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驱动开发5 阻塞IO实例、IO多路复用

news 2025/9/15 23:15:11

1 阻塞IO

进程1

#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>int main(int argc, char const *argv[])
{char buf[128] = {0};int a,b;int fd = open("/dev/myled0",O_RDWR);if(fd < 0){printf("打开设备文件失败\n");exit(-1);}while(1){memset(buf,0,sizeof(buf));read(fd,buf,sizeof(buf));printf("buf:%s\n",buf);}
}

进程2

#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>int main(int argc, char const *argv[])
{char buf[128] = "hello world";int a,b;int fd = open("/dev/myled0",O_RDWR);if(fd < 0){printf("打开设备文件失败\n");exit(-1);}write(fd,buf,sizeof(buf));
}

驱动程序

#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/io.h>
#include <linux/device.h>
#include <linux/wait.h>
#include <linux/uaccess.h>int major;
char kbuf[128] = {0};unsigned int *vir_rcc;
struct class *cls;
struct device *dev;
//定义等待队列
wait_queue_head_t wq_head;
unsigned int condition=0;
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__);if(file->f_flags&O_NONBLOCK)//用户程序以非阻塞读写数据{}else{wait_event_interruptible(wq_head,condition);//判断condition的值，为假则进程休眠}//将获取到的硬件数据拷贝到用户int ret = copy_to_user(ubuf,kbuf,size);if(ret){printk("copy_to_user filed\n");return -EIO;}condition = 0; //表示下一次数据没有准备就绪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__);int ret;ret = copy_from_user(kbuf,ubuf,size);if (ret){printk("copy_from_user filed\n");return -EIO;}condition = 1;//表示硬件数据就绪wake_up_interruptible(&wq_head);//唤醒休眠的进程return 0;
}
int mycdev_close(struct inode *inode, struct file *file)
{printk("%s:%s:%d\n",__FILE__,__func__,__LINE__);return 0;
}//定义操作方法结构体变量并赋值
struct file_operations fops={.open = mycdev_open,.read = mycdev_read,.write = mycdev_write,.release = mycdev_close,
};
static int __init mycdev_init(void)
{//初始化等待队列init_waitqueue_head(&wq_head);//字符设备驱动major = register_chrdev(0,"mychrdev",&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);//向上提交目录 class_createcls = class_create(THIS_MODULE,"mychrdev");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");//向上提交设备节点信息 device_createint i;for(i=0;i<3;i++){dev = device_create(cls,NULL,MKDEV(major,i),NULL,"myled%d",i);if(IS_ERR(dev)){printk("向上提交设备节点失败\n");return -PTR_ERR(dev);}}printk("向上提交设备节点信息成功\n");return 0;
}
static void __exit mycdev_exit(void)
{//1.销毁设备节点信息int i;for(i=0;i<3;i++){device_destroy(cls,MKDEV(major,i));}//2.销毁目录class_destroy(cls);//3.注销字符设备驱动unregister_chrdev(major,"mychrdev");
}
module_init(mycdev_init);
module_exit(mycdev_exit);
MODULE_LICENSE("GPL");

Makefile

modname ?= demo
arch ?= arm
ifeq ($(arch),arm)  #通过命令行传过来的架构决定怎么编译
#KERBELDIR保存开发板内核源码路径
KERNELDIR := /home/ubuntu/FSMP1A/linux-stm32mp-5.10.61-stm32mp-r2-r0/linux-5.10.61
else
#保存UBUNTU内核源码路径
KERNELDIR := /lib/modules/$(shell uname -r)/build
endif#PWD保存当前内核模块的路径
PWD := $(shell pwd)
all:
#make modules是模块化编译命令
#make -C $(KERNLEDIR) 执行make之前先切换到KERNELDIR对应的路径
#M=$(PWD)表示进行模块化编译的路径是PWD保存的路径make -C $(KERNELDIR) M=$(PWD) modules
clean:
#编译清除make -C $(KERNELDIR) M=$(PWD) clean
#将obj-m保存的文件单独链接为内核模块
obj-m :=  $(modname).o

