https://harmonyos.51cto.com
一、流程总览
驱动调用的流程和纯代码开发的流程十分相似，本文着重点在于驱动调用的逻辑。
创建目录及相应源码文件–>编写驱动调用代码–>编写编译构建文件BUILD.gn–>编译烧录运行
二、源码目录结构
在./applications/BearPi/BearPi-HM_Micro/samples/目录下创建
my_led_app 源码目录
*my_led_app.c 驱动调用源码
*BUILD.gn 源码编译脚本
如图所示
三、编写驱动调用代码
在my_led_app.c中编写如下代码
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <unistd.h>
#include <stdio.h>
#include "hdf_sbuf.h"
#include "hdf_io_service_if.h"
#define LED_WRITE_READ 1
#define LED_SERVICE "hdf_led"
static int SendEvent(struct HdfIoService *serv, uint8_t eventData)
{
int ret = 0;
struct HdfSBuf *data = HdfSBufObtainDefaultSize();
if (data == NULL)
{
printf("fail to obtain sbuf data!\r\n");
return 1;
}
struct HdfSBuf *reply = HdfSBufObtainDefaultSize();
if (reply == NULL)
{
printf("fail to obtain sbuf reply!\r\n");
ret = HDF_DEV_ERR_NO_MEMORY;
goto out;
}
if (!HdfSbufWriteUint8(data, eventData))
{
printf("fail to write sbuf!\r\n");
ret = HDF_FAILURE;
goto out;
}
ret = serv->dispatcher->Dispatch(&serv->object, LED_WRITE_READ, data, reply);
if (ret != HDF_SUCCESS)
{
printf("fail to send service call!\r\n");
goto out;
}
int replyData = 0;
if (!HdfSbufReadInt32(reply, &replyData))
{
printf("fail to get service call reply!\r\n");
ret = HDF_ERR_INVALID_OBJECT;
goto out;
}
printf("\r\nGet reply is: %d\r\n", replyData);
out:
HdfSBufRecycle(data);
HdfSBufRecycle(reply);
return ret;
}
int main(int argc, char **argv)
{
int i;
struct HdfIoService *serv = HdfIoServiceBind(LED_SERVICE);
if (serv == NULL)
{
printf("fail to get service %s!\r\n", LED_SERVICE);
return HDF_FAILURE;
}
for (i=0; i < argc; i++)
{
printf("\r\nArgument %d is %s.\r\n", i, argv[i]);
}
SendEvent(serv, atoi(argv[1]));
HdfIoServiceRecycle(serv);
printf("exit");
return HDF_SUCCESS;
}这一部分是本文的重点部分
OpenHarmony的设备开发中的驱动调用与单片机的驱动开发不太相同，以往单片机的驱动调用往往是采用库函数调用的方式，但OpenHarmony的驱动调用采用的是驱动程序暴露出一个server，程序通过Dispatch发送指令的方式。有点类似与ROS的消息通信机制中的话题发布和订阅。在OpenHarmony中驱动调用的这部分程序属于用户程序，是用户态的内容，而驱动是内核态的内容。所以用户程序无法直接访问驱动，上面代码通过Dispatch向驱动程序发送指令从而实现LED灯的亮灭。
3.1 发送指令到驱动程序
我们看下my_led_app.c中SendEvent函数中通过Dispatch发送到驱动的代码
ret = serv->dispatcher->Dispatch(&serv->object, LED_WRITE_READ, data, reply);
if (ret != HDF_SUCCESS)
{
printf("fail to send service call!\r\n");
goto out;
}
int replyData = 0;这段代码实现将指令发送到驱动程序
驱动程序指令接受的的代码在上一篇文章中的led.c驱动代码中的LedDriverDispatch函数
// Dispatch是用来处理用户态发下来的消息
int32_t LedDriverDispatch(struct HdfDeviceIoClient *client, int cmdCode, struct HdfSBuf *data, struct HdfSBuf *reply)
{
uint8_t contrl;
HDF_LOGE("Led driver dispatch");
if (client == NULL || client->device == NULL)
{
HDF_LOGE("Led driver device is NULL");
return HDF_ERR_INVALID_OBJECT;
}
switch (cmdCode)
{
case LED_WRITE_READ:
HdfSbufReadUint8(data,&contrl);
switch (contrl)
{
case LED_ON:
GpioWrite(g_Stm32Mp1ILed.gpioNum, GPIO_VAL_LOW);
status = 1;
break;
case LED_OFF:
GpioWrite(g_Stm32Mp1ILed.gpioNum, GPIO_VAL_HIGH);
status = 0;
break;
case LED_TOGGLE:
if(status == 0)
{
GpioWrite(g_Stm32Mp1ILed.gpioNum, GPIO_VAL_LOW);
status = 1;
}
else
{
GpioWrite(g_Stm32Mp1ILed.gpioNum, GPIO_VAL_HIGH);
status = 0;
}
break;
default:
break;
}
if (!HdfSbufWriteInt32(reply, status))
{
HDF_LOGE("replay is fail");
return HDF_FAILURE;
}
break;
default:
break;
}
return HDF_SUCCESS;
}3.2 从驱动程序接受数据
刚刚实现了用户态向内核态发送指令，同理，内核态也可以向用户态发送数据。
让我们看看驱动代码中向用户发送LED状态信息的代码(在led.c中LedDriverDispatch函数的一部分)
if (!HdfSbufWriteInt32(reply, status))
{
HDF_LOGE("replay is fail");
return HDF_FAILURE;
}下面是用户程序接收的部分
if (!HdfSbufReadInt32(reply, &replyData))
{
printf("fail to get service call reply!\r\n");
ret = HDF_ERR_INVALID_OBJECT;
goto out;
}
printf("\r\nGet reply is: %d\r\n", replyData);四、编写编译构建文件BUILD.gn
在BUILD.gn中添加以下代码
import("//build/lite/config/component/lite_component.gni")
HDF_FRAMEWORKS = "//drivers/framework"
executable("led_lib") {
output_name = "my_led"
sources = [
"my_led_app.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",
]
}
lite_component("my_led_app") {
features = [
":led_lib",
]
}五、编译烧录
参考之前文章Linux下配置小熊派-鸿蒙·叔设备开发(南向)的开发环境
六、运行
串口连接小熊派终端
./bin/my_led 0 #关闭LED
./bin/my_led 1 #开启LED
./bin/my_led 2 #翻转LED
