Android车机DIY开发之软件篇(十八)从HAL到APP编程

本文链接：https://blog.youkuaiyun.com/u010163301/article/details/145945163

一、HAL编写

/hardware/libhardware/include/hardware 添加hello.h
/hardware/libhardware/modules 添加hello文件夹下面是hello.c和amdroid.bp文件
hello.h文件如下

#include <sys/cdefs.h>
#include <sys/types.h>
#include <hardware/hardware.h>
//HAL模块名
#define HELLO_HARDWARE_MODULE_ID "hello"
//HAL版本号
#define HELLO_MODULE_API_VERSION_1_0 HARDWARE_MODULE_API_VERSION(0, 1)
//设备名
#define HARDWARE_HELLO "hello"

//自定义HAL模块结构体
typedef struct hello_module {
    struct hw_module_t common;
} hello_module_t;

//自定义HAL设备结构体
typedef struct hello_device {
    struct hw_device_t common;
    //加法函数
    int (*additionTest)(const struct hello_device *dev,int a,int b,int* total);
} hello_device_t;

//给外部调用提供打开设备的函数
static inline int _hello_open(const struct hw_module_t *module,
        hello_device_t **device) {
    return module->methods->open(module, HARDWARE_HELLO,
            (struct hw_device_t **) device);
}

hello.c文件如下：

#define LOG_TAG "HelloHal"

#include <malloc.h>
#include <stdint.h>
#include <string.h>

#include <log/log.h>

#include <hardware/hello.h>
#include <hardware/hardware.h>

//加法函数实现
static int additionTest(const struct hello_device *dev,int a,int b,int *total)
{
	if(!dev){
		return -1;
	}
    *total = a + b;
    return 0;
}

//关闭设备函数
static int hello_close(hw_device_t *dev)
{
    if (dev) {
        free(dev);
        return 0;
    } else {
        return -1;
    }
}
//打开设备函数
static int hello_open(const hw_module_t* module,const char __unused *id,
                            hw_device_t** device)
{
    if (device == NULL) {
        ALOGE("NULL device on open");
        return -1;
    }

    hello_device_t *dev = malloc(sizeof(hello_device_t));
    memset(dev, 0, sizeof(hello_device_t));

    dev->common.tag = HARDWARE_DEVICE_TAG;
    dev->common.version = HELLO_MODULE_API_VERSION_1_0;
    dev->common.module = (struct hw_module_t*) module;
    dev->common.close = hello_close;
    dev->additionTest = additionTest;

    *device = &(dev->common);
    return 0;
}

static struct hw_module_methods_t hello_module_methods = {
    .open = hello_open,
};
//导出符号HAL_MODULE_INFO_SYM，指向自定义模块
hello_module_t HAL_MODULE_INFO_SYM = {
    .common = {
        .tag                = HARDWARE_MODULE_TAG,
        .module_api_version = HELLO_MODULE_API_VERSION_1_0,
        .hal_api_version    = HARDWARE_HAL_API_VERSION,
        .id                 = HELLO_HARDWARE_MODULE_ID,
        .name               = "Demo Hello HAL",
        .author             = "dongjiao.tang@tcl.com",
        .methods            = &hello_module_methods,
    },
};

```Android.bp文件如下

```bash
cc_library_shared {
    name: "hello.default",
    relative_install_path: "hw",
    proprietary: true,
    srcs: ["hello.c"],
    header_libs: ["libhardware_headers"],
    shared_libs: ["liblog"],
}