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Android灯光系统(2)——HAL实现

2022年07月19日140lautakyan007

1.Android系统中定义了如下一些灯

/frameworks/android_hardware/libhardware/include/hardware/lights.h 
#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" 
还有两个未实现的： 
#define LIGHT_ID_BLUETOOTH          "bluetooth" 
#define LIGHT_ID_WIFI               "wifi"

2.编写lights的hal文件

好的参考例子，sony手机使用的，移植这个程序: https://android.googlesource.com/device/sony/lt26/+/master/liblight/lights.c
移植后的hal文件如下：

/* 
移植: 
https://android.googlesource.com/device/sony/lt26/+/master/liblight/lights.c 
 
*/ 
 
/*是在发布版软件中的ALOGV()能打印出来*/ 
#define LOG_NDEBUG 0 
 
#define LOG_TAG "lights" 
#include <cutils/log.h> 
#include <stdint.h> 
#include <string.h> 
#include <unistd.h> 
#include <errno.h> 
#include <fcntl.h> 
#include <pthread.h> 
#include <sys/ioctl.h> 
#include <sys/types.h> 
#include <hardware/lights.h> 
 
char const*const RED_LED_FILE                 = "/sys/class/leds/led1/brightness"; 
char const*const GREEN_LED_FILE             = "/sys/class/leds/led2/brightness"; 
char const*const BLUE_LED_FILE             = "/sys/class/leds/led3/brightness"; 
 
char const*const RED_LED_FILE_TRIGGER        = "/sys/class/leds/led1/trigger"; 
char const*const GREEN_LED_FILE_TRIGGER    = "/sys/class/leds/led2/trigger"; 
char const*const BLUE_LED_FILE_TRIGGER    = "/sys/class/leds/led3/trigger"; 
 
char const*const RED_LED_FILE_DELAYON        = "/sys/class/leds/led1/delay_on"; 
char const*const GREEN_LED_FILE_DELAYON    = "/sys/class/leds/led2/delay_on"; 
char const*const BLUE_LED_FILE_DELAYON    = "/sys/class/leds/led3/delay_on"; 
 
char const*const RED_LED_FILE_DELAYOFF    = "/sys/class/leds/led1/delay_off"; 
char const*const GREEN_LED_FILE_DELAYOFF = "/sys/class/leds/led2/delay_off"; 
char const*const BLUE_LED_FILE_DELAYOFF    = "/sys/class/leds/led3/delay_off"; 
 
char const*const LCD_BACKLIGHT_FILE       = "/dev/backlight-1wire"; 
 
/* Synchronization primities */ 
static pthread_once_t g_init = PTHREAD_ONCE_INIT; 
static pthread_mutex_t g_lock = PTHREAD_MUTEX_INITIALIZER; 
/* Mini-led state machine */ 
static struct light_state_t g_notification; 
static struct light_state_t g_battery; 
 
 
static int write_int (const char *path, int value) { 
    int fd; 
    /*使用这个静态变量只提示一次*/ 
    static int already_warned = 0; 
    fd = open(path, O_RDWR); 
    if (fd < 0) { 
        int errno_ret = errno; 
        if (already_warned == 0) { 
            ALOGE("write_int open %s failed，ret=%d\n", path, fd); 
            already_warned = 1; 
        } 
        return -errno_ret; 
    } 
    char buffer[20]; 
     
    /*sysfs文件写入的是字符串，因此还需要将数值转换为字符串后写入*/ 
    int bytes = snprintf(buffer, sizeof(buffer), "%d\n", value); 
    int written = write (fd, buffer, bytes); 
    close(fd); 
    return written == -1 ? -errno : 0; 
} 
 
static int write_string (const char *path, const char *value) { 
    int fd; 
    static int already_warned = 0; 
    fd = open(path, O_RDWR); 
    if (fd < 0) { 
        int errno_ret = errno; 
        if (already_warned == 0) { 
            ALOGE("write_string failed to open %s\n", path); 
            already_warned = 1; 
        } 
        return -errno_ret; 
    } 
    char buffer[20]; 
    int bytes = snprintf(buffer, sizeof(buffer), "%s\n", value); 
    int written = write (fd, buffer, bytes); 
    close(fd); 
    return written == -1 ? -errno : 0; 
} 
 
/* Color tools */ 
static int is_lit (struct light_state_t const* state) { 
    return state->color & 0x00ffffff; 
} 
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; 
} 
 
