Android Automotive（四） Vehicle Property

在介绍CarService之前，先介绍一下Vehicle Property（车辆属性），车辆属性是Android Automotive 中最重要的内容之一，使用它来传递车辆上的一些重要信息。

车辆属性是硬件抽象层定义的汽车设备制造商可以实现的属性，并会包含属性元数据（例如，属性是否为 int 以及允许使用哪些更改模式）。Vehicle HAL 提供接口对车辆属性进行访问（读取、写入、订阅）。

车辆属性使用HIDL语言定义，代码位于hardware/interfaces/automotive/vehicle/2.0/types.hal中。

车辆属性可以是只读、只写、也可以是读写。每个车辆属性都由一个int32键唯一标识，且具有预定义的数据类型。区域属性可能具有多个值，具体取决于属性支持区域的数量

车辆属性的定义是由四个整型值做或运算取得的。它们描述了车辆属性的ID、分组、类型和区域。

INFO_VIN = (0x0100| VehiclePropertyGroup:SYSTEM| VehiclePropertyType:STRING| VehicleArea:GLOBAL)

除了定义所需的必须属性，车辆属性的额外信息以注释的形式标记在文件中。包括车辆属性的变化类型、读写性、单位、取值的数据结构等等。

/*** VIN of vehicle** @change_mode VehiclePropertyChangeMode:STATIC* @access VehiclePropertyAccess:READ*/
INFO_VIN =

具体如下

注释	描述	类型
@change_mode	变化模式	VehiclePropertyChangeMode STATIC 静态 ON_CHANGE 变化 CONTINUOUS 持续
@access	读写性质	VehiclePropertyAccess READ 只读 WRITE 只写 READ_WRITE 读写
@unit	单位	VehicleUnit
@data_enum	数据结构
@since	增加的版本

属性ID

是一个int数值，通常是4位16进制，占半个字节。在车辆属性中使用“4567”后四位表示属性ID，如0x0000****。通常省略高位0，写成0x****的形式。

属性分组

分组表示了车辆属性的来源，区分是原生属性还是扩展属性。原生属性是指AOSP定义的属性，扩展属性是指OEM厂商自己定义增加的属性。在车辆属性中使用第0位占位0x*000000。

//types.hal中定义
enum VehiclePropertyGroup : int32_t {/*** Properties declared in AOSP must have this flag.*/SYSTEM         = 0x10000000, //268435456/*** Properties declared by vendors must have this flag.*/VENDOR         = 0x20000000, //536870912MASK           = 0xf0000000, //-268435456
};

SYSTEM：Google原生属性定义使用
VENDOR：OME自定义属性使用

属性	十六进制	十进制
SYSTEM	0x10000000	268435456
VENDOR	0x20000000	536870912

扩展属性必须使用VENDOR声明

属性类型

表示车辆属性对应值的数据类型，占0x00**0000第“23”位。
目前支持的数据类型如下

STRING
BOOLEAN
INT32
INT32_VEC (INT32[])
INT64
INT64_VEC (INT64[])
FLOAT
FLOAT_VEC (FLOAT[])
BYTES

//types.hal中定义
/*** Enumerates supported data type for VehicleProperty.** Used to create property ID in VehicleProperty enum.*/
enum VehiclePropertyType : int32_t {STRING          = 0x00100000,BOOLEAN         = 0x00200000,INT32           = 0x00400000,INT32_VEC       = 0x00410000,INT64           = 0x00500000,INT64_VEC       = 0x00510000,FLOAT           = 0x00600000,FLOAT_VEC       = 0x00610000,BYTES           = 0x00700000,/*** Any combination of scalar or vector types. The exact format must be* provided in the description of the property.** For vendor MIXED type properties, configArray needs to be formatted in this* structure.* configArray[0], 1 indicates the property has a String value* configArray[1], 1 indicates the property has a Boolean value .* configArray[2], 1 indicates the property has an Integer value.* configArray[3], the number indicates the size of Integer[] in the property.* configArray[4], 1 indicates the property has a Long value.* configArray[5], the number indicates the size of Long[] in the property.* configArray[6], 1 indicates the property has a Float value.* configArray[7], the number indicates the size of Float[] in the property.* configArray[8], the number indicates the size of byte[] in the property.* For example:* {@code configArray = {1, 1, 1, 3, 0, 0, 0, 0, 0}} indicates the property has* a String value, a Boolean value, an Integer value and an array with 3 integers.*/MIXED           = 0x00e00000,MASK            = 0x00ff0000
};

属性	十六进制	十进制
STRING	0x00100000	1048576
BOOLEAN	0x00200000	2097152
INT32	0x00400000	4194304
INT32_VEC	0x00410000	4259840
INT64	0x00500000	5242880
INT64_VEC	0x00510000	5308416
FLOAT	0x00600000	6291456
FLOAT_VEC	0x00610000	6356992
BYTES	0x00700000	7340032
MIXED	0x00e00000	14680064

