Linux poll机制介绍
发布时间：2021-11-18 14:46:57 所属栏目：教程 来源：互联网
导读：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
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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%xn", 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 == 0) { /* [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[1]; fd = open("/dev/event1", O_RDWR | O_NONBLOCK); //printf("fd = 0x%xn", fd); if (fd < 0) { printf("can't open!n"); } /* [cgw]: 设置文件标识符 */ fds[0].fd = fd; /* [cgw]: 设置应用程序要响应的事件 */ fds[0].events = POLLIN; while (1) { /* [cgw]: 休眠5S */ ret = poll(fds, 1, 5000); /* [cgw]: 唤醒或超时 */ printf("wake up!n"); if (ret == 0) { printf("time outn"); } else { my_signal_fun(arg); } } return 0; } 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 # ./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  （编辑：东莞站长网） 【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容! |
