Android之build.prop属性详解

注：本篇文章是基于MSD648项目（AndroidTV）的prop进行说明。

Android版本：4.4.4

内核版本：3.10.86

1.生成build.prop

　　build.prop的生成是由make系统解析build/core/Makefile完成

　　1.1.Makefile生成build.prop的主要代码如下

$(INSTALLED_BUILD_PROP_TARGET): $(BUILDINFO_SH) $(INTERNAL_BUILD_ID_MAKEFILE) $(BUILD_SYSTEM)/version_defaults.mk $(system_prop_file)
    @echo Target buildinfo: $@
    @mkdir -p $(dir $@)
    $(hide) TARGET_BUILD_TYPE="$(TARGET_BUILD_VARIANT)" \
            TARGET_DEVICE="$(TARGET_DEVICE)" \
            PRODUCT_NAME="$(TARGET_PRODUCT)" \
            PRODUCT_BRAND="$(PRODUCT_BRAND)" \
            PRODUCT_DEFAULT_LANGUAGE="$(call default-locale-language,$(PRODUCT_LOCALES))" \
            PRODUCT_DEFAULT_REGION="$(call default-locale-region,$(PRODUCT_LOCALES))" \
            PRODUCT_DEFAULT_WIFI_CHANNELS="$(PRODUCT_DEFAULT_WIFI_CHANNELS)" \
            PRODUCT_MODEL="$(PRODUCT_MODEL)" \
            PRODUCT_MANUFACTURER="$(PRODUCT_MANUFACTURER)" \
            PRIVATE_BUILD_DESC="$(PRIVATE_BUILD_DESC)" \
            BUILD_ID="$(BUILD_ID)" \
            BUILD_DISPLAY_ID="$(BUILD_DISPLAY_ID)" \
            BUILD_NUMBER="$(BUILD_NUMBER)" \
            PLATFORM_VERSION="$(PLATFORM_VERSION)" \
            PLATFORM_SDK_VERSION="$(PLATFORM_SDK_VERSION)" \
            PLATFORM_VERSION_CODENAME="$(PLATFORM_VERSION_CODENAME)" \
            BUILD_VERSION_TAGS="$(BUILD_VERSION_TAGS)" \
            TARGET_BOOTLOADER_BOARD_NAME="$(TARGET_BOOTLOADER_BOARD_NAME)" \
            BUILD_FINGERPRINT="$(BUILD_FINGERPRINT)" \
            TARGET_BOARD_PLATFORM="$(TARGET_BOARD_PLATFORM)" \
            TARGET_CPU_ABI="$(TARGET_CPU_ABI)" \
            TARGET_CPU_ABI2="$(TARGET_CPU_ABI2)" \
            TARGET_AAPT_CHARACTERISTICS="$(TARGET_AAPT_CHARACTERISTICS)" \
            bash $(BUILDINFO_SH) > $@
    $(hide) $(foreach file,$(system_prop_file), \
        if [ -f "$(file)" ]; then \
            echo "#" >> $@; \
            echo Target buildinfo from: "$(file)"; \
            echo "# from $(file)" >> $@; \
            echo "#" >> $@; \
            cat $(file) >> $@; \
        fi;)
    $(if $(ADDITIONAL_BUILD_PROPERTIES), \
        $(hide) echo >> $@; \
                echo "#" >> $@; \
                echo "# ADDITIONAL_BUILD_PROPERTIES" >> $@; \
                echo "#" >> $@; )
    $(hide) $(foreach line,$(ADDITIONAL_BUILD_PROPERTIES), \
        echo "$(line)" >> $@;)
    $(hide) build/tools/post_process_props.py $@

build_desc :=

　　1.2.目标文件为$(INSTALLED_BUILD_PROP_TARGET)，其定义为：

INSTALLED_BUILD_PROP_TARGET := $(TARGET_OUT)/build.prop

　　1.3.首先对属性进行赋值，如BUILD_ID="$(BUILD_ID)"，最后执行bash脚本：bash $(BUILDINFO_SH) > $@，其定义为

BUILDINFO_SH := build/tools/buildinfo.sh

　　1.4.开始执行sh脚本中的内容

#!/bin/bash

echo "# begin build properties"
echo "# autogenerated by buildinfo.sh"

