编写驱动代码，初步实现串口输入逻辑控制开发板的LED灯的亮灭

代码示例

head.h

#ifndef __HEAD_H__
#define __HEAD_H__

typedef struct
{
    unsigned int MODER;
    unsigned int OTYPER;
    unsigned int OSPEEDR;
    unsigned int PUPD;
    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

#endif 

test.c

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

int main(int argc,const char * argv[])
{
    char buf[1024] = {0};
    int fd = open("/dev/mycdev0",O_RDWR); 
    if(fd < 0)
    {
        printf("打开设备失败\n");
        exit(-1);
    }

    while (1)
    {
        printf("输入两个数，选择控制逻辑；第一个数控制灯,第二个数控制灯的状态 > \n");
        fgets(buf,sizeof(buf),stdin);


        buf[strlen(buf)-1]='\0';
        write(fd,buf,sizeof(buf));
    }
    close(fd);
    return 0;
}

Character_device.c

#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/uaccess.h>
#include <linux/io.h>
#include <linux/device.h>
#include "head.h"

unsigned int major;
char kbuf[1024] = {0};

gpio_t *vir_led1;
gpio_t *vir_led2;
gpio_t *vir_led3;

unsigned int *vir_rcc;

//
struct class *cls;
struct device *dev;

// 封装操作方法
int mycdev_open(struct inode *inode, struct file *file)
{
    printk("%s:%s:%d\n", __FILE__, __func__, __LINE__);
    return 0;
}

ssize_t mycdev_read(struct file *file, char *ubuf, size_t size, loff_t *lof)
{
    printk("%s:%s:%d\n", __FILE__, __func__, __LINE__);
    long ret;
    ret = copy_to_user(ubuf, kbuf, size);
    if (ret)
    {
        printk("copy_to_user failed\n");
        return -EIO;
    }
    return 0;
}

ssize_t mycdev_write(struct file *file, const char *ubuf, size_t size, loff_t *lof)
{
    printk("%s:%s:%d\n", __FILE__, __func__, __LINE__);
    long ret;
    ret = copy_from_user(kbuf, ubuf, size);
    if (ret)
    {
        printk("copy_from_user failed\n");
        return -EIO;
    }
    switch (kbuf[0]){
    case '1': // LED1
        if (kbuf[1] == '0')
            vir_led1->ODR &= (~(0x1 << 10));
        else
            vir_led1->ODR |= 0x1 << 10;
        break;
    case '2': // LED2
        if (kbuf[1] == '0')
            vir_led2->ODR &= (~(0x1 << 10));
        else
            vir_led2->ODR |= 0x1 << 10;
        break;
    case '3': // LED3
        if (kbuf[1] == '0')
            vir_led3->ODR &= (~(0x1 << 8));
        else
            vir_led3->ODR |= 0x1 << 8;
        break;
    }
    return 0;
}

int mycdev_close(struct inode *inode, struct file *file)
{
    printk("%s:%s:%d\n", __FILE__, __func__, __LINE__);
    return 0;
}

struct file_operations fops = {
    .open = mycdev_open,
    .release = mycdev_close,
    .read = mycdev_read,
    .write = mycdev_write,
};

// 寄存器地址映射
int all_led_init(void)
{
    vir_led1 = ioremap(PHY_LED1_ADDR, sizeof(gpio_t));
    if (vir_led1 == NULL)
    {
        printk("物理内存映射失败%d\n", __LINE__);
        return -EFAULT;
    }

    vir_led2 = ioremap(PHY_LED2_ADDR,sizeof(gpio_t));
    if (vir_led2 == NULL)
    {
        printk("物理内存映射失败%d\n", __LINE__);
        return -EFAULT;
    }
    vir_led3 = vir_led1;
    vir_rcc = ioremap(PHY_RCC_ADDR, 4);
    if (vir_rcc == NULL)
    {
        printk("物理内存映射失败%d\n", __LINE__);
        return -EFAULT;
    }
    printk("物理内存映射成功\n");
    //rcc
    (*vir_rcc) |= 0x3 << 4;
    //LED1
    vir_led1->MODER &= (~(0x3 << 20));
    vir_led1->MODER |= 0x1 << 20;
    vir_led1->ODR &= (~(0x1 << 10));
    //LED2
    vir_led2->MODER &= (~(0x3 << 20));
    vir_led2->MODER |= 0x1 << 20;
    vir_led2->ODR &= (~(0x1 << 10));
    //LED3
    vir_led3->MODER &= (~(0x3 << 16));
    vir_led3->MODER |= 0x1 << 16;
    vir_led3->ODR &= (~(0x1 << 8));

    return 0;
}

static int __init mycdev_init(void)
{
    int i;
    // 注册设备字符驱动
    major = register_chrdev(0, "mycdev", &fops);
    if (major < 0)
    {
        printk("注册字符设备驱动失败\n");
        return major;
    }
    printk("注册字符设备驱动成功major=%d\n", major);

    all_led_init();

    // 向上提交目录信息
    cls = class_create(THIS_MODULE, "mycdev");
    if (IS_ERR(cls))
    {
        printk("向上提交目录信息失败\n");
        return -PTR_ERR(cls);
    }
    printk("向上提交目录信息成功\n");

    // 向上提交设备信息
    for (i = 0; i < 3; i++)
    {
        dev = device_create(cls, NULL, MKDEV(major, i), NULL, "mycdev%d", i);
        if (IS_ERR(dev))
        {
            printk("向上提交设备节点失败\n");
            return -PTR_ERR(cls);
        }
    }
    printk("向上提交设备节点成功\n");
    return 0;
}

static void __exit mycdev_exit(void)
{
    // 取消物理映射
    iounmap(vir_led1);
    iounmap(vir_led2);
    iounmap(vir_rcc);

    // 销毁设备信息
    int i;
    for (i = 0; i < 3; i++)
    {
        device_destroy(cls, MKDEV(major, i));
    }
    // 销毁目录信息
    class_destroy(cls);
    // 字符设备注销
    unregister_chrdev(major, "mycdev");
}
module_init(mycdev_init);
module_exit(mycdev_exit);
MODULE_LICENSE("GPL");

运行结果