# 驱动消息机制管理 - [使用场景](#section33014541954) - [接口说明](#section538852311616) - [开发步骤](#section946912121153) ## 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

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](driver-hdf-servicemanage.md)）。 ``` 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 HdfDeviceObject *device, int cmdCode, struct HdfSBuf *data, struct HdfSBuf *reply) { HDF_LOGE("sample driver lite A dispatch"); return 0; } int32_t SampleDriverBind(struct HdfDeviceObject *device) { HDF_LOGE("test for lite os sample driver A Open!"); if (device == NULL) { HDF_LOGE("test for lite os sample driver A Open failed!"); return -1; } static struct ISampleDriverService sampleDriverA = { .ioService.Dispatch = SampleDriverDispatch, .ServiceA = SampleDriverServiceA, .ServiceB = SampleDriverServiceB, }; device->service = (struct IDeviceIoService *)(&sampleDriverA); return 0; } ``` 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 -1; } struct HdfIoService *serv = HdfIoServiceBind("sample_driver"); if (serv == NULL) { HDF_LOGE("fail to get service"); return -1; } struct HdfSBuf *data = HdfSBufObtainDefaultSize(); if (data == NULL) { HDF_LOGE("fail to obtain sbuf data"); return -1; } 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); HdfSBufRecycle(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_LOGE("%s received event at %llu.%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 -1; } HDF_LOGE("%s: dev event received: %d %s", (char *)priv, id, string); return 0; } ``` 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 -1; } static struct HdfDevEventlistener listener = { .callBack = OnDevEventReceived, .priv ="Service0" }; if (HdfDeviceRegisterEventListener(serv, &listener) != 0) { HDF_LOGE("fail to register event listener"); return -1; } ...... HdfDeviceUnregisterEventListener(serv, &listener); HdfIoServiceRecycle(serv); return 0; } ``` 3. 驱动上报事件。 ``` int32_t SampleDriverDispatch(struct HdfDeviceObject *device, int cmdCode, struct HdfSBuf *data, struct HdfSBuf *reply) { ... // process api call here return HdfDeviceSendEvent(deviceObject, cmdCode, data); } ```