驱动消息机制管理

使用场景

当用户态应用和内核态驱动需要交互时，可以使用HDF框架的消息机制来实现。

接口说明

消息机制的功能主要有以下两种：

1. 用户态应用发送消息到驱动。
2. 用户态应用接收驱动主动上报事件。

表 1 消息机制接口

开发步骤

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

```

1. device_sample :: Device {
2. policy = 2;
3. ...
4. } ```
5. 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。
6. 在服务实现过程中，实现服务基类成员IDeviceIoService中的Dispatch方法。

```

1. // Dispatch是用来处理用户态发下来的消息
2. int32_t SampleDriverDispatch(struct HdfDeviceObject device, int cmdCode, struct HdfSBuf data, struct HdfSBuf *reply)
3. {
4. HDF_LOGE("sample driver lite A dispatch");
5. return 0;
6. }
7. int32_t SampleDriverBind(struct HdfDeviceObject *device)
8. {
9. HDF_LOGE("test for lite os sample driver A Open!");
10. if (device == NULL) {
11. HDF_LOGE("test for lite os sample driver A Open failed!");
12. return -1;
13. }
14. static struct ISampleDriverService sampleDriverA = {
15. .ioService.Dispatch = SampleDriverDispatch,
16. .ServiceA = SampleDriverServiceA,
17. .ServiceB = SampleDriverServiceB,
18. };
19. device->service = (struct IDeviceIoService *)(&sampleDriverA);
20. return 0;
21. } ```
22. 驱动定义消息处理函数中的cmd类型。

```

1. define SAMPLE_WRITE_READ 1 // 读写操作码1

   ```
2. 用户态获取服务接口并发送消息到驱动。

```

1. int SendMsg(const char *testMsg)
2. {
3. if (testMsg == NULL) {
4. HDF_LOGE("test msg is null");
5. return -1;
6. }
7. struct HdfIoService *serv = HdfIoServiceBind("sample_driver", 0);
8. if (serv == NULL) {
9. HDF_LOGE("fail to get service");
10. return -1;
11. }
12. struct HdfSBuf *data = HdfSBufObtainDefaultSize();
13. if (data == NULL) {
14. HDF_LOGE("fail to obtain sbuf data");
15. return -1;
16. }
17. struct HdfSBuf *reply = HdfSBufObtainDefaultSize();
18. if (reply == NULL) {
19. HDF_LOGE("fail to obtain sbuf reply");
20. ret = HDF_DEV_ERR_NO_MEMORY;
21. goto out;
22. }
23. if (!HdfSbufWriteString(data, testMsg)) {
24. HDF_LOGE("fail to write sbuf");
25. ret = HDF_FAILURE;
26. goto out;
27. }
28. int ret = serv->dispatcher->Dispatch(&serv->object, SAMPLE_WRITE_READ, data, reply);
29. if (ret != HDF_SUCCESS) {
30. HDF_LOGE("fail to send service call");
31. goto out;
32. }
33. out:
34. HdfSBufRecycle(data);
35. HdfSBufRecycle(reply);
36. HdfIoServiceRecycle(serv);
37. return ret;
38. } ```

39. 用户态接收该驱动上报的消息。

40. 用户态编写驱动上报消息的处理函数。

    ```

    1. static int OnDevEventReceived(void priv, uint32_t id, struct HdfSBuf data)
    2. {
    3. OsalTimespec time;
    4. OsalGetTime(&time);

    5. HDF_LOGE("%s received event at %llu.%llu", (char *)priv, time.sec, time.usec);

    6. const char *string = HdfSbufReadString(data);

    7. if (string == NULL) {
    8. HDF_LOGE("fail to read string in event data");
    9. return -1;
    10. }
    11. HDF_LOGE("%s: dev event received: %d %s", (char *)priv, id, string);
    12. return 0;
    13. } ```
    14. 用户态注册接收驱动上报消息的操作方法。

    ```

    1. int RegisterListen()
    2. {
    3. struct HdfIoService *serv = HdfIoServiceBind("sample_driver", 0);
    4. if (serv == NULL) {
    5. HDF_LOGE("fail to get service");
    6. return -1;
    7. }
    8. static struct HdfDevEventlistener listener = {
    9. .callBack = OnDevEventReceived,
    10. .priv ="Service0"
    11. };
    12. if (HdfDeviceRegisterEventListener(serv, &listener) != 0) {
    13. HDF_LOGE("fail to register event listener");
    14. return -1;
    15. }
    16. ......
    17. HdfDeviceUnregisterEventListener(serv, &listener);
    18. HdfIoServiceRecycle(serv);
    19. return 0;
    20. } ```
    21. 驱动上报事件。

    ```

    1. int32_t SampleDriverDispatch(struct HdfDeviceObject device, int cmdCode, struct HdfSBuf data, struct HdfSBuf *reply)
    2. {
    3. ... // process api call here
    4. return HdfDeviceSendEvent(deviceObject, cmdCode, data);
    5. } ```