属性区域

属性区域定义了车辆属性归属车辆的哪一个模块，比如门或者窗。占位0x0*000000，第1位。

Android P 删除了ZONE区域，新增WHEEL区域。

每个区域属性都必须使用预定义的区域类型。每种区域类型都有一组在区域类型的枚举中定义的位标记。

//types.hal中定义
/*** Vehicle Areas* Used to construct property IDs in the VehicleProperty enum.** Some properties may be associated with particular vehicle areas. For* example, VehicleProperty:DOOR_LOCK property must be associated with* particular door, thus this property must be marked with* VehicleArea:DOOR flag.** Other properties may not be associated with particular vehicle area.* These kinds of properties must have VehicleArea:GLOBAL flag.** [Definition] Area: An area represents a unique element of an AreaType.*   For instance, if AreaType is WINDOW, then an area may be FRONT_WINDSHIELD.** [Definition] AreaID: An AreaID is a combination of one or more areas,*   and is represented using a bitmask of Area enums. Different AreaTypes may*   not be mixed in a single AreaID. For instance, a window area cannot be*   combined with a seat area in an AreaID.** Rules for mapping a zoned property to AreaIDs:*  - A property must be mapped to an array of AreaIDs that are impacted when*    the property value changes.*  - Each element in the array must represent an AreaID, in which the*    property value can only be changed together in all the areas within*    the AreaID and never independently. That is, when the property value*    changes in one of the areas in an AreaID in the array, then it must*    automatically change in all other areas in the AreaID.*  - The property value must be independently controllable in any two*    different AreaIDs in the array.*  - An area must only appear once in the array of AreaIDs. That is, an*    area must only be part of a single AreaID in the array.** [Definition] Global Property: A property that applies to the entire car*   and is not associated with a specific area. For example, FUEL_LEVEL,*   HVAC_STEERING_WHEEL_HEAT.** Rules for mapping a global property to AreaIDs:*  - A global property must not be mapped to AreaIDs.
*/
enum VehicleArea : int32_t {GLOBAL      = 0x01000000,/** WINDOW maps to enum VehicleAreaWindow *///ZONE         = 0x02000000, //android P开始删除WINDOW      = 0x03000000,/** MIRROR maps to enum VehicleAreaMirror */MIRROR      = 0x04000000,/** SEAT maps to enum VehicleAreaSeat */SEAT        = 0x05000000,/** DOOR maps to enum VehicleAreaDoor */DOOR        = 0x06000000,/** WHEEL maps to enum VehicleAreaWheel */WHEEL       = 0x07000000,MASK        = 0x0f000000,
};

属性	十六进制	十进制
GLOBAL	0x01000000	16777216
ZONE	0x02000000	33554432
WINDOW	0x03000000	50331648
MIRROR	0x04000000	67108864
SEAT	0x05000000	83886080
DOOR	0x06000000	100663296
WHEEL	0x07000000	117440512

GLOBAL

此属性是单一实例，不具备多个区域。

ZONE

用于空调并将汽车划分为物理区域。

在Android P版本删除。使用枚举类VehicleAreaZone。Android P 开始删除此属性

//types.hal中定义
/*** Various zones in the car.** Zones are used for Air Conditioning purposes and divide the car into physical* area zones.*/
enum VehicleAreaZone : int32_t {ROW_1_LEFT = 0x00000001,ROW_1_CENTER = 0x00000002,ROW_1_RIGHT = 0x00000004,ROW_1 = 0x00000008,ROW_2_LEFT = 0x00000010,ROW_2_CENTER = 0x00000020,ROW_2_RIGHT = 0x00000040,ROW_2 = 0x00000080,ROW_3_LEFT = 0x00000100,ROW_3_CENTER = 0x00000200,ROW_3_RIGHT = 0x00000400,ROW_3 = 0x00000800,ROW_4_LEFT = 0x00001000,ROW_4_CENTER = 0x00002000,ROW_4_RIGHT = 0x00004000,ROW_4 = 0x00008000,WHOLE_CABIN = 0x80000000,
};

WINDOW

基于车窗的区域。使用枚举类VehicleAreaWindow

FRONT_WINDSHIELD 前挡风玻璃
REAR_WINDSHIELD 后挡风玻璃
ROW_1_LEFT 第一排左侧车窗
ROW_1_RIGHT 第一排右侧车窗
ROW_2_LEFT 第二排左侧车窗
ROW_2_RIGHT 第二排右侧车窗
ROW_3_LEFT 第三排左侧车窗
ROW_3_RIGHT 第三排右侧车窗
ROOF_TOP_1 天窗1
ROOF_TOP_2 天窗2

// hardware/interfaces/automotive/vehicle/2.0/types.hal
/*** Various windshields/windows in the car.*/
enum VehicleAreaWindow : int32_t {FRONT_WINDSHIELD  = 0x00000001,REAR_WINDSHIELD   = 0x00000002,ROW_1_LEFT        = 0x00000010,ROW_1_RIGHT       = 0x00000040,ROW_2_LEFT        = 0x00000100,ROW_2_RIGHT       = 0x00000400,ROW_3_LEFT        = 0x00001000,ROW_3_RIGHT       = 0x00004000,ROOF_TOP_1        = 0x00010000,ROOF_TOP_2        = 0x00020000,};

属性	十六进制	十进制
FRONT_WINDSHIELD	0x00000001	1
REAR_WINDSHIELD	0x00000002	2
ROW_1_LEFT	0x00000010	16
ROW_1_RIGHT	0x00000040	64
ROW_2_LEFT	0x00000100	256
ROW_2_RIGHT	0x00000400	1024
ROW_3_LEFT	0x00001000	4096
ROW_3_RIGHT	0x00004000	16384
ROOF_TOP_1	0x00010000	65536
ROOF_TOP_2	0x00020000	131072

MIRROR

基于车镜的区域。使用枚举类VehicleAreaMirror

DRIVER_LEFT 左后视镜
DRIVER_RIGHT 右后视镜
DRIVER_CENTER 中央后视镜

// hardware/interfaces/automotive/vehicle/2.0/types.hal
enum VehicleAreaMirror : int32_t {DRIVER_LEFT = 0x00000001,DRIVER_RIGHT = 0x00000002,DRIVER_CENTER = 0x00000004,
};

属性	十六进制	十进制
DRIVER_LEFT	0x00000001	1
DRIVER_RIGHT	0x00000002	2
DRIVER_CENTER	0x00000004	4

