Android燈光系統(2)——HAL實現

1.Android系統中定義了以下一些燈

/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" 還有兩個未實現的： #define LIGHT_ID_BLUETOOTH          "bluetooth"
#define LIGHT_ID_WIFI               "wifi"

2.編寫lights的hal文件

好的參考例子，sony手機使用的，移植這個程序: https://android.googlesource.com/device/sony/lt26/+/master/liblight/lights.c
移植後的hal文件以下：

/* 移植: https://android.googlesource.com/device/sony/lt26/+/master/liblight/lights.c */

/*是在發佈版軟件中的ALOGV()能打印出來*/
#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; /*使用這個靜態變量只提示一次*/
    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文件寫入的是字符串，所以還須要將數值轉換爲字符串後寫入*/
    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); /*加個鎖表示但願是線程安全的*/ pthread_mutex_lock(&g_lock); /* App傳下來brightness 0-255，可是驅動只支持0-127，所以除以2 */ write_int (LCD_BACKLIGHT_FILE, brightness/2); pthread_mutex_unlock(&g_lock); return 0; } /*這個實驗中的三個燈模擬的是一個燈*/
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; /*須要led閃爍，三個led所有閃爍*/
    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"); } /*雖然上面同時觸發了閃爍，可是若是寫的是0，會關閉對應的led*/ write_int (RED_LED_FILE, r); write_int (GREEN_LED_FILE, g); write_int (BLUE_LED_FILE, b); } /*sony的通知燈和電池燈共用一個led,通知燈的優先級更高*/
static void handle_shared_battery_locked (struct light_device_t *dev) { /*優先做爲通知燈使用*/
    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; } /*這個參數可能被傳入多個name,獲取多個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); /*若獲取的是"backlight"燈，就返回"backlight"燈的設置方法*/
    if (0 == strcmp(LIGHT_ID_BACKLIGHT, name)) { set_light = set_light_backlight; }/*若獲取的是"battery"燈，就返回"battery"燈的設置方法*/
    else if (0 == strcmp(LIGHT_ID_BATTERY, name)) { set_light = set_light_battery; }/*若獲取的是"notifications"燈，就返回"notifications"燈的設置方法*/
    else if (0 == strcmp(LIGHT_ID_NOTIFICATIONS, name)) { set_light = set_light_notifications; }/*其它燈不支持*/
    else { /*沒獲取到幫JNI設置爲NULL*/
        *device = NULL; return -EINVAL; } /* * 這句確保只執行一次，對於hal文件這個技術和有用，由於可能要支持多線程，並且只須要執行一次. * 此處使用靜態變量效率應該還高一些。 */ 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; /*這個是對應燈的設置方法*/

    /*這個結構體返回給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, };

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而後放在hardware/libhardware/modules/lights/下，移植Android.mk進行編譯。

同時還要把系統原有的那個不開源的lights.tiny4412.so從系統中移除：
vi vendor/friendly-arm/tiny4412/device-tiny4412.mk

ifeq ($(BOARD_USES_PWMLIGHTS),false) # 註釋掉這兩行 # PRODUCT_COPY_FILES += \ # $(VENDOR_PATH)/proprietary/lights.tiny4412.so:system/lib/hw/lights.tiny4412.so endif

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3.編譯遇到問題一：
編譯進system.img裏面的lights.tiny4412.so仍是這個不開源的，不是咱們實現的，可是
out/target/product/tiny4412/system/lib/hw/lights.tiny4412.so已是咱們實現的了。此時刪除out/target/product/tiny4412/system.img
和頂層目錄下的system.img,而後從新make snod, ./gen-img.sh，而後生成的system.img裏面就是使用咱們本身實現的hal了。

4.遇到問題二：
hal文件中的ALOGV()的打印並無打印出來，在/system/.../cutil/log.h中有說明在發佈版軟件中ALOGV()的打印是會被丟棄的，若不被想
丟在源文件的最上面加：#define LOG_NDEBUG 0
所以不重要的信息儘可能使用ALOGV()來打印，這樣軟件在release版本中會自動去除。

5.遇到問題三：
/sys/class/leds/led1/trigger沒法使用open(O_RDWR)打開，緣由是權限不夠，Android和Linux不一樣，Android是以普通用戶登陸的，屬性
文件制定644權限是不可寫的，所以須要將trigger，brightness，delay_off，delay_on中須要寫的設置爲0666權限。

6.mmm -B 強制編譯，沒有修改代碼可是要從新編譯的時候使用

7.tiny4412上調節背光的操做：
Setting --> Display --> Brightness Level -->能夠手動調節背光的亮度

8.LCD背光燈調節
tiny4412操做LCD背光，這個4412廠家沒有給出源碼，只給出了一個.so的庫,源文件在vendor/friendly-arm/tiny4412/proprietary/lights.tiny4412.so
文件系統中在/system/lib/hw/lights.tiny4412.so。
如果不知道這個庫操做的是哪一個設備文件，能夠把這個庫反彙編出來，而後看它操做了哪些設備文件。
其實也不用反彙編，使用AltraEdit打開它而後查找，選擇ASCII,搜索/dev，發現其打開的設備文件是/dev/backlight-1wire

在tiny4412上果真有/dev/backlight-1wire，對應內核中文件爲tiny4412_1wire_host.c，由其write()看出只須要向裏面寫個整數值就能調整背光，測試：shell@tiny4412:/system # echo 127 > /dev/backlight-1wire //背光開到最大 shell@tiny4412:/system # echo 0 > /dev/backlight-1wire //關閉背光shell@tiny4412:/system # echo 10 > /dev/backlight-1wire //調節背光會自動把"127"轉換爲127