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
cpp
#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
cpp
#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
cpp
#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LED1
switch (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LED2
switch (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LED3
switch (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);
// led1
vir_led1->MODER &= (~(3 << 20));
vir_led1->MODER |= (1 << 20);
vir_led1->ODR &= (~(1 << 10));
// led2
vir_led2->MODER &= (~(3 << 20));
vir_led2->MODER |= (1 << 20);
vir_led2->ODR &= (~(1 << 10));
// led3
vir_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");