/*
 * 说明：用于演示一个驱动如何管理多个设备。
 */
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>

#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/cdev.h>
#include <linux/slab.h>
#include <linux/uaccess.h>

#include "ioctl.h"

#define FSDEV_MAJOR	250
#define	FSDEV_MINOR	0
#define FSDEV_NR	2
#define FSDEV_NAME	"fsdev"

struct fsdev {
	struct cdev cdev;
	unsigned char buf[256];
};

static struct fsdev *fsdev[FSDEV_NR];

static int fschr_open(struct inode *inode, struct file *filp)
{
	struct fsdev *fsdev;

	/* 根据保存在inode节点中的cdev指针，反向查询到包含该cdev的结构体，
	 * 将该结构体指针保存在打开的文件结构体的私有数据中，可以在之后
	 * 的read、write以及ioctl当中通过file结构体指针顺利获得反查得到的
	 * 结构体指针，这是实现一个驱动管理多个设备的关键
	 */
	fsdev = container_of(inode->i_cdev, struct fsdev, cdev);
	filp->private_data = fsdev;

	return 0;
}

static int fschr_close(struct inode *inode, struct file *filp)
{
	return 0;
}

static ssize_t fschr_read(struct file *filp, char __user *buf, size_t count, loff_t *fops)
{
	int len;
	int ret;
	struct fsdev *fsdev = filp->private_data;//通过filp的private_data得到是哪一个设备的操作

	len = count > 256 ? 256 : count;
	ret = copy_to_user(buf, fsdev->buf, len);

	return len - ret;
}

static ssize_t fschr_write(struct file *filp, const char __user *buf, size_t count, loff_t *fops)
{
	int len;
	int ret;
	struct fsdev *fsdev = filp->private_data;

	len = count > 256 ? 256 : count;
	ret = copy_from_user(fsdev->buf, buf, len);

	return len - ret;
}

static int fschr_ioctl(struct inode *inode, struct file *filp, unsigned int cmd, unsigned long arg)
{
	int ret = 0;
	struct fsdev *fsdev = filp->private_data;

	if (_IOC_TYPE(cmd) != FS_IOC_MAGIC)
		return -ENOTTY;
	if (_IOC_NR(cmd) > FS_IOC_MAXNR)
		return -ENOTTY;

	if (_IOC_DIR(cmd) & _IOC_READ)
		ret = !access_ok(VERIFY_WRITE, (void __user *)arg, _IOC_SIZE(cmd));
	else if (_IOC_DIR(cmd) & _IOC_WRITE)
		ret =  !access_ok(VERIFY_READ, (void __user *)arg, _IOC_SIZE(cmd));
	if (ret)
		return -EFAULT;

	switch (cmd) {
	case FS_IOC_SET_BUF:
		memset(fsdev->buf, *(char *)arg, sizeof(fsdev->buf));
		break;
	}

	return 0;
}

static struct file_operations fsfops = {
	.owner = THIS_MODULE,
	.open = fschr_open,
	.release = fschr_close,
	.read = fschr_read,
	.write = fschr_write,
	.ioctl = fschr_ioctl
};

static int __init fschr_init(void)
{
	int i;
	int ret;
	int alloc_num = 0;
	int add_num = 0;
	dev_t devno;

	devno = MKDEV(FSDEV_MAJOR, FSDEV_MINOR);
	ret = register_chrdev_region(devno, FSDEV_NR, FSDEV_NAME);
	if (ret) {
		printk(KERN_ERR "fschr: register chrdev region failed\n");
		goto reg_err;
	}

	for (i = 0; i < FSDEV_NR; i++)
	{
		fsdev[i] = (struct fsdev *)kzalloc(sizeof(struct fsdev), GFP_KERNEL);
		if (!fsdev[i]) {
			printk(KERN_ERR "fschr: kzalloc failure\n");
			alloc_num = i;
			ret = -ENOMEM;
			goto alloc_err;
		}
	}
	alloc_num = FSDEV_NR;

	for (i = 0; i < FSDEV_NR; i++) {
		cdev_init(&fsdev[i]->cdev, &fsfops);
		fsdev[i]->cdev.owner = THIS_MODULE;
		ret = cdev_add(&fsdev[i]->cdev, devno + i, 1);
		if (ret) {
			printk(KERN_ERR "fschr: add cdev failed");
			add_num = i;
			goto add_err;
		}
	}

	return 0;

add_err:
	for (i = 0; i < add_num; i++)
		cdev_del(&fsdev[i]->cdev);
alloc_err:		
	for (i = 0; i < alloc_num; i++)
		kfree(fsdev[i]);
	unregister_chrdev_region(devno, FSDEV_NR);
reg_err:
	return ret;
}

static void __exit fschr_exit(void)
{
	int i;
	dev_t devno;

	devno = MKDEV(FSDEV_MAJOR, FSDEV_MINOR);

	for