getevent 简单分析

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我是靠谱客的博主缥缈红酒，这篇文章主要介绍getevent 简单分析，现在分享给大家，希望可以做个参考。

getevent是安卓系统下代码的小工具能很好的确认底层是否有某些事件的上报。

在Android 释放的源代码里 alps/docs/source.android.com/en/devices/input 有该小工具的一些基本使用方法。

adb shell getevent -p

用来显示当前系统的各个input设备的上报功能。

adb shell getevent -lp

加上-l会显示对应的事件文本标号。

adb shell getevent -lt

显示活动事件，经常用来实时抓取。

LOCAL_MODULE := toolbox

可发现统一了几个小工具的入口。用的是三个不同的链接。

LOCAL_POST_INSTALL_CMD := $(hide) $(foreach t,$(ALL_TOOLS),ln -sf toolbox $(TARGET_OUT)/bin/$(t);)

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 28 int main(int argc, char** argv) {
 29     // Let's assume that none of this code handles broken pipes. At least ls,
 30     // ps, and top were broken (though I'd previously added this fix locally
 31     // to top). We exit rather than use SIG_IGN because tools like top will
 32     // just keep on writing to nowhere forever if we don't stop them.
 33     signal(SIGPIPE, SIGPIPE_handler);
 34    
 35     char* cmd = strrchr(argv[0], '/');
 36     char* name = cmd ? (cmd + 1) : argv[0];
 37    
 38     for (size_t i = 0; tools[i].name; i++) {
 39         if (!strcmp(tools[i].name, name)) {
 40             return tools[i].func(argc, argv);
 41         }
 42     }
 43    
 44     printf("%s: no such tooln", argv[0]);
 45     return 127;
 46 }

而tools[i] 的定义用的比较灵活。

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 11 static struct {
 12     const char* name;      
 13     int (*func)(int, char**);
 14 } tools[] = {
 15 #define TOOL(name) { #name, name##_main },
 16 #include "tools.h"
 17 #undef TOOL
 18     { 0, 0 },
 19 };

tools[i] 这个数组的生成是结合了Android.mk.

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 39 $(LOCAL_PATH)/toolbox.c: $(intermediates)/tools.h
 40  
 41 TOOLS_H := $(intermediates)/tools.h
 42 $(TOOLS_H): PRIVATE_TOOLS := toolbox $(ALL_TOOLS)
 43 $(TOOLS_H): PRIVATE_CUSTOM_TOOL = echo "/* file generated automatically */" > $@ ; for t in $(PRIVATE_TOOLS) ; do echo "TOOL($$t)" >> $@ ; done

自动生成在out/target/product/k80_bsp/obj/EXECUTABLES/toolbox_intermediates/tools.h

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6

  1 /* file generated automatically */
  2 TOOL(toolbox)
  3 TOOL(dd)
  4 TOOL(getevent)
  5 TOOL(newfs_msdos)

对应TOOL(getevent)就可以发现实际上是导入到了 getevent 的入口

int getevent_main(int argc, char *argv[])

通过 c = getopt(argc, argv, "tns:Sv::dpilqc:rh");

分析用户输入命令的参数。

分别存放到不同的flag中。主要flag为 print_flags，使用它的不同位数进行标记。

getopt 处理的只是对应的- 后面的参数，后面会对文件路径参数进行处理。

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599     if(dont_block == -1)                                                                                                                                                                                      
600         dont_block = 0;
601  
602     if (optind + 1 == argc) {
603         device = argv[optind];
604         optind++;
605     }
606     if (optind != argc) {
607         usage(argv[0]);
608         exit(1);
609     }
610     nfds = 1;
611     ufds = calloc(1, sizeof(ufds[0]));
612     ufds[0].fd = inotify_init();
613     ufds[0].events = POLLIN;
614     if(device) {
615         if(!print_flags_set)
616             print_flags |= PRINT_DEVICE_ERRORS;
617         res = open_device(device, print_flags);
618         if(res < 0) {
619             return 1;
620         }
621     } else {
622         if(!print_flags_set)
623             print_flags |= PRINT_DEVICE_ERRORS | PRINT_DEVICE | PRINT_DEVICE_NAME;
624         print_device = 1;
625         res = inotify_add_watch(ufds[0].fd, device_path, IN_DELETE | IN_CREATE);
626         if(res < 0) {
627             fprintf(stderr, "could not add watch for %s, %sn", device_path, strerror(errno));
628             return 1;
629         }
630         res = scan_dir(device_path, print_flags);
631         if(res < 0) {
632             fprintf(stderr, "scan dir failed for %sn", device_path);
633             return 1;
634         }
635     }

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599     if(dont_block == -1)                                                                                                                                                                                      
600         dont_block = 0;
601  
602     if (optind + 1 == argc) {
603         device = argv[optind];
604         optind++;
605     }
606     if (optind != argc) {
607         usage(argv[0]);
608         exit(1);
609     }
610     nfds = 1;
611     ufds = calloc(1, sizeof(ufds[0]));
612     ufds[0].fd = inotify_init();
613     ufds[0].events = POLLIN;
614     if(device) {
615         if(!print_flags_set)
616             print_flags |= PRINT_DEVICE_ERRORS;
617         res = open_device(device, print_flags);
618         if(res < 0) {
619             return 1;
620         }
621     } else {
622         if(!print_flags_set)
623             print_flags |= PRINT_DEVICE_ERRORS | PRINT_DEVICE | PRINT_DEVICE_NAME;
624         print_device = 1;
625         res = inotify_add_watch(ufds[0].fd, device_path, IN_DELETE | IN_CREATE);
626         if(res < 0) {
627             fprintf(stderr, "could not add watch for %s, %sn", device_path, strerror(errno));
628             return 1;
629         }
630         res = scan_dir(device_path, print_flags);
631         if(res < 0) {
632             fprintf(stderr, "scan dir failed for %sn", device_path);
633             return 1;
634         }
635     }

mian-》open_device

打印传入的dev，进行一些version product等的打印。

如果没有传入打印的参数。将对 main--》scan_dir --》open_device所以目录进行。依次打开。

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473 static int scan_dir(const char *dirname, int print_flags)
474 {
475     char devname[PATH_MAX];
476     char *filename;
477     DIR *dir;
478     struct dirent *de;
479     dir = opendir(dirname);
480     if(dir == NULL)
481         return -1;
482     strcpy(devname, dirname);
483     filename = devname + strlen(devname);
484     *filename++ = '/';
485     while((de = readdir(dir))) {
486         if(de->d_name[0] == '.' &&
487            (de->d_name[1] == '' ||
488             (de->d_name[1] == '.' && de->d_name[2] == '')))
489             continue;
490         strcpy(filename, de->d_name);
491         open_device(devname, print_flags);
492     }                                                                                                                                                                                                         
493     closedir(dir);
494     return 0;
495 }

最后不断的等待我们的event 节点内的信息的出现，读取出来进行显示。给到命令输入者。

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652                        
653     while(1) {         
654         //int pollres =
655         poll(ufds, nfds, -1);
656         //printf("poll %d, returned %dn", nfds, pollres);
657         if(ufds[0].revents & POLLIN) {
658             read_notify(device_path, ufds[0].fd, print_flags);
659         }              
660         for(i = 1; i < nfds; i++) {
661             if(ufds[i].revents) {
662                 if(ufds[i].revents & POLLIN) {
663                     res = read(ufds[i].fd, &event, sizeof(event));
664                     if(res < (int)sizeof(event)) {
665                         fprintf(stderr, "could not get eventn");
666                         return 1;
667                     }  
668                     if(get_time) {
669                         printf("[%8ld.%06ld] ", event.time.tv_sec, event.time.tv_usec);
670                     }  
671                     if(print_device)
672                         printf("%s: ", device_names[i]);
673                     print_event(event.type, event.code, event.value, print_flags);                                                                                                                            
674                     if(sync_rate && event.type == 0 && event.code == 0) {
675                         int64_t now = event.time.tv_sec * 1000000LL + event.time.tv_usec;
676                         if(last_sync_time)
677                             printf(" rate %lld", 1000000LL / (now - last_sync_time));
678                         last_sync_time = now;
679                     }  
680                     printf("%s", newline);
681                     if(event_count && --event_count == 0)
682                         return 0;
683                 }      
684             }          
685         }              
686     }

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652                        
653     while(1) {         
654         //int pollres =
655         poll(ufds, nfds, -1);
656         //printf("poll %d, returned %dn", nfds, pollres);
657         if(ufds[0].revents & POLLIN) {
658             read_notify(device_path, ufds[0].fd, print_flags);
659         }              
660         for(i = 1; i < nfds; i++) {
661             if(ufds[i].revents) {
662                 if(ufds[i].revents & POLLIN) {
663                     res = read(ufds[i].fd, &event, sizeof(event));
664                     if(res < (int)sizeof(event)) {
665                         fprintf(stderr, "could not get eventn");
666                         return 1;
667                     }  
668                     if(get_time) {
669                         printf("[%8ld.%06ld] ", event.time.tv_sec, event.time.tv_usec);
670                     }  
671                     if(print_device)
672                         printf("%s: ", device_names[i]);
673                     print_event(event.type, event.code, event.value, print_flags);                                                                                                                            
674                     if(sync_rate && event.type == 0 && event.code == 0) {
675                         int64_t now = event.time.tv_sec * 1000000LL + event.time.tv_usec;
676                         if(last_sync_time)
677                             printf(" rate %lld", 1000000LL / (now - last_sync_time));
678                         last_sync_time = now;
679                     }  
680                     printf("%s", newline);
681                     if(event_count && --event_count == 0)
682                         return 0;
683                 }      
684             }          
685         }              
686     }