echo "ro.build.id=$BUILD_ID"
echo "ro.build.display.id=$BUILD_DISPLAY_ID"
echo "ro.build.version.incremental=$BUILD_NUMBER"
echo "ro.build.version.sdk=$PLATFORM_SDK_VERSION"
echo "ro.build.version.codename=$PLATFORM_VERSION_CODENAME"
echo "ro.build.version.release=$PLATFORM_VERSION"
echo "ro.build.date=`date`"
echo "ro.build.date.utc=`date +%s`"
echo "ro.build.type=$TARGET_BUILD_TYPE"
echo "ro.build.user=$USER"
echo "ro.build.host=`hostname`"
echo "ro.build.tags=$BUILD_VERSION_TAGS"
echo "ro.product.model=$PRODUCT_MODEL"
echo "ro.product.brand=$PRODUCT_BRAND"
echo "ro.product.name=$PRODUCT_NAME"
echo "ro.product.device=$TARGET_DEVICE"
echo "ro.product.board=$TARGET_BOOTLOADER_BOARD_NAME"
echo "ro.product.cpu.abi=$TARGET_CPU_ABI"
if [ -n "$TARGET_CPU_ABI2" ] ; then
  echo "ro.product.cpu.abi2=$TARGET_CPU_ABI2"
fi
echo "ro.product.manufacturer=$PRODUCT_MANUFACTURER"
if [ -n "$PRODUCT_DEFAULT_LANGUAGE" ] ; then
  echo "ro.product.locale.language=$PRODUCT_DEFAULT_LANGUAGE"
fi
if [ -n "$PRODUCT_DEFAULT_REGION" ] ; then
  echo "ro.product.locale.region=$PRODUCT_DEFAULT_REGION"
fi
echo "ro.wifi.channels=$PRODUCT_DEFAULT_WIFI_CHANNELS"
echo "ro.board.platform=$TARGET_BOARD_PLATFORM"

echo "# ro.build.product is obsolete; use ro.product.device"
echo "ro.build.product=$TARGET_DEVICE"

echo "# Do not try to parse ro.build.description or .fingerprint"
echo "ro.build.description=$PRIVATE_BUILD_DESC"
echo "ro.build.fingerprint=$BUILD_FINGERPRINT"
echo "ro.build.characteristics=$TARGET_AAPT_CHARACTERISTICS"

echo "# end build properties"

　　1.5.最后追加余下的属性

    $(hide) $(foreach file,$(system_prop_file), \
        if [ -f "$(file)" ]; then \
            echo "#" >> $@; \
            echo Target buildinfo from: "$(file)"; \
            echo "# from $(file)" >> $@; \
            echo "#" >> $@; \
            cat $(file) >> $@; \
        fi;)
    $(if $(ADDITIONAL_BUILD_PROPERTIES), \
        $(hide) echo >> $@; \
                echo "#" >> $@; \
                echo "# ADDITIONAL_BUILD_PROPERTIES" >> $@; \
                echo "#" >> $@; )
    $(hide) $(foreach line,$(ADDITIONAL_BUILD_PROPERTIES), \
        echo "$(line)" >> $@;)
    $(hide) build/tools/post_process_props.py $@

　　　　其中system_prop_file定义：

ifdef TARGET_SYSTEM_PROP
system_prop_file := $(TARGET_SYSTEM_PROP)
else
system_prop_file := $(wildcard $(TARGET_DEVICE_DIR)/system.prop)
endif

　　　　即$(TARGET_DEVICE_DIR)/system.prop文件

　　到此，prop文件生成完毕！

2.对生成的build.prop的属性进行说明：

# begin build properties
# autogenerated by buildinfo.sh
ro.build.id=KTU84P　　#版本ID
ro.build.display.id=aosp_almond-userdebug 4.4. KTU84P TVOS-04.19.010.02..Mooney test-keys　　#具体版本号
ro.build.version.incremental=TVOS-04.19.010.02..Mooney　　#版本增量说明
ro.build.version.sdk=19　　#SDK版本
ro.build.version.codename=REL　　#版本代号
ro.build.version.release=4.4.4　　#Android系统版本
ro.build.date=2017年 07月 13日 星期四 :: CST　　#编译时间
ro.build.date.utc=1499927987　　#编译时间(UTC)
ro.build.type=userdebug　　#编译类型(eng/user)
ro.build.user=pngcui　　#编译者
ro.build.host=Sky-pngcui　　#编译机器名
ro.build.tags=test-keys　　#系统标记
ro.product.model=MSD6A648　　#设备型号
ro.product.brand=MStar　　#设备品牌
ro.product.name=aosp_almond　　#产品名
ro.product.device=almond　　#采用的设备名
ro.product.board=almond　　#采用的主板名
ro.product.cpu.abi=armeabi-v7a　　#CPU版本
ro.product.cpu.abi2=armeabi　　#CPU品牌
ro.product.manufacturer=Skyworth-qx, Inc.　　#产品制造商
ro.product.locale.language=zh
ro.product.locale.region=CN
ro.wifi.channels=　　#无线局域网络的通信信道,空白表示自动识别
ro.board.platform=mooney　　#主板平台
# ro.build.product is obsolete; use ro.product.device
ro.build.product=almond　　#设备名，已被废弃，使用ro.product.device
# Do not try to parse ro.build.description or .fingerprint
ro.build.description=aosp_almond-userdebug 4.4. KTU84P TVOS-04.19.010.02..Mooney test-keys　　#用户key
ro.build.fingerprint=MStar/aosp_almond/almond:4.4./KTU84P/TVOS-04.19.010.02..Mooney:userdebug/test-keys　　#机身码
ro.build.characteristics=tv
# end build properties