/* The actual lights controlling section */ 
static int set_light_backlight (struct light_device_t *dev, struct light_state_t const *state) { 
    int brightness = rgb_to_brightness(state); 
    ALOGV("%s brightness=%d color=0x%08x", __func__,brightness, state->color); 
 
    /*加个锁表示希望是线程安全的*/ 
    pthread_mutex_lock(&g_lock); 
    /* App传下来brightness 0-255，但是驱动只支持0-127，因此除以2 */ 
    write_int (LCD_BACKLIGHT_FILE, brightness/2); 
    pthread_mutex_unlock(&g_lock); 
     
    return 0; 
} 
 
/*这个实验中的三个灯模拟的是一个灯*/ 
static void set_shared_light_locked (struct light_device_t *dev, struct light_state_t *state) { 
    int r, g, b; 
    int delayOn,delayOff; 
    r = (state->color >> 16) & 0xFF; 
    g = (state->color >> 8) & 0xFF; 
    b = (state->color) & 0xFF; 
    delayOn = state->flashOnMS; 
    delayOff = state->flashOffMS; 
    /*需要led闪烁，三个led全部闪烁*/ 
    if (state->flashMode != LIGHT_FLASH_NONE) { 
        write_string (RED_LED_FILE_TRIGGER, "timer"); 
        write_string (GREEN_LED_FILE_TRIGGER, "timer"); 
        write_string (BLUE_LED_FILE_TRIGGER, "timer"); 
        write_int (RED_LED_FILE_DELAYON, delayOn); 
        write_int (GREEN_LED_FILE_DELAYON, delayOn); 
        write_int (BLUE_LED_FILE_DELAYON, delayOn); 
        write_int (RED_LED_FILE_DELAYOFF, delayOff); 
        write_int (GREEN_LED_FILE_DELAYOFF, delayOff); 
        write_int (BLUE_LED_FILE_DELAYOFF, delayOff); 
    } else { 
        write_string (RED_LED_FILE_TRIGGER, "none"); 
        write_string (GREEN_LED_FILE_TRIGGER, "none"); 
        write_string (BLUE_LED_FILE_TRIGGER, "none"); 
    } 
 
    /*虽然上面同时触发了闪烁，但是如果写的是0，会关闭对应的led*/ 
    write_int (RED_LED_FILE, r); 
    write_int (GREEN_LED_FILE, g); 
    write_int (BLUE_LED_FILE, b); 
} 
 
/*sony的通知灯和电池灯共用一个led,通知灯的优先级更高*/ 
static void handle_shared_battery_locked (struct light_device_t *dev) { 
    /*优先作为通知灯使用*/ 
    if (is_lit (&g_notification)) { 
        set_shared_light_locked (dev, &g_notification); 
    } else { 
        set_shared_light_locked (dev, &g_battery); 
    } 
} 
static int set_light_battery (struct light_device_t *dev, struct light_state_t const* state) { 
 
    ALOGV("%s flashMode=%d onMS = %d offMS = %d color=0x%08x", __func__,state->flashMode,state->flashOnMS,state->flashOffMS,state->color); 
 
    pthread_mutex_lock (&g_lock); 
    g_battery = *state; 
    handle_shared_battery_locked(dev); 
    pthread_mutex_unlock (&g_lock); 
    return 0; 
} 
static int set_light_notifications (struct light_device_t *dev, struct light_state_t const* state) { 
    ALOGV("%s flashMode=%d onMS = %d offMS = %d color=0x%08x", __func__,state->flashMode,state->flashOnMS,state->flashOffMS,state->color); 
    pthread_mutex_lock (&g_lock); 
    g_notification = *state; 
    handle_shared_battery_locked(dev); 
    pthread_mutex_unlock (&g_lock); 
    return 0; 
} 
/* Initializations */ 
void init_globals () { 
    pthread_mutex_init (&g_lock, NULL); 
} 
/* Glueing boilerplate */ 
static int close_lights (struct light_device_t *dev) { 
    if (dev) 
        free(dev); 
    return 0; 
} 
 
/*这个参数可能被传入多个name,获取多个name的led*/ 
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); 
 
    /*若获取的是"backlight"灯，就返回"backlight"灯的设置方法*/ 
    if (0 == strcmp(LIGHT_ID_BACKLIGHT, name)) { 
        set_light = set_light_backlight; 
    }/*若获取的是"battery"灯，就返回"battery"灯的设置方法*/ 
    else if (0 == strcmp(LIGHT_ID_BATTERY, name)) { 
        set_light = set_light_battery; 
    }/*若获取的是"notifications"灯，就返回"notifications"灯的设置方法*/ 
    else if (0 == strcmp(LIGHT_ID_NOTIFICATIONS, name)) { 
        set_light = set_light_notifications; 
    }/*其它灯不支持*/ 
    else { 
        /*没获取到帮JNI设置为NULL*/ 
        *device = NULL; 
        return -EINVAL; 
    } 
 
