4 编写HAL代码
源码下载方法
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没有HAL
git checkout v2 // 有JNI,HAL
git checkout v3 // add MODULE TAG, DEVICE TAG
JNI 向上提供本地函数, 向下加载HAL文件并调用HAL的函数
HAL 负责访问驱动程序执行硬件操作
dlopen
external\chromium_org\third_party\hwcplus\src\hardware.c (参考代码)
hw_get_module("led")
1. 模块名==>文件名
hw_get_module_by_class("led", NULL)
name = "led"
property_get xxx是某个属性
hw_module_exists 判断是否存在led.xxx.so
它用来判断"name"."subname".so文件是否存在
查找的目录：
a. HAL_LIBRARY_PATH 环境变量
b. /vendor/lib/hw
c. /system/lib/hw
/vendor/lib/hw 这个目录下没有文件，tiny4412所以只能去/system/lib/hw这个目录下找
2. 加载
load
dlopen(filename)
dlsym("HMI") 从SO文件中获得名为HMI的hw_module_t结构体
strcmp(id, hmi->id) 判断名字是否一致(hmi->id, "led")
V2:
(3) JNI: 重新上传
frameworks/base/services/core/jni/com_android_server_LedService.cpp
(4) HAL: led_hal.h
led_hal.c
把新文件上传到服务器, 所在目录:
hardware/libhardware/include/hardware/led_hal.h
hardware/libhardware/modules 在这个目录下创建一个目录led,放入led_hal.c和自己写一个Android.mk
hardware/libhardware/modules/led/led_hal.c
hardware/libhardware/modules/led/Android.mk
Android.mk内容如下:
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)
编译：
$ mmm frameworks/base/services
$ mmm hardware/libhardware/modules/led
$ make snod
$ ./gen-img.sh
最终生成system.img文件
打印信息简介：
a. 有三类打印信息: app, system, radio
程序里使用 ALOGx, SLOGx, RLOGx来打印
b. x表示6种打印级别，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. 打印出来的格式为:
I/LedHal ( 1987): led_open : 65
(级别) LOG_TAG 进程号 打印信息
d. 使用 logcat 命令查看
logcat LedHal:I *:S
选出自己感兴趣的信息：
和上一个章节相比，主要修改了
com_android_server_LedService.cpp
添加了led_hal.h led_hal.c Android.mk
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));
}
}
led_hal.c
#define LOG_TAG "LedHal"
/* 1. 实现一个名为HMI的hw_module_t结构体 */
/* 2. 实现一个open函数, 它返回led_device_t结构体 */
/* 3. 实现led_device_t结构体 */
/* 参考 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;
else
return -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,
};
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_DECLS
struct 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