3.修改prop的属性的说明，需要对照build/tools/buildinfo.sh进行

　　3.1.ro.build.id属性(build/core/build_id.mk)

export BUILD_ID=8M648

　　3.2.ro.build.display.id(build/core/Makefile)

build_desc := $(TARGET_PRODUCT)-$(TARGET_BUILD_VARIANT) $(PLATFORM_VERSION) $(BUILD_ID) $(BUILD_NUMBER) $(BUILD_VERSION_TAGS)

# Display parameters shown under Settings -> About Phone
ifeq ($(TARGET_BUILD_VARIANT),user)
  # User builds should show:
  # release build number or branch.buld_number non-release builds

  # Dev. branches should have DISPLAY_BUILD_NUMBER set
  ifeq "true" "$(DISPLAY_BUILD_NUMBER)"
    BUILD_DISPLAY_ID := $(BUILD_ID).$(BUILD_NUMBER) $(BUILD_KEYS)
  else
    BUILD_DISPLAY_ID := $(BUILD_ID) $(BUILD_KEYS)
  endif
else
  # Non-user builds should show detailed build information
    BUILD_DISPLAY_ID := $(build_desc)
endif

　　3.3.ro.build.version.incremental(device/mstar/almond/BoardConfigCommon.mk)

BUILD_NUMBER := TVOS-04.19.010.02..Mooney

　　3.4.ro.product.model、ro.product.brand、ro.product.name、ro.product.device、ro.product.manufacturer(device/mstar/almond/aosp_almond.mk)

# Set those variables here to overwrite the inherited values.
PRODUCT_NAME := aosp_almond
PRODUCT_DEVICE := almond
PRODUCT_BRAND := MStar
PRODUCT_MODEL := MSD6A648
PRODUCT_MANUFACTURER := Skyworth-qx, Inc.

　　注：PRODUCT_DEVICE会决定device下目录的选择，故尽量不要更改

　　3.5.ro.build.description(build/core/Makefile)

build_desc := $(TARGET_PRODUCT)-$(TARGET_BUILD_VARIANT) $(PLATFORM_VERSION) $(BUILD_ID) $(BUILD_NUMBER) $(BUILD_VERSION_TAGS)

$(INSTALLED_BUILD_PROP_TARGET): PRIVATE_BUILD_DESC := $(build_desc)

　　3.6.ro.product.board(device/mstar/almond/BoardConfig.mk)

TARGET_BOOTLOADER_BOARD_NAME := almond

4.Android系统中Setting.apk中内核版本

　　packages/apps/Settings/src/com/android/settings/DeviceInfoSettings.java

 private static final String FILENAME_PROC_VERSION = "/proc/version";
 private static final String KEY_KERNEL_VERSION = "kernel_version";

 @Override
 public void onCreate(Bundle icicle) {
 　　findPreference(KEY_KERNEL_VERSION).setSummary(getFormattedKernelVersion());
 }

     public static String getFormattedKernelVersion() {
         try {
             return formatKernelVersion(readLine(FILENAME_PROC_VERSION));

         } catch (IOException e) {
             Log.e(LOG_TAG,
                 "IO Exception when getting kernel version for Device Info screen",
                 e);

             return "Unavailable";
         }
     }

 　　public static String formatKernelVersion(String rawKernelVersion) {
         // Example (see tests for more):
         // Linux version 3.0.31-g6fb96c9 (android-build@xxx.xxx.xxx.xxx.com) \
         //     (gcc version 4.6.x-xxx 20120106 (prerelease) (GCC) ) #1 SMP PREEMPT \
         //     Thu Jun 28 11:02:39 PDT 2012

         final String PROC_VERSION_REGEX =
             "Linux version (\\S+) " + /* group 1: "3.0.31-g6fb96c9" */
             "\\((\\S+?)\\) " +        /* group 2: "x@y.com" (kernel builder) */
             "(?:\\(gcc.+? \\)) " +    /* ignore: GCC version information */
             "(#\\d+) " +              /* group 3: "#1" */
             "(?:.*?)?" +              /* ignore: optional SMP, PREEMPT, and any CONFIG_FLAGS */
             "((Sun|Mon|Tue|Wed|Thu|Fri|Sat).+)"; /* group 4: "Thu Jun 28 11:02:39 PDT 2012" */

         Matcher m = Pattern.compile(PROC_VERSION_REGEX).matcher(rawKernelVersion);
         if (!m.matches()) {
             Log.e(LOG_TAG, "Regex did not match on /proc/version: " + rawKernelVersion);
             return "Unavailable";
         } else if (m.groupCount() < 4) {
             Log.e(LOG_TAG, "Regex match on /proc/version only returned " + m.groupCount()
                     + " groups");
             return "Unavailable";
         }
         return m.group(1) + "\n" +                 // 3.0.31-g6fb96c9
             m.group(2) + " " + m.group(3) + "\n" + // x@y.com #1
             m.group(4);                            // Thu Jun 28 11:02:39 PDT 2012
     }
             

　　即从/proc/version文件中提取相应信息。