Detailed use
xxxxxxxx:/ # getevent -h
Usage: getevent [-t] [-n] [-s switchmask] [-S] [-v [mask]] [-d] [-p] [-i] [-l] [-q] [-c count] [-r] [device]
-t: show time stamps -显示事件的发生时间
-n: don't print newlines
-s: print switch states for given bits
-S: print all switch states
-v: verbosity mask (errs=1, dev=2, name=4, info=8, vers=16, pos. events=32, props=64)
-d: show HID descriptor, if available
-p: show possible events (errs, dev, name, pos. events)
-i: show all device info and possible events
-l: label event types and names in plain text -这里表示要把event事件类型名字打印出来
-q: quiet (clear verbosity mask)
-c: print given number of events then exit
-r: print rate events are received -显示一下接受事件速率
commonly used isgetevent -lrt
xxxx:/ # getevent -lrt
add device 1: /dev/input/event0
name: "ACCDET"
add device 2: /dev/input/event7
name: "ln4912"
add device 3: /dev/input/event10
name: "mtk-tpd"
add device 4: /dev/input/event6
name: "ln4913"
add device 5: /dev/input/event2
name: "dbmdx4"
add device 6: /dev/input/event8
name: "fts_ts"
add device 7: /dev/input/event4
name: "als"
add device 8: /dev/input/event3
name: "tcs3408"
add device 9: /dev/input/event1
name: "mtk-kpd"
add device 10: /dev/input/event5
name: "flicker"
add device 11: /dev/input/event9
name: "fts_ts,pen"
[ 104.141089] /dev/input/event8: EV_ABS ABS_MT_SLOT 00000000 //代表第一个手指，其实第一个也可以没有，有的机器就第一次0是没有这个slot
[ 104.141089] /dev/input/event8: EV_ABS ABS_MT_TRACKING_ID 00000007 //第一个手指对应的TRACKING_ID
[ 104.141089] /dev/input/event8: EV_ABS ABS_MT_TOUCH_MAJOR 00000040 //第一个手指按下时接触屏幕的椭圆长轴。
[ 104.141089] /dev/input/event8: EV_ABS ABS_MT_POSITION_X 0000044d //第一个手指按下的X轴坐标
[ 104.141089] /dev/input/event8: EV_ABS ABS_MT_POSITION_Y 0000020b //第一个手指按下的y轴坐标
[ 104.141089] /dev/input/event8: EV_KEY BTN_TOUCH DOWN //触摸按下
[ 104.141089] /dev/input/event8: EV_SYN SYN_REPORT 00000000 //第一个手指同步事件完
[ 104.157111] /dev/input/event8: EV_ABS ABS_MT_SLOT 00000001 //代表第二个手指
[ 104.157111] /dev/input/event8: EV_ABS ABS_MT_TRACKING_ID 00000008 //第二个手指对应的TRACKING_ID
[ 104.157111] /dev/input/event8: EV_ABS ABS_MT_TOUCH_MAJOR 00000040 //第二个手指按下时接触屏幕的椭圆长轴。
[ 104.157111] /dev/input/event8: EV_ABS ABS_MT_POSITION_X 000005b5 //第二个手指按下的X轴坐标
[ 104.157111] /dev/input/event8: EV_ABS ABS_MT_POSITION_Y 0000025e //第二个手指按下的y轴坐标
[ 104.157111] /dev/input/event8: EV_SYN SYN_REPORT 00000000 //第二个手指同步事件完 rate 62
[ 104.189299] /dev/input/event8: EV_ABS ABS_MT_POSITION_X 000005b2
[ 104.189299] /dev/input/event8: EV_SYN SYN_REPORT 00000000 rate 31
[ 104.199057] /dev/input/event8: EV_ABS ABS_MT_SLOT 00000000
[ 104.199057] /dev/input/event8: EV_ABS ABS_MT_POSITION_X 0000044c
[ 104.199057] /dev/input/event8: EV_SYN SYN_REPORT 00000000 rate 102
[ 104.206137] /dev/input/event8: EV_ABS ABS_MT_POSITION_X 0000044a
[ 104.206137] /dev/input/event8: EV_ABS ABS_MT_POSITION_Y 0000020c
[ 104.206137] /dev/input/event8: EV_ABS ABS_MT_SLOT 00000001
[ 104.206137] /dev/input/event8: EV_ABS ABS_MT_POSITION_X 000005af
[ 104.206137] /dev/input/event8: EV_ABS ABS_MT_POSITION_Y 00000260
[ 104.206137] /dev/input/event8: EV_SYN SYN_REPORT 00000000 rate 141
[ 104.214889] /dev/input/event8: EV_ABS ABS_MT_SLOT 00000000
[ 104.214889] /dev/input/event8: EV_ABS ABS_MT_POSITION_X 00000443
[ 104.214889] /dev/input/event8: EV_ABS ABS_MT_POSITION_Y 0000020f
[ 104.214889] /dev/input/event8: EV_ABS ABS_MT_SLOT 00000001
[ 104.214889] /dev/input/event8: EV_ABS ABS_MT_POSITION_X 000005aa
[ 104.214889] /dev/input/event8: EV_ABS ABS_MT_POSITION_Y 00000262
