android button light 流程分析(二) — HAL & JNI

一、基础数据信息

首先看一下HAL定义的light类型：

/**
 * The id of this module
 */
#define LIGHTS_HARDWARE_MODULE_ID "lights"

/*
 * These light IDs correspond to logical lights, not physical.
 * So for example, if your INDICATOR light is in line with your
 * BUTTONS, it might make sense to also light the INDICATOR
 * light to a reasonable color when the BUTTONS are lit.
 */
#define LIGHT_ID_BACKLIGHT          "backlight"
#define LIGHT_ID_KEYBOARD           "keyboard"
#define LIGHT_ID_BUTTONS            "buttons"
#define LIGHT_ID_BATTERY            "battery"
#define LIGHT_ID_NOTIFICATIONS      "notifications"
#define LIGHT_ID_ATTENTION          "attention"

/*
 * These lights aren't currently supported by the higher
 * layers, but could be someday, so we have the constants
 * here now.
 */
#define LIGHT_ID_BLUETOOTH          "bluetooth"
#define LIGHT_ID_WIFI               "wifi"

可以看到我们常用的backlight，以及我们主要分析的buttons，当然还有呼吸灯的定义。然后看下定义的一些状态：

#define LIGHT_FLASH_NONE            0

/**
 * To flash the light at a given rate, set flashMode to LIGHT_FLASH_TIMED,
 * and then flashOnMS should be set to the number of milliseconds to turn
 * the light on, followed by the number of milliseconds to turn the light
 * off.
 */
#define LIGHT_FLASH_TIMED           1

/**
 * To flash the light using hardware assist, set flashMode to
 * the hardware mode.
 */
#define LIGHT_FLASH_HARDWARE        2

/**
 * Light brightness is managed by a user setting.
 */
#define BRIGHTNESS_MODE_USER        0

/**
 * Light brightness is managed by a light sensor.
 */
#define BRIGHTNESS_MODE_SENSOR      1

/**
 * The parameters that can be set for a given light.
 *
 * Not all lights must support all parameters.  If you
 * can do something backward-compatible, you should.
 */
struct light_state_t {
    /**
     * The color of the LED in ARGB.
     *
     * Do your best here.
     *   - If your light can only do red or green, if they ask for blue,
     *     you should do green.
     *   - If you can only do a brightness ramp, then use this formula:
     *      unsigned char brightness = ((77*((color>>16)&0x00ff))
     *              + (150*((color>>8)&0x00ff)) + (29*(color&0x00ff))) >> 8;
     *   - If you can only do on or off, 0 is off, anything else is on.
     *
     * The high byte should be ignored.  Callers will set it to 0xff (which
     * would correspond to 255 alpha).
     */
    unsigned int color;

    /**
     * See the LIGHT_FLASH_* constants
     */
    int flashMode;
    int flashOnMS;
    int flashOffMS;

    /**
     * Policy used by the framework to manage the light's brightness.
     * Currently the values are BRIGHTNESS_MODE_USER and BRIGHTNESS_MODE_SENSOR.
     */
    int brightnessMode;
};

可以看到在flashMode为LIGHT_FLASH_TIMED时是呼吸灯的工作机制，flashOnMS定义了led从亮度0% - 100%经过的时间，flashOffMS定义了led从亮度100% - 0%经过的时间，需要驱动去实现渐变，如果不能渐变就只能是亮或灭两个状态。color值定义了不同情况下的亮度，可以按照说明进行转换。brightnessMode则定义了lcd背光的调整模式。接下来定义了light的设备模型：

struct light_device_t {
    struct hw_device_t common;

    /**
     * Set the provided lights to the provided values.
     *
     * Returns: 0 on succes, error code on failure.
     */
    int (*set_light)(struct light_device_t* dev,
            struct light_state_t const* state);
};

其中set_light为设置各个light的接口，设备模型需要继承于HAL层统一的结构hw_device_t：

/**
 * Every device data structure must begin with hw_device_t
 * followed by module specific public methods and attributes.
 */
typedef struct hw_device_t {
    /** tag must be initialized to HARDWARE_DEVICE_TAG */
    uint32_t tag;

