自己写的scull驱动程序

自己写的scull驱动程序，一开始的代码如下：

 

#include <linux/module.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/moduleparam.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/fcntl.h>
#include <linux/cdev.h>
#include <asm/system.h>
#include <asm/uaccess.h>

int scull_major = 0;
int scull_minor = 0;
int scull_num = 1;

module_param(scull_major, int , S_IRUGO);
module_param(scull_minor, int , S_IRUGO);
module_param(scull_num, int, S_IRUGO);

MODULE_LICENSE("Dual BSD/GPL");

struct scull_dev{
    struct cdev cdev;
    struct semaphore sem;    
};

struct scull_dev *scull_devices;

static int scull_init_module(void);
ssize_t scull_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos);
ssize_t scull_write(struct file *filp, char __user *buf, size_t count, loff_t *f_pos);
int scull_open(struct inode *inode, struct file *filp);
int scull_release(struct inode *inode, struct file *filp);

struct file_operations scull_fops = {
    .owner = THIS_MODULE,
    .read = scull_read,
    .write = scull_write,
    .open = scull_open,
    .release = scull_release,
};

static int scull_init_module(void)
{
    int result, i;
    int err;
    int devt = MKDEV(scull_major, scull_minor);
    dev_t dev = 0;
    
    printk(KERN_ALERT "init\n");

    if(scull_major)
    {
        dev = MKDEV(scull_major, scull_minor);
        result = register_chrdev_region(dev, scull_num, "scull");
    }
    else
    {
        result = alloc_chrdev_region(&dev, scull_minor, scull_num, "scull");
        scull_major = MAJOR(dev);
    }

    if(result < 0)
    {
        printk(KERN_ALERT "scull: can't get major d\n", scull_major);
        return result;
    }

    scull_devices = kmalloc(sizeof(struct scull_dev), GFP_KERNEL);
    if(!scull_devices)
    {
        result = -ENOMEM;
        goto fail;
    }

    cdev_init(&(scull_devices->cdev), &scull_fops);
    scull_devices->cdev.owner = THIS_MODULE;
    scull_devices->cdev.ops = &scull_fops;
    err = cdev_add(&(scull_devices->cdev), devt, 1);
    printk(KERN_ALERT "add\n");    

    if(err)
    {
        printk(KERN_ALERT "add failed\n");
    }

    return 0;

fail:
    return result;

}

static void scull_cleanup_module(void)
{


    dev_t devno = MKDEV(scull_major, scull_minor);

    printk(KERN_ALERT "clean\n");

    if(scull_devices)
    {
        cdev_del(&(scull_devices->cdev));
    }
    kfree(scull_devices);

    unregister_chrdev_region(devno, 1);
}


int scull_open(struct inode *inode, struct file *filp)
{
    struct scull_dev *dev;
    dev = container_of(inode->i_cdev, struct scull_dev, cdev);
    filp->private_data = dev;

    printk(KERN_ALERT "open\n");

    if((filp->f_flags & O_ACCMODE) == O_WRONLY)
    {
        printk(KERN_ALERT "write only\n");
    }

    return 0;
}

int scull_release(struct inode *inode, struct file *filp)
{
    printk(KERN_ALERT "release\n");
    return 0;
}

ssize_t scull_read(struct file *filp, char __user *data, size_t total, loff_t *f_pos)
{
    ssize_t retval = 10;
    struct scull_dev *dev = filp->private_data;
    printk(KERN_ALERT "read\n");    

    return retval;
}

ssize_t scull_write(struct file *filp, char __user *data, size_t total, loff_t *f_pos)
{
    struct scull_dev *dev = filp->private_data;
    ssize_t retval = 40;
    
    printk(KERN_ALERT "write\n");

    return retval;
}

module_init(scull_init_module);
module_exit(scull_cleanup_module);


make后生成scull.ko

insmod scull.ko生成主设备号253

mknod /dev/scull c 253 0生成设备也成功

然后用下面的程序测试：

 

#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>

int main()
{
    int fd;
    ssize_t num = 0;
    char buf[] = "hello scull!\n";
    char *readf;

    fd = open("/dev/scull", O_RDWR);
    if(fd == -1)
    {
        printf("open error\n");
        perror("open error\n");
    }

    printf("fd: %d\n", fd);

    num = write(fd, buf, sizeof(buf));
    printf("unm=%d\n", num);

    readf = (char*)malloc(sizeof(char)*100);

    num = read(fd, readf, 10);
    printf("num:%d\n", num);

    printf("read:%s\n", readf);

    return 0;
}


但总是提示打开失败，“No such device or address”

