platform/shared/idl/host_messages.fbs

// Copyright (C) 2017 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

namespace chre.fbs;

/// Represents a message sent to/from a nanoapp from/to a client on the host
table NanoappMessage {
  app_id:ulong = 0;
  message_type:uint = 0;

  /// Identifies the host-side endpoint on the host that sent or should receive
  /// this message. The default value is a special value defined in the HAL and
  /// elsewhere that indicates that the endpoint is unspecified.
  host_endpoint:ushort = 0xfffe;

  /// Vector containing arbitrary application-specific message data
  message:[ubyte] (required);
}

table HubInfoRequest {}
table HubInfoResponse {
  /// The name of the hub. Nominally a UTF-8 string, but note that we're not
  /// using the built-in "string" data type from FlatBuffers here, because the
  /// generated C++ uses std::string which is not well-supported in CHRE. This
  /// applies for vendor and toolchain as well.
  name:[byte];
  vendor:[byte];
  toolchain:[byte];

  /// Legacy platform version reported in the HAL; semantics not strictly
  /// defined
  platform_version:uint;

  /// Toolchain version reported in the HAL; semantics not strictly defined
  toolchain_version:uint;

  peak_mips:float;
  stopped_power:float;
  sleep_power:float;
  peak_power:float;

  /// Maximum size message that can be sent to a nanoapp
  max_msg_len:uint;

  /// @see chreGetPlatformId()
  platform_id:ulong;

  /// @see chreGetVersion()
  chre_platform_version:uint;

  // TODO: list of connected sensors
}

table NanoappListRequest {}

table NanoappListEntry {
  app_id:ulong;
  version:uint;
  enabled:bool = true;

  /// Whether the nanoapp is a pre-loaded "system" nanoapp, i.e. one that should
  /// not show up in the list of nanoapps in the context hub HAL. System
  /// nanoapps are typically used to leverage CHRE for some device functionality
  /// and do not interact via the context hub HAL.
  is_system:bool = false;

  // TODO: memory usage
}

table NanoappListResponse {
  nanoapps:[NanoappListEntry] (required);
}

/// A union that joins together all possible messages. Note that in FlatBuffers,
/// unions have an implicit type
union ChreMessage {
  NanoappMessage,

  HubInfoRequest,
  HubInfoResponse,

  NanoappListRequest,
  NanoappListResponse,

  // TODO: extend with system-specific messages, e.g. load app command, etc.
}

/// The top-level container that encapsulates all possible messages. Note that
/// per FlatBuffers requirements, we can't use a union as the top-level structure
/// (root type), so we must wrap it in a table.
table MessageContainer {
  message:ChreMessage (required);
}

root_type MessageContainer;