    /** version number for hw_device_t */
    uint32_t version;

    /** reference to the module this device belongs to */
    struct hw_module_t* module;

    /** padding reserved for future use */
    uint32_t reserved[12];

    /** Close this device */
    int (*close)(struct hw_device_t* device);

} hw_device_t;

其中定义了一些公共接口和属性。其中hw_module_t定义了一些特殊信息：

/**
 * Every hardware module must have a data structure named HAL_MODULE_INFO_SYM
 * and the fields of this data structure must begin with hw_module_t
 * followed by module specific information.
 */
typedef struct hw_module_t {
    /** tag must be initialized to HARDWARE_MODULE_TAG */
    uint32_t tag;

    /** major version number for the module */
    uint16_t version_major;

    /** minor version number of the module */
    uint16_t version_minor;

    /** Identifier of module */
    const char *id;

    /** Name of this module */
    const char *name;

    /** Author/owner/implementor of the module */
    const char *author;

    /** Modules methods */
    struct hw_module_methods_t* methods;

    /** module's dso */
    void* dso;

    /** padding to 128 bytes, reserved for future use */
    uint32_t reserved[32-7];

} hw_module_t;

typedef struct hw_module_methods_t {
    /** Open a specific device */
    int (*open)(const struct hw_module_t* module, const char* id,
            struct hw_device_t** device);

} hw_module_methods_t;

二、代码流程分析

在HAL层一般采用固定格式定义一个新模块：

/** Open a new instance of a lights device using name */
static int open_lights(const struct hw_module_t* module, char const* name,
        struct hw_device_t** device)
{
    int (*set_light)(struct light_device_t* dev,
            struct light_state_t const* state);

    if (0 == strcmp(LIGHT_ID_BACKLIGHT, name)) {  // 根据名称设置相应的接口
        set_light = set_light_backlight;
    }
    else if (0 == strcmp(LIGHT_ID_BUTTONS, name)) {
        set_light = set_light_buttons;
    }
    else if (0 == strcmp(LIGHT_ID_BATTERY, name)) {
        set_light = set_light_battery;
    }
    else if (0 == strcmp(LIGHT_ID_NOTIFICATIONS, name)) {
        set_light = set_light_notifications;
    }
    else if (0 == strcmp(LIGHT_ID_ATTENTION, name)) {
        set_light = set_light_attention;
    }
    else {
        LOGE("name %s\n", name);
        return -EINVAL;
    }

    pthread_once(&g_init, init_globals);
    // 创建light_device_t
    struct light_device_t *dev = malloc(sizeof(struct light_device_t));
    memset(dev, 0, sizeof(*dev));

    dev->common.tag = HARDWARE_DEVICE_TAG;
    dev->common.version = 0;
    dev->common.module = (struct hw_module_t*)module;
    // 关闭接口
    dev->common.close = (int (*)(struct hw_device_t*))close_lights;
    dev->set_light = set_light;

    *device = (struct hw_device_t*)dev;
    return 0;
}


static struct hw_module_methods_t lights_module_methods = {
    .open =  open_lights,
};

/*
 * The lights Module
 */
const struct hw_module_t HAL_MODULE_INFO_SYM = {
    .tag = HARDWARE_MODULE_TAG,       // 规定的tag
    .version_major = 1,
    .version_minor = 0,
    .id = LIGHTS_HARDWARE_MODULE_ID,  // 模块id
    .name = "atxx lights Module",     // 名称
    .author = "xxx",
    .methods = &lights_module_methods,// 方法
};

