Hi!
I just tried RTAI0.8 and maybe somebody is interested
in the experiences i have made ... :-)
Installation:
-------------
Not very complicate, although the source-tree
looks a little bit "dearranged". After unpacking
the .tgz, you have just to do "./copyto" within the
rtai-0.8/linux-2.2.13 directory.
It's a little bit confusing, that the README
says that "irq.c" will not copied (although it is).
Also i wouldn't recomend that the installation-script
is copying the stuff straight to /usr/src/linux-2.2.13/...,
since the usual way is to have a link from "linux" to
the approporate directory, i.e. "linux-2.2.13-RTAI0.8".
I realy suggest to invent a kernel-patch instead
if copying whole files. With that, it would be
possible to add the "EXTRAVERSION=-RTAI0.8" in
the toplevel-Makefile automaticaly (prevents you
from overwriