OpenHarmony系统-如何向系统添加一个自定义服务

本文以HelloWorld为例,讲述给Openharmony添加一个开机服务的过程

实现helloworld服务源码

在third_party目录创建一个helloworl目录,并在目录下实现helloworld.c

#include 

int main() {
    printf("Hello, World!\n");
    return 0;
}

然后再在当前目录创建一个BUILD.gn文件, 来定义如何编译构建helloworld模块

import("//build/ohos.gni")

ohos_executable("helloworld") {
  sources = [
    "helloworld.c",
  ]
  
  # 如果需要定义编译标志
  cflags = [ "-Wall" ]
  
  # 安装到系统bin目录
  install_enable = true
  install_images = [ "system" ]
  #output_dir = "bin"
  
  part_name = "helloworld"
  subsystem_name = "thirdparty"
}

再在当前目录创建一个元数据文件bound.json. 用来注册和描述helloworld组件，以便helloworld组件可以被集成进整个系统

{
  "name": "helloworld",
  "version": "1.0.0",
  "publishAs": "code-segment",
  "component": {
    "name": "helloworld",
    "subsystem": "thirdparty",
    "syscap": [],
    "features": [],
    "adapted_system_type": ["standard"],
    "rom": "100KB",
    "ram": "100KB",
    "deps": {
      "components": [],
      "third_party": []
    },
    "build": {
      "sub_component": [
        "//third_party/helloworld:helloworld"
      ],
      "inner_kits": [],
      "test": []
    }
  }
}

至此helloworld服务源码就实现好了,其在third_party目录的结构如下

third_party/helloworld/
├── BUILD.gn
├── bundle.json
└── helloworld.c

0 directories, 3 files

在平台代码中将helloworld模块添加进编译系统

这里以DAYU200为例,其平台代码的位置为:vendor/hihope/rk3568/config.json
我们需要修改该文件添加以下内容:

@@ -264,6 +264,16 @@
           ]
         }
       ]
+    },
+    {
+      "subsystem": "thirdparty",
+      "components": [
+        { 
+         "component": "helloworld", 
+         "features": [] 
+       }
+      ]
+
     }
   ]
 }

将helloworld无法添加到系统服务列表中,并让开机启动执行一次

我们需要修改base/startup/init/services/etc/init.cfg文件,注册和声明该服务.最后在late-fs中启动它

@@ -151,7 +151,8 @@
         }, {
             "name" : "late-fs",
             "cmds" : [
-                "chmod 0755 /sys/kernel/debug/tracing"
+                "chmod 0755 /sys/kernel/debug/tracing", 
+               "start helloworld"
             ]
         }, {
             "name" : "post-fs-data",
@@ -215,5 +216,13 @@
                 "init_trace start"
             ]
         }
-    ]
+    ],
+    "services" : [{
+        "name" : "helloworld",
+        "path" : ["/system/bin/helloworld"],
+        "uid" : "root",
+        "gid" : "root",
+        "once" : 1,
+        "importance" : 0
+    }]
 }