Upgrading notes

API changes and code migration

AttributePersistenceProvider

AttributePersistenceProvider was moved to src/app/persistence and its interface was updated:

• Read/write operate over pure buffers, without type information

This update was done so that the interface is decoupled from ember and metadata types. The reasons for this approach:

• simpler/more modular code (easier to maintain)
• Have more generic storage support (including variable size data)
• Ability to preserve backward compatibility with existing products without increasing flash size by adding additional abstraction layers

Callers will validate data validity on read instead of relying on data validation by the persistence provider.

See https://github.com/project-chip/connectedhomeip/pull/39693 for changes.

The only change is that the EmberAfAttributeMetadata argument is not passed in anymore into Read and implementations are expected to just return the opaque data stored. API updates changed:

• FROM OLD

  ReturnErrorOnFailure(ReadValue(aPath, aMetadata, aByteSpan));
  

• TO NEW

  ReturnErrorOnFailure(ReadValue(aPath, aByteSpan));
  ReturnErrorOnFailure(ValidateData(aByteSpan, aMetadata));
  

  Where callers would implement ValidateData. Implementations do not have the use of aMetadata anymore and cluster data is opaque now.

CommandHandler

CommandHandler ability to directly invoke Prepare/TLV-Write/Finish cycles has been changed to only expose AddResponse/AddStatus/AddClusterSpecific*.

Original versions of CommandHandler exposed the following low-level implementation-specific methods: PrepareCommand, PrepareInvokeResponseCommand, GetCommandDataIBTLVWriter and FinishCommand. These are not exposed anymore and instead one should use AddResponse or AddResponseData. When using an EncodableToTLV argument, the same functionality should be achievable.

Example

Before:

const CommandHandler::InvokeResponseParameters prepareParams(requestPath);
ReturnOnFailure(commandHandler->PrepareInvokeResponseCommand(path, prepareParams));

TLV::TLVWriter *writer = commandHandler->GetCommandDataIBTLVWriter();
ReturnOnFailure(writer->Put(chip::TLV::ContextTag(1), 123));
ReturnOnFailure(writer->Put(chip::TLV::ContextTag(2), 234));
return commandHandler->FinishCommand();

After:

class ReplyEncoder : public DataModel::EncodableToTLV
{
public:
    CHIP_ERROR EncodeTo(TLV::TLVWriter & writer, TLV::Tag tag) const override
    {
        TLV::TLVType outerType;
        ReturnErrorOnFailure(writer.StartContainer(tag, TLV::kTLVType_Structure, outerType));

        ReturnOnFailure(writer.Put(chip::TLV::ContextTag(1), 123));
        ReturnOnFailure(writer.Put(chip::TLV::ContextTag(2), 234));

        return writer.EndContainer(outerType);
    }
};

// ...
ReplyEncoder replyEncoder;
commandHandler->AddResponse(path, kReplyCommandId, replyEncoder);

// or if error handling is implemented:
//
// ReturnErrorOnFailure(commandHandler->AddResponseData(path, kReplyCommandId, replyEncoder));
//
// In many cases error recovery from not being able to send a reply is not easy or expected,
// so code does AddResponse rather than AddResponseData.

CommandHandlerInterface in chip::app::InteractionModelEngine

Command handler lists were placed in a separate registry class that is independent of the InteractionModelEngine class.

The following replacements exist:

• chip::app::InteractionModelEngine::RegisterCommandHandler replaced by chip::app::CommandHandlerInterfaceRegistry::Instance().RegisterCommandHandler
• chip::app::InteractionModelEngine::UnregisterCommandHandler replaced by chip::app::CommandHandlerInterfaceRegistry::Instance().UnregisterCommandHandler
• chip::app::InteractionModelEngine::FindCommandHandler replaced by chip::app::CommandHandlerInterfaceRegistry::Instance().GetCommandHandler
• chip::app::InteractionModelEngine::UnregisterCommandHandlers replaced by chip::app::CommandHandlerInterfaceRegistry::Instance().UnregisterAllCommandHandlersForEndpoint

AttributeAccessInterface registration and removal

A new object exists for the attribute access interface registry, accessible as chip::app::AttributeHandlerInterfaceRegistry::Instance()

Replacements for methods are:

• registerAttributeAccessOverride replaced by chip::app::AttributeAccessInterfaceRegistry::Instance().Register
• unregisterAttributeAccessOverride replaced by chip::app::AttributeAccessInterfaceRegistry::Instance().Unregister
• unregisterAllAttributeAccessOverridesForEndpoint replaced by chip::app::AttributeAccessInterfaceRegistry::Instance().UnregisterAllForEndpoint
• chip::app::GetAttributeAccessOverride replaced by chip::app::AttributeAccessInterfaceRegistry::Instance().Get

ServerInitParams::dataModelProvider in Server::Init and FactoryInitParams

Server and controller initialization require a set data model provider to work rather than auto-initializing ember-compatible code-generated data models.

To preserve codegen/zap generated logic, use CodegenDataModelProviderInstance (see changes in 36558 and 36613 ).

To use default attribute persistence, you need to pass in a PersistentStorageDelegate to CodegenDataModelProviderInstance. See example changes in 36658 ).