【Linux内核驱动】字符设备驱动框架模板

本文详细介绍了在Linux环境下如何从零开始开发一个字符设备驱动，包括设备号的静态与动态分配、字符设备的添加与删除、设备节点的创建与销毁等关键步骤。通过具体代码示例，展示了模块初始化与退出过程中的设备资源管理。

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本文转自https://blog.youkuaiyun.com/wr132/article/details/77849488

#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/kdev_t.h>
#include <linux/slab.h>
#include <linux/device.h>

#define DEVICE_NAME "chrdev_test"
#define DEVICE_MAJOR 0
#define MINOR_BASE 0
#define MINOR_NUM 1

MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("colorfulshark@hotmail.com");

static int major = DEVICE_MAJOR;
static int minor_base = MINOR_BASE;
static int minor_num = MINOR_NUM;
static dev_t devno;
static struct cdev *pcdev;
static struct class *test_class;
static struct device *test_device;

static struct file_operations fops = {
    .owner = THIS_MODULE,
};

#if 0
module_param(major, int, S_IRWXU);
module_param(minor_base, int, S_IRWXU);
module_param(minor_num, int, S_IRWXU);
#endif

static void request_devno(void) //申请设备号
{
    int ret;
    if(major) {  //静态申请设备号
        printk(KERN_ALERT "alloc device number static\n");
        devno = MKDEV(major, minor_base);
        ret = register_chrdev_region(devno, minor_num, DEVICE_NAME);
    } else {  //动态申请设备号
        printk(KERN_ALERT "alloc device number dynamic\n");
        ret = alloc_chrdev_region(&devno, minor_base, minor_num, DEVICE_NAME);
        printk(KERN_ALERT "alloc major : %d\n", MAJOR(devno));
    }
    if(ret < 0) {
        printk(KERN_ALERT "register chrdev region failed\n");
    }
}

static void free_devno(void) //释放设备号
{
    unregister_chrdev_region(devno, minor_num);
}

static int add_cdev(void) //添加字符设备
{
    int error;
    pcdev = cdev_alloc();
    if(pcdev == NULL) {
        goto err_no_mem;
    }
    cdev_init(pcdev, &fops);
    pcdev->owner = THIS_MODULE;
    error = cdev_add(pcdev, devno, minor_num);
    if(error)
        goto err_cdev_add;
    printk(KERN_ALERT "success to add cdev\n");
    return 0;
err_no_mem:
    printk(KERN_ALERT "no enough memory\n");
    free_devno();
    return -ENOMEM;
err_cdev_add:
    printk(KERN_ALERT "fail to add cdev\n");
    free_devno();
    return error;
}

static void del_cdev(void) //删除字符设备
{
    cdev_del(pcdev);
}

static void add_dev_node(void) //创建设备节点，自动创建；如果代码中不创建的话需mknode手动创建
{
    test_class = class_create(THIS_MODULE, "test_class");
    test_device = device_create(test_class, NULL, devno, NULL, "chrdev_test");
}

static void del_dev_node(void) //删除设备节点
{
    device_destroy(test_class, devno);
    class_destroy(test_class);
}



static int chrdev_init(void)
{
    printk(KERN_ALERT "chrdev init\n");
    request_devno();
    add_cdev();
    add_dev_node();
    return 0;
}

static void chrdev_exit(void)
{
    del_dev_node();
    del_cdev();
    free_devno();
    printk(KERN_ALERT "chrdev exit\n");
}

module_init(chrdev_init);
module_exit(chrdev_exit);