookup */
	NULL,			/* link */
	NULL,			/* unlink */
	NULL,			/* symlink */
	NULL,			/* mkdir */
	NULL,			/* rmdir */
	NULL,			/* mknod */
	NULL,			/* rename */
	NULL,			/* readlink */
	NULL,			/* follow_link */
	NULL,			/* bmap */
	NULL,			/* truncate */
	NULL			/* permission */
};

/*
 * Called every time a character special file is opened
 */
int chrdev_open(struct inode * inode, struct file * filp)
{
	int i;

	i = MAJOR(inode->i_rdev);
	if (i >= MAX_CHRDEV || !chrdevs[i].fops)
		return -ENODEV;
	filp->f_op = chrdevs[i].fops;
	if (filp->f_op->open)
		return filp->f_op->open(inode,filp);
	return 0;
}

/*
 * Dummy default file-operations: the only thing this does
 * is contain the open that then fills in the correct operations
 * depending on the special file...
 */
struct file_operations def_chr_fops = {
	NULL,		/* lseek */
	NULL,		/* read */
	NULL,		/* write */
	NULL,		/* readdir */
	NULL,		/* select */
	NULL,		/* ioctl */
	NULL,		/* mmap */
	chrdev_open,	/* open */
	NULL,		/* release */
};

struct inode_operations chrdev_inode_operations = {
	&def_chr_fops,		/* default file operations */
	NULL,			/* create */
	NULL,			/* lookup */
	NULL,			/* link */
	NULL,			/* unlink */
	NULL,			/* symlink */
	NULL,			/* mkdir */
	NULL,			/* rmdir */
	NULL,			/* mknod */
	NULL,			/* rename */
	NULL,			/* readlink */
	NULL,			/* follow_link */
	NULL,			/* bmap */
	NULL,			/* truncate */
	NULL			/* permission */
};