HDF驱动框架探路：openharmony最新源码，打通应用态到内核态

Posted 2021-12-03 HarmonyOS技术社区

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老规矩还是将最终希望跑出来的效果放出来。如下：

@toc

前言

1.首先本文章的源码是2021.11.25拉的openharmony的master分支。之前也有一些大神基于3516应用态打通到了内核态，不过都很久远了，尤其是3.0LTS发布之后，整个框架都改动过了，按照大神们的操作我这边基于最新的源码都没有测试成功。有大佬可以留言指导一拨儿。
2.本文章是基于Hi3516轻量系统来打造的。
应用态打通内核态的总体框架图

从上图可以很直观的看出驱动开发的过程中基于linux开发和基于openharmony开发的最大区别

1.linux驱动开发中会涉及到应用层的glic等，以及驱动层的内核函数调用，但是在openharmony这些以及都被HDF框架给隐藏起来了，所以我们只需要根据HDF框架来进行openharmony框架开发，就可以了。
2.openharmony应用层其实是调用了HDF框架的驱动消息机制
1.应用程序

2.1 应用层业务代码
1.在源码根目录下新建myapp目录

2.然后进入myapp目录新建helloworld_test.c，然后将下列代码拷贝入内


#include <fcntl.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <unistd.h>
#include "hdf_log.h"
#include "hdf_sbuf.h"
#include "hdf_io_service_if.h"

#define HDF_LOG_TAG "sample_test"
#define SAMPLE_SERVICE_NAME "GPIO_TEST"

#define SAMPLE_WRITE_READ 0

int g_replyFlag = 0;

static int OnDevEventReceived(void priv, uint32_t id, struct HdfSBuf data)
{
const char string = HdfSbufReadString(data);
if (string == NULL) {
HDF_LOGE("fail to read string in event data");
g_replyFlag = 1;
return HDF_FAILURE;
}
HDF_LOGE("%s: dev event received: %u %s", (char )priv, id, string);
g_replyFlag = 1;
return HDF_SUCCESS;
}

static int SendEvent(struct Hdfioservice serv, char eventData)
{
int ret = 0;
struct HdfSBuf *data = HdfSBufObtainDefaultSize();
if (data == NULL) {
HDF_LOGE("fail to obtain sbuf data");
return 1;
}

struct HdfSBuf *reply = HdfSBufObtainDefaultSize();
if (reply == NULL) {
    HDF_LOGE("fail to obtain sbuf reply");
    ret = HDF_DEV_ERR_NO_MEMORY;
    goto out;
}

if (!HdfSbufWriteString(data, eventData)) {
    HDF_LOGE("fail to write sbuf");
    ret = HDF_FAILURE;
    goto out;
}

ret = serv->dispatcher->Dispatch(&serv->object, SAMPLE_WRITE_READ, data, reply);
if (ret != HDF_SUCCESS) {
    HDF_LOGE("fail to send service call");
    goto out;
}

int replyData = 0;
if (!HdfSbufReadInt32(reply, &replyData)) {
    HDF_LOGE("fail to get service call reply");
    ret = HDF_ERR_INVALID_OBJECT;
    goto out;
}
HDF_LOGE("Get reply is: %d", replyData);

out:
HdfSBufRecycle(data);
HdfSBufRecycle(reply);
return ret;
}

int main()
{
char sendData = "hi";
struct HdfIoService serv = HdfIoServiceBind(SAMPLE_SERVICE_NAME);
if (serv == NULL) {
HDF_LOGE("fail to get service %s", SAMPLE_SERVICE_NAME);
return HDF_FAILURE;
}
HDF_LOGE("success to get service %s", SAMPLE_SERVICE_NAME);

static struct HdfDevEventlistener listener = {
    .callBack = OnDevEventReceived,
    .priv ="Service0"
};

if (HdfDeviceRegisterEventListener(serv, &listener) != HDF_SUCCESS) {
    HDF_LOGE("fail to register event listener");
    return HDF_FAILURE;
}
HDF_LOGE("success to register event listener");
if (SendEvent(serv, sendData)) {
    HDF_LOGE("fail to send event");
    return HDF_FAILURE;
}

/* wait for event receive event finishing */
while (g_replyFlag == 0) {
    sleep(1);
}

if (HdfDeviceUnregisterEventListener(serv, &listener)) {
    HDF_LOGE("fail to  unregister listener");
    return HDF_FAILURE;
}

HdfIoServiceRecycle(serv);
return HDF_SUCCESS;

}

## 1.2 应用层业务代码以可执行文件编译进系统
- 进入源码目录找到drivers/adapter/uhdf/manager/BUILD.gn 文件，然后在文件末尾拷贝下述代码。

```c
HDF_FRAMEWORKS = "//drivers/framework"

executable("helloworld_test") {
  sources = ["//myapp/helloworld_test.c" ]
  include_dirs = [
    "$HDF_FRAMEWORKS/ability/sbuf/include",
    "$HDF_FRAMEWORKS/core/shared/include",
    "$HDF_FRAMEWORKS/core/host/include",
    "$HDF_FRAMEWORKS/core/master/include",
    "$HDF_FRAMEWORKS/include/core",
    "$HDF_FRAMEWORKS/include/utils",
    "$HDF_FRAMEWORKS/utils/include",
    "$HDF_FRAMEWORKS/include/osal",
    "//drivers/adapter/uhdf/posix/include",
    "//third_party/bounds_checking_function/include",
    "//base/hiviewdfx/hilog_lite/interfaces/native/innerkits",
  ]

  deps = [
    "//base/hiviewdfx/hilog_lite/frameworks/featured:hilog_shared",
    "//drivers/adapter/uhdf/manager:hdf_core",
    "//drivers/adapter/uhdf/posix:hdf_posix_osal",
  ]

  public_deps = [ "//third_party/bounds_checking_function:libsec_shared" ]
  defines = [ "__USER__" ]

  cflags = [
    "-Wall", 
    "-Wextra",
    "-Wno-format",
    "-Wno-format-extra-args",
  ]
}