android應(yīng)用如何訪(fǎng)問(wèn)C庫(kù) - 落魄影子 - 博客頻道 - CSDN.NET ?http://blog.csdn.net/ab198604/article/details/51249303

Android硬件訪(fǎng)問(wèn)服務(wù)框架代碼編寫(xiě) - 落魄影子 - 博客頻道 - CSDN.NET ?http://blog.csdn.net/ab198604/article/details/51397586

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4 編寫(xiě)HAL代碼

源碼下載方法
第一次:
git clone https://github.com/weidongshan/SYS_0001_LEDDemo.git
更新:
git pull origin
取出指定版本:
git checkout v1 // 有JNI沒(méi)有HAL
git checkout v2 // 有JNI,HAL
git checkout v3 // add MODULE TAG, DEVICE TAG

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JNI 向上提供本地函數(shù), 向下加載HAL文件并調(diào)用HAL的函數(shù)
HAL 負(fù)責(zé)訪(fǎng)問(wèn)驅(qū)動(dòng)程序執(zhí)行硬件操作

dlopen

external\chromium_org\third_party\hwcplus\src\hardware.c ? (參考代碼)
hw_get_module("led")

1. 模塊名==>文件名
hw_get_module_by_class("led", NULL)
name = "led"
property_get xxx是某個(gè)屬性
hw_module_exists 判斷是否存在led.xxx.so

它用來(lái)判斷"name"."subname".so文件是否存在
查找的目錄：
a. HAL_LIBRARY_PATH 環(huán)境變量

b. /vendor/lib/hw

c. /system/lib/hw

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?/vendor/lib/hw 這個(gè)目錄下沒(méi)有文件，tiny4412所以只能去/system/lib/hw這個(gè)目錄下找

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2. 加載
load
dlopen(filename)
dlsym("HMI") 從SO文件中獲得名為HMI的hw_module_t結(jié)構(gòu)體
strcmp(id, hmi->id) 判斷名字是否一致(hmi->id, "led")

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V2:
(3) JNI: 重新上傳
frameworks/base/services/core/jni/com_android_server_LedService.cpp

(4) HAL: led_hal.h
led_hal.c
把新文件上傳到服務(wù)器, 所在目錄:
hardware/libhardware/include/hardware/led_hal.h

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hardware/libhardware/modules 在這個(gè)目錄下創(chuàng)建一個(gè)目錄led,放入led_hal.c和自己寫(xiě)一個(gè)Android.mk

hardware/libhardware/modules/led/led_hal.c
hardware/libhardware/modules/led/Android.mk

Android.mk內(nèi)容如下:
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := led.default
LOCAL_MODULE_RELATIVE_PATH := hw
LOCAL_C_INCLUDES := hardware/libhardware
LOCAL_SRC_FILES := led_hal.c
LOCAL_SHARED_LIBRARIES := liblog
LOCAL_MODULE_TAGS := eng

include $(BUILD_SHARED_LIBRARY)

編譯：

$ mmm frameworks/base/services
$ mmm hardware/libhardware/modules/led
$ make snod
$ ./gen-img.sh

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最終生成system.img文件

打印信息簡(jiǎn)介：
a. 有三類(lèi)打印信息: app, system, radio
程序里使用 ALOGx, SLOGx, RLOGx來(lái)打印
b. x表示6種打印級(jí)別，有:
V ? ?Verbose
D ? ?Debug
I ? ? Info
W ? Warn
E ? ?Error
F ? ?Fatal

比如:
#define LOG_TAG "LedHal"
ALOGI("led_open : %d", fd);

c. 打印出來(lái)的格式為:
I/LedHal ( 1987): led_open : 65
(級(jí)別) LOG_TAG 進(jìn)程號(hào) 打印信息

d. 使用 logcat 命令查看
logcat LedHal:I *:S

選出自己感興趣的信息：

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和上一個(gè)章節(jié)相比，主要修改了

com_android_server_LedService.cpp

添加了led_hal.h ??led_hal.c ?Android.mk

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?com_android_server_LedService.cpp