SEAT

基于座椅的区域，使用枚举类VehicleAreaSeat

ROW_1_LEFT 第一排左侧
ROW_1_CENTER 第一排中间
ROW_1_RIGHT 第一排右侧
ROW_2_LEFT 第二排左侧
ROW_2_CENTER 第二排中间
ROW_2_RIGHT 第二排右侧
ROW_3_LEFT 第三排左侧
ROW_3_CENTER 第三排中间
ROW_3_RIGHT 第三排右侧

// hardware/interfaces/automotive/vehicle/2.0/types.hal
/*** Various Seats in the car.*/
enum VehicleAreaSeat : int32_t {ROW_1_LEFT   = 0x0001,ROW_1_CENTER = 0x0002,ROW_1_RIGHT  = 0x0004,ROW_2_LEFT   = 0x0010,ROW_2_CENTER = 0x0020,ROW_2_RIGHT  = 0x0040,ROW_3_LEFT   = 0x0100,ROW_3_CENTER = 0x0200,ROW_3_RIGHT  = 0x0400
};

属性	十六进制	十进制
ROW_1_LEFT	0x0001	1
ROW_1_CENTER	0x0002	2
ROW_1_RIGHT	0x0004	4
ROW_2_LEFT	0x0010	16
ROW_2_CENTER	0x0020	32
ROW_2_RIGHT	0x0040	64
ROW_3_LEFT	0x0100	256
ROW_3_CENTER	0x0200	512
ROW_3_RIGHT	0x0400	1024

DOOR

基于车门的区域。使用枚举类VehicleAreaDoor

ROW_1_LEFT 第一排左侧门
ROW_1_RIGHT 第一排右侧门
ROW_2_LEFT 第二排左侧门
ROW_2_RIGHT 第二排右侧门
ROW_3_LEFT 第三排左侧门
ROW_3_RIGHT 第三排右侧门
HOOD 前车厢门
REAR 后车厢门

// hardware/interfaces/automotive/vehicle/2.0/types.hal
enum VehicleAreaDoor : int32_t {ROW_1_LEFT = 0x00000001,ROW_1_RIGHT = 0x00000004,ROW_2_LEFT = 0x00000010,ROW_2_RIGHT = 0x00000040,ROW_3_LEFT = 0x00000100,ROW_3_RIGHT = 0x00000400,HOOD = 0x10000000,REAR = 0x20000000,
};

属性	十六进制	十进制
ROW_1_LEFT	0x00000001	1
ROW_1_RIGHT	0x00000004	4
ROW_2_LEFT	0x00000010	16
ROW_2_RIGHT	0x00000040	64
ROW_3_LEFT	0x00000100	256
ROW_3_RIGHT	0x00000400	1024
HOOD	0x10000000	268435456
REAR	0x20000000	536870912

WHEEL

基于车轮的区域。使用枚举类VehicleAreaWheel

UNKNOWN 未知
LEFT_FRONT 左前轮胎
RIGHT_FRONT 右前轮胎
LEFT_REAR 左后轮胎
RIGHT_REAR 右后轮胎

// hardware/interfaces/automotive/vehicle/2.0/types.hal
enum VehicleAreaWheel : int32_t {UNKNOWN = 0x0,LEFT_FRONT = 0x1,RIGHT_FRONT = 0x2,LEFT_REAR = 0x4,RIGHT_REAR = 0x8,
};

属性	十六进制	十进制
UNKNOWN	0x0	0
LEFT_FRONT	0x1	1
RIGHT_FRONT	0x2	2
LEFT_REAR	0x4	4
RIGHT_REAR	0x8	8

每个区域属性都必须使用预定义的区域类型。每种区域类型都有一组在区域类型的枚举中定义的位标记

区域 ID

区域属性通过区域 ID 进行处理。每个区域属性都可以支持一个或多个区域 ID。区域 ID 由其各自枚举中的一个或多个标记组成。例如，使用 VehicleAreaSeat 的属性可能会使用以下区域 ID:

ROW_1_LEFT | ROW_1_RIGHT
区域 ID 适用于两个前排座椅。
ROW_2_LEFT
仅适用于左后座椅。
ROW_2_RIGHT
仅适用于右后座椅。

属性操作

车辆属性的可见性标识该属性是否只读，只写，读写。在types.hal中以注释@access的形式出现
如：@access VehiclePropertyAccess::READ_WRITE

NONE 不可读不可写
READ 只读
WRITE 只写
READ_WRITE 读写

// hardware/interfaces/automotive/vehicle/2.0/types.hal
/*** Property config defines the capabilities of it. User of the API* must first get the property config to understand the output from get()* commands and also to ensure that set() or events commands are in sync with* the expected output.*/
enum VehiclePropertyAccess : int32_t {NONE = 0x00,READ = 0x01,WRITE = 0x02,READ_WRITE = 0x03,
};

属性	说明	Android版本
NONE	不可读不可写
READ	只读	8.0~
WRITE	只写	8.0~
READ_WRITE	读写	8.0~

属性	十六进制	十进制
NONE	0x00	0
READ	0x01	1
WRITE	0x02	2
READ_WRITE	0x03	3

属性变化模式

属性的变化模式，在types.hal中以注释@change_mode的形式出现

如：@change_mode VehiclePropertyChangeMode::ON_CHANGE

// hardware/interfaces/automotive/vehicle/2.0/types.hal
/*** This describes how value of property can change.*/
enum VehiclePropertyChangeMode : int32_t {/*** Property of this type must never be changed. Subscription is not supported* for these properties.*/STATIC = 0x00,/*** Property of this type must be reported when there is a change.* IVehicle#get call must return the current value.* Set operation for this property is assumed to be asynchronous. When the* property is read (using IVehicle#get) after IVehicle#set, it may still* return old value until underlying H/W backing this property has actually* changed the state. Once state is changed, the property must dispatch* changed value as event.*/ON_CHANGE = 0x01,/*** Property of this type change continuously and requires fixed rate of* sampling to retrieve the data.*/CONTINUOUS = 0x02,/*** Property of this type may be polled to get the current value.*/POLL = 0x03,/*** This is for property where change event must be sent only when the* value is set from external component. Normal value change must not trigger* event. For example, clock property can send change event only when it is* set, outside android, for case like user setting time or time getting* update. There is no need to send it per every value change.*/ON_SET = 0x04,
};

