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

http://blog.youkuaiyun.com/zhangjie201412/article/details/7332606

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.youkuaiyun.com/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

[cpp] view plain copy print ?

1. #define LOG_TAG "light"   
2.   
3. #include <hardware/lights.h>   
4. #include <fcntl.h>   
5. #include <errno.h>   
6. #include <stdlib.h>   
7. #include <cutils/log.h>   
8. #include <cutils/atomic.h>   
9. #include <cutils/properties.h>   
10.   
11.   
12.   
13. #define MAX_BRIGHTNESS  255   
14. #define DEF_BACKLIGHT_DEV   "android-backlight"   
15. #define DEF_BACKLIGHT_PATH  "/sys/class/backlight/"   
16.   
17. /***************************************************************/  
18. struct lights_module_t{  
19.     struct hw_module_t common;  
20. };  
21.   
22. static int lights_device_open(const struct hw_module_t* module,  
23.         const char* name,struct hw_device_t** device);  
24.   
25. static struct hw_module_methods_t lights_module_methods = {  
26.     .open=lights_device_open  
27. };  
28.   
29. const struct lights_module_t HAL_MODULE_INFO_SYM = {  
30.     .common= {  
31.         .tag= HARDWARE_MODULE_TAG,  
32.         .version_major= 1,  
33.         .version_minor= 0,  
34.         .id= LIGHTS_HARDWARE_MODULE_ID,  
35.         .name= "Lights module",  
36.         .author= "Freescale Semiconductor",  
37.         .methods= &lights_module_methods,  
38.     }  
39. };  
40.   
41. static char max_path[256], path[256];  
42. // ****************************************************************************   
43. // module   
44. // ****************************************************************************   
45. static int set_light_backlight(struct light_device_t* dev,  
46.                                struct light_state_t const* state)  
47. {  
48.     int result = -1;  
49.     unsigned int color = state->color;  
50.     unsigned int brightness = 0, max_brightness = 0;  
51.     FILE *file;  
52.   
53.     brightness = ((77*((color>>16)&0x00ff)) + (150*((color>>8)&0x00ff)) +  
54.                  (29*(color&0x00ff))) >> 8;  
55.     LOGV("set_light, get brightness=%d", brightness);  
56.   
57.     file = fopen(max_path, "r");  
58.     if (!file) {  
59.         LOGE("can not open file %s\n", max_path);  
60.     return result;  
61.     }  
62.     fread(&max_brightness, 1, 3, file);  
63.     fclose(file);  
64.   
65.     max_brightness = atoi((char *) &max_brightness);  
66.     brightness = brightness * max_brightness / MAX_BRIGHTNESS;  
67.     LOGV("set_light, max_brightness=%d, target brightness=%d",  
68.         max_brightness, brightness);  
69.   
70.     file = fopen(path, "w");  
71.     if (!file) {  
72.         LOGE("can not open file %s\n", path);  
73.         return result;  
74.     }  
75.     fprintf(file, "%d", brightness);  
76.     fclose(file);  
77.   
78.     result = 0;  
79.     return result;  
80. }  
81.   
82. static int light_close_backlight(struct hw_device_t *dev)  
83. {  
84.     struct light_device_t *device = (struct light_device_t*)dev;  
85.     if (device)  
86.         free(device);  
87.     return 0;  
88. }  
89.   
90. /*****************************************************************************/  
91. static int lights_device_open(const struct hw_module_t* module,  
92.                               const char* name, struct hw_device_t** device)  
93. {  
94.     int status = -EINVAL;  
95.     LOGV("lights_device_open\n");  
96.     if (!strcmp(name, LIGHT_ID_BACKLIGHT)) {  
97.         struct light_device_t *dev;  
98.         char value[PROPERTY_VALUE_MAX];  
99.   
100.         dev = malloc(sizeof(*dev));  
101.   
102.         /* initialize our state here */  
103.         memset(dev, 0, sizeof(*dev));  
104.   
105.         /* initialize the procs */  
106.         dev->common.tag = HARDWARE_DEVICE_TAG;  
107.         dev->common.version = 0;  
108.         dev->common.module = (struct hw_module_t*) module;  
109.         dev->common.close = light_close_backlight;  
110.   
111.         dev->set_light = set_light_backlight;  
112.   
113.     *device = &dev->common;  
114.   
115. //        property_get("hw.backlight.dev", value, DEF_BACKLIGHT_DEV);   
116. //        strcpy(path, DEF_BACKLIGHT_PATH);   
117. //        strcat(path, value);   
118. //        strcpy(max_path, path);   
119. //        strcat(max_path, "/max_brightness");   
120. //        strcat(path, "/brightness");   
121.     strcpy(path, "/sys/devices/platform/android-backlight.0/backlight/android-backlight.0/brightness");  
122.     strcpy(max_path, "/sys/devices/platform/android-backlight.0/backlight/android-backlight.0/max_brightness");  
123.     LOGI("max backlight file is %s\n", max_path);  
124.         LOGI("backlight brightness file is %s\n", path);  
125.   
126.         status = 0;  
127.     }  
128.   
129.     /* todo other lights device init */  
130.     return status;  
131. }  

#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

[cpp] view plain copy print ?

1. LOCAL_PATH := $(call my-dir)  
2.   
3. # HAL module implemenation, not prelinked and stored in hw/   
4. include $(CLEAR_VARS)  
5. LOCAL_MODULE_TAGS := optional  
6. LOCAL_PRELINK_MODULE := false  
7. LOCAL_MODULE_PATH := $(TARGET_OUT_SHARED_LIBRARIES)/hw  
8. LOCAL_SHARED_LIBRARIES := liblog libcutils  
9. LOCAL_SRC_FILES := android_light.c  
10. LOCAL_MODULE := lights.default  
11. #LOCAL_MODULE_TAGS := eng   
12. include $(BUILD_SHARED_LIBRARY)  

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

[cpp] view plain copy print ?

1. #add by Jay   
2.     chmod 777 /sys/bus/iio/devices/device0/lux  
3.     chmod 777 /sys/bus/iio/devices/device1/value  
4.     chmod 777 /sys/bus/iio/devices/device1/active  
5.     chmod 777 /sys/class/backlight/android-backlight.0/brightness  
6.     chmod 777 /sys/class/backlight/android-backlight.0/max_brightness  

#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。