效果演示

2 IO多路复用

驱动程序

#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/io.h>
#include <linux/device.h>
#include <linux/wait.h>
#include <linux/uaccess.h>
#include <linux/poll.h>int major;
char kbuf[128] = {0};unsigned int *vir_rcc;
struct class *cls;
struct device *dev;
//定义等待队列
wait_queue_head_t wq_head;
unsigned int condition=0;
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__);if(file->f_flags&O_NONBLOCK)//用户程序以非阻塞读写数据{}else{// wait_event_interruptible(wq_head,condition);//判断condition的值，为假则进程休眠}//将获取到的硬件数据拷贝到用户int ret = copy_to_user(ubuf,kbuf,size);if(ret){printk("copy_to_user filed\n");return -EIO;}condition = 0; //表示下一次数据没有准备就绪return 0;
}__poll_t mycdev_poll(struct file *file, struct  poll_table_struct *wait)
{__poll_t mask = 0;// 向上提交等待队列队头poll_wait(file, &wq_head, wait);// 根据数据是否就绪给定一个合适的返回值if (condition)mask = POLLIN;return mask;
}
ssize_t mycdev_write(struct file *file, const char *ubuf, size_t size,loff_t *lof)
{printk("%s:%s:%d\n",__FILE__,__func__,__LINE__);int ret = copy_from_user(kbuf,ubuf,size);if (ret){printk("copy_from_user filed\n");return -EIO;}condition = 1;//表示硬件数据就绪wake_up_interruptible(&wq_head);//唤醒休眠的进程return 0;
}
int mycdev_close(struct inode *inode, struct file *file)
{printk("%s:%s:%d\n",__FILE__,__func__,__LINE__);return 0;
}//定义操作方法结构体变量并赋值
struct file_operations fops={.open = mycdev_open,.read = mycdev_read,.write = mycdev_write,.poll = mycdev_poll,.release = mycdev_close,
};static int __init mycdev_init(void)
{//初始化等待队列init_waitqueue_head(&wq_head);//字符设备驱动major = register_chrdev(0,"mychrdev",&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);//向上提交目录 class_createcls = class_create(THIS_MODULE,"mychrdev");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");//向上提交设备节点信息 device_createint i;for(i=0;i<3;i++){dev = device_create(cls,NULL,MKDEV(major,i),NULL,"myled%d",i);if(IS_ERR(dev)){printk("向上提交设备节点失败\n");return -PTR_ERR(dev);}}printk("向上提交设备节点信息成功\n");return 0;
}
static void __exit mycdev_exit(void)
{//1.销毁设备节点信息int i;for(i=0;i<3;i++){device_destroy(cls,MKDEV(major,i));}//2.销毁目录class_destroy(cls);//3.注销字符设备驱动unregister_chrdev(major,"mychrdev");
}
module_init(mycdev_init);
module_exit(mycdev_exit);
MODULE_LICENSE("GPL");

进程1：监听多个事件

#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <sys/select.h>
#include <sys/time.h>int main(int argc, char const *argv[])
{char buf[128] = {0};int fd1,fd2;fd1 = open("/dev/input/mouse0",O_RDWR);if(fd1 < 0){printf("打开鼠标设备失败\n");return -1;}fd2 = open("/dev/myled0",O_RDWR);if(fd2 < 0){printf("打开设备失败\n");return -1;}// 定义读事件集合fd_set readfds;while(1){// 清空集合FD_ZERO(&readfds);// 将要监听的事件添加进集合FD_SET(fd1, &readfds);FD_SET(fd2, &readfds); // 阻塞监听事件int ret;ret = select(fd2 + 1, &readfds, NULL, NULL, NULL);if(ret < 0){printf("select 调用失败\n");return -1;}// 判断事件是否发生if(FD_ISSET(fd1, &readfds));{memset(buf, 0, sizeof(buf));read(fd1, buf, sizeof(buf));printf("鼠标事件发生buf:%s\n", buf);}if(FD_ISSET(fd2, &readfds)){memset(buf,0,sizeof(buf));read(fd2,buf,sizeof(buf));printf("事件发生buf:%s\n",buf);}}// 关闭文件描述符close(fd1);close(fd2);return 0;
}

进程2：模拟自定义事件就绪

#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>int main(int argc, char const *argv[])
{char buf[128] = "hello world";int a,b;int fd = open("/dev/myled0",O_RDWR);if(fd < 0){printf("打开设备文件失败\n");exit(-1);}write(fd,buf,sizeof(buf));
}