属性	说明	Android版本
STATIC	决不能更改此类型的属性。不支持订阅这些属性	8.0~
ON_CHANGE	发生改变时，必须报告此类型的属性。 IVehicle#get调用必须返回当前值。假如设置是异步的，当在IVehicle#set之后读取属性时，它可能返回旧值，直到此属性的底层H/W实际更改了状态。状态更改后，属性必须将更改的值作为事件分派。	8.0~
CONTINUOUS	此种类型的属性不断变化，需要固定的采样率来检索数据。实现者可以选择在重大值更改时发送额外的通知。如车速	8.0~
POLL	可以轮询此类型的属性以获取当前值	8.0
ON_SET	变化时不需要一直上报，只有上层主动获取才上报，比如时间更新	8.0

POLL 和 ON_SET在Android P上被删除，不再使用

属性单位

某些属性的值需要配合国际单位来表示，比如车速的单位是米每秒（MILLIMETER）。

属性值的单位, 在types.hal中以注释@unit的形式出现，表示车辆属性表示含义的单位。

如：@unit VehicleUnit:YEAR表示单位是年

// hardware/interfaces/automotive/vehicle/2.0/types.hal
/*** Units used for int or float type with no attached enum types.*/
enum VehicleUnit : int32_t {SHOULD_NOT_USE      = 0x000,METER_PER_SEC       = 0x01,RPM                 = 0x02,HERTZ               = 0x03,PERCENTILE          = 0x10,MILLIMETER          = 0x20,METER               = 0x21,KILOMETER           = 0x23,MILE                = 0x24,CELSIUS             = 0x30,FAHRENHEIT          = 0x31,KELVIN              = 0x32,MILLILITER          = 0x40,LITER               = 0x41,/** deprecated. Use US_GALLON instead. */GALLON              = 0x42,US_GALLON           = 0x42,IMPERIAL_GALLON     = 0x43,NANO_SECS           = 0x50,SECS                = 0x53,YEAR                = 0x59,// Electrical UnitsWATT_HOUR           = 0x60,MILLIAMPERE         = 0x61,MILLIVOLT           = 0x62,MILLIWATTS          = 0x63,AMPERE_HOURS        = 0x64,KILOWATT_HOUR       = 0x65,KILOPASCAL          = 0x70,PSI                 = 0x71,BAR                 = 0x72,DEGREES             = 0x80,MILES_PER_HOUR      = 0x90,KILOMETERS_PER_HOUR = 0x91,
};

SHOULD_NOT_USE, 不使用
METER_PER_SEC, 米每秒
RPM, 转速
HERTZ, 赫兹
PERCENTILE, 百分比
MILLIMETER, 毫米
METER, 米
KILOMETER, 千米，公里
MILE, 英里
CELSIUS, 摄氏度
FAHRENHEIT, 华氏度
KELVIN, 开尔文
MILLILITER, 毫升
LITER, 升
US_GALLON, 美国加仑
IMPERIAL_GALLON, 英制加仑
NANO_SECS, 纳秒
SECS, 秒
YEAR, 年
KILOPASCAL, 千帕
WATT_HOUR, 瓦时
MILLIAMPERE, 毫安
MILLIVOLT, 毫伏
MILLIWATTS, 毫瓦
AMPERE_HOURS, 安倍小时
KILOWATT_HOUR, 千瓦时
PSI, 磅/平方英寸
BAR, 巴压强的单位
DEGREES, 度
MILES_PER_HOUR, 英里每小时
KILOMETERS_PER_HOUR 公里每小时

属性数据结构

某些属性，将属性的可取值封装成一个对象，这样可以方便调用，比如VehicleGear表示档位。

// hardware/interfaces/automotive/vehicle/2.0/types.hal
/*** Various gears which can be selected by user and chosen in system.*/
enum VehicleGear: int32_t {GEAR_NEUTRAL = 0x0001,GEAR_REVERSE = 0x0002,GEAR_PARK = 0x0004,GEAR_DRIVE = 0x0008,GEAR_LOW = 0x0010,GEAR_1 = 0x0010,GEAR_2 = 0x0020,GEAR_3 = 0x0040,GEAR_4 = 0x0080,GEAR_5 = 0x0100,GEAR_6 = 0x0200,GEAR_7 = 0x0400,GEAR_8 = 0x0800,GEAR_9 = 0x1000,
};

