Android模拟器学framework和driver之battery & backlight-----6. backlight in hal

这里我们来介绍下backlight hal层，和之前一样，跟之前我们介绍的temperature的hal差不多，比sensor的hal还简单，这里我就不多说hal的介绍了，之前都有介绍的比较详细了，不清楚的可以参考前面的文章：

http://blog.csdn.net/zhangjie201412/article/details/7225617

首先要明确我们的目标，这里主要是封装一些方法，然后给android framework层使用（jni layer），打开一个sysfs中的节点，然后read/write，

明白这点就够了，直接贴代码：

/hardware/libhardware/module/lights/android_light.c

#define LOG_TAG "light" #include <hardware/lights.h> #include <fcntl.h> #include <errno.h> #include <stdlib.h> #include <cutils/log.h> #include <cutils/atomic.h> #include <cutils/properties.h> #define MAX_BRIGHTNESS 255 #define DEF_BACKLIGHT_DEV "android-backlight" #define DEF_BACKLIGHT_PATH "/sys/class/backlight/" /***************************************************************/ struct lights_module_t{ struct hw_module_t common; }; static int lights_device_open(const struct hw_module_t* module, const char* name,struct hw_device_t** device); static struct hw_module_methods_t lights_module_methods = { .open=lights_device_open }; const struct lights_module_t HAL_MODULE_INFO_SYM = { .common= { .tag= HARDWARE_MODULE_TAG, .version_major= 1, .version_minor= 0, .id= LIGHTS_HARDWARE_MODULE_ID, .name= "Lights module", .author= "Freescale Semiconductor", .methods= &lights_module_methods, } }; static char max_path[256], path[256]; // **************************************************************************** // module // **************************************************************************** static int set_light_backlight(struct light_device_t* dev, struct light_state_t const* state) { int result = -1; unsigned int color = state->color; unsigned int brightness = 0, max_brightness = 0; FILE *file; brightness = ((77*((color>>16)&0x00ff)) + (150*((color>>8)&0x00ff)) + (29*(color&0x00ff))) >> 8; LOGV("set_light, get brightness=%d", brightness); file = fopen(max_path, "r"); if (!file) { LOGE("can not open file %s\n", max_path); return result; } fread(&max_brightness, 1, 3, file); fclose(file); max_brightness = atoi((char *) &max_brightness); brightness = brightness * max_brightness / MAX_BRIGHTNESS; LOGV("set_light, max_brightness=%d, target brightness=%d", max_brightness, brightness); file = fopen(path, "w"); if (!file) { LOGE("can not open file %s\n", path); return result; } fprintf(file, "%d", brightness); fclose(file); result = 0; return result; } static int light_close_backlight(struct hw_device_t *dev) { struct light_device_t *device = (struct light_device_t*)dev; if (device) free(device); return 0; } /*****************************************************************************/ static int lights_device_open(const struct hw_module_t* module, const char* name, struct hw_device_t** device) { int status = -EINVAL; LOGV("lights_device_open\n"); if (!strcmp(name, LIGHT_ID_BACKLIGHT)) { struct light_device_t *dev; char value[PROPERTY_VALUE_MAX]; dev = malloc(sizeof(*dev)); /* initialize our state here */ memset(dev, 0, sizeof(*dev)); /* initialize the procs */ dev->common.tag = HARDWARE_DEVICE_TAG; dev->common.version = 0; dev->common.module = (struct hw_module_t*) module; dev->common.close = light_close_backlight; dev->set_light = set_light_backlight; *device = &dev->common; // property_get("hw.backlight.dev", value, DEF_BACKLIGHT_DEV); // strcpy(path, DEF_BACKLIGHT_PATH); // strcat(path, value); // strcpy(max_path, path); // strcat(max_path, "/max_brightness"); // strcat(path, "/brightness"); strcpy(path, "/sys/devices/platform/android-backlight.0/backlight/android-backlight.0/brightness"); strcpy(max_path, "/sys/devices/platform/android-backlight.0/backlight/android-backlight.0/max_brightness"); LOGI("max backlight file is %s\n", max_path); LOGI("backlight brightness file is %s\n", path); status = 0; } /* todo other lights device init */ return status; }
接下来是android.mk

LOCAL_PATH := $(call my-dir) # HAL module implemenation, not prelinked and stored in hw/ include $(CLEAR_VARS) LOCAL_MODULE_TAGS := optional LOCAL_PRELINK_MODULE := false LOCAL_MODULE_PATH := $(TARGET_OUT_SHARED_LIBRARIES)/hw LOCAL_SHARED_LIBRARIES := liblog libcutils LOCAL_SRC_FILES := android_light.c LOCAL_MODULE := lights.default #LOCAL_MODULE_TAGS := eng include $(BUILD_SHARED_LIBRARY)
这里我要声明的是，在读写之前先把文件的权限打开，在init.rc中去做

#add by Jay chmod 777 /sys/bus/iio/devices/device0/lux chmod 777 /sys/bus/iio/devices/device1/value chmod 777 /sys/bus/iio/devices/device1/active chmod 777 /sys/class/backlight/android-backlight.0/brightness chmod 777 /sys/class/backlight/android-backlight.0/max_brightness
好了，hal层我们就添加到这边，我们来重新编译，然后打开我们的模拟器，

打开setting中的display，然后调节屏幕亮度，然后再cat brightness会发现节点中的值改变了

把亮度调到最高，值变成了255.

结束！！！！下面会分析android framework中jni去实现lightService。