#define LOG_TAG "LedService"#include "jni.h"
#include "JNIHelp.h"
#include "android_runtime/AndroidRuntime.h"#include <utils/misc.h>
#include <utils/Log.h>#include <stdio.h>#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <hardware/led_hal.h>namespace android
{static led_device_t* led_device;jint ledOpen(JNIEnv *env, jobject cls)
{jint err;hw_module_t* module;hw_device_t* device;ALOGI("native ledOpen ...");/* 1. hw_get_module */err = hw_get_module("led", (hw_module_t const**)&module);if (err == 0) {/* 2. get device : module->methods->open */err = module->methods->open(module, NULL, &device);if (err == 0) {/* 3. call led_open */led_device = (led_device_t *)device;return led_device->led_open(led_device);} else {return -1;}}return -1;    
}void ledClose(JNIEnv *env, jobject cls)
{//ALOGI("native ledClose ...");//close(fd);
}jint ledCtrl(JNIEnv *env, jobject cls, jint which, jint status)
{ALOGI("native ledCtrl %d, %d", which, status);return led_device->led_ctrl(led_device, which, status);
}static const JNINativeMethod methods[] = {{"native_ledOpen", "()I", (void *)ledOpen},{"native_ledClose", "()V", (void *)ledClose},{"native_ledCtrl", "(II)I", (void *)ledCtrl},
};int register_android_server_LedService(JNIEnv *env)
{return jniRegisterNativeMethods(env, "com/android/server/LedService",methods, NELEM(methods));
}}

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led_hal.c

#define LOG_TAG "LedHal"/* 1. 實(shí)現(xiàn)一個(gè)名為HMI的hw_module_t結(jié)構(gòu)體 *//* 2. 實(shí)現(xiàn)一個(gè)open函數(shù), 它返回led_device_t結(jié)構(gòu)體 *//* 3. 實(shí)現(xiàn)led_device_t結(jié)構(gòu)體 *//* 參考 hardware\libhardware\modules\vibrator\vibrator.c*/#include <hardware/vibrator.h>
#include <hardware/hardware.h>#include <cutils/log.h>#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>#include <hardware/led_hal.h>#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <utils/Log.h>static int fd;/** Close this device */
static int led_close(struct hw_device_t* device)
{close(fd);return 0;
}static int led_open(struct led_device_t* dev)
{fd = open("/dev/leds", O_RDWR);ALOGI("led_open : %d", fd);if (fd >= 0)return 0;elsereturn -1;
}static int led_ctrl(struct led_device_t* dev, int which, int status)
{int ret = ioctl(fd, status, which);ALOGI("led_ctrl : %d, %d, %d", which, status, ret);return ret;
}static struct led_device_t led_dev = {.common = {.tag   = HARDWARE_DEVICE_TAG,.close = led_close,},.led_open  = led_open,.led_ctrl  = led_ctrl,
};static int led_device_open(const struct hw_module_t* module, const char* id,struct hw_device_t** device)
{*device = &led_dev;return 0;
}static struct hw_module_methods_t led_module_methods = {.open = led_device_open,
};struct hw_module_t HAL_MODULE_INFO_SYM = {.tag = HARDWARE_MODULE_TAG,.id = "led",.methods = &led_module_methods,
};

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led_hal.h

#ifndef ANDROID_LED_INTERFACE_H
#define ANDROID_LED_INTERFACE_H#include <stdint.h>
#include <sys/cdefs.h>
#include <sys/types.h>#include <hardware/hardware.h>__BEGIN_DECLSstruct led_device_t {struct hw_device_t common;int (*led_open)(struct led_device_t* dev);int (*led_ctrl)(struct led_device_t* dev, int which, int status);
};__END_DECLS#endif  // ANDROID_LED_INTERFACE_H

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轉(zhuǎn)載于:https://www.cnblogs.com/zhulinhaibao/p/6995461.html

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