在A20上演示老罗的Android硬件抽象层（HAL）概要介绍和学习计划3--关于hal部分

关于/dev/hello的权限，修改的地方的方法有很多，我现在把它放在device/softwinner/wing-xxxx/下的ueventd.sun7i.rc修改：

diff --git a/ueventd.sun7i.rc b/ueventd.sun7i.rc

index d79557e..0bb9fb0 100644

--- a/ueventd.sun7i.rc

+++ b/ueventd.sun7i.rc

@@ -16,5 +16,6 @@

/dev/ttyACM2 0777 system system

/dev/gps 0777 system system

/dev/pa_dev 0777 system system

+/dev/hello 0777 system system

/dev/sunxi_mem 0666 media media

/dev/g2d 0666 system system

----------------------------------------------------------------------------------------------------

关于 HAL层的代码我也习惯喜欢放在/device/softwinner/common/hardware下面，一般不去hardware/libhardware下增加模块，但道理是一样的。

现在在device/softwinner/common/hardware/下增加hello的文件夹，这个hello文件夹放下面三个文件：

1,Android.mk:

# Copyright (C) 2008 The Android Open Source Project

#

# Licensed under the Apache License, Version 2.0 (the "License");

# you may not use this file except in compliance with the License.

# You may obtain a copy of the License at

#

# http://www.apache.org/licenses/LICENSE-2.0
#

# Unless required by applicable law or agreed to in writing, software

# distributed under the License is distributed on an "AS IS" BASIS,

# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

# See the License for the specific language governing permissions and

# limitations under the License.

LOCAL_PATH := $(call my-dir)

# HAL module implemenation, not prelinked, and stored in

# hw/<SENSORS_HARDWARE_MODULE_ID>.<ro.product.board>.so

include $(CLEAR_VARS)

LOCAL_PRELINK_MODULE := false

LOCAL_MODULE_PATH := $(TARGET_OUT_SHARED_LIBRARIES)/hw

LOCAL_MODULE := hello.default

LOCAL_MODULE_TAGS := eng optional

LOCAL_SRC_FILES := hello.c

LOCAL_SHARED_LIBRARIES := liblog libcutils libdl

include $(BUILD_SHARED_LIBRARY)

2,hello.h:

#ifndef ANDROID_HELLO_INTERFACE_H

#define ANDROID_HELLO_INTERFACE_H

#include <hardware/hardware.h>

__BEGIN_DECLS

/*定义模块ID*/

#define HELLO_HARDWARE_MODULE_ID "hello"

/*硬件模块结构体*/

struct hello_module_t {

struct hw_module_t common;

};

/*硬件接口结构体*/

struct hello_device_t {

struct hw_device_t common;

int fd;

int (*set_val)(struct hello_device_t* dev, int val);

int (*get_val)(struct hello_device_t* dev, int* val);

};

__END_DECLS

#endif

3:hello.c:

#define LOG_TAG "HelloStub"

#include <hardware/hardware.h>

#include "hello.h"

#include <fcntl.h>

#include <errno.h>

#include <utils/Atomic.h>

#include <utils/Log.h>

#include <cutils/log.h>

#include <cutils/properties.h>

#include <linux/input.h>

#include <dirent.h>

#include <math.h>

#include <stdlib.h>

#define DEVICE_NAME "/dev/hello"

#define MODULE_NAME "Hello"

#define MODULE_AUTHOR "shyluo@gmail.com"

/*设备打开和关闭接口*/

static int hello_device_open(const struct hw_module_t* module, const char* name, struct hw_device_t** device);

//static int hello_device_close(struct hw_device_t* device);

/*设备访问接口*/

//static int hello_set_val(struct hello_device_t* dev, int val);

//static int hello_get_val(struct hello_device_t* dev, int* val);

/*模块方法表*/

static struct hw_module_methods_t hello_module_methods = {

open: hello_device_open

};

/*模块实例变量*/

struct hello_module_t HAL_MODULE_INFO_SYM = {

common: {

tag: HARDWARE_MODULE_TAG,

version_major: 1,

version_minor: 0,

id: HELLO_HARDWARE_MODULE_ID,

name: MODULE_NAME,

author: MODULE_AUTHOR,

methods: &hello_module_methods,

}

};

static int hello_device_close(struct hw_device_t* device) {

struct hello_device_t* hello_device = (struct hello_device_t*)device;

if(hello_device) {

close(hello_device->fd);

free(hello_device);

}

return 0;

}

static int hello_set_val(struct hello_device_t* dev, int val) {

ALOGI("Hello Stub: set value %d to device.", val);

write(dev->fd, &val, sizeof(val));

return 0;

}

static int hello_get_val(struct hello_device_t* dev, int* val) {

if(!val) {

ALOGE("Hello Stub: error val pointer");

return -EFAULT;

}

read(dev->fd, val, sizeof(*val));

ALOGI("Hello Stub: get value %d from device", *val);

return 0;

}

static int hello_device_open(const struct hw_module_t* module, const char* name, struct hw_device_t** device) {

struct hello_device_t* dev;

dev = (struct hello_device_t*)malloc(sizeof(struct hello_device_t));

if(!dev) {

ALOGE("Hello Stub: failed to alloc space");

return -EFAULT;

}

memset(dev, 0, sizeof(struct hello_device_t));

dev->common.tag = HARDWARE_DEVICE_TAG;

dev->common.version = 0;

dev->common.module = (hw_module_t*)module;

dev->common.close = hello_device_close;

dev->set_val = hello_set_val;

dev->get_val = hello_get_val;

if((dev->fd = open(DEVICE_NAME, O_RDWR)) == -1) {

ALOGE("Hello Stub: failed to open /dev/hello -- %s.", strerror(errno));free(dev);

return -EFAULT;

}

*device = &(dev->common);

ALOGI("Hello Stub: open /dev/hello successfully.");

return 0;

}

这样就可以在编译的时候把它编译进system/lib/hw/了。