[ 104.214889] /dev/input/event8: EV_SYN SYN_REPORT 00000000 rate 114
[ 104.222955] /dev/input/event8: EV_ABS ABS_MT_SLOT 00000000
[ 104.222955] /dev/input/event8: EV_ABS ABS_MT_POSITION_X 0000043e
[ 104.222955] /dev/input/event8: EV_ABS ABS_MT_POSITION_Y 00000213
[ 104.222955] /dev/input/event8: EV_ABS ABS_MT_SLOT 00000001
[ 104.222955] /dev/input/event8: EV_ABS ABS_MT_POSITION_X 000005a1
[ 104.222955] /dev/input/event8: EV_ABS ABS_MT_POSITION_Y 00000266
[ 104.222955] /dev/input/event8: EV_SYN SYN_REPORT 00000000 rate 123
[ 104.231189] /dev/input/event8: EV_ABS ABS_MT_SLOT 00000000
[ 104.231189] /dev/input/event8: EV_ABS ABS_MT_POSITION_X 00000436
[ 104.231189] /dev/input/event8: EV_ABS ABS_MT_POSITION_Y 00000219
[ 104.231189] /dev/input/event8: EV_ABS ABS_MT_SLOT 00000001
[ 104.231189] /dev/input/event8: EV_ABS ABS_MT_POSITION_X 00000596
[ 104.231189] /dev/input/event8: EV_ABS ABS_MT_POSITION_Y 0000026b
[ 104.231189] /dev/input/event8: EV_SYN SYN_REPORT 00000000 rate 121
[ 104.239773] /dev/input/event8: EV_ABS ABS_MT_SLOT 00000000
[ 104.239773] /dev/input/event8: EV_ABS ABS_MT_POSITION_X 0000042e
[ 104.239773] /dev/input/event8: EV_ABS ABS_MT_POSITION_Y 0000021f
[ 104.239773] /dev/input/event8: EV_ABS ABS_MT_SLOT 00000001
[ 104.239773] /dev/input/event8: EV_ABS ABS_MT_POSITION_X 00000588
[ 104.239773] /dev/input/event8: EV_ABS ABS_MT_POSITION_Y 00000271
[ 104.239773] /dev/input/event8: EV_SYN SYN_REPORT 00000000 rate 116
[ 104.248354] /dev/input/event8: EV_ABS ABS_MT_SLOT 00000000
[ 104.248354] /dev/input/event8: EV_ABS ABS_MT_POSITION_X 00000424
[ 104.248354] /dev/input/event8: EV_ABS ABS_MT_POSITION_Y 00000226
[ 104.248354] /dev/input/event8: EV_ABS ABS_MT_SLOT 00000001
[ 104.248354] /dev/input/event8: EV_ABS ABS_MT_POSITION_X 00000573
[ 104.248354] /dev/input/event8: EV_ABS ABS_MT_POSITION_Y 00000279
[ 104.248354] /dev/input/event8: EV_SYN SYN_REPORT 00000000 rate 116
[ 104.260568] /dev/input/event8: EV_ABS ABS_MT_SLOT 00000000 //第一个手指
[ 104.260568] /dev/input/event8: EV_ABS ABS_MT_TRACKING_ID ffffffff //TRACKING_ID为-1,代表第一个手指抬起消失
[ 104.260568] /dev/input/event8: EV_ABS ABS_MT_SLOT 00000001 //第二个手指
[ 104.260568] /dev/input/event8: EV_ABS ABS_MT_TRACKING_ID ffffffff //TRACKING_ID为-1,代表第二个手指抬起消失
[ 104.260568] /dev/input/event8: EV_KEY BTN_TOUCH UP //触摸抬起
[ 104.260568] /dev/input/event8: EV_SYN SYN_REPORT 00000000 rate 81
[ 112248.432102] /dev/input/event8: EV_SYN SYN_REPORT 00000000 rate 117
Time Specific node file name Event type Event code Event value rate Receive rate
event type
1. After the EV_SYN
synchronous event is completed, there will be
corresponding when the event starts or finishes code:
0004: represents the start of an event (not necessary, not necessarily displayed)
0005: represents the start of an event (not necessary, not necessarily displayed)
SYN_REPORT: represents the end of an event (required)
2. An absolute coordinate type of EV_ABS
event Corresponding to code:
2.0 ABS_MT_SLOT
essentially represents different fingers, and its value represents the finger id
2.1 ABS_MT_TRACKING_ID
Unique to type B, in fact, each slotwill IDcorrespond to one, a non-negative number means a touch, -1 means it is useless slot(or understood as the end of a touch). slotDrivers should disable this by changing this value whenever there is a corresponding change in the type of contact slot. And the value of the next touch IDwill be the value of this time plus 1.