    /* 
     * 这句确保只执行一次，对于hal文件这个技术和有用，因为可能要支持多线程，而且只需要执行一次. 
     * 此处使用静态变量效率应该还高一些。 
     */ 
    pthread_once (&g_init, init_globals); 
     
    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; 
    dev->common.close     = (int (*)(struct hw_device_t*))close_lights; 
    dev->set_light     = set_light; /*这个是对应灯的设置方法*/ 
 
    /*这个结构体返回给JNI*/ 
    *device = (struct hw_device_t*)dev; 
     
    return 0; 
} 
 
 
static struct hw_module_methods_t lights_module_methods = { 
    .open = open_lights, 
}; 
 
struct hw_module_t HAL_MODULE_INFO_SYM = { 
    .tag = HARDWARE_MODULE_TAG, 
    .version_major = 1, 
    .version_minor = 0, 
    .id = LIGHTS_HARDWARE_MODULE_ID, /*"lights"*/ 
    .name = "Transplant from Sony lights module", 
    .author = "Freedom Mr.Sun", 
    .methods = &lights_module_methods, 
};

然后放在hardware/libhardware/modules/lights/下，移植Android.mk进行编译。

同时还要把系统原有的那个不开源的lights.tiny4412.so从系统中移除：
vi vendor/friendly-arm/tiny4412/device-tiny4412.mk

ifeq ($(BOARD_USES_PWMLIGHTS),false) 
# 注释掉这两行 
# PRODUCT_COPY_FILES += \ 
#       $(VENDOR_PATH)/proprietary/lights.tiny4412.so:system/lib/hw/lights.tiny4412.so 
endif

3.编译遇到问题一：
编译进system.img里面的lights.tiny4412.so还是这个不开源的，不是我们实现的，但是
out/target/product/tiny4412/system/lib/hw/lights.tiny4412.so已经是我们实现的了。此时删除out/target/product/tiny4412/system.img
和顶层目录下的system.img,然后重新make snod, ./gen-img.sh，然后生成的system.img里面就是使用我们自己实现的hal了。

4.遇到问题二：
hal文件中的ALOGV()的打印并没有打印出来，在/system/.../cutil/log.h中有说明在发布版软件中ALOGV()的打印是会被丢弃的，若不被想
丢在源文件的最上面加：#define LOG_NDEBUG 0
因此不重要的信息尽量使用ALOGV()来打印，这样软件在release版本中会自动去除。

5.遇到问题三：
/sys/class/leds/led1/trigger无法使用open(O_RDWR)打开，原因是权限不够，Android和Linux不同，Android是以普通用户登录的，属性
文件制定644权限是不可写的，因此需要将trigger，brightness，delay_off，delay_on中需要写的设置为0666权限。

6.mmm -B 强制编译，没有修改代码但是要重新编译的时候使用

7.tiny4412上调节背光的操作：
Setting --> Display --> Brightness Level -->可以手动调节背光的亮度

8.LCD背光灯调节
tiny4412操作LCD背光，这个4412厂家没有给出源码，只给出了一个.so的库,源文件在vendor/friendly-arm/tiny4412/proprietary/lights.tiny4412.so
文件系统中在/system/lib/hw/lights.tiny4412.so。
若是不知道这个库操作的是哪个设备文件，可以把这个库反汇编出来，然后看它操作了哪些设备文件。
其实也不用反汇编，使用AltraEdit打开它然后查找，选择ASCII,搜索/dev，发现其打开的设备文件是/dev/backlight-1wire

在tiny4412上果然有/dev/backlight-1wire，对应内核中文件为tiny4412_1wire_host.c，由其write()看出只需要向里面写个整数值就能调整
背光，测试：
shell@tiny4412:/system # echo 127 > /dev/backlight-1wire //背光开到最大
shell@tiny4412:/system # echo 0 > /dev/backlight-1wire //关闭背光
shell@tiny4412:/system # echo 10 > /dev/backlight-1wire //调节背光
会自动把"127"转换为127


本文参考链接：https://www.cnblogs.com/hellokitty2/p/10812208.html
  文章来源：
  https://www.itguest.com/post/fjf2b6.html
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