属性权限

属性的权限是Android在系统框架层增加的，只有声明权限的应用才可以访问相关的车辆属性。

属性的权限检测在CarService中，配置在PropertyHalServiceIds.java中使用，关联到各个车辆属性。

// packages/services/Car/service/src/com/android/car/hal/PropertyHalServiceIds.java
// default vendor permission
private static final int PERMISSION_CAR_VENDOR_DEFAULT = 0x00000000;// permissions for the property related with window
private static final int PERMISSION_SET_CAR_VENDOR_CATEGORY_WINDOW = 0X00000001;
private static final int PERMISSION_GET_CAR_VENDOR_CATEGORY_WINDOW = 0x00000002;
// permissions for the property related with door
private static final int PERMISSION_SET_CAR_VENDOR_CATEGORY_DOOR = 0x00000003;
private static final int PERMISSION_GET_CAR_VENDOR_CATEGORY_DOOR = 0x00000004;
// permissions for the property related with seat
private static final int PERMISSION_SET_CAR_VENDOR_CATEGORY_SEAT = 0x00000005;
private static final int PERMISSION_GET_CAR_VENDOR_CATEGORY_SEAT = 0x00000006;
// permissions for the property related with mirror
private static final int PERMISSION_SET_CAR_VENDOR_CATEGORY_MIRROR = 0x00000007;
private static final int PERMISSION_GET_CAR_VENDOR_CATEGORY_MIRROR = 0x00000008;// permissions for the property related with car's information
private static final int PERMISSION_SET_CAR_VENDOR_CATEGORY_INFO = 0x00000009;
private static final int PERMISSION_GET_CAR_VENDOR_CATEGORY_INFO = 0x0000000A;
// permissions for the property related with car's engine
private static final int PERMISSION_SET_CAR_VENDOR_CATEGORY_ENGINE = 0x0000000B;
private static final int PERMISSION_GET_CAR_VENDOR_CATEGORY_ENGINE = 0x0000000C;
// permissions for the property related with car's HVAC
private static final int PERMISSION_SET_CAR_VENDOR_CATEGORY_HVAC = 0x0000000D;
private static final int PERMISSION_GET_CAR_VENDOR_CATEGORY_HVAC = 0x0000000E;
// permissions for the property related with car's light
private static final int PERMISSION_SET_CAR_VENDOR_CATEGORY_LIGHT = 0x0000000F;
private static final int PERMISSION_GET_CAR_VENDOR_CATEGORY_LIGHT = 0x00000010;// permissions reserved for other vendor permission
private static final int PERMISSION_SET_CAR_VENDOR_CATEGORY_1 = 0x00010000;
private static final int PERMISSION_GET_CAR_VENDOR_CATEGORY_1 = 0x00011000;
private static final int PERMISSION_SET_CAR_VENDOR_CATEGORY_2 = 0x00020000;
private static final int PERMISSION_GET_CAR_VENDOR_CATEGORY_2 = 0x00021000;
private static final int PERMISSION_SET_CAR_VENDOR_CATEGORY_3 = 0x00030000;
private static final int PERMISSION_GET_CAR_VENDOR_CATEGORY_3 = 0x00031000;
private static final int PERMISSION_SET_CAR_VENDOR_CATEGORY_4 = 0x00040000;
private static final int PERMISSION_GET_CAR_VENDOR_CATEGORY_4 = 0x00041000;
private static final int PERMISSION_SET_CAR_VENDOR_CATEGORY_5 = 0x00050000;
private static final int PERMISSION_GET_CAR_VENDOR_CATEGORY_5 = 0x00051000;
private static final int PERMISSION_SET_CAR_VENDOR_CATEGORY_6 = 0x00060000;
private static final int PERMISSION_GET_CAR_VENDOR_CATEGORY_6 = 0x00061000;
private static final int PERMISSION_SET_CAR_VENDOR_CATEGORY_7 = 0x00070000;
private static final int PERMISSION_GET_CAR_VENDOR_CATEGORY_7 = 0x00071000;
private static final int PERMISSION_SET_CAR_VENDOR_CATEGORY_8 = 0x00080000;
private static final int PERMISSION_GET_CAR_VENDOR_CATEGORY_8 = 0x00081000;
private static final int PERMISSION_SET_CAR_VENDOR_CATEGORY_9 = 0x00090000;
private static final int PERMISSION_GET_CAR_VENDOR_CATEGORY_9 = 0x00091000;
private static final int PERMISSION_SET_CAR_VENDOR_CATEGORY_10 = 0x000A0000;
private static final int PERMISSION_GET_CAR_VENDOR_CATEGORY_10 = 0x000A1000;
// Not available for android
private static final int PERMISSION_CAR_VENDOR_NOT_ACCESSIBLE = 0xF0000000;

