Subversion Repositories openrisc_2011-10-31

#

#  $Id: README,v 1.2 2001-09-27 11:59:44 chris Exp $

#

#

# Please send any comments, improvements, or bug reports to:

#       Chris Johns

#       Objective Design Systems

#       35 Cairo Street

#       Cammeray

#       Sydney, NSW 2062

# ccj@acm.org

#

#

# Overview

# ~~~~~~~~

# This board support package is not a board support package at all, but

# a means to build the RTEMS kernel without using a specific BSP.

#

# You should be able to build to build this BSP for any cpu type.

#

# You must provide the standard BSP type functions and support yourself

# externally to RTEMS.

#

# This BSP is intended to be used by people who fit one or more of the

# categories below :

#

# 1) using custom hardware of little use or interest to others. If you

#    intend to use hardware available to others, please create a BSP

#    and send to OARCorp.

#

# 2) production code cannot depend on software which can change. BSP code

#    can change with-out notice, while RTEMS has very tightly defined

#    interfaces which do not change.

#

# 3) the need to extend or change an existing BSP in ways which are not

#    of interest to others or the BSP maintainer.

#

# I fit all the above.

#

# Issues

# ~~~~~~

# I do not consider the bare BSP as a starting point for RTEMS. The

# BSP code integrated into the RTEMS build tree has the advantage of

# building all the test and sample code. The sample and test code is

# important for validatation of your tools, and getting your BSP

# working correctly.

#

# Once you gain experience with RTEM and your application matures the

# need to break the BSP code out from the kernel becomes important. It

# is at this point in time that the bare BSP becomes useful.

#

# Once free you are able to upgrade without the worry of makefile or

# build tree changes which can break your BSP.

#

# How To Configure

# ~~~~~~~~~~~~~~~~

# RTEMS requires you to select a BSP inorder to build the kernel.

# If you take a close look at a BSP which is closest to your

# needs you will find somewhere the CPU model and CPU compile

# flags are specified. This is the only piece of information

# required by the kernel inorder for it to build.

#

# This highlights the clean design of the kernel and its

# independence from the particulars of target hardware.

#

# The CPU model is the RTEMS model and usually tries to match with

# the GCC model. There are variations on some processors. If you are

# unsure please ask on the RTEMS list. Someone will know (I hope).

#

# The CPU flags allow you to select specific operating modes for

# GCC. For example the PowerPC has specific flags to control various

# cache resouces. Another example is the 68000 family of embedded

# processor do not have FPU hardware and require software emulation.

#

# An example configuration command line is:

#

#  ../rtems-4.0/configure  --target=m68k-rtems \

#                          --prefix=/ods/egcs/test \

#                          --enable-cxx \

#                          --enable-gmake-print-directory \

#                          --disable-tests \

#                          --disable-posix \

#                          --enable-networking \

#                          --enable-bare-cpu-cflags=-mcpu32 \

#                          --enable-bare-cpu-model=mcpu32 \

#                          --enable-rtemsbsp=bare

#

# Building RTEMS

# ~~~~~~~~~~~~~~

# You are required to do nothing special here. Just follow the documented

# steps. The samples are built but no linking occurs. The link command

# is stubbed out to produce a Unix shell script.

#

# After installation you will find a directory called 'bare'. The nature

# of the RTEMS build system means the bare BSP will only install into the

# the bare directory under the specifed configuration prefix.

#

# I therefore suggest you move the directory to another name. This allows

# you to make and install another bare BSP for a different variant of

# CPU without over writing the last installed variant.

#

# I have provided a script file I use to configure and build RTEMS

# from the arcihve. Take a copy and use it if you find it useful.

#

# Creating an Application.

# ~~~~~~~~~~~~~~~~~~~~~~~~

# This is something which is usually specific to your local environment.

# The bare BSP does not lock you into any specific makefile or build

# system. A couple of suggestions are:

#

#   o Get the sample bare BSP application, or

#   o Watch RTEMS build a BSP which is closest to yours and copy

#     the command lines used.

#