2.2 ABS_MT_POSITION_X,ABS_MT_POSITION_Y
x,y coordinates relative to the center of the screen.
2.3 ABS_MT_TOUCH_MAJOR
The major axis length of the contact part. Equivalent to the major axis of the ellipse.
2.4 ABS_MT_TOUCH_MINOR
The minor axis length of the contact part. Equivalent to the minor axis of the ellipse.
2.5 ABS_MT_PRESSURE
represents pressing pressure, some devices may not have it
3. A type of EV_KEY event. Indicates that it is a button (not only refers to the physical button but also TOUCH) event
Correspondence code:
3.1 BTN_TOUCH
Touch the button. Its value is DOWNor UP.
3.2 BTN_TOOL_FINGER
The button is yes finger, and its value is also DOWNor UP, not necessarily exist
Source code anatomy
android-12.0.0_r28/system/core/toolbox/getevent.c
int getevent_main(int argc, char *argv[])
{
...
const char *device = NULL;
const char *device_path = "/dev/input";
/* disable buffering on stdout */
setbuf(stdout, NULL);
....
if (optind + 1 == argc) {
device = argv[optind];
optind++;
}
if (optind != argc) {
usage(argv[0]);
exit(1);
}
// 通过poll机制监听文件
nfds = 1;
ufds = calloc(1, sizeof(ufds[0]));
ufds[0].fd = inotify_init();
ufds[0].events = POLLIN;
//device 就是有没有带文件路径，比如getevent -lrt /dev/input/event8
if(device) {
if(!print_flags_set)
print_flags |= PRINT_DEVICE_ERRORS;
res = open_device(device, print_flags);
if(res < 0) {
return 1;
}
} else {
if(!print_flags_set)
print_flags |= PRINT_DEVICE_ERRORS | PRINT_DEVICE | PRINT_DEVICE_NAME;
print_device = 1;
//监听device_path目录(/dev/input/)
res = inotify_add_watch(ufds[0].fd, device_path, IN_DELETE | IN_CREATE);
if(res < 0) {
fprintf(stderr, "could not add watch for %s, %s\n", device_path, strerror(errno));
return 1;
}
res = scan_dir(device_path, print_flags);
if(res < 0) {
fprintf(stderr, "scan dir failed for %s\n", device_path);
return 1;
}
}
...
if(dont_block)
return 0;
while(1) {
//int pollres =
poll(ufds, nfds, -1);
//printf("poll %d, returned %d\n", nfds, pollres);
if(ufds[0].revents & POLLIN) {
read_notify(device_path, ufds[0].fd, print_flags);
}
for(i = 1; i < nfds; i++) {
if(ufds[i].revents) {
if(ufds[i].revents & POLLIN) {
res = read(ufds[i].fd, &event, sizeof(event));
if(res < (int)sizeof(event)) {
fprintf(stderr, "could not get event\n");
return 1;
}
if(get_time) {
printf("[%8ld.%06ld] ", event.time.tv_sec, event.time.tv_usec);
}
if(print_device)
printf("%s: ", device_names[i]);
print_event(event.type, event.code, event.value, print_flags);
if(sync_rate && event.type == 0 && event.code == 0) {
int64_t now = event.time.tv_sec * 1000000LL + event.time.tv_usec;
if(last_sync_time)
printf(" rate %lld", 1000000LL / (now - last_sync_time));
last_sync_time = now;
}
printf("%s", newline);
if(event_count && --event_count == 0)
return 0;
}
}
}
}
return 0;
}
static int scan_dir(const char *dirname, int print_flags)
{
char devname[PATH_MAX];
char *filename;
DIR *dir;
struct dirent *de;
dir = opendir(dirname);
if(dir == NULL)
return -1;
strcpy(devname, dirname);
filename = devname + strlen(devname);
*filename++ = '/';
while((de = readdir(dir))) {
if(de->d_name[0] == '.' &&
(de->d_name[1] == '\0' ||
(de->d_name[1] == '.' && de->d_name[2] == '\0')))
continue;
strcpy(filename, de->d_name);
open_device(devname, print_flags);
}
closedir(dir);
return 0;
}
static int open_device(const char *device, int print_flags)
{
....
ufds[nfds].fd = fd;
ufds[nfds].events = POLLIN;
device_names[nfds] = strdup(device);
nfds++;
return 0;
}