在HAL层定义

// hardware/interfaces/automotive/vehicle/2.0/types.hal
/*** Used by SUPPORT_CUSTOMIZE_VENDOR_PERMISSION to indicate the permission of vendor properties.*/
enum VehicleVendorPermission : int32_t {PERMISSION_DEFAULT = 0x00000000,// permissions for the property related with windowPERMISSION_SET_VENDOR_CATEGORY_WINDOW= 0X00000001,PERMISSION_GET_VENDOR_CATEGORY_WINDOW = 0x00000002,// permissions for the property related with doorPERMISSION_SET_VENDOR_CATEGORY_DOOR  = 0x00000003,PERMISSION_GET_VENDOR_CATEGORY_DOOR   = 0x00000004,// permissions for the property related with seatPERMISSION_SET_VENDOR_CATEGORY_SEAT  = 0x00000005,PERMISSION_GET_VENDOR_CATEGORY_SEAT   = 0x00000006,// permissions for the property related with mirrorPERMISSION_SET_VENDOR_CATEGORY_MIRROR= 0x00000007,PERMISSION_GET_VENDOR_CATEGORY_MIRROR = 0x00000008,// permissions for the property related with car's informationPERMISSION_SET_VENDOR_CATEGORY_INFO  = 0x00000009,PERMISSION_GET_VENDOR_CATEGORY_INFO   = 0x0000000A,// permissions for the property related with car's enginePERMISSION_SET_VENDOR_CATEGORY_ENGINE= 0x0000000B,PERMISSION_GET_VENDOR_CATEGORY_ENGINE = 0x0000000C,// permissions for the property related with car's HVACPERMISSION_SET_VENDOR_CATEGORY_HVAC  = 0x0000000D,PERMISSION_GET_VENDOR_CATEGORY_HVAC   = 0x0000000E,// permissions for the property related with car's lightPERMISSION_SET_VENDOR_CATEGORY_LIGHT = 0x0000000F,PERMISSION_GET_VENDOR_CATEGORY_LIGHT  = 0x00000010,// permissions reserved for other vendor permissionPERMISSION_SET_VENDOR_CATEGORY_1  = 0x00010000,PERMISSION_GET_VENDOR_CATEGORY_1   = 0x00011000,PERMISSION_SET_VENDOR_CATEGORY_2  = 0x00020000,PERMISSION_GET_VENDOR_CATEGORY_2   = 0x00021000,PERMISSION_SET_VENDOR_CATEGORY_3  = 0x00030000,PERMISSION_GET_VENDOR_CATEGORY_3   = 0x00031000,PERMISSION_SET_VENDOR_CATEGORY_4  = 0x00040000,PERMISSION_GET_VENDOR_CATEGORY_4   = 0x00041000,PERMISSION_SET_VENDOR_CATEGORY_5  = 0x00050000,PERMISSION_GET_VENDOR_CATEGORY_5   = 0x00051000,PERMISSION_SET_VENDOR_CATEGORY_6  = 0x00060000,PERMISSION_GET_VENDOR_CATEGORY_6   = 0x00061000,PERMISSION_SET_VENDOR_CATEGORY_7  = 0x00070000,PERMISSION_GET_VENDOR_CATEGORY_7   = 0x00071000,PERMISSION_SET_VENDOR_CATEGORY_8  = 0x00080000,PERMISSION_GET_VENDOR_CATEGORY_8   = 0x00081000,PERMISSION_SET_VENDOR_CATEGORY_9  = 0x00090000,PERMISSION_GET_VENDOR_CATEGORY_9   = 0x00091000,PERMISSION_SET_VENDOR_CATEGORY_10 = 0x000A0000,PERMISSION_GET_VENDOR_CATEGORY_10  = 0x000A1000,// Indicate not available for android to access.PERMISSION_NOT_ACCESSIBLE = 0xF0000000
};

在Framework中VehicleVendorPermission定义了应用使用的权限字符串。

// packages/services/Car/car-lib/src/android/car/hardware/property/VehicleVendorPermission.java
// permissions for the property related with window
public static final String PERMISSION_GET_CAR_VENDOR_CATEGORY_WINDOW ="android.car.permission.GET_CAR_VENDOR_CATEGORY_WINDOW";
public static final String PERMISSION_SET_CAR_VENDOR_CATEGORY_WINDOW ="android.car.permission.SET_CAR_VENDOR_CATEGORY_WINDOW";// permissions for the property related with door
public static final String PERMISSION_GET_CAR_VENDOR_CATEGORY_DOOR ="android.car.permission.GET_CAR_VENDOR_CATEGORY_DOOR";
public static final String PERMISSION_SET_CAR_VENDOR_CATEGORY_DOOR ="android.car.permission.SET_CAR_VENDOR_CATEGORY_DOOR";// permissions for the property related with seat
public static final String PERMISSION_GET_CAR_VENDOR_CATEGORY_SEAT ="android.car.permission.GET_CAR_VENDOR_CATEGORY_SEAT";
public static final String PERMISSION_SET_CAR_VENDOR_CATEGORY_SEAT ="android.car.permission.SET_CAR_VENDOR_CATEGORY_SEAT";// permissions for the property related with mirror
public static final String PERMISSION_GET_CAR_VENDOR_CATEGORY_MIRROR ="android.car.permission.GET_CAR_VENDOR_CATEGORY_MIRROR";
public static final String PERMISSION_SET_CAR_VENDOR_CATEGORY_MIRROR ="android.car.permission.SET_CAR_VENDOR_CATEGORY_MIRROR";// permissions for the property related with car's information
public static final String PERMISSION_GET_CAR_VENDOR_CATEGORY_INFO ="android.car.permission.GET_CAR_VENDOR_CATEGORY_INFO";
public static final String PERMISSION_SET_CAR_VENDOR_CATEGORY_INFO ="android.car.permission.SET_CAR_VENDOR_CATEGORY_INFO";// permissions for the property related with car's engine
public static final String PERMISSION_GET_CAR_VENDOR_CATEGORY_ENGINE ="android.car.permission.GET_CAR_VENDOR_CATEGORY_ENGINE";
public static final String PERMISSION_SET_CAR_VENDOR_CATEGORY_ENGINE ="android.car.permission.SET_CAR_VENDOR_CATEGORY_ENGINE";// permissions for the property related with car's HVAC
public static final String PERMISSION_GET_CAR_VENDOR_CATEGORY_HVAC ="android.car.permission.GET_CAR_VENDOR_CATEGORY_HVAC";
public static final String PERMISSION_SET_CAR_VENDOR_CATEGORY_HVAC ="android.car.permission.SET_CAR_VENDOR_CATEGORY_HVAC";// permissions for the property related with car's light
public static final String PERMISSION_GET_CAR_VENDOR_CATEGORY_LIGHT ="android.car.permission.GET_CAR_VENDOR_CATEGORY_LIGHT";
public static final String PERMISSION_SET_CAR_VENDOR_CATEGORY_LIGHT ="android.car.permission.SET_CAR_VENDOR_CATEGORY_LIGHT";// permissions reserved for other vendor permission
public static final String PERMISSION_GET_CAR_VENDOR_CATEGORY_1 ="android.car.permission.GET_CAR_VENDOR_CATEGORY_1";
public static final String PERMISSION_SET_CAR_VENDOR_CATEGORY_1 ="android.car.permission.SET_CAR_VENDOR_CATEGORY_1";
public static final String PERMISSION_GET_CAR_VENDOR_CATEGORY_2 ="android.car.permission.GET_CAR_VENDOR_CATEGORY_2";
public static final String PERMISSION_SET_CAR_VENDOR_CATEGORY_2 ="android.car.permission.SET_CAR_VENDOR_CATEGORY_2";
public static final String PERMISSION_GET_CAR_VENDOR_CATEGORY_3 ="android.car.permission.GET_CAR_VENDOR_CATEGORY_3";
public static final String PERMISSION_SET_CAR_VENDOR_CATEGORY_3 ="android.car.permission.SET_CAR_VENDOR_CATEGORY_3";
public static final String PERMISSION_GET_CAR_VENDOR_CATEGORY_4 ="android.car.permission.GET_CAR_VENDOR_CATEGORY_4";
public static final String PERMISSION_SET_CAR_VENDOR_CATEGORY_4 ="android.car.permission.SET_CAR_VENDOR_CATEGORY_4";
public static final String PERMISSION_GET_CAR_VENDOR_CATEGORY_5 ="android.car.permission.GET_CAR_VENDOR_CATEGORY_5";
public static final String PERMISSION_SET_CAR_VENDOR_CATEGORY_5 ="android.car.permission.SET_CAR_VENDOR_CATEGORY_5";
public static final String PERMISSION_GET_CAR_VENDOR_CATEGORY_6 ="android.car.permission.GET_CAR_VENDOR_CATEGORY_6";
public static final String PERMISSION_SET_CAR_VENDOR_CATEGORY_6 ="android.car.permission.SET_CAR_VENDOR_CATEGORY_6";
public static final String PERMISSION_GET_CAR_VENDOR_CATEGORY_7 ="android.car.permission.GET_CAR_VENDOR_CATEGORY_7";
public static final String PERMISSION_SET_CAR_VENDOR_CATEGORY_7 ="android.car.permission.SET_CAR_VENDOR_CATEGORY_7";
public static final String PERMISSION_GET_CAR_VENDOR_CATEGORY_8 ="android.car.permission.GET_CAR_VENDOR_CATEGORY_8";
public static final String PERMISSION_SET_CAR_VENDOR_CATEGORY_8 ="android.car.permission.SET_CAR_VENDOR_CATEGORY_8";
public static final String PERMISSION_GET_CAR_VENDOR_CATEGORY_9 ="android.car.permission.GET_CAR_VENDOR_CATEGORY_9";
public static final String PERMISSION_SET_CAR_VENDOR_CATEGORY_9 ="android.car.permission.SET_CAR_VENDOR_CATEGORY_9";
public static final String PERMISSION_GET_CAR_VENDOR_CATEGORY_10 ="android.car.permission.GET_CAR_VENDOR_CATEGORY_10";
public static final String PERMISSION_SET_CAR_VENDOR_CATEGORY_10 ="android.car.permission.SET_CAR_VENDOR_CATEGORY_10";

