Android灯光系统(2)——HAL实现

1.Android系统中定义了以下一些灯

/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文件以下：

/* 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，所以还须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); /*加个锁表示但愿是线程安全的*/ pthread_mutex_lock(&g_lock); /* App传下来brightness 0-255，可是驱动只支持0-127，所以除以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; /*须要led闪烁，三个led所有闪烁*/
    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，可是若是写的是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) { /*优先做为通知灯使用*/
    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，由于可能要支持多线程，并且只须要执行一次. * 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, };

View Code

而后放在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

View Code

3.编译遇到问题一：
编译进system.img里面的lights.tiny4412.so仍是这个不开源的，不是咱们实现的，可是
out/target/product/tiny4412/system/lib/hw/lights.tiny4412.so已是咱们实现的了。此时删除out/target/product/tiny4412/system.img
和顶层目录下的system.img,而后从新make snod, ./gen-img.sh，而后生成的system.img里面就是使用咱们本身实现的hal了。

4.遇到问题二：
hal文件中的ALOGV()的打印并无打印出来，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
所以不重要的信息尽可能使用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没法使用open(O_RDWR)打开，缘由是权限不够，Android和Linux不一样，Android是以普通用户登陆的，属性
文件制定644权限是不可写的，所以须要将trigger，brightness，delay_off，delay_on中须要写的设置为0666权限。

6.mmm -B 强制编译，没有修改代码可是要从新编译的时候使用

7.tiny4412上调节背光的操做：
Setting --> Display --> Brightness Level -->能够手动调节背光的亮度

8.LCD背光灯调节
tiny4412操做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。
如果不知道这个库操做的是哪一个设备文件，能够把这个库反汇编出来，而后看它操做了哪些设备文件。
其实也不用反汇编，使用AltraEdit打开它而后查找，选择ASCII,搜索/dev，发现其打开的设备文件是/dev/backlight-1wire

在tiny4412上果真有/dev/backlight-1wire，对应内核中文件为tiny4412_1wire_host.c，由其write()看出只须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