HarmonyOS 鸿蒙驱动消息机制管理_鸿蒙消息推送机制(2)，HarmonyOS鸿蒙移动应用开发教程清华大学

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 here return HdfDeviceSendEvent(client->device, cmdCode, data); }

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