驱动开发，基于gpio子系统编写LED灯的驱动，亮灭控制

1.gpio子系统介绍

        一个芯片厂商生产出芯片后会给linux提供一个当前芯片中gpio外设的驱动，我们当前只需要调用对应的厂商驱动即可完成硬件的控制。而linux内核源码中的gpio厂商驱动有很多，这里linux内核对厂商驱动做了一些封装，提供了一系列的API，我们在自己编写的设备驱动中只需要调用这些API即可访问对应的厂商驱动，进而完成GPIO的控制。

 

2.实现框图

 

 3.代码

---gpiod_dri.c---驱动程序

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

unsigned int major;
struct device_node *dnode;
struct gpio_desc *gpiono1;
struct gpio_desc *gpiono2;
struct gpio_desc *gpiono3;
struct class *cls;
struct device *dev;
char kbuf[128] = {0};

// 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)
{
    int ret;

    ret = copy_to_user(ubuf, kbuf, size);
    if (ret)
    {
        printk("copy_to_ user err\n");
        return -EIO;
    }

    return 0;
}
ssize_t mycdev_write(struct file *file, const char *ubuf, size_t size, loff_t *lof)
{
    int ret;
    if (size > sizeof(kbuf))
        size = sizeof(kbuf);
    // 从用户拷贝数据
    ret = copy_from_user(kbuf, ubuf, size);
    if (ret)
    {
        printk("copy_from_user err\n");
        return -EIO;
    }

    switch (kbuf[0])
    {
    case '1':
        gpiod_set_value(gpiono1,!gpiod_get_value(gpiono1));
        break;
    case '2':
        gpiod_set_value(gpiono2,!gpiod_get_value(gpiono2));
        break;
    case '3':
        gpiod_set_value(gpiono3,!gpiod_get_value(gpiono3));
        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,
    .read = mycdev_read,
    .write = mycdev_write,
    .release = mycdev_close,
};

static int __init mycdev_init(void)
{
    // 1字符设备驱动注册
    major = register_chrdev(0, "myled", &fops);
    if (major < 0)
    {
        printk("字符设备驱动注册失败\n");
        return major;
    }
    printk("字符设备驱动注册成功:major=%d\n", major);

    // 2向上提交目录
    cls = class_create(THIS_MODULE, "MYLED");
    if (IS_ERR(cls))
    {
        printk("向上提交目录失败\n");
        return -PTR_ERR(cls);
    }
    printk("向上提交目录成功\n");

    // 3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");
            return -PTR_ERR(dev);
        }
    }
    printk("向上提交设备节点信息成功\n");

    // 4解析LED的设备树节点
    dnode = of_find_node_by_path("/myled");
    if (dnode == NULL)
    {
        printk("解析设备树节点失败\n");
        return -1;
    }
    printk("解析GPIO信息成功\n");
    // 5申请gpio对象
    gpiono1 = gpiod_get_from_of_node(dnode, "led1-gpio", 0, GPIOD_OUT_LOW, NULL);
    if (IS_ERR(gpiono1))
    {
        printk("申请gpio1对象失败\n");
        return -ENXIO;
    }
    gpiono2 = gpiod_get_from_of_node(dnode, "led2-gpio", 0, GPIOD_OUT_LOW, NULL);
    if (IS_ERR(gpiono2))
    {
        printk("申请gpio2对象失败\n");
        return -ENXIO;
    }
    gpiono3 = gpiod_get_from_of_node(dnode, "led3-gpio", 0, GPIOD_OUT_LOW, NULL);
    if (IS_ERR(gpiono3))
    {
        printk("申请gpio3对象失败\n");
        return -ENXIO;
    }
    printk("申请gpio信息对象成功\n");

    return 0;
}
static void __exit mycdev_exit(void)
{
    // 灭灯
    gpiod_set_value(gpiono1, 0);
    gpiod_set_value(gpiono2, 0);
    gpiod_set_value(gpiono3, 0);

    // 释放GPIO编号
    gpiod_put(gpiono1);
    gpiod_put(gpiono2);
    gpiod_put(gpiono3);

    // 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);

    // 字符设备驱动注销
    unregister_chrdev(major, "myled");
}
module_init(mycdev_init);
module_exit(mycdev_exit);
MODULE_LICENSE("GPL");

---test.c---应用程序测试程序

#include 
#include 
#include 
#include 
#include 
#include 
#include 

int main(int argc, char const *argv[])
{
    int a;
    char buf[128] = {0};
    int fd = open("/dev/myled0", O_RDWR);

    if (fd < 0)
    {
        printf("设备文件打开失败\n");
        exit(-1);
    }

    while (1)
    {
        printf("请输入控制的灯：1(LED1) 2(LED2) 3(LED3)\n");
        fgets(buf,sizeof(buf),stdin);
        buf[strlen(buf)-1] = '\0';
        //像设备文件中写
        write(fd,buf,sizeof(buf));
    }

    close(fd);

    return 0;
}

 

4.测试现象 

        输入灯编号，对状态取反；