OpenHarmony——驱动消息机制管理开发

1.将驱动配置信息中服务策略policy字段设置为2（SERVICE_POLICY_CAPACITY，policy定义）。

device_sample :: Device {
    policy = 2;
    ...
}

2.配置驱动信息中的服务设备节点权限（permission字段）是框架给驱动创建设备节点的权限，默认是0666，驱动开发者根据驱动的实际使用场景配置驱动设备节点的权限。

3.在服务实现过程中，实现服务基类成员IDeviceIoService中的Dispatch方法。

// Dispatch是用来处理用户态发下来的消息
int32_t SampleDriverDispatch(struct HdfDeviceIoClient *device, int cmdCode, struct HdfSBuf *data, struct HdfSBuf *reply)
{
    HDF_LOGI("sample driver lite A dispatch");
    return HDF_SUCCESS;
}
int32_t SampleDriverBind(struct HdfDeviceObject *device)
{
    HDF_LOGI("test for lite os sample driver A Open!");
    if (device == NULL) {
        HDF_LOGE("test for lite os sample driver A Open failed!");
        return HDF_FAILURE;
    }
    static struct ISampleDriverService sampleDriverA = {
        .ioService.Dispatch = SampleDriverDispatch,
        .ServiceA = SampleDriverServiceA,
        .ServiceB = SampleDriverServiceB,
    };
    device->service = (struct IDeviceIoService *)(&sampleDriverA);
    return HDF_SUCCESS;
}

4.驱动定义消息处理函数中的cmd类型。

#define SAMPLE_WRITE_READ 1    // 读写操作码1

5.用户态获取服务接口并发送消息到驱动。

int SendMsg(const char *testMsg)
{
    if (testMsg == NULL) {
        HDF_LOGE("test msg is null");
        return HDF_FAILURE;
    }
    struct HdfIoService *serv = HdfIoServiceBind("sample_driver");
    if (serv == NULL) {
        HDF_LOGE("fail to get service");
        return HDF_FAILURE;
    }
    struct HdfSBuf *data = HdfSbufObtainDefaultSize();
    if (data == NULL) {
        HDF_LOGE("fail to obtain sbuf data");
        return HDF_FAILURE;
    }
    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, testMsg)) {
        HDF_LOGE("fail to write sbuf");
        ret = HDF_FAILURE;
        goto out;
    }
    int ret = serv->dispatcher->Dispatch(&serv->object, SAMPLE_WRITE_READ, data, reply);
    if (ret != HDF_SUCCESS) {
        HDF_LOGE("fail to send service call");
        goto out;
    }
out:
    HdfSbufRecycle(data);
    HdfSbbufRecycle(reply);
    HdfIoServiceRecycle(serv);
    return ret;
}

6.用户态接收该驱动上报的消息。

1. 用户态编写驱动上报消息的处理函数。

   static int OnDevEventReceived(void *priv,  uint32_t id, struct HdfSBuf *data)
   {
       OsalTimespec time;
       OsalGetTime(&time);
       HDF_LOGI("%{public}s received event at %{public}llu.%{public}llu", (char *)priv, time.sec, time.usec);
   
       const char *string = HdfSbufReadString(data);
       if (string == NULL) {
           HDF_LOGE("fail to read string in event data");
           return HDF_FAILURE;
       }
       HDF_LOGI("%{public}s: dev event received: %{public}d %{public}s",  (char *)priv, id, string);
       return HDF_SUCCESS;
   }

   2.用户态注册接收驱动上报消息的操作方法。

   int RegisterListen()
   {
       struct HdfIoService *serv = HdfIoServiceBind("sample_driver");
       if (serv == NULL) {
           HDF_LOGE("fail to get service");
           return HDF_FAILURE;
       }
       static struct HdfDevEventlistener listener = {
           .callBack = OnDevEventReceived,
           .priv ="Service0"
       };
       if (HdfDeviceRegisterEventListener(serv, &listener) != 0) {
           HDF_LOGE("fail to register event listener");
           return HDF_FAILURE;
       }
       ......
       HdfDeviceUnregisterEventListener(serv, &listener);
       HdfIoServiceRecycle(serv);
       return HDF_SUCCESS;
   }

   3.驱动上报事件。

   int32_t SampleDriverDispatch(HdfDeviceIoClient *client, int cmdCode, struct HdfSBuf *data, struct HdfSBuf *reply)
   {
       ... // process api call here
       return HdfDeviceSendEvent(client->device, cmdCode, data);
   }