需求：

用配置寄存器方式控制点灯非常原始，现在采用更方便的Linux提供的pctrl和gpio子系统编写字符驱动

1.设备树配置：

现将开发板中呼吸灯关闭掉防止占用到我需要使用的引脚

	/* Narnat 2025-5-29 RK3568 GPIO 无需设置pinctrl*/gpioled{compatible = "atkrk3568-gpio-led";led-gpio = <&gpio0 RK_PC0 GPIO_ACTIVE_HIGH>;status = "okay";};

下图为设备树中GPIO0的地址

在设备树根节点下添加gpioled节点，标明引脚，配置完设备树后将kernel单独编译，将生成的boot.img烧到设备中可以看到如下节点：

可以用cat读取相关信息

2.驱动编写：

驱动中需要读取上述gpioled设备节点找到对应的引脚，向内核申请这个引脚的使用权gpio_request(gpioled.led_gpio, “LED-GPIO”);这样能防止多个驱动程序抢夺一个引脚问题，申请使用权成功后就能使用Linux自带的GPIO函数了ret = gpio_direction_output(gpioled.led_gpio, 0);然后就是在/dev目录下创建设备节点了，创建设备节点分为：创建设备号、初始化并添加字符驱动、创建类、创建设备

驱动代码：

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/io.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_address.h>
#include <linux/of_gpio.h>
#include <asm/uaccess.h>
#include <asm/io.h>#define GPIOLED_CNT    1   // 设备号数目
#define GPIOLED_NAME   "gpioled" // 名字
#define LEDOFF         0 // 关灯
#define LEDON          1 // 开灯struct gpioled_dev{  // 设备结构体dev_t devid;       // 设备号int major;         // 主设备号int minor;         // 次设备号struct cdev cdev;  // 字符设备struct class* class; // 类struct device_node* nd; // 设备节点struct device* device; // 设备int led_gpio;  // led所使用的编号
};struct gpioled_dev gpioled; // led设备static int led_open(struct inode* inode, struct file* filp){filp->private_data = &gpioled; // 设置私有数据return 0;
}static ssize_t led_read(struct file* filp, char __user* buf, size_t cnt, loff_t* offt){return 0;
}static ssize_t led_write(struct file* filp, const char __user* buf, size_t cnt, loff_t* offt){int retvalue;unsigned char databuf[1];unsigned char ledstat;struct gpioled_dev* dev = filp->private_data;retvalue = copy_from_user(databuf, buf, cnt);if(retvalue < 0){printk("kernel write failed \r\n");return -1;}ledstat = databuf[0];if(ledstat == LEDON){gpio_set_value(dev->led_gpio, 1); // 打开LED}else if(ledstat == LEDOFF){gpio_set_value(dev->led_gpio, 0); // 关灯}return 0;
}static int led_release(struct inode* inode, struct file* filp){return 0;
}static struct file_operations gpioled_fops = { // 设备操作函数.owner = THIS_MODULE,.open = led_open,.read = led_read,.write = led_write,.release =  led_release,
};static int __init led_init(void){int ret = 0;const char* str;/* 设置LED所使用的GPIO */// 1.获取设备节点gpioled.nd = of_find_node_by_path("/gpioled");if(gpioled.nd == NULL){printk("gpioled node not find \r\n");return -1;}// 2.读取status属性ret = of_property_read_string(gpioled.nd, "status", &str);if(ret < 0){printk("read status error \r\n");return -1;}if(strcmp(str, "okay")){printk("status is not okay \r\n");return -1;}// 3.读取compatible属性值ret = of_property_read_string(gpioled.nd, "compatible", &str);if(ret < 0){printk("read compatible error \r\n");return -1;}if(strcmp(str, "atkrk3568-gpio-led")){printk("compatible is not atkrk3568-gpio-led \r\n");return -1;}//4.获取设备树中的gpio属性，得到LED所使用的LED编号gpioled.led_gpio = of_get_named_gpio(gpioled.nd, "led-gpio", 0); // 0取第一个if(gpioled.led_gpio < 0){printk("cant get led-gpio \r\n");return -1;}printk("led-gpio num = %d \r\n", gpioled.led_gpio);//5.向gpio子系统申请使用GPIO 当前驱动独自占有此驱动ret = gpio_request(gpioled.led_gpio, "LED-GPIO");if(ret){printk("request led-gpio failed \r\n");return -1;}//6.设置GPIO为输出，并且输出低电平，关闭LED灯ret = gpio_direction_output(gpioled.led_gpio, 0);if(ret < 0){printk("cant set gpio \r\n");return -1;}/* 注册字符设备驱动 */// 1.创建设备号if(gpioled.major){gpioled.devid = MKDEV(gpioled.major, 0);ret = register_chrdev_region(gpioled.devid, GPIOLED_CNT, GPIOLED_NAME); // 注册字符设备号if(ret < 0){gpio_free(gpioled.led_gpio);printk("cant register %s char driver ret = %d \r\n", GPIOLED_NAME, ret);return -1;}}else{ret = alloc_chrdev_region(&gpioled.devid, 0, GPIOLED_CNT, GPIOLED_NAME);  // 申请设备号if(ret < 0){gpio_free(gpioled.led_gpio);printk("cant alloc_chrdev_region %s, ret = %d \r\n", GPIOLED_NAME, ret);return -1;}gpioled.major = MAJOR(gpioled.devid);gpioled.minor = MINOR(gpioled.devid); // 获取主次设备号}printk("%s gpioled major = %d, minnor=%d \r\n", GPIOLED_NAME, gpioled.major, gpioled.minor);// 2.初始化字符驱动gpioled.cdev.owner = THIS_MODULE;cdev_init(&gpioled.cdev, &gpioled_fops);// 3.添加一个字符驱动cdev_add(&gpioled.cdev, gpioled.devid, GPIOLED_CNT);if(ret < 0){  // 添加失败unregister_chrdev_region(gpioled.devid, GPIOLED_CNT); // 注销掉设备号gpio_free(gpioled.led_gpio);return -1;}// 4.创建类gpioled.class = class_create(THIS_MODULE, GPIOLED_NAME);if(IS_ERR(gpioled.class)){ // 创建类失败cdev_del(&gpioled.cdev); // 删掉字符驱动unregister_chrdev_region(gpioled.devid, GPIOLED_CNT); // 注销掉设备号gpio_free(gpioled.led_gpio);return -1;}// 5.创建设备gpioled.device = device_create(gpioled.class, NULL, gpioled.devid, NULL, GPIOLED_NAME);if(IS_ERR(gpioled.device)){ // 设备创建失败class_destroy(gpioled.class); // 删掉类cdev_del(&gpioled.cdev); // 删掉字符驱动unregister_chrdev_region(gpioled.devid, GPIOLED_CNT); // 注销掉设备号gpio_free(gpioled.led_gpio);return -1;}return 0;
}static void __exit led_exit(void){device_destroy(gpioled.class, gpioled.devid); // 注销设备class_destroy(gpioled.class); // 删掉类cdev_del(&gpioled.cdev); // 删掉字符驱动unregister_chrdev_region(gpioled.devid, GPIOLED_CNT); // 注销掉设备号gpio_free(gpioled.led_gpio);
}module_init(led_init);
module_exit(led_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Narnat");

应用层代码：略

开灯关灯命令：

效果图：略