08-Poll方式获取输入设备状态

 

#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <linux/input.h>
#include <string.h>
#include <poll.h>

int main(int argc, char **argv)
{
	int fd;
	int len;
	int ret;
	struct input_event event;	
	struct pollfd fds[1];
	nfds_t nfds = 1;
	
	if(argc != 2)
	{
		printf("Usage: %s <dev>\n",argv[0]);
		return -1;
	}

	/*设为noblock 可以一次事件读多次信息*/
	fd = open(argv[1],O_RDWR | O_NONBLOCK);
	if (fd < 0)
	{
		printf("open %s err\n", argv[1]);
		return -1;
	}

	while(1)
	{
		fds[0].fd = fd;
		fds[0].events = POLLIN;//读数据
		fds[0].revents = 0;
		ret = poll(fds,nfds,3000);//超时时间3000ms

		if(ret > 0)
		{
			if(fds[0].revents == POLLIN)
			{
				while(read(fd,&event,sizeof(event)) == sizeof(event))
				{
					printf("get event: type = 0x%x, code = 0x%x, value = 0x%x \n",event.type,event.code,event.value);
				}
			}	
		}
		else if(ret == 0)
		{
			printf("time out\n");
		}
		else
		{
			printf("poll error!\n");
		}
	}
	close(fd);
	return 0;
}

运行结果

[root@100ask:/mnt]# ./input_poll  /dev/input/event2
time out
time out
time out
time out

按下按键之后：

get event: type = 0x1, code = 0x3, value = 0x1 
get event: type = 0x0, code = 0x0, value = 0x0 
get event: type = 0x1, code = 0x3, value = 0x0 
get event: type = 0x0, code = 0x0, value = 0x0