JNI则调用如下方法获得操作接口：

enum {
    LIGHT_INDEX_BACKLIGHT = 0,
    LIGHT_INDEX_KEYBOARD = 1,
    LIGHT_INDEX_BUTTONS = 2,
    LIGHT_INDEX_BATTERY = 3,
    LIGHT_INDEX_NOTIFICATIONS = 4,
    LIGHT_INDEX_ATTENTION = 5,
    LIGHT_INDEX_BLUETOOTH = 6,
    LIGHT_INDEX_WIFI = 7,
    LIGHT_COUNT
};

struct Devices {
    light_device_t* lights[LIGHT_COUNT];
};

static light_device_t* get_device(hw_module_t* module, char const* name)
{
    int err;
    hw_device_t* device;
    err = module->methods->open(module, name, &device);
    if (err == 0) {
        return (light_device_t*)device;
    } else {
        return NULL;
    }
}

static jint init_native(JNIEnv *env, jobject clazz)
{
    int err;
    hw_module_t* module;
    Devices* devices;
    
    devices = (Devices*)malloc(sizeof(Devices));

    err = hw_get_module(LIGHTS_HARDWARE_MODULE_ID, (hw_module_t const**)&module);
    if (err == 0) {
        devices->lights[LIGHT_INDEX_BACKLIGHT]
                = get_device(module, LIGHT_ID_BACKLIGHT);
        devices->lights[LIGHT_INDEX_KEYBOARD]
                = get_device(module, LIGHT_ID_KEYBOARD);
        devices->lights[LIGHT_INDEX_BUTTONS]
                = get_device(module, LIGHT_ID_BUTTONS);
        devices->lights[LIGHT_INDEX_BATTERY]
                = get_device(module, LIGHT_ID_BATTERY);
        devices->lights[LIGHT_INDEX_NOTIFICATIONS]
                = get_device(module, LIGHT_ID_NOTIFICATIONS);
        devices->lights[LIGHT_INDEX_ATTENTION]
                = get_device(module, LIGHT_ID_ATTENTION);
        devices->lights[LIGHT_INDEX_BLUETOOTH]
                = get_device(module, LIGHT_ID_BLUETOOTH);
        devices->lights[LIGHT_INDEX_WIFI]
                = get_device(module, LIGHT_ID_WIFI);
    } else {
        memset(devices, 0, sizeof(Devices));
    }

    return (jint)devices;
}

static void finalize_native(JNIEnv *env, jobject clazz, int ptr)
{
    Devices* devices = (Devices*)ptr;
    if (devices == NULL) {
        return;
    }

    free(devices);
}

static void setLight_native(JNIEnv *env, jobject clazz, int ptr,
        int light, int colorARGB, int flashMode, int onMS, int offMS, int brightnessMode)
{
    Devices* devices = (Devices*)ptr;
    light_state_t state;

    if (light < 0 || light >= LIGHT_COUNT || devices->lights[light] == NULL) {
        return ;
    }

    memset(&state, 0, sizeof(light_state_t));
    state.color = colorARGB;
    state.flashMode = flashMode;
    state.flashOnMS = onMS;
    state.flashOffMS = offMS;
    state.brightnessMode = brightnessMode;

    devices->lights[light]->set_light(devices->lights[light], &state);
}

static JNINativeMethod method_table[] = {
    { "init_native", "()I", (void*)init_native },
    { "finalize_native", "(I)V", (void*)finalize_native },
    { "setLight_native", "(IIIIIII)V", (void*)setLight_native },
};

int register_android_server_LightsService(JNIEnv *env)
{
    return jniRegisterNativeMethods(env, "com/android/server/LightsService",
            method_table, NELEM(method_table));
}

