Linux设备驱动例解

1) 最小框架 

#include <linux/module.h>

static int __init hello_init(void)
{
    printk("Hello Example Init/n");
    return 0;
}
static void __exit hello_exit(void)
{
    printk("Hello Example Exit/n");
}

module_init(hello_init); //模块加载
module_exit(hello_exit); //模块卸载

MODULE_AUTHOR("OOO");
MODULE_DESCRIPTION("Hello Example");
MODULE_LICENSE("GPL");

2) 增加调用接口

#include <linux/module.h>
#include <linux/fs.h>

#define HELLO_MAJOR 242

static int debug_enable = 0;
module_param(debug_enable, int, 0);
MODULE_PARM_DESC(debug_enable,"Enable module debug mode.");

struct file_operations hello_fops;

static int hello_open(struct inode *inode, struct file *file)
{
    printk("hello_open: successful/n");
    return 0;
}

static int hello_release(struct inode *inode, struct file *file)
{
    printk("hello_release: successful/n");
    return 0;
}

static ssize_t hello_read(struct file *file, char *buf, size_t count, loff_t *ptr)
{
    printk("hello_read: returning zero bytes/n");
    return 0;
}

static ssize_t hello_write(struct file *file, const char *buf, size_t count, loff_t *ppos)
{
    printk("hello_write: accepting zero bytes/n");
    return 0;
}

static int hello_ioctl(struct inode *inode, struct file *file,unsigned int cmd, unsigned long arg)
{
    printk("hello_ioctl: cmd=%d, arg=%ld/n", cmd, arg);
    return 0;
}

static int __init hello_init(void)
{
    int ret;
    printk("Hello Example Init - debug mode is %s/n",debug_enable ? "enabled" : "disabled");
    ret = register_chrdev(HELLO_MAJOR, "hello", &hello_fops);
    if(ret < 0)
    {
        printk("Error registering hello device/n");
        goto hello_fail;
    }
    printk("Hello: registered module successfully!/n");
    return 0;

hello_fail:
    return ret;
}

static void __exit hello_exit(void)
{
    printk("Hello Exaple Exit/n");
}

struct file_operations hello_fops = {
    owner: THIS_MODULE,
    read: hello_read,
    write: hello_write,
    ioctl: hello_ioctl,
    open: hello_open,
    release: hello_release,
};

module_init(hello_init);
module_exit(hello_exit);

MODULE_DESCRIPTION("Hello Module Example");
MODULE_LICENSE("GPL");
MODULE_AUTHOR("OOO");

在linux源码树添加相关配置文件，生成hello.ko

3) 测试该模块

在目标平台上，创建设备节点（mknod **** , insmod ****）

然后，编写测试程序:

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

int main(int argc, char **argv)
{
    int fd;
    int rc = 0;
    char *rd_buf[16];

    printf("%s: entered/n", argv[0]);

    fd = open("/dev/hello", O_RDWR);
    if(fd == -1)
    {
        printf("open failed");
        rc = fd;
        exit(-1);
    }
    printf("%s: open successful: %d/n", argv[0], fd);
    close(fd);
}