3 I/O多路复用（select/poll/epoll)
int poll(struct pollfd *fds, nfds_t nfds, int timeout);
参数1 ：一个结构体指针 struct pollfd *fds
struct pollfd {
int fd; //文件描述符
short events; //产生的事件如读写错误
POLLIN 读写
POLLOUT 写
POLLERR 出错
short revents; //结果描述，表示当前的fd是否可读，写初错
//用于判断出错
POLLIN 读写
POLLOUT 写
POLLERR 出错
}
参数2 nfds：要监视的描述符的数目
参数3 timeout 超时时间 是指定poll在返回前没有接收事件时应该等待的时间。
timeout值:
INFTIM 永远等待(为负数)
0 立即返回，不阻塞进程
>0 等待指定数目的毫秒数
返回值:
负数：表示出错
大于0 表示fd有数据
小于0 表示时间到
如果在应用中使用了poll对设备文件进行了监控，那么在驱动中必须必须实现poll
unsigned int xxx_poll(struct file *filp,struct poll_table_struct *pts)
{
//返回一个mask数值
unsigned int mask;
//调用poll_wait，将当前的等待队列注册系统中
poll_wait();
//当没有数据的时候返回一个0(通过判断队列的状态)
//当有数据的时候返回一个POLLIN
}
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/device.h>
#include<linux/uaccess.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <asm/arch/regs-gpio.h>
#include <asm/hardware.h>
#include <linux/interrupt.h>
#include <linux/poll.h>
struct led_dev_struct{
int major;
struct class *dev_class;
struct device *device_class;
wait_queue_head_t wq; //定义等待队列头
};
struct led_dev_struct *key_drv;
#define GPFx 0x56000050
#define GPGx 0x56000060
volatile unsigned int *gpfcon;
volatile unsigned int *gpfdat;
volatile unsigned int *gpgcon;
volatile unsigned int *gpgdat;
static unsigned int key_val;
/* 中断事件标志, 中断服务程序将它置1，third_drv_read将它清0 */
static volatile int ev_press = 0;
static irqreturn_t key_interrupt(int irq, void *dev_id)
{
if(irq==IRQ_EINT0)
{
printk("key1-----------\n");
key_val=*gpfdat;
key_val=(key_val&(1<<0))?0:1;
}
if(irq==IRQ_EINT2)
{
printk("key2------------\n");
key_val=*gpfdat;
key_val=(key_val&(1<<2))?0:1;
}
if(irq==IRQ_EINT11)
{
printk("key3-----------\n");
key_val=*gpgdat;
key_val=(key_val&(1<<3))?0:1;
}
ev_press = 1; /* 表示中断发生了 */
wake_up_interruptible(&(key_drv->wq)); /* 唤醒休眠的进程 */
return IRQ_HANDLED;//表示中断完成
}
static int key_open(struct inode *inode, struct file *file)
{
//申请中断
int ret;
ret=request_irq(IRQ_EINT0, key_interrupt,IRQF_TRIGGER_RISING|IRQF_TRIGGER_FALLING,"key1",NULL);
if(ret)
{
return -EINVAL;
}
ret=request_irq(IRQ_EINT2, key_interrupt,IRQF_TRIGGER_RISING|IRQF_TRIGGER_FALLING,"key2",NULL);
if(ret)
{
return -EINVAL;
}
ret=request_irq(IRQ_EINT11,key_interrupt,IRQF_TRIGGER_RISING|IRQF_TRIGGER_FALLING,"key11",NULL);
if(ret)
{
return -EINVAL;
}
return 0;
}
static ssize_t key_read(struct file *file, char __user *buffer, size_t size, loff_t *ppos)
{
printk("%d\n",key_val);
/* 如果没有按键动作, 休眠 */
wait_event_interruptible(key_drv->wq, ev_press);
copy_to_user(buffer,&key_val,sizeof(key_val));
printk("rrrrrrrrrrrrrrrrrrrrrr\n");
ev_press = 0;
return sizeof(key_val);
}
static ssize_t key_write(struct file *file, const char __user *buffer, size_t size,loff_t *ppos)
{
printk("xxxxxxxxxxxxxx\n");
return 0;
}
//poll机制
static unsigned key_poll(struct file *file, poll_table *wait)
{
unsigned int mask = 0;
poll_wait(file, &key_drv->wq, wait); // 不会立即休眠
if (ev_press)
mask |= POLLIN | POLLRDNORM;
return mask;
}
struct file_operations key_fops={
.open = key_open,
.read = key_read,
.write = key_write,
.poll = key_poll,
};
//入口函数
static int __init key_init(void)
{
int ret;
//给机构体申请空间
key_drv=kmalloc(sizeof(struct led_dev_struct), GFP_KERNEL);
//申请设备号
key_drv->major=register_chrdev(0, "key_led", &key_fops);
if ( key_drv->major < 0) {
printk("register_chrdev error\n");
ret=-EINVAL;
}
//创建类
key_drv->dev_class=class_create(THIS_MODULE, "leds");
if (IS_ERR( key_drv->dev_class)) {
ret= PTR_ERR( key_drv->dev_class);
goto flag1;
}
//创建设备
key_drv->device_class=device_create(key_drv->dev_class, NULL,MKDEV( key_drv->major,0), "led1");
if (IS_ERR( key_drv->device_class)){
ret=PTR_ERR( key_drv->device_class);
goto flag2;
}
init_waitqueue_head(&(key_drv->wq));//初始化等待队列头
//进行映射把物理地址变成虚拟地址
gpfcon= ioremap(GPFx, 16);
gpfdat=gpfcon+1;
gpgcon=ioremap(GPGx,12);
gpgdat=gpgcon+1;
return 0;
flag2:
class_destroy( key_drv->dev_class);
flag1:
unregister_chrdev(0, "key_led");
return ret;
}
//出口函数
static void __exit key_exit(void)
{
iounmap( gpgcon);
iounmap( gpfcon);
device_destroy(key_drv->dev_class, MKDEV( key_drv->major,0));
class_destroy(key_drv->dev_class);
unregister_chrdev(0, "key_led");
kfree(key_drv);
free_irq(IRQ_EINT0,NULL);
free_irq(IRQ_EINT2,NULL);
free_irq(IRQ_EINT11,NULL);
}
//入口函数和出口函数的修饰
module_init(key_init);
module_exit(key_exit);
MODULE_LICENSE("GPL");
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <poll.h>
#include<stdio.h>
int main(int argc,char *argv[])
{
int fd,ret;
unsigned int key_val;
struct pollfd fds[2];
char buf[100]={0};
fd=open("/dev/led1", O_RDWR);//后续的I/O操作都是非阻塞的方式
if(fd<0)
{
perror("open\n");
return -1;
}
while (1)
{
fds[0].fd = fd;
fds[0].events = POLLIN;
fds[1].fd = 0;
fds[1].events=POLLIN;
ret = poll(fds, 2, -1);
if (ret > 0)
{
if(fds[0].revents&POLLIN)
{
read(fd, &key_val, 1);
printf("key_val = 0x%x\n", key_val);
}
if(fds[1].revents&POLLIN)
{
memset(buf,0,sizeof(buf));
fgets(buf,sizeof(buf),stdin);
printf("%s\n",buf);
}
}
else
{
perror("poll\n");
}
}
return 0;
}