Android 6.0中添加硬件抽象层(HAL)

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在目录hardware/libhardware/include/hardware中添加freg.h文件

hardware/└── freg.h

在目录hardware/libhardware/modules中添加freg目录，并在freg目录中添加如下文件

freg/├── Android.mk└── freg.cpp

freg.h和freg.cpp是源代码文件， Android.mk是模块的编译脚本文件

freg.h文件代码

/************************************************************************** 文件: freg.h* 作者: fantasy* 邮箱: fantasy@gmail.com * 创建时间: 2016年07月22日 星期五 20时17分16秒*************************************************************************/#ifndef ANDROID_FREG_INTERFACE_H#define ANDROID_FREG_INTERFACE_H#include <hardware/hardware.h>__BEGIN_DECLS/** * 定义模块ID */#define FREG_HARDWARE_MODULE_ID "freg"/** * 定义设备ID */#define FREG_HARDWARE_DEVICE_ID "freg"#define FREG_MODULE_API_VERSION_1_0 HARDWARE_MODULE_API_VERSION(1, 0)#define FREG_MODULE_API_VERSION_CURRENT FREG_MODULE_API_VERSION_1_0#define FREG_DEVICE_API_VERSION_1_0 HARDWARE_DEVICE_API_VERSION(1, 0)#define FREG_DEVICE_API_VERSION_CURRENT FREG_DEVICE_API_VERSION_1_0/** * 自定义模块结构体 */struct freg_module_t{    struct hw_module_t common;};/** * 自定义设备结构体 */struct freg_device_t{    struct hw_device_t common;    int fd;    int (*set_val)(struct freg_device_t *dev, int val);    int (*get_val)(struct freg_device_t *dev, int *val);};__END_DECLS#endif

freg.cpp文件

/************************************************************************** 文件: freg.cpp* 作者: fantasy* 邮箱: fantasy@gmail.com * 创建时间: 2016年07月22日 星期五 20时25分31秒*************************************************************************/#define LOG_TAG "freg_hw"#include <hardware/hardware.h>#include <hardware/freg.h>#include <fcntl.h>#include <errno.h>#include <malloc.h>#include <cutils/log.h>#include <cutils/atomic.h>#define DEVICE_NAME "/dev/freg"#define MODULE_NAME "Freg"#define MODULE_AUTHOR "wuxiaoer@gmail.com"/** * 设备打开和关闭接口 */static int freg_device_open(const struct hw_module_t *module, const char *id, struct hw_device_t **device);static int freg_device_close(struct hw_device_t *device);/** * 设备寄存器读写接口 */static int freg_get_val(struct freg_device_t *dev, int *val);static int freg_set_val(struct freg_device_t *dev, int val);/** * 定义模块操作方法结构体变量 */static struct hw_module_methods_t freg_module_methods = {    .open = freg_device_open,};/** * 定义模块结构体变量 */struct freg_module_t HAL_MODULE_INFO_SYM = {    .common = {        .tag = HARDWARE_MODULE_TAG,        .version_major = 1,        .version_minor = 0,        .id = FREG_HARDWARE_MODULE_ID,        .name = MODULE_NAME,        .author = MODULE_AUTHOR,        .methods = &freg_module_methods,    }};static int freg_device_open(const struct hw_module_t *module, const char *id, struct hw_device_t **device){    if (!strcmp(id, FREG_HARDWARE_DEVICE_ID))    {        struct freg_device_t *dev;        dev = (struct freg_device_t*)malloc(sizeof(struct freg_device_t));        if (!dev)        {            ALOGE("Failed to alloc space for freg_device_t.");            return -ENOMEM;        }        memset(dev, 0, sizeof(struct freg_device_t));        dev->common.tag = HARDWARE_DEVICE_TAG;        dev->common.version = HARDWARE_DEVICE_API_VERSION(1, 0);        dev->common.module = (hw_module_t*)module;        dev->common.close = freg_device_close;        dev->set_val = freg_set_val;        dev->get_val = freg_get_val;        if ((dev->fd = open(DEVICE_NAME, O_RDWR)) == -1)        {            ALOGE("Failed to open device file /dev/freg -- %s.", strerror(errno));            free(dev);            return -EFAULT;        }else        {            ALOGE("Open device file /dev/freg successfully.");        }       // *device = &(dev->common);        *device = (hw_device_t*)dev;        return 0;    }    return -EFAULT;}static int freg_device_close(struct hw_device_t *device){    struct freg_device_t *freg_device = (struct freg_device_t*)device;    if (freg_device)    {        close(freg_device->fd);        free(freg_device);    }    return 0;}static int freg_get_val(struct freg_device_t *dev, int *val){    if (!dev)    {        ALOGE("Null dev pointer");        return -EFAULT;    }    if (!val)    {        ALOGE("Null val pointer");        return -EFAULT;    }    read(dev->fd, val, sizeof(*val));    ALOGI("Get value %d from device file /dev/freg.", *val);    return 0;}static int freg_set_val(struct freg_device_t *dev, int val){    if (!dev)    {        ALOGE("Null dev pointer");        return -EFAULT;    }    ALOGI("Set value %d to device file /dev/freg.", val);    write(dev->fd, &val, sizeof(val));    return 0;}

Android.mk文件

LOCAL_PATH := $(call my-dir)include $(CLEAR_VARS)LOCAL_MODULE := freg.defaultLOCAL_MODULE_RELATIVE_PATH := hwLOCAL_SRC_FILES := freg.cppLOCAL_SHARED_LIBRARIES := liblog libcutilsLOCAL_MODULE_TAGS := optional#LOCAL_CFLAGS := -Wno-unused-parameterinclude $(BUILD_SHARED_LIBRARY)

$ mmm ./hardware/libhardware/modules/freg/

然后通过如下命令打包生成的.so文件

$ make snod

通过adb shell查看是否生成.so文件

参考

1. 《Android系统源代码情景分析》第2.3节

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