HarmonyOS 鸿蒙驱动消息机制管理-编程知识

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：

用户态应用发送消息到驱动。
用户态应用接收驱动主动上报事件。

表1 消息机制接口

方法	描述
struct HdfIoService HdfIoServiceBind(const char serviceName);	用户态获取驱动的服务，获取该服务之后通过服务中的Dispatch方法向驱动发送消息。
void HdfIoServiceRecycle(struct HdfIoService *service);	释放驱动服务。
int HdfDeviceRegisterEventListener(struct HdfIoService target, struct HdfDevEventlistener listener);	用户态程序注册接收驱动上报事件的操作方法。
int HdfDeviceSendEvent(struct HdfDeviceObject deviceObject, uint32_t id, struct HdfSBuf data);	驱动主动上报事件接口。

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）。

   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

4.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。

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;}

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;}

驱动上报事件。

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

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