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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。
消息机制的功能主要有以下两种:
表 1 消息机制接口
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;
...
}
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。
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;
}
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
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", 0);
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;
}
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_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;
}
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", 0);
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;
}
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);
}
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