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
1 #include <sys/types.h> 2 #include <sys/stat.h> 3 #include <fcntl.h> 4 #include <stdio.h> 5 #include <poll.h> 6 #include <signal.h> 7 #include <sys/types.h> 8 #include <unistd.h> 9 #include <fcntl.h> 10 11 #include <linux/input.h> 12 13 14 15 int fd; 16 17 void my_signal_fun(int signum) 18 { 19 struct input_event buttons_event, leds_event; 20 21 /* [cgw]: 异步通知产生时返回的数据 */ 22 read(fd, &buttons_event, sizeof(struct input_event)); 23 24 /* [cgw]: 打印事件类型，事件码，事件值 */ 25 printf("type: 0x%x code: 0x%x value: 0x%x ", 26 buttons_event.type, 27 buttons_event.code, 28 buttons_event.value); 29 30 /* [cgw]: 返回的是KEY_L或KEY_S值 */ 31 if (buttons_event.code == KEY_L || buttons_event.code == KEY_S) { 32 /* [cgw]: 按键弹起 */ 33 if (buttons_event.value == 0) { 34 35 /* [cgw]: 构造一个EV_LED事件 */ 36 37 //leds_event.type = EV_SND; 38 leds_event.type = EV_LED; 39 //leds_event.code = SND_BELL; 40 leds_event.code = LED_MUTE; 41 42 /* [cgw]: KEY_L和KEY_S控制LED的亮灭 */ 43 if (buttons_event.code == KEY_L) { 44 leds_event.value = 0xAA; 45 } else if (buttons_event.code == KEY_S) { 46 leds_event.value = 0xEE; 47 } 48 49 /* [cgw]: 发送LED控制事件 */ 50 write(fd, &leds_event, sizeof(struct input_event)); 51 52 printf("led write! "); 53 } 54 } 55 } 56 57 int main(int argc, char **argv) 58 { 59 int ret, arg; 60 struct pollfd fds[1]; 61 62 fd = open("/dev/event1", O_RDWR | O_NONBLOCK); 63 64 //printf("fd = 0x%x ", fd); 65 66 if (fd < 0) 67 { 68 printf("can't open! "); 69 } 70 71 /* [cgw]: 设置文件标识符 */ 72 fds[0].fd = fd; 73 /* [cgw]: 设置应用程序要响应的事件 */ 74 fds[0].events = POLLIN; 75 76 while (1) 77 { 78 /* [cgw]: 休眠5S */ 79 ret = poll(fds, 1, 5000); 80 81 /* [cgw]: 唤醒或超时 */ 82 printf("wake up! "); 83 if (ret == 0) 84 { 85 printf("time out "); 86 } 87 else 88 { 89 my_signal_fun(arg); 90 } 91 } 92 93 return 0; 94 }
2. 实验
2.1
安装驱动程序：
insmod input_subsys_drv.ko
1 # insmod input_subsys_drv.ko 2 input: input_subsys_dev as /class/input/input1 3 input subsys open! 4 input subsys init!
运行应用程序
./input_subsys_test
1 # ./input_subsys_test 2 wake up! 3 type: 0x1 code: 0x26 value: 0x1 4 wake up! 5 type: 0x1 code: 0x26 value: 0x0 6 led event! 7 value: 0xaa 8 led write! 9 wake up! 10 type: 0x11 code: 0x7 value: 0xaa 11 wake up! 12 type: 0x1 code: 0x1f value: 0x1 13 wake up! 14 type: 0x1 code: 0x1f value: 0x0 15 led event! 16 value: 0xee 17 led write! 18 wake up! 19 type: 0x11 code: 0x7 value: 0xee 20 wake up! 21 type: 0x1 code: 0x1c value: 0x1 22 wake up! 23 type: 0x1 code: 0x1c value: 0x0 24 wake up! 25 time out 26 wake up! 27 time out
3. 现象分析
按一下按键KEY_L，终端输出：
1 wake up! 2 type: 0x1 code: 0x26 value: 0x1 3 wake up! 4 type: 0x1 code: 0x26 value: 0x0 5 led event! 6 value: 0xaa 7 led write! 8 wake up! 9 type: 0x11 code: 0x7 value: 0xaa
