练习:
驱动代码段
#include "head.h"
int major, minor = 0;
struct cdev *cdev;
struct class *cls;
struct device *dev;
//定义一个指向设备节点的指针
struct device_node *node;
struct device_node *node_led;
struct device_node *node_irq;
struct property *pr; //属性结构体指针
int gpiono1;
struct gpio_desc *desc_led1;
int irqno;
int number = 0;
wait_queue_head_t wq_head; //定义等待对头
int condition = 0;
int chdev_open(struct inode *inode, struct file *file)
{
return 0;
}
int chdev_close(struct inode *inode, struct file *file)
{
return 0;
}
ssize_t chdev_read(struct file *file, char __user *ubuf, size_t size, loff_t *loff)
{
int ret;
//阻塞
ret = wait_event_interruptible(wq_head, condition);
if (ret)
{
printk("接收阻塞休眠\n");
return ret;
}
//把父进程拷贝到内核的数据再拷贝给子进程
if (size > sizeof(number))
size = sizeof(number);
ret = copy_to_user(ubuf, &number, size);
if (ret)
{
printk("数据从内核向用户拷贝失败\n");
return -EIO;
}
condition = 0;
return size;
}
ssize_t chdev_write(struct file *file, const char __user *ubuf, size_t size, loff_t *loff)
{
return 0;
}
long ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
return 0;
}
//中断处理函数
irqreturn_t irq_handler(int irq, void *dev)
{
gpiod_set_value(desc_led1, !gpiod_get_value(desc_led1));
number ^= 1;
//唤醒
condition = 1;
wake_up_interruptible(&wq_head);
return IRQ_HANDLED;
}
struct file_operations fops = {
.open = chdev_open,
.read = chdev_read,
.write = chdev_write,
.release = chdev_close,
.unlocked_ioctl = ioctl,
};
int pdrv_probe(struct platform_device *pdr)
{
//获取设备信息
printk("%s:%d\n", __FILE__, __LINE__);
irqno = platform_get_irq(pdr, 0);
if (irqno < 0)
{
printk("获取资源失败\n");
return irqno;
}
if (request_irq(irqno, irq_handler, IRQF_TRIGGER_FALLING, NULL, NULL))
{
printk("注册中断失败\n");
return -1;
}
//获取GPIO编号
desc_led1 = gpiod_get_from_of_node(pdr->dev.of_node, "led1", 0, GPIOD_OUT_LOW, NULL);
if (IS_ERR(desc_led1))
{
printk("获取GPIO编号失败\n");
return PTR_ERR(desc_led1);
}
return 0;
}
int pdrv_remove(struct platform_device *pdr)
{
printk("%s:%d\n", __FILE__, __LINE__);
return 0;
}
//定义compatible表
struct of_device_id oftable[] = {
{.compatible = "hqyj,myplatform"},
{},
};
//定义并初始化对象
struct platform_driver pdrv = {
.probe = pdrv_probe,
.remove = pdrv_remove,
.driver = {
.name = "test",
.of_match_table = oftable, //设备树匹配
},
};
static int __init mycdev_init(void)
{
int ret;
dev_t devno;
cdev = cdev_alloc();
if (NULL == cdev)
{
printk("初始化驱动设备对象失败\n");
ret = -ENOMEM;
goto ERR1;
}
cdev_init(cdev, &fops);
ret = alloc_chrdev_region(&devno, minor, 1, "my_led");
if (ret)
{
printk("申请设备号失败\n");
goto ERR2;
}
major = MAJOR(devno);
minor = MINOR(devno);
ret = cdev_add(cdev, MKDEV(major, minor), 1);
if (ret)
{
printk("字符设备驱动注册失败\n");
goto ERR3;
}
cls = class_create(THIS_MODULE, "chdev_led");
if (IS_ERR(cls))
{
printk("向上提交节点失败\n");
goto ERR4;
}
dev = device_create(cls, NULL, MKDEV(major, 0), NULL, "led");
if (IS_ERR(dev))
{
printk("创建逻辑节点失败\n");
ret = PTR_ERR(dev);
goto ERR5;
}
//注册对象
platform_driver_register(&pdrv);
//初始化队列头
init_waitqueue_head(&wq_head);
return 0;
ERR5:
device_destroy(cls, MKDEV(major, 0));
class_destroy(cls);
ERR4:
cdev_del(cdev);
ERR3:
unregister_chrdev_region(MKDEV(major, minor), 1);
ERR2:
kfree(cdev);
ERR1:
return ret;
}
static void __exit mycdev_exit(void)
{
//销毁设备节点
device_destroy(cls, MKDEV(major, 0));
class_destroy(cls);
// 注销字符设备驱动
cdev_del(cdev);
// 释放设备号
unregister_chrdev_region(MKDEV(major, minor), 1);
// 释放动态申请的空间
kfree(cdev);
gpiod_set_value(desc_led1, 0);
gpiod_put(desc_led1);
//注销中断
free_irq(irqno, NULL);
//注销对象
platform_driver_unregister(&pdrv);
}
module_init(mycdev_init);
module_exit(mycdev_exit);
MODULE_LICENSE("GPL");
应用程序代码段
#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/wait.h>
#include <sys/ioctl.h>
#include <sys/select.h>
#include <sys/time.h>
int main(int argc, char const *argv[])
{
int fd;
int number;
char buf[128] = {};
int which;
fd = open("/dev/led", O_RDWR);
if (fd < 0)
{
printf("打开文件失败\n");
exit(-1);
}
while (1)
{
read(fd, &number, sizeof(number));
printf("number = %d\n", number);
}
close(fd);
return 0;
}
实验结果