1.1 Overview

The Iris interface consists of the following:

  • A generic function call interface. Functions are called by name. Arguments and return values are passed by name and by value.
  • An object model. Iris systems consist of a set of instances. Instances are entities that can send and receive Iris function calls, for instance modeled components, hardware targets, debuggers, plug-ins, and framework components. All instances can:
    • Discover and communicate with all other instances.
    • Call functions on and receive function calls from all other instances.
    Each instance is identified by an instance id, instId.
  • A defined set of functions that are supported by instances. Most are optional.

It has the following design principles:

  • Function calls are generally split into a request and an asynchronous response.
  • Function calls and responses are represented using JSON data types, for example integers, strings, arrays, objects, and booleans.
  • All types of events, for instance trace, debug, and semihosting events, are exposed through the same event mechanism.
  • When calling a function, the caller can generally choose between sending:
    • A request. The callee sends a response back to the caller when it has finished processing the function. This is called a synchronous or blocking function call, as the caller is blocked while waiting for the response.
    • A notification. The callee does not send a response, so the caller does not know when the callee has finished. This is called an asynchronous or non-blocking function call. It is faster than a request and is preferred.
  • Instances can connect to a simulation either using Inter-Process Communication (IPC) or within the same process. In either case, the interface is the same.
  • JSON RPC 2.0 semantics are used for all function calls, whether using IPC or in-process.
  • It uses U64JSON, a proprietary binary equivalent of JSON that is based on a sequence of uint64_t values, in-process to remove the JSON parsing overhead.
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