试了很多遍都不行。

最后将代码改为如下,实际上就是将原来init模块中的红色代码放到函数static void scull_setup_cdev(struct scull_dev *dev, int index)中，然后调用此函数初始化cdev并添加

 

#include <linux/module.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/moduleparam.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/fcntl.h>
#include <linux/cdev.h>
#include <asm/system.h>
#include <asm/uaccess.h>

int scull_major = 0;
int scull_minor = 0;
int scull_num = 1;

module_param(scull_major, int , S_IRUGO);
module_param(scull_minor, int , S_IRUGO);
module_param(scull_num, int, S_IRUGO);

MODULE_LICENSE("Dual BSD/GPL");

struct scull_dev{
    struct cdev cdev;
    struct semaphore sem;    
};

struct scull_dev *scull_devices;

static int scull_init_module(void);
ssize_t scull_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos);
ssize_t scull_write(struct file *filp, char __user *buf, size_t count, loff_t *f_pos);
int scull_open(struct inode *inode, struct file *filp);
int scull_release(struct inode *inode, struct file *filp);
static void scull_setup_cdev(struct scull_dev *dev, int index);

struct file_operations scull_fops = {
    .owner = THIS_MODULE,
    .read = scull_read,
    .write = scull_write,
    .open = scull_open,
    .release = scull_release,
};

static int scull_init_module(void)
{
    int result, i;
    //int err;

    //int devt = MKDEV(scull_major, scull_minor);

    dev_t dev = 0;
    
    printk(KERN_ALERT "init\n");

    if(scull_major)
    {
        dev = MKDEV(scull_major, scull_minor);
        result = register_chrdev_region(dev, scull_num, "scull");
    }
    else
    {
        result = alloc_chrdev_region(&dev, scull_minor, scull_num, "scull");
        scull_major = MAJOR(dev);
    }

    if(result < 0)
    {
        printk(KERN_ALERT "scull: can't get major d\n", scull_major);
        return result;
    }

    scull_devices = kmalloc(sizeof(struct scull_dev), GFP_KERNEL);
    if(!scull_devices)
    {
        result = -ENOMEM;
        goto fail;
    }

    memset(scull_devices, 0, sizeof(struct scull_dev));

    scull_setup_cdev(scull_devices, 0);
    //cdev_init(&(scull_devices->cdev), &scull_fops);

    //scull_devices->cdev.owner = THIS_MODULE;

    //scull_devices->cdev.ops = &scull_fops;

    //err = cdev_add(&(scull_devices->cdev), devt, 1);

    //printk(KERN_ALERT "add\n");    


    //if(err)

    //{

    //    printk(KERN_ALERT "add failed\n");

    //}


    return 0;

fail:
    return result;

}

static void scull_setup_cdev(struct scull_dev *dev, int index)
{
    int err, devno = MKDEV(scull_major, scull_minor+index);
    
    cdev_init(&dev->cdev, &scull_fops);
    dev->cdev.owner = THIS_MODULE;
    dev->cdev.ops = &scull_fops;
    err = cdev_add(&dev->cdev, devno, 1);

    if(err)
    {printk(KERN_ALERT "Error adding scull\n");}
}


static void scull_cleanup_module(void)
{


    dev_t devno = MKDEV(scull_major, scull_minor);

    printk(KERN_ALERT "clean\n");

    if(scull_devices)
    {
        cdev_del(&(scull_devices->cdev));
    }
    kfree(scull_devices);

    unregister_chrdev_region(devno, 1);
}


int scull_open(struct inode *inode, struct file *filp)
{
    struct scull_dev *dev;
    printk(KERN_ALERT "opne1\n");

    dev = container_of(inode->i_cdev, struct scull_dev, cdev);
    filp->private_data = dev;

    printk(KERN_ALERT "open\n");

    if((filp->f_flags & O_ACCMODE) == O_WRONLY)
    {
        printk(KERN_ALERT "write only\n");
    }

    return 0;
}

int scull_release(struct inode *inode, struct file *filp)
{
    printk(KERN_ALERT "release\n");
    return 0;
}

ssize_t scull_read(struct file *filp, char __user *data, size_t total, loff_t *f_pos)
{
    ssize_t retval = 10;
    struct scull_dev *dev = filp->private_data;
    printk(KERN_ALERT "read\n");    

    return retval;
}

ssize_t scull_write(struct file *filp, char __user *data, size_t total, loff_t *f_pos)
{
    struct scull_dev *dev = filp->private_data;
    ssize_t retval = 40;
    
    printk(KERN_ALERT "write\n");

    return retval;
}

module_init(scull_init_module);
module_exit(scull_cleanup_module);


此时再测试就通过了。但是还不清楚为什么在init模块中直接注册设备不行，非要卸载函数中调用才可以。