属性状态

每个属性值都随附一个 VehiclePropertyStatus 值。该值指示相应属性的当前状态：

AVAILABLE
属性可用，且值有效。
UNAVAILABLE
属性值目前不可用。该值用于受支持属性的暂时停用的功能。
ERROR
该属性有问题。

如果车辆不支持某个属性，则不应将其包含在 VHAL 中。您不得将属性状态永久性设置为 UNAVAILABLE 来表示不受支持的属性。

配置属性

在硬件抽象层会用一个VehiclePropConfig结构体来维护车辆属性的配置。

// hardware/interfaces/automotive/vehicle/2.0/types.hal
struct VehiclePropConfig {/** Property identifier */int32_t prop;/*** Defines if the property is read or write or both.*/VehiclePropertyAccess access;/*** Defines the change mode of the property.*/VehiclePropertyChangeMode changeMode;/*** Contains per-area configuration.*/vec<VehicleAreaConfig> areaConfigs;/** Contains additional configuration parameters */vec<int32_t> configArray;/*** Some properties may require additional information passed over this* string. Most properties do not need to set this.*/string configString;/*** Min sample rate in Hz.* Must be defined for VehiclePropertyChangeMode::CONTINUOUS*/float minSampleRate;/*** Must be defined for VehiclePropertyChangeMode::CONTINUOUS* Max sample rate in Hz.*/float maxSampleRate;
};

prop 属性ID
access 属性读写权限
changeMode 属性变化模式
areaConfigs 属性每个区域的配置
configArray 配置相关的数组
configString 配置的描述
minSampleRate 最小的变化频率，通知频率，变化模式必须定义为CONTINUOUS
maxSampleRate 最大的变化频率，通知频率，变化模式必须定义为CONTINUOUS

字段	描述
prop	属性ID
access	属性读写权限
changeMode	属性变化模式
areaConfigs	属性每个区域的配置
configArray	配置相关的数组
configString	配置的描述
minSampleRate	最小的变化频率，通知频率，变化模式必须定义为CONTINUOUS
maxSampleRate	最大的变化频率，通知频率，变化模式必须定义为CONTINUOUS