HAL层实现具体操作的代码如下：

static pthread_once_t g_init = PTHREAD_ONCE_INIT;
static pthread_mutex_t g_lock = PTHREAD_MUTEX_INITIALIZER;
// 操作led的名称以及句柄
struct led_prop {
    const char *filename;
    int fd;
};
// 3个操作的集合
struct led {
    struct led_prop brightness;
    struct led_prop flash_on_ms;
    struct led_prop flash_off_ms;
};
// 系统拥有的light
enum {
    RED_LED,
    GREEN_LED,
    BLUE_LED,
    LCD_BACKLIGHT,
    BUTTONS_LED,
    NUM_LEDS,
};
// 操作各light的节点
struct led leds[NUM_LEDS] = {
    [RED_LED] = {
        .brightness = { "/sys/class/leds/red/brightness", -1},
        .flash_on_ms = { "/sys/class/leds/red/delay_on", -1},
        .flash_off_ms = { "/sys/class/leds/red/delay_off", -1},
    },
    [GREEN_LED] = {
        .brightness = { "/sys/class/leds/green/brightness", -1},
        .flash_on_ms = { "/sys/class/leds/green/delay_on", -1},
        .flash_off_ms = { "/sys/class/leds/green/delay_off", -1},
    },
    [BLUE_LED] = {
        .brightness = { "/sys/class/leds/blue/brightness", -1},
        .flash_on_ms = { "/sys/class/leds/blue/delay_on", -1},
        .flash_off_ms = { "/sys/class/leds/blue/delay_off", -1},
    },
    [LCD_BACKLIGHT] = {
        .brightness = { "/sys/class/backlight/backlight/brightness", -1},
    },
    [BUTTONS_LED] = {
        .brightness = {"/sys/class/leds/button-backlight/brightness", -1},
    },
};

static int is_battery_light_on = 0;
/**
 * device methods
 */
// 初始化单个节点
static int init_prop(struct led_prop *prop)
{
    int fd;

    prop->fd = -1;
    if (!prop->filename)
        return 0;
    fd = open(prop->filename, O_RDWR);
    if (fd < 0) {
        LOGE("init_prop: %s cannot be opened (%s)\n", prop->filename,
             strerror(errno));
        return -errno;
    }

    prop->fd = fd;
    return 0;
}
// 关闭节点
static void close_prop(struct led_prop *prop)
{
    int fd;

    if (prop->fd > 0)
        close(prop->fd);
    return;
}
// 初始化全部节点
void init_globals(void)
{
    int i;
    pthread_mutex_init(&g_lock, NULL);

    for (i = 0; i < NUM_LEDS; ++i) {
        init_prop(&leds[i].brightness);
        init_prop(&leds[i].flash_on_ms);
        init_prop(&leds[i].flash_off_ms);
    }
}
// 向节点写数据控制light
static int write_int(struct led_prop *prop, int value)
{
    char buffer[20];
    int bytes;
    int amt;

    if (prop->fd < 0)
        return 0;

    LOGV("%s %s: 0x%x\n", __func__, prop->filename, value);

    bytes = snprintf(buffer, sizeof(buffer), "%d\n", value);
    while (bytes > 0) {
        amt = write(prop->fd, buffer, bytes);
        if (amt < 0) {
            if (errno == EINTR)
                continue;
            return -errno;
        }
        bytes -= amt;
    }

    return 0;
}
// 用于呼吸灯控制
static int set_speaker_light(struct light_device_t* dev,
        struct light_state_t const* state)
{
    int len;
    int value;
    unsigned int colorRGB;
    unsigned int colorR;
    unsigned int colorG;
    unsigned int colorB;

    colorRGB = state->color & 0xFFFFFF;
    if (colorRGB == 0xFFFFFF) { /* white */
        colorRGB = 0x0;
    }
    colorR = (colorRGB >> 16) & 0x00ff;
    colorG = (colorRGB >> 8) & 0x00ff;
    colorB = colorRGB & 0x00ff;

    pthread_mutex_lock(&g_lock);
    switch (state->flashMode) {
        case LIGHT_FLASH_TIMED:
        case LIGHT_FLASH_HARDWARE:
            if (colorR) {
                write_int(&leds[RED_LED].flash_on_ms, state->flashOnMS);
                write_int(&leds[RED_LED].flash_off_ms, state->flashOffMS);
            } else {  /*off*/
                write_int(&leds[RED_LED].flash_on_ms, 0);
            }
            if (colorG) {
                write_int(&leds[GREEN_LED].flash_on_ms, state->flashOnMS);
                write_int(&leds[GREEN_LED].flash_off_ms, state->flashOffMS);
            } else {  /*off*/
                write_int(&leds[GREEN_LED].flash_on_ms, 0);
            }
            if (colorB) {
                write_int(&leds[BLUE_LED].flash_on_ms, state->flashOnMS);
                write_int(&leds[BLUE_LED].flash_off_ms, state->flashOffMS);
            } else {  /*off*/
                write_int(&leds[BLUE_LED].flash_on_ms, 0);
            }
            break;

