【FFH】小熊派驅動調用流程（以調用LED燈驅動為例）
原創作者：Wait_Aurora
驅動調用的流程和純代碼開發的流程十分相似，本文著重點在于驅動調用的邏輯。
??https://harmonyos.51cto.com??
一、流程總覽
驅動調用的流程和純代碼開發的流程十分相似，本文著重點在于驅動調用的邏輯。
創建目錄及相應源碼文件–>編寫驅動調用代碼–>編寫編譯構建文件BUILD.gn–>編譯燒錄運行
二、源碼目錄結構
在./applications/BearPi/BearPi-HM_Micro/samples/目錄下創建
my_led_app 源碼目錄
*my_led_app.c 驅動調用源碼
*BUILD.gn 源碼編譯腳本
如圖所示
三、編寫驅動調用代碼
在my_led_app.c中編寫如下代碼
#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;
}
/* 寫入數據 */
if (!HdfSbufWriteUint8(data, eventData))
{
printf("fail to write sbuf!\r\n");
ret = HDF_FAILURE;
goto out;
}
/* 通過Dispatch發送到驅動 */
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;
/* 讀取驅動的回復數據 */
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;
/* 獲取服務 */
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;
}
這一部分是本文的重點部分
OpenHarmony的設備開發中的驅動調用與單片機的驅動開發不太相同，以往單片機的驅動調用往往是采用庫函數調用的方式，但OpenHarmony的驅動調用采用的是驅動程序暴露出一個server，程序通過Dispatch發送指令的方式。有點類似與ROS的消息通信機制中的話題發布和訂閱。在OpenHarmony中驅動調用的這部分程序屬于用戶程序，是用戶態的內容，而驅動是內核態的內容。所以用戶程序無法直接訪問驅動，上面代碼通過Dispatch向驅動程序發送指令從而實現LED燈的亮滅。
3.1 發送指令到驅動程序
我們看下my_led_app.c中SendEvent函數中通過Dispatch發送到驅動的代碼
/* 通過Dispatch發送到驅動 */
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;
這段代碼實現將指令發送到驅動程序
驅動程序指令接受的的代碼在上一篇文章中的led.c驅動代碼中的LedDriverDispatch函數
// Dispatch是用來處理用戶態發下來的消息
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)
{
/* 接收到用戶態發來的LED_WRITE_READ命令 */
case LED_WRITE_READ:
/* 讀取data里的數據，賦值給contrl */
HdfSbufReadUint8(data,&contrl);
switch (contrl)
{
/* 開燈 */
case LED_ON:
GpioWrite(g_Stm32Mp1ILed.gpioNum, GPIO_VAL_LOW);
status = 1;
break;
/* 關燈 */
case LED_OFF:
GpioWrite(g_Stm32Mp1ILed.gpioNum, GPIO_VAL_HIGH);
status = 0;
break;
/* 狀態翻轉 */
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;
}
/* 把LED的狀態值寫入reply, 可被帶至用戶程序 */
if (!HdfSbufWriteInt32(reply, status))
{
HDF_LOGE("replay is fail");
return HDF_FAILURE;
}
break;
default:
break;
}
return HDF_SUCCESS;
}
3.2 從驅動程序接受數據
剛剛實現了用戶態向內核態發送指令，同理，內核態也可以向用戶態發送數據。
讓我們看看驅動代碼中向用戶發送LED狀態信息的代碼(在led.c中LedDriverDispatch函數的一部分)
/* 把LED的狀態值寫入reply, 可被帶至用戶程序 */
if (!HdfSbufWriteInt32(reply, status))
{
HDF_LOGE("replay is fail");
return HDF_FAILURE;
}
下面是用戶程序接收的部分
/* 讀取驅動的回復數據 */
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、編寫編譯構建文件BUILD.gn
在BUILD.gn中添加以下代碼
import("http://build/lite/config/component/lite_component.gni")
HDF_FRAMEWORKS = "http://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",
"http://drivers/adapter/uhdf/posix/include",
"http://third_party/bounds_checking_function/include",
"http://base/hiviewdfx/hilog_lite/interfaces/native/innerkits",
]
deps = [
"http://base/hiviewdfx/hilog_lite/frameworks/featured:hilog_shared",
"http://drivers/adapter/uhdf/manager:hdf_core",
"http://drivers/adapter/uhdf/posix:hdf_posix_osal",
]
}
lite_component("my_led_app") {
features = [
":led_lib",
]
}
五、編譯燒錄
參考之前文章Linux下配置小熊派-鴻蒙·叔設備開發(南向)的開發環境
六、運行
串口連接小熊派終端
./bin/my_led 0 #關閉LED
./bin/my_led 1 #開啟LED
./bin/my_led 2 #翻轉LED
??https://harmonyos.51cto.com??
責任編輯：jianghua
來源：
鴻蒙社區
