linux驱动摸索 --驱动框架初始化（结合韦东山视频教程）

一.驱动框架

初始化：insmod 加载

     1.确定主设备号：

            分为静态和动态分配，其中LED_GPIO_SIZE 表示支持的次设备号数目，一般默认为1. 相关实现代码如下：

   int result;
dev_t dev;

   /*分配主设备号*/
   if (scull_major)   /*静态分配一个主设备号*/
   {
    dev = MKDEV(scull_major,0);
    result = register_chrdev_region(dev,LED_GPIO_SIZE,DEVICE_NAME);
   }
else               /*动态分配一个主设备号*/
{
    result = alloc_chrdev_region(&dev,0,LED_GPIO_SIZE,DEVICE_NAME);
    scull_major = MAJOR(dev);
}
if(result <0)
{
    printk("LED:can not get major:%d
",scull_major);
    return result;
}

    2.构造 file_operations 结构：结构成员对应相应的处理函数：

static struct file_operations mini2440_leds_fops = {
    .owner  =   THIS_MODULE,    /* 这是一个宏，推向编译模块时自动创建的__this_module变量 */
    .open   =   mini2440_leds_open,
    .write  =   mini2440_leds_write,
};

 3.将相关操作告诉内核：

     内核用cdev结构来表示字符设备，cev_init()将文件操作和cdev关联。cdev_add（）将之前生成的主次设备号和cdev连接在一起，

led_class = class_create(THIS_MODULE,DEVICE_NAME);
   cdev_init(&led_gpio_cdev, &mini2440_leds_fops);
result = cdev_add(&led_gpio_cdev, dev, 1);
if(result <0)
{
    printk("LED:cdev_add error
");
    return result;
}

device_create(led_class, NULL, MKDEV(scull_major, 0), NULL, "led0");

卸载驱动 rmmod 卸载 代码实现如下：

dev_t dev_id = MKDEV(scull_major, 0);

/*卸载主设备号*/
unregister_chrdev_region(dev_id, LED_GPIO_SIZE);

device_destroy(led_class,MKDEV(scull_major, 0));
cdev_del(&led_gpio_cdev);

class_destroy(led_class);

最后附上一个较为完整的驱动框架，其中创建了主设备号和次设备号，驱动代码如下：

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <asm/uaccess.h>
#include <asm/irq.h>
#include <mach/io.h>
#include <mach/regs-gpio.h>
#include <mach/hardware.h>
#include <linux/device.h>

#include <linux/cdev.h>


#define DEVICE_NAME "led_1"
#define LED_GPIO_SIZE 4

static int scull_major = 0;

static struct class *led_class;
static struct cdev led_gpio_cdev[LED_GPIO_SIZE];

static int mini2440_leds_open(struct inode *inode, struct file *file)
{

    int minor = MINOR(inode->i_rdev); //MINOR(inode->i_cdev);
    printk("/dev/led%d has opened
",minor);
    return 0;
}


static ssize_t mini2440_leds_write(struct file *filp, const char __user *buf, size_t count, loff_t * ppos)
{
    char val;
    int minor = MINOR(filp->f_dentry->d_inode->i_rdev);
    copy_from_user(&val, buf, 1);

    printk("/dev/led%d write the val = %d
",minor,val);
    return 0;
}

static struct file_operations mini2440_leds_fops = {
    .owner  =   THIS_MODULE,    /* 这是一个宏，推向编译模块时自动创建的__this_module变量 */
    .open   =   mini2440_leds_open,
    .write  =   mini2440_leds_write,
};

/*
 * 执行insmod命令时就会调用这个函数
 */

static int mini2440_leds_init(void)
{

    int result,i;
    dev_t dev;

    /*分配主设备号*/
    if (scull_major)   /*静态分配一个主设备号*/
    {
        dev = MKDEV(scull_major,0);
        result = register_chrdev_region(dev,LED_GPIO_SIZE,DEVICE_NAME);
    }
    else               /*动态分配一个主设备号*/
    {
        result = alloc_chrdev_region(&dev,0,LED_GPIO_SIZE,DEVICE_NAME);
        scull_major = MAJOR(dev);
    }
    if(result <0)
    {
        printk("LED:can not get major:%d
",scull_major);
        return result;
    }

    led_class = class_create(THIS_MODULE,DEVICE_NAME);
    if (IS_ERR(led_class)) {
        return PTR_ERR(led_class);
    }

    for (i=0; i<LED_GPIO_SIZE;i++)
    {
        cdev_init(&led_gpio_cdev[i], &mini2440_leds_fops);
        result = cdev_add(&led_gpio_cdev[i], (dev+i), 1);
        if(result <0)
        {
            printk("LED:cdev_add error
");
            return result;
        }
        device_create(led_class, NULL, MKDEV(scull_major, i), NULL, "led%d",i);
    }

    return 0;
}

/*
 * 执行rmmod命令时就会调用这个函数
 */
static void mini2440_leds_exit(void)
{
    int i;
    dev_t dev_id = MKDEV(scull_major, 0);

    /*卸载主设备号*/
    unregister_chrdev_region(dev_id, LED_GPIO_SIZE);

    for(i=0;i<LED_GPIO_SIZE;i++)
    {
        device_destroy(led_class,MKDEV(scull_major, i));
        cdev_del(&led_gpio_cdev[i]);
    }
    class_destroy(led_class);

}


/* 这两行指定驱动程序的初始化函数和卸载函数 */
module_init(mini2440_leds_init);
module_exit(mini2440_leds_exit);

/* 描述驱动程序的一些信息，不是必须的 */

MODULE_LICENSE("GPL");

linux 测试代码：

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


/*
  *  ledtest <dev> <on|off>
  */

void print_usage(char *file)
{
    printf("Usage:
");
    printf("%s <dev> <on|off>
",file);
    printf("eg. 
");
    printf("%s /dev/led0 a
", file);
    printf("%s /dev/led1 b
", file);
    printf("%s /dev/led2 c
", file);
    printf("%s /dev/led3 d
", file);
}

int main(int argc, char **argv)
{
    int fd;
    char* filename;
    char val;

    if (argc != 3)
    {
        print_usage(argv[0]);
        return 0;
    }

    filename = argv[1];

    fd = open(filename, O_RDWR);
    if (fd < 0)
    {
        printf("error, can't open %s
", filename);
        return 0;
    }

    if (!strcmp("a", argv[2]))
    {
        val = 10;
        write(fd, &val, 1);
    }
    else if (!strcmp("b", argv[2]))
    {
        val = 11;
        write(fd, &val, 1);
    }
    else if (!strcmp("c", argv[2]))
    {
        val = 12;
        write(fd, &val, 1);
    }
    else if (!strcmp("d", argv[2]))
    {

        val = 13;
        write(fd, &val, 1);
    }



    return 0;
}