RTEMS BSD USB and TCP/IP Developers Guide
=========================================
Joel Sherrill <joel.sherrill@oarcorp.com>
:Author Initials: JRS
:toc:
:icons:
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:website: http://www.rtems.org/

RTEMS uses FreeBSD as the source of its TCP/IP and USB stacks.
This is a developers guide which captures information on the
process of merging code from FreeBSD, building this library,
RTEMS specific support files, and general guidelines on what
modifications to the FreeBSD source are permitted.

**************************************************************
This is a work in progress and is very likely to be incomplete.
Please help by adding to it.
**************************************************************

== Source Code Version Information

* FreeBSD 8.2 SVN r222496
* RTEMS 4.11
  - BSP must have support for all new BSD sys sections
  - It is preferable if the BSP uses linkcmds.base.
  - BSP must be from an architecture with Programmable Interrupt Controller
    interrupt model.

== To Do
* Adapt generic IRQ PIC interface code to Simple Vectored Interrupt Model
  so that those architectures can use new TCP/IP and USB code. 
* in_cksum implementations for architectures not supported by FreeBSD.
  This will require figuring out where to put implementations that do
  not originate from FreeBSD and are populated via the script.
* generic in_cksum implementation is missing in_cksum_split so currently
  cannot be used.

== FreeBSD Source

You should be able to rely on FreebSD manual pages and documentation
for details on the code itself.

=== Automatically Generated FreeBSD Files

The FreeBSD source tarball includes a file named Makefile.rtems which
has stanzas to automatically generate some files.

http://www.freebsd.org/cgi/man.cgi?query=kobj&apropos=0&sektion=0&manpath=FreeBSD+9.0-RELEASE&arch=default&format=html

=== Rules for Modifying FreeBSD Source

* Only add lines.  Subtract code by added "ifndef __rtems__". This makes
merging easier in the future.

== libbsd Source

=== What is in git

The git source is a self-contained kit with FreeBSD and RTEMS components
pre-merged. The Makefile in this kit is automatically generated.

Any changes to sources in the freebsd or contrib directories will need to
be merged upstream into our master FreeBSD svn checkout.

=== Building git

You need to configure RTEMS for the desired BSP and install it. Then edit
the file config.inc to set RTEMS_MAKEFILE_PATH appropriately.

[listing]
----
make
make install
make -C testsuite
----

At this point, we expect multiple linker errors. That is what we are
currently working on.


=== Organization

The top level directory contains a few directories and files. The following
are important to understand:

* freebsd-to-rtems.py - script to convert to and free FreeBSD and RTEMS trees
* Makefile - automatically generated
* contrib/ - from FreeBSD by script.
* freebsd/ - from FreeBSD by script.
* rtemsbsd/ - RTEMS specific implementations of FreeBSD kernel support routines.
* testsuite/ - RTEMS specific tests
* libbsd.txt - Documentation in Asciidoc