在Android N上使用 vehicle_prop_config_t 进行配置

使用 vehicle_prop_config_t 为每个属性提供配置信息。具体信息包括：

access（r、w、rw）

changeMode（表示监视属性的方式：变化模式还是连续模式）

areaConfigs（areaId、最小值和最大值）

configArray（其他配置参数）

configString（以字符串的形式传递的其他信息）

minSampleRate、max_sample_rate

prop（属性 ID、int）

属性取值

属性的取值，也就是属性所带的数据使用VehiclePropValue来维护。在types.hal中定义。

// hardware/interfaces/automotive/vehicle/2.0/types.hal
/*** Encapsulates the property name and the associated value. It* is used across various API calls to set values, get values or to register for* events.*/
struct VehiclePropValue {/** Time is elapsed nanoseconds since boot */int64_t timestamp;/*** Area type(s) for non-global property it must be one of the value from* VehicleArea* enums or 0 for global properties.*/int32_t areaId;/** Property identifier */int32_t prop;/** Status of the property */VehiclePropertyStatus status;/*** Contains value for a single property. Depending on property data type of* this property (VehiclePropetyType) one field of this structure must be filled in.*/struct RawValue {/*** This is used for properties of types VehiclePropertyType#INT* and VehiclePropertyType#INT_VEC*/vec<int32_t> int32Values;/*** This is used for properties of types VehiclePropertyType#FLOAT* and VehiclePropertyType#FLOAT_VEC*/vec<float> floatValues;/** This is used for properties of type VehiclePropertyType#INT64 */vec<int64_t> int64Values;/** This is used for properties of type VehiclePropertyType#BYTES */vec<uint8_t> bytes;/** This is used for properties of type VehiclePropertyType#STRING */string stringValue;};RawValue value;
};

字段`	描述
timestamp	时间戳，标记属性更新的时间
areaId	表示的区域
prop	属性ID
status	属性的状态
value	用RawValue来维护具体的属性值
int32Values	维护整型数据的数组，布尔类型也是用此维护
int64Values	维护长整型数据的数组
floatValues	维护浮点型数据的数组
bytes	维护字节型数据的数组
stringValue	维护字符串类型

常量接口

前面我们知道HAL文件是使用HIDL语言定义，它在编译时，会生成C++和JAVA接口。

typs.hal也是一样，里面定义的车辆属性会编译出系统框架层和硬件抽象层使用的接口。

编译产物

源码下automotive生成的文件如下：

代码路径：out/soong/.intermediates/hardware/interfaces/automotive/vehicle/2.0

out/soong/.intermediates/hardware/interfaces/automotive/vehicle/2.0
├── android.hardware.automotive.vehicle@2.0
│   ├── android_arm64_armv8-a_core_shared
│   │   └── android.hardware.automotive.vehicle@2.0.so
│   ├── android_arm64_armv8-a_core_static
│   │   ├── android.hardware.automotive.vehicle@2.0.a
│   │   └── obj
│   ├── android_arm_armv7-a-neon_cortex-a9_core_shared
│   │   └── android.hardware.automotive.vehicle@2.0.so
│   └── android_arm_armv7-a-neon_cortex-a9_core_static
│       ├── android.hardware.automotive.vehicle@2.0.a
│       └── obj
├── android.hardware.automotive.vehicle@2.0_genc++
│   └── gen
│       └── android
├── android.hardware.automotive.vehicle@2.0_genc++_headers
│   └── gen
│       └── android
├── android.hardware.automotive.vehicle-V2.0-java
│   └── android_common
│       ├── combined
│       ├── javac
│       ├── turbine
│       └── turbine-combined
└── android.hardware.automotive.vehicle-V2.0-java_gen_java└── gen└── android

hidl-gen

hidl-gen时编译HIDL文件的一个工具

工具路径 out/host/linux-x86/bin/hidl-gen，源代码路径 system/tools/hidl

使用说明

usage: hidl-gen [-p <root path>] -o <output path> -L <language> [-O <owner>] (-r <interface root>)+ [-v] [-d <depfile>] FQNAME...Process FQNAME, PACKAGE(.SUBPACKAGE)*@[0-9]+.[0-9]+(::TYPE)?, to create output.-h: Prints this menu.-L <language>: The following options are available:check           : Parses the interface to see if valid but doesn't write any files.c++             : (internal) (deprecated) Generates C++ interface files for talking to HIDL interfaces.c++-headers     : (internal) Generates C++ headers for interface files for talking to HIDL interfaces.c++-sources     : (internal) Generates C++ sources for interface files for talking to HIDL interfaces.export-header   : Generates a header file from @export enumerations to help maintain legacy code.c++-impl        : Generates boilerplate implementation of a hidl interface in C++ (for convenience).c++-impl-headers: c++-impl but headers onlyc++-impl-sources: c++-impl but sources onlyc++-adapter     : Takes a x.(y+n) interface and mocks an x.y interface.c++-adapter-headers: c++-adapter but helper headers onlyc++-adapter-sources: c++-adapter but helper sources onlyc++-adapter-main: c++-adapter but the adapter binary source onlyjava            : (internal) Generates Java library for talking to HIDL interfaces in Java.java-constants  : (internal) Like export-header but for Java (always created by -Lmakefile if @export exists).vts             : (internal) Generates vts proto files for use in vtsd.makefile        : (removed) Used to generate makefiles for -Ljava and -Ljava-constants.androidbp       : (internal) Generates Soong bp files for -Lc++-headers, -Lc++-sources, -Ljava, -Ljava-constants, and -Lc++-adapter.androidbp-impl  : Generates boilerplate bp files for implementation created with -Lc++-impl.hash            : Prints hashes of interface in `current.txt` format to standard out.-O <owner>: The owner of the module for -Landroidbp(-impl)?.-o <output path>: Location to output files.-p <root path>: Android build root, defaults to $ANDROID_BUILD_TOP or pwd.-r <package:path root>: E.g., android.hardware:hardware/interfaces.-v: verbose output.-d <depfile>: location of depfile to write to.

hidl-gen 工具会将hal文件转换为相应的类文件, 例:

启动环境

. build/envsetup.sh
lunch

命令

./out/host/linux-x86/bin/hidl-gen -o ./demo -Ljava -randroid.hardware:hardware/interfaces  -randroid.hidl:system/libhidl/transport android.hardware.automotive.vehicle@2.0

说明

-o: 生成文件的目录
-Lc+±headers: 生成c++ 头文件
-Ljava : 生成java文件
-r:指定包号和root路径