一、字符设备驱动内部注册过程
通过对register_chrdev内部的实现过程进行分析，其实注册字符设备驱动的过程就是下面几步：
1.分配struct cdev对象空间
2.初始化struct cdev对象
3.注册cdev对象
完成上面的三步，就完成了字符设备驱动的注册。
二、通过字符设备驱动分步注册方式编写LED驱动，完成设备文件和设备的绑定
头文件
#ifndef __HEAD_H__
#define __HEAD_H__
typedef struct{unsigned int MODER;unsigned int OTYPER;unsigned int OSPEEDR;unsigned int PUPDR;unsigned int IDR;unsigned int ODR;
}gpio_t;
#define PHY_LED1_ADDR 0X50006000
#define PHY_LED2_ADDR 0X50007000
#define PHY_LED3_ADDR 0X50006000
#define PHY_RCC_ADDR 0X50000A28//构建LED开关的功能码
#define LED_ON _IO('l',1)
#define LED_OFF _IO('l',0)
#endif 测试文件
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include "head.h"
int main(int argc, const char *argv[])
{char buf[128] = "";int a;int fd;while (1){printf("请选择要打开的灯(1,2,3)\n");scanf(" %d", &a);switch (a){case 1:fd = open("/dev/myled0", O_RDWR);if (fd < 0){printf("设备文件打开失败\n");exit(-1);}printf("打开文件myled0成功\n");break;case 2:fd = open("/dev/myled1", O_RDWR);if (fd < 0){printf("设备文件打开失败\n");exit(-1);}printf("打开文件myled1成功\n");break;case 3:fd = open("/dev/myled2", O_RDWR);if (fd < 0){printf("设备文件打开失败\n");exit(-1);}printf("打开文件myled2成功\n");break;default:printf("请输入范围内的数\n");}int b;printf("请开灯关灯(0/1)\n");scanf(" %d",&b);switch(b){case 1:ioctl(fd,LED_ON);break;case 0:ioctl(fd,LED_OFF);break;default:printf("请输入'0'或'1'\n");}close(fd);printf("关闭文件\n"); }return 0;
}驱动文件
#include <linux/init.h>
#include <linux/module.h>
#include<linux/cdev.h>
#include <linux/fs.h>
#include <linux/io.h>
#include <linux/device.h>
#include<linux/uaccess.h>
#include<linux/slab.h>
#include "head.h"struct cdev *cdev;
char kbuf[128]={0};
unsigned int major=0;
unsigned int minor=0;
dev_t devno;
module_param(major,uint,0664);//方便在命令行传递major的值
struct class*cls;
struct device *dev;gpio_t *vir_led1;
gpio_t *vir_led2;
gpio_t *vir_led3;
unsigned int *vir_rcc;int mycdev_open(struct inode *inode, struct file *file)
{int min=MINOR(inode->i_rdev);//根据打开的文件对应的设备号获取次设备号file->private_data=(void *)min;printk("%s:%s:%d\n", __FILE__, __func__, __LINE__);return 0;
}long mycdev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{int min=(int)file->private_data;switch(min){case 0://控制LED1switch (cmd){case LED_ON: // 开灯vir_led1->ODR |= 1 << 10;break;case LED_OFF://关灯vir_led1->ODR &= (~(1 << 10));break;}break;case 1://控制LED2switch (cmd){case LED_ON: // 开灯vir_led2->ODR |= 1 << 10;break;case LED_OFF://关灯vir_led2->ODR &= (~(1 << 10));break;}break;case 2://控制LED3switch (cmd){case LED_ON: // 开灯vir_led3->ODR |= 1 << 8;break;case LED_OFF://关灯vir_led2->ODR &= (~(1 << 8));break;}break;}return 0;
}
int mycdev_close(struct inode *inode, struct file *file)
