Re: [Xenomai-help] Links between RTAI and Xenomai

[Philippe Gerum <rpm@xenomai.org>]

Germain Olivier wrote:
> Hello
>
> I have a few questions about the links between RTAI and Xenomai
> 
> -When RTAI and Xenomai merged to RTAI/Fusion, which code of each was used ?
> I mean that in the project, which fonctionnalities of each was kept.
> 

RTAI and Xenomai merged as projects back in 2003, unfortunately (or fortunately) 
they never managed to merge as technologies because their respective core 
implementation just cannot match. This means that the two code bases were at the 
best side-by-side in the same RTAI distros (see the sched/xenomai and 
addons/skins dirs in RTAI's 3.0 and 3.1 releases), and not even in the same CVS 
tree during the RTAI/fusion effort.

For this reason, the RTAI/fusion project - started in April 2004 - once 
envisioned a closer convergence of both systems at the API level, but on top of 
the Xenomai core. This is the kind of convergence the RTAI project eventually 
refused, unless some original RTAI code would be merged in RTAI/fusion. Since 
this solution was unacceptable to us for various reasons, we did some kind of 
"retro-merger", and Xenomai recovered its independence.

> -With the actual Xenomai, which portion of RTAI remain in the code ? How

Interestingly enough, things are going the other way around actually. I have 
founded the Xenomai project back in 2001 [1], then published the first Adeos 
patches in June 2002, and finally ported Xenomai 1.x over Adeos a few weeks 
later as the first illustration of the capabilities of the latter to provide 
support to RTOS [2]. Then, upon RTAI's founder request, I've accepted to 
implement a new hw abstraction layer for RTAI 24.1.10 based on Adeos in 
replacement of the legacy RTHAL, which eventually led to RTAI 24.1.11 [3]. So 
regarding this matter, at least, it's Xenomai's know-how that went to RTAI, and 
not the other way around.

> futur development of RTAI will be merged to Xenomai, as it is also a skin
> ?
> 

I guess that you now have the answer. On the specific RTAI skin issue, it has 
been contributed by the Nextream fellows the way we once envisioned to port the 
whole RTAI API over the Xenomai core, that is to say a clean room implementation 
of such API over Xeno's abstract RTOS core. The existing RTAI skin over Xenomai 
will be extended as far as people contribute code to it the same way, but there 
is no plan to track RTAI developments on a regular basis.

[1] formerly hosted by the Savannah project.
[2] http://www.ussg.iu.edu/hypermail/linux/kernel/0207.2/0497.html
[3] http://www.aero.polimi.it/~rtai/news/
     http://www.linuxdevices.com/news/NS4995268611.html

-- 

Philippe.