testapp.c

mp3键盘驱动源码,同时支持滚动和按键两种方式

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/select.h>
#include <sys/time.h>
#include <errno.h>

int main(void)
{
	int pad_fd;
	int key_value;
 	fd_set rds;
	int ret,ret1;


	printf(" open pad ... ...\n");
	pad_fd = open("/dev/pad", 0);
	if (pad_fd < 0) 
	{
        	perror("open device pad\n");
		exit(1);
	}
	printf(" open pad ok!\n");
	for (;;) 
	{
       		FD_ZERO(&rds); //clear the fd_set
		FD_SET(pad_fd, &rds);//add pad_fd to the fd_set

		ret = select(pad_fd + 1, &rds, NULL, NULL, NULL); //if the fd_set is readbles or writeable?
		if (ret < 0) 
		{
			perror("select");
			exit(1);
		}
		if (ret == 0) 
		{
			printf("Timeout.\n");
		} 
		else if (FD_ISSET(pad_fd, &rds)) //if the pad_fd in the fd_set
		{
              		 ret1 = read(pad_fd, &key_value, sizeof key_value);
              		if (ret1 != sizeof key_value) 
			{
				if (errno != EAGAIN)
				perror("read buttons\n");
				continue;
			} 
			else 
			{
				printf("buttons_value: %d\n", key_value);
              		}
                  
        	}
    	}

    	close(pad_fd);
    	return 0;
}