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

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本篇文章主要介绍了"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",主要涉及到在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部分方面的内容,对于在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部分感兴趣的同学可以参考一下。

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 "[email protected]"   /*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。

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