android app 控制背光,android 背光控制

电玩女神 2022-10-05 00:43 232阅读 0赞

echo 23 > /sys/devices/platform/atmel\_lcdfb.0/backlight/backlight/brightness

android 源代码

http://blog.chinaunix.net/u1/49742/showart\_2077813.html android 知识总结

http://www.limodev.cn/

Android 背光的控制：

屏幕背光设置

packages/apps/Settings/src/com/android/settings/BrightnessPreference.java

背光设置滚动条和关闭按钮都会调用 setBrightness(mOldBrightness);

public void onProgressChanged(SeekBar seekBar, int progress,boolean fromTouch)

protected void onDialogClosed(boolean positiveResult)

private void setBrightness(int brightness) \{

try \{

IHardwareService hardware = IHardwareService.Stub.asInterface(

ServiceManager.getService("hardware"));

if (hardware != null) \{

hardware.setBacklights(brightness);

\} catch (RemoteException doe) \{

调用硬件服务器 HardwareService 的 setBacklights 函数

HardwareService.java (frameworks\\base\\services\\java\\com\\android\\server):

public void setBacklights(int brightness)

. . .

// Don't let applications turn the screen all the way off

brightness = Math.max(brightness, Power.BRIGHTNESS\_DIM);

setLightBrightness\_UNCHECKED(LIGHT\_ID\_BACKLIGHT, brightness);

setLightBrightness\_UNCHECKED(LIGHT\_ID\_KEYBOARD, brightness);

setLightBrightness\_UNCHECKED(LIGHT\_ID\_BUTTONS, brightness);

. . .

void setLightOff\_UNCHECKED(int light)

//本地调用 setLight\_native

setLight\_native(mNativePointer, light, 0, LIGHT\_FLASH\_NONE, 0, 0);

void setLightBrightness\_UNCHECKED(int light, int brightness) \{

int b = brightness & 0x000000ff;

b = 0xff000000 | (b << 16) | (b << 8) | b;

setLight\_native(mNativePointer, light, b, LIGHT\_FLASH\_NONE, 0, 0);

因为有：

com\_android\_server\_HardwareService.cpp (frameworks\\base\\services\\jni):

static JNINativeMethod method\_table\[\] = \{

\{ "init\_native", "()I", (void\*)init\_native \},

\{ "finalize\_native", "(I)V", (void\*)init\_native \},

\{ "setLight\_native", "(IIIIII)V", (void\*)setLight\_native \},

\{ "vibratorOn", "(J)V", (void\*)vibratorOn \},

\{ "vibratorOff", "()V", (void\*)vibratorOff \}

\};

所以最终调用的是文件：

com\_android\_server\_HardwareService.cpp (frameworks\\base\\services\\jni)中的函数：

static void setLight\_native(JNIEnv \*env, jobject clazz, int ptr,

int light, int colorARGB, int flashMode, int onMS, int offMS)

Devices\* devices = (Devices\*)ptr;

light\_state\_t state;

if (light < 0 || light >= LIGHT\_COUNT || devices->lights\[light\] == NULL) \{

return ;

memset(&state, 0, sizeof(light\_state\_t));

state.color = colorARGB;

state.flashMode = flashMode;

state.flashOnMS = onMS;

state.flashOffMS = offMS;

devices->lights\[light\]->set\_light(devices->lights\[light\], &state);

Lights.h (hardware\\libhardware\\include\\hardware):\#define LIGHTS\_HARDWARE\_MODULE\_ID "lights"

com\_android\_server\_HardwareService.cpp (frameworks\\base\\services\\jni)

err = hw\_get\_module(LIGHTS\_HARDWARE\_MODULE\_ID, (hw\_module\_t const\*\*)&module);

static const char \*variant\_keys\[\] = \{

"ro.hardware", /\* This goes first so that it can pick up a different

file on the emulator. \*/

"ro.product.board",

"ro.board.platform",

"ro.arch"

\};

int hw\_get\_module(const char \*id, const struct hw\_module\_t \*\*module)

status = load(id, prop, &hmi);

status = load(id, HAL\_DEFAULT\_VARIANT, &hmi);

static int load(const char \*id, const char \*variant,const struct hw\_module\_t \*\*pHmi)

snprintf(path, sizeof(path), "%s/%s.%s.so", HAL\_LIBRARY\_PATH, id, variant);

