Spinel vendor hooks - how to access received frame in VendorHandleValueIs(aKey)

[boumabouma]

TLDR: I don't understand how I can get access to the received data (body) in VendorHandleValueIs(aKey), it is not passed as parameter and doesn't seem to be available otherwise. Am I misunderstanding how to use these hooks?

I'm trying to use the Spinel Vendor Hooks to communicate with an RCP while the OpenThread stack is running. In particular, to stream raw bytes data back and forth (cut into Spinel frames of course). My host is a POSIX system, the RCP node is running on an ESP32C6 (FreeRtos based firmware with ESP HAL and OpenThread).

I couldn't find any documentation, but I did find example_vendor_hook.hpp and .cpp. I reverse engineered how everything should probably work and successfully set OT_SPINEL_VENDOR_HOOK_HEADER, OT_SPINEL_VENDOR_HOOK_SOURCEandOT_SPINEL_VENDOR_HOOK_SOURCE_DIR`.

I'm currently focussing on the host side, which should be the master and initiate setting a property (raw data stream) and then expects a response (raw data).

Looking at example_vendor_hook.*, and the source code of radio_spinel.cpp I arrived at the following implementation of VendorRadioSpinel.

otError VendorRadioSpinel::SendOtaData(uint8_t* buf, size_t len)
{
    return Set(static_cast<spinel_prop_key_t>(SPINEL_PROP_VENDOR_DONGLE_OTA),
               SPINEL_DATATYPE_ARRAY_S(SPINEL_DATATYPE_UINT8_S) SPINEL_DATATYPE_UINT32_S, buf, len);
}


// Implement vendor notification handler
otError RadioSpinel::VendorHandleValueIs(spinel_prop_key_t aPropKey)
{
    otError error = OT_ERROR_NONE;

    switch (aPropKey)
    {
    case SPINEL_PROP_VENDOR_DONGLE_OTA:
    {
        // Where is the data?
        break;
    }
    default:
        error = OT_ERROR_NOT_FOUND;
        break;
    }
    return error;
}

I think I understand how to use Set() and how this will generate a Spinel frame and send it.

However, I don't understand how to get the incoming data. I found that:

1. VendorHandleValueIs(aKey) is invoked by void RadioSpinel::HandleValueIs(spinel_prop_key_t aKey, const uint8_t *aBuffer, uint16_t aLength). This function is a large if/else train with handlers for each aKey.
2. In the body of each handler, the received data (aBuffer and aLength) are unpacked / used to process the incoming value.
3. But when (in the final else if block) the call to VendorHandleValueIs(aKey) is made, aBuffer and aLength are not passed.

The comments in example_vendor_hook.cpp and radio_spinel.hpp describing VendorHandleValueIs(aKey) are contradicting each other. One is saying data should be fetched from "the NCP buffer". The other is saying data should be pushed into "the NCP buffer". It is not clear to me how to do either of those things.

I don't understand how I can get access to the received data (body) in VendorHandleValueIs(aKey) if it is not passed. Am I misunderstanding how to use these hooks?

Thank you for any input you may provide.

[abtink]

Support for the RadioSpinel vendor hook was added in the following PR:

• [spinel] add vendor hook for the host side of spinel #9560

I am not personally familiar with the RadioSpinel vendor hook.

I designed the Vendor-related support on the RCP/NCP side. In those modules, NcpBase::VendorGetPropertyHandler and VendorSetPropertyHandler have access to the mEncoder and mDecoder members, which can be used to encode the "getprop" result or decode the value content from a received Spinel "setprop" message.

It appears RadioSpinel::VendorHandleValueIs was intended to follow the same pattern but missed that RadioSpinel does not use Spinel::Encoder or Spinel::Decoder, and therefore has no way to access the received content. I agree that this implementation seems to be flawed because it provides no way to get the content.

It seems reasonable to me to update VendorHandleValueIs to pass the content.

@thcu-gp, can you also please provide your input?

[thcu-gp]

The application I used if for

• only used VendorSetPropertyHandler and VendorGetPropertyHandler. Those only use the aKey since they have access to mEncoder and mDecoder, nu buffers were needed (I might have mixed up the VendorSetPropertyHandler and VendorHandleValueIs when writing the example file
• had it's own extension file, so the example files were never used (and only had to compile)

Seeing @abtink's analysis, the VendorHandleValueIs is probably incomplete and need buffer and length arguments

[boumabouma]

Thank you both for your answers. How to proceed?