        case LIGHT_FLASH_NONE:
            if (colorR) {
                write_int(&leds[RED_LED].flash_on_ms, 255);
                write_int(&leds[RED_LED].flash_off_ms, 0);
            } else {  /*off*/
                write_int(&leds[RED_LED].flash_on_ms, 0);
            }
            if (colorG) {
                write_int(&leds[GREEN_LED].flash_on_ms, 255);
                write_int(&leds[GREEN_LED].flash_off_ms, 0);
            } else {  /*off*/
                write_int(&leds[GREEN_LED].flash_on_ms, 0);
            }
            if (colorB) {
                write_int(&leds[BLUE_LED].flash_on_ms, 255);
                write_int(&leds[BLUE_LED].flash_off_ms, 0);
            } else {  /*off*/
                write_int(&leds[BLUE_LED].flash_on_ms, 0);
            }
            break;

        default:
            LOGE("set_led_state colorRGB=%08X, unknown mode %d\n",
                  colorRGB, state->flashMode);
    }
    pthread_mutex_unlock(&g_lock);
    return 0;
}
// rgb数据转换成背光值
static int rgb_to_brightness(struct light_state_t const* state)
{
    int color = state->color & 0x00ffffff;
    return ((77*((color>>16)&0x00ff))            
            + (150*((color>>8)&0x00ff)) + (29*(color&0x00ff))) >> 8;
}
// 设置按键灯亮度
static int set_light_buttons(struct light_device_t* dev,
        struct light_state_t const* state)
{
    int err = 0;
    int brightness = rgb_to_brightness(state);
    LOGE("%s brightness=%d color=0x%08x",
            __func__, brightness, state->color);
    err = write_int(&leds[BUTTONS_LED].brightness, brightness);
	return err;
}
// 设置lcd背光亮度
static int set_light_backlight(struct light_device_t* dev,
        struct light_state_t const* state)
{
    int err = 0;
    int brightness = rgb_to_brightness(state);
    LOGV("%s brightness=%d color=0x%08x",
            __func__, brightness, state->color);
    err = write_int(&leds[LCD_BACKLIGHT].brightness, brightness);
    return err;
}
// 设置低电light
static int set_light_battery(struct light_device_t* dev,
        struct light_state_t const* state)
{
    int colorRGB = state->color & 0xFFFFFF;
    LOGD("%s flashMode %d, flashOnMs %d, flashOffMs %d, color=0x%08x\n",
            __func__, state->flashMode, state->flashOnMS, state->flashOffMS, state->color);
    if (colorRGB != 0x0 && colorRGB != 0xFFFFFF) {
        is_battery_light_on = 1;
    } else  {
        is_battery_light_on = 0;
    }
    return set_speaker_light(dev, state);
}
// 设置通知light
static int set_light_notifications(struct light_device_t* dev,
        struct light_state_t const* state)
{
    LOGD("%s flashMode %d, flashOnMs %d, flashOffMs %d, color=0x%08x\n",
            __func__, state->flashMode, state->flashOnMS, state->flashOffMS, state->color);
    if (!is_battery_light_on) {
        set_speaker_light(dev, state);
    }
    return 0;
}
// 设置提醒light
static int set_light_attention(struct light_device_t* dev,
        struct light_state_t const* state)
{
    LOGD("%s flashMode %d, flashOnMs %d, flashOffMs %d, color=0x%08x\n",
            __func__, state->flashMode, state->flashOnMS, state->flashOffMS, state->color);
    if (!is_battery_light_on) {
        set_speaker_light(dev, state);
    }
    return 0;
}

// 关闭light
static int close_lights(struct light_device_t *dev)
{
    int i;

    for (i = 0; i < NUM_LEDS; ++i) {
        close_prop(&leds[i].brightness);
        close_prop(&leds[i].flash_on_ms);
        close_prop(&leds[i].flash_off_ms);
    }

    if (dev) {
        free(dev);
    }
    return 0;
}