驱动开发5 阻塞IO实例、IO多路复用

1 阻塞IO

进程1

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

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

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

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_create
    cls = 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_create
    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 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

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_create
    cls = 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_create
    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 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

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

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));
}

效果演示