使用POLL机制代替linux输入子系统（input subsystem）之按键输入和LED控制中的异步通知，实现同样的效果。
1.代码
只简单修改input_subsys_test.c， input_subsys_drv.c不变
input_subsys_test.c
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <poll.h>
#include <signal.h>
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h> #include <linux/input.h> int fd; void my_signal_fun(int signum)
{
struct input_event buttons_event, leds_event; /* [cgw]: 异步通知产生时返回的数据 */
read(fd, &buttons_event, sizeof(struct input_event)); /* [cgw]: 打印事件类型，事件码，事件值 */
printf("type: 0x%x code: 0x%x value: 0x%x\n",
buttons_event.type,
buttons_event.code,
buttons_event.value); /* [cgw]: 返回的是KEY_L或KEY_S值 */
if (buttons_event.code == KEY_L || buttons_event.code == KEY_S) {
/* [cgw]: 按键弹起 */
if (buttons_event.value == ) { /* [cgw]: 构造一个EV_LED事件 */ //leds_event.type = EV_SND;
leds_event.type = EV_LED;
//leds_event.code = SND_BELL;
leds_event.code = LED_MUTE; /* [cgw]: KEY_L和KEY_S控制LED的亮灭 */
if (buttons_event.code == KEY_L) {
leds_event.value = 0xAA;
} else if (buttons_event.code == KEY_S) {
leds_event.value = 0xEE;
} /* [cgw]: 发送LED控制事件 */
write(fd, &leds_event, sizeof(struct input_event)); printf("led write!\n");
}
}
} int main(int argc, char **argv)
{
int ret, arg;
struct pollfd fds[]; fd = open("/dev/event1", O_RDWR | O_NONBLOCK); //printf("fd = 0x%x\n", fd); if (fd < )
{
printf("can't open!\n");
} /* [cgw]: 设置文件标识符 */
fds[].fd = fd;
/* [cgw]: 设置应用程序要响应的事件 */
fds[].events = POLLIN; while ()
{
/* [cgw]: 休眠5S */
ret = poll(fds, , ); /* [cgw]: 唤醒或超时 */
printf("wake up!\n");
if (ret == )
{
printf("time out\n");
}
else
{
my_signal_fun(arg);
}
} return ;
}
2. 实验
2.1
安装驱动程序：
insmod input_subsys_drv.ko
# insmod input_subsys_drv.ko
input: input_subsys_dev as /class/input/input1
input subsys open!
input subsys init!
运行应用程序
./input_subsys_test
# ./input_subsys_test
wake up!
type: 0x1 code: 0x26 value: 0x1
wake up!
type: 0x1 code: 0x26 value: 0x0
led event!
value: 0xaa
led write!
wake up!
type: 0x11 code: 0x7 value: 0xaa
wake up!
type: 0x1 code: 0x1f value: 0x1
wake up!
type: 0x1 code: 0x1f value: 0x0
led event!
value: 0xee
led write!
wake up!
type: 0x11 code: 0x7 value: 0xee
wake up!
type: 0x1 code: 0x1c value: 0x1
wake up!
type: 0x1 code: 0x1c value: 0x0
wake up!
time out
wake up!
time out
3. 现象分析
按一下按键KEY_L，终端输出：
wake up!
type: 0x1 code: 0x26 value: 0x1
wake up!
type: 0x1 code: 0x26 value: 0x0
led event!
value: 0xaa
led write!
wake up!
type: 0x11 code: 0x7 value: 0xaa