Documentation/driver-api/rapidio/rapidio.rst

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============
Introduction
============

The RapidIO standard is a packet-based fabric interconnect standard designed for
use in embedded systems. Development of the RapidIO standard is directed by the
RapidIO Trade Association (RTA). The current version of the RapidIO specification
is publicly available for download from the RTA web-site [1].

This document describes the basics of the Linux RapidIO subsystem and provides
information on its major components.

1 Overview
==========

Because the RapidIO subsystem follows the Linux device model it is integrated
into the kernel similarly to other buses by defining RapidIO-specific device and
bus types and registering them within the device model.

The Linux RapidIO subsystem is architecture independent and therefore defines
architecture-specific interfaces that provide support for common RapidIO
subsystem operations.

2. Core Components
==================

A typical RapidIO network is a combination of endpoints and switches.
Each of these components is represented in the subsystem by an associated data
structure. The core logical components of the RapidIO subsystem are defined
in include/linux/rio.h file.

2.1 Master Port
---------------

A master port (or mport) is a RapidIO interface controller that is local to the
processor executing the Linux code. A master port generates and receives RapidIO
packets (transactions). In the RapidIO subsystem each master port is represented
by a rio_mport data structure. This structure contains master port specific
resources such as mailboxes and doorbells. The rio_mport also includes a unique
host device ID that is valid when a master port is configured as an enumerating
host.

RapidIO master ports are serviced by subsystem specific mport device drivers
that provide functionality defined for this subsystem. To provide a hardware
independent interface for RapidIO subsystem operations, rio_mport structure
includes rio_ops data structure which contains pointers to hardware specific
implementations of RapidIO functions.

2.2 Device
----------

A RapidIO device is any endpoint (other than mport) or switch in the network.
All devices are presented in the RapidIO subsystem by corresponding rio_dev data
structure. Devices form one global device list and per-network device lists
(depending on number of available mports and networks).

2.3 Switch
----------

A RapidIO switch is a special class of device that routes packets between its
ports towards their final destination. The packet destination port within a
switch is defined by an internal routing table. A switch is presented in the
RapidIO subsystem by rio_dev data structure expanded by additional rio_switch
data structure, which contains switch specific information such as copy of the
routing table and pointers to switch specific functions.

The RapidIO subsystem defines the format and initialization method for subsystem
specific switch drivers that are designed to provide hardware-specific
implementation of common switch management routines.

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