最简单的LED驱动

#include "asm-generic/errno-base.h"
#include "asm-generic/gpio.h"
#include "asm/uaccess.h"
#include <linux/module.h>
#include <linux/poll.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/miscdevice.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/mutex.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/stat.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/tty.h>
#include <linux/kmod.h>
#include <linux/gfp.h>
#include <linux/gpio/consumer.h>
#include <linux/platform_device.h>
#include <linux/of_gpio.h>
#include <linux/of_irq.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/slab.h>
#include <linux/fcntl.h>
#include <linux/timer.h>

//gpio结构体
struct gpio_desc{
	int gpio; //GPIO编号
	int irq;    //中断号
    char *name; //名字
} ;

//PI0 = LED0      PF3 = LED1
static struct gpio_desc gpios[2] = {
    {128, 0, "led0", },
    {83, 0, "led1", },
};

static int major = 0; //设备号
static struct class *gpio_class;

//读函数
static ssize_t gpio_drv_read (struct file *file, char __user *buf, size_t size, loff_t *offset)
{
	char tmp_buf[2];
	int err;
    int count = sizeof(gpios)/sizeof(gpios[0]); //计算GPIO个数

	if (size != 2) //应用层必须是读2个字节
		return -EINVAL;

    //先读一下应用层buf来判断需要读取哪个IO引脚
	err = copy_from_user(tmp_buf, buf, 1); 

	if (tmp_buf[0] >= count) //判断读取的引脚号是否超出范围
		return -EINVAL;
    
    //获取GPIO引脚电平
	tmp_buf[1] = gpio_get_value(gpios[tmp_buf[0]].gpio);

	err = copy_to_user(buf, tmp_buf, 2); //返回给应用层
	
	return 2;
}

//写函数
static ssize_t gpio_drv_write(struct file *file, const char __user *buf, size_t size, loff_t *offset)
{
    unsigned char ker_buf[2];
    int err;

    if (size != 2) //应用层必须是写两个字节
        return -EINVAL;

    //读一下应用层buf来判断需要写哪个IO引脚
    err = copy_from_user(ker_buf, buf, size);
    
    if (ker_buf[0] >= sizeof(gpios)/sizeof(gpios[0]))//判断要写的引脚号是否超出范围
        return -EINVAL;

    //根据写指定的GPIO引脚与电平
    gpio_set_value(gpios[ker_buf[0]].gpio, ker_buf[1]);
    return 2;    
}

//字符操作集
static struct file_operations gpio_key_dev_fops = {
	.owner	 = THIS_MODULE,
    .read    = gpio_drv_read,
	.write   = gpio_drv_write,
};



static int __init gpio_drv_init(void)
{
    int err;
    int i;
    //计算有几个gpio 
    int count = sizeof(gpios)/sizeof(gpios[0]);
    
	printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
    for ( i = 0; i  < count; i++){
        err = gpio_request(gpios[i].gpio, gpios[i].name); //向内核申请gpio
        if (err < 0) {
			printk("can not request gpio %s %d\n", gpios[i].name, gpios[i].gpio);
			return -ENODEV;
		}
		//配置GPIO为输出，默认电平为高
		gpio_direction_output(gpios[i].gpio, 1);
    }
    //注册字符设备
    major = register_chrdev(0, "100ask_led", &gpio_key_dev_fops);
    //创建类
    gpio_class = class_create(THIS_MODULE, "100ask_led_class");
    if (IS_ERR(gpio_class)) {
		printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
		unregister_chrdev(major, "100ask_led_class");
		return PTR_ERR(gpio_class);
	}
    //创建设备
    device_create(gpio_class, NULL, MKDEV(major, 0), NULL, "100ask_led");

    return err;
}

//驱动出口函数
//注意：注销时一定要后注册(创建)的要先注销(摧毁)
static void __exit gpio_drv_exit(void)
{
    int i;
    int count = sizeof(gpios)/sizeof(gpios[0]);
    //摧毁设备
    device_destroy(gpio_class, MKDEV(major, 0));
    //摧毁类
    class_destroy(gpio_class);
    //注销字符设备
    unregister_chrdev(major, "100ask_led");

    for(i = 0; i < count; i++){
        //释放GPIO
        gpio_free(gpios[i].gpio);
    }
}

module_init(gpio_drv_init);
module_exit(gpio_drv_exit);

MODULE_LICENSE("GPL");

应用层

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

static int fd;

int main(int argc, char * argv[])
{
    int ret;
    char buf[2];
    int i;
    if(argc < 2){
        printf("Usage: %s <0|1|2|...> [on | off]\n", argv[0]);
		return -1;
    }

    fd = open("/dev/100ask_led", O_RDWR);
    if(fd < 0){
        printf("can not open file /dev/100ask_led\n");
		return -1;
    }

    if(argc == 3){
        buf[0] = strtol(argv[1], NULL, 0);
        if (strcmp(argv[2], "on") == 0)
			buf[1] = 0;
		else
			buf[1] = 1;
        
        ret = write(fd, buf, 2);
        if(ret < 0){
            printf("write error\r\n");
        }
    }
    else
	{
		buf[0] = strtol(argv[1], NULL, 0);
		ret = read(fd, buf, 2);
		if (ret == 2)
		{
			printf("led %d status is %s\n", buf[0], buf[1] == 0 ? "on" : "off");
		}
	}
	
	close(fd);

    return 0;
}