IOUserClientMethodArguments structure* always null

Question

Created Aug ’20

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I'm trying to communicate application <-> driverkit driver.

In IOUserClient ExternalMethod method, IOUserClientMethodArguments->structureOutput and IOUserClientMethodArguments->structureOutputDescriptor always null.

below is my code

- IOUserClient --

Code Block languageAbout IOUserClientMethodDispatch
Methods[1].function = myClient::myFunction;
Methods[1].checkScalarInputCount = 10;
Methods[1].checkStructureInputSize = kIOUserClientVariableStructureSize;
Methods[1].checkScalarOutputCount = 10;
Methods[1].checkStructureOutputSize = kIOUserClientVariableStructureSize;

- MyApplication --

Code Block languageuint64_t ScalarIn[10];
uint64_t ScalarOut[10];
uint16_t SturctureOut = 0;
size_t StructureOutSize = sizeof(uint16_t);
kern_return_t kRet = IOConnectCallMethod(Device, 1, ScalarIn, 10, NULL, 0, ScalarOut, 10, &StructureOut, (size_t*)&StructureOutSize);

IOConnectCallMethod return Success.
But In Client ExternalMethod, structureOutput and structureOutputDescriptor always null. structureOutputMaximumSize is correct.

Does anyone can help, how can i pass structure param correctly?

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Answer 1

anshu1102 OP

Sep ’20

Hi,
I'm also facing same issue. For me also structureOutput value as 0 receiving in UserClient.

One more issue I'm facing is that even structure Input data is not matching what sent by application.

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