\#define HAL\_DEFAULT\_VARIANT "default"

\#define HAL\_LIBRARY\_PATH "/system/lib/hw"

所以path等于：

/system/lib/hw/light.marvell.so

/system/lib/hw/light.default.so

我们编译的light模块放在 /system/lib/hw/light.default.so 所以初始化成功。

property\_get(variant\_keys\[i\], prop, NULL) 只有 ro.hardware 存在 \[ro.hardware\]: \[marvell\]

static int lights\_device\_open(const struct hw\_module\_t\* module, const char\* name,struct hw\_device\_t\*\* device)

dev->set\_light = set\_light\_backlight;

static struct hw\_module\_methods\_t lights\_module\_methods = \{

open: lights\_device\_open

\};

hardware/libhardware/modules/lights/Android.mk

LOCAL\_MODULE:= lights.default

err = module->methods->open(module, name, &device);

执行的是 ： lights\_device\_open

const char \* const brightness\_file = "/sys/class/backlight/micco-bl/brightness";

static int set\_light\_backlight(struct light\_device\_t\* dev,

struct light\_state\_t const\* state)

｛

. . .

color = state->color;

tmp = ((77\*((color>>16)&0x00ff)) + (150\*((color>>8)&0x00ff)) + (29\*(color&0x00ff))) >> 8;

brightness = tmp/16;

LOGD("---->calling %s(),line=%d state->color=%d,brightness=%d\\n",\_\_FUNCTION\_\_,\_\_LINE\_\_,state->color,brightness);

len = sprintf(buf,"%d",brightness);

len = write(fd, buf, len);

. . .

｝

上面的函数完成了与内核的交互

综上所述，程序调用流程如下，上层应用通过 /sys/class/leds/lcd-backlight/brightnes 于内核打交道

设置模块 -> 硬件服务器 -> 本地调用 ->功能库 -> 读写 /sys/class/leds/lcd-backlight/brightness 函数与内核交互

Init.rc (vendor\\marvell\\littleton): chown system system /sys/class/leds/keyboard-backlight/brightness

Init.rc (vendor\\marvell\\littleton): chown system system /sys/class/leds/lcd-backlight/brightness

Init.rc (vendor\\marvell\\littleton): chown system system /sys/class/leds/button-backlight/brightness

这个是博客中记录的，非常详细，很具有参考价值。

在 Atmel 开发板的背光问题解决中使用了 另外一个路径：

\# pwd

/sys/class/backlight

\# ls -l

lrwxrwxrwx root root 1970-01-01 00:00 backlight -> ../../devices/platform/atmel\_lcdfb.0/backlight/backlight

改变该路径的属性： 可读可写。 init.rc

MK 文件

LOCAL\_PATH:= $(call my-dir)

\# HAL module implemenation, not prelinked and stored in

\# hw/..so

include $(CLEAR\_VARS)

LOCAL\_SRC\_FILES := lights.c

LOCAL\_PRELINK\_MODULE := false

LOCAL\_MODULE\_PATH := $(TARGET\_OUT\_SHARED\_LIBRARIES)/hw

LOCAL\_SHARED\_LIBRARIES := liblog

LOCAL\_MODULE := lights.atmel

include $(BUILD\_SHARED\_LIBRARY)

改变 lights.c 文件中的路径。

\# ls -l /system/lib/hw

\-rwxrwxrwx root root 9560 2010-07-06 10:21 lights.default.so

\-rwxrwxrwx root root 14040 2010-07-06 09:03 gralloc.default.so

\-rwxrwxrwx root root 9560 2010-07-06 09:03 light.atmel.so.bak

\-rwxrwxrwx root root 9752 2010-07-06 10:21 alsa.default.so

\-rwxrwxrwx root root 9848 2010-07-06 09:03 sensors.goldfish.so

\-rwxrwxrwx root root 5308 2010-07-06 10:21 acoustics.default.so

lights.default.so light.atmel.so 均可实现亮度控制。

android app 控制背光,android 背光控制

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