{printk("%s:%s:%d\n", __FILE__, __func__, __LINE__);return 0;
}// 定义操作方法结构体变量并赋值
struct file_operations fops = {.open = mycdev_open,.unlocked_ioctl = mycdev_ioctl,.release = mycdev_close,
};int all_led_init(void)
{// 寄存器地址的映射vir_led1 = ioremap(PHY_LED1_ADDR, sizeof(gpio_t));if (vir_led1 == NULL){printk("ioremap filed：%d\n", __LINE__);return -ENOMEM;}vir_led2 = ioremap(PHY_LED2_ADDR, sizeof(gpio_t));if (vir_led2 == NULL){printk("ioremap filed：%d\n", __LINE__);return -ENOMEM;}vir_led3 = vir_led1;vir_rcc = ioremap(PHY_RCC_ADDR, 4);if (vir_rcc == NULL){printk("ioremap filed：%d\n", __LINE__);return -ENOMEM;}printk("物理地址映射成功\n");// 寄存器的初始化// rcc(*vir_rcc) |= (0X3 << 4);// led1vir_led1->MODER &= (~(3 << 20));vir_led1->MODER |= (1 << 20);vir_led1->ODR &= (~(1 << 10));// led2vir_led2->MODER &= (~(3 << 20));vir_led2->MODER |= (1 << 20);vir_led2->ODR &= (~(1 << 10));// led3vir_led3->MODER &= (~(3 << 16));vir_led1->MODER |= (1 << 16);vir_led1->ODR &= (~(1 << 8));printk("寄存器初始化成功\n");return 0;
}static int __init mycdev_init(void)
{int ret;//为字符设备驱动对象申请空间cdev=cdev_alloc();if(cdev==NULL){printk("字符设备驱动对象申请空间失败\n");ret=-EFAULT;goto out1;}printk("申请对象空间成功\n");//初始化字符设备驱动对象cdev_init(cdev,&fops);//申请设备号if(major>0)//静态指定设备号{ret=register_chrdev_region(MKDEV(major,minor),3,"myled");if(ret){printk("静态申请设备号失败\n");goto out2;}}else if(major==0)//动态申请设备号{ret=alloc_chrdev_region(&devno,minor,3,"myled");if(ret){printk("动态申请设备号失败\n");goto out2;}major=MAJOR(devno);//获取主设备号minor=MINOR(devno);//获取次设备号}printk("申请设备号成功\n");//注册字符设备驱动对象ret=cdev_add(cdev,MKDEV(major,minor),3);if(ret){printk("注册字符设备驱动对象失败\n");goto out3;}printk("注册字符设备驱动对象成功\n");//寄存器映射及初始化all_led_init();//向上提交目录信息cls=class_create(THIS_MODULE,"myled");if(IS_ERR(cls)){printk("向上提交目录失败\n");ret=-PTR_ERR(cls);goto out4;}printk("向上提交目录成功\n");//向上提交设备节点信息int i;for(i=0;i<3;i++){dev=device_create(cls,NULL,MKDEV(major,i),NULL,"myled%d",i);if(IS_ERR(dev)){printk("向上提交设备节点信息失败\n");ret=-PTR_ERR(dev);goto out5;}}printk("向上提交设备信息成功\n");return 0;
out5://释放前一次提交成功的设备信息for(--i;i>=0;i--){device_destroy(cls,MKDEV(major,i));}class_destroy(cls);//释放目录
out4:cdev_del(cdev);
out3:unregister_chrdev_region(MKDEV(major,minor),3);
out2:kfree(cdev);
out1:return ret;
}
static void __exit mycdev_exit(void)
{/*销毁设备节点信息*/int i;for (i = 0; i < 3; i++){device_destroy(cls, MKDEV(major, i));}// 销毁目录信息class_destroy(cls);//注销驱动对象cdev_del(cdev);//释放设备号unregister_chrdev_region(MKDEV(major,minor),3);//释放对象空间kfree(cdev);// 取消地址映射iounmap(vir_led1);iounmap(vir_led2);iounmap(vir_rcc);
}
module_init(mycdev_init);
module_exit(mycdev_exit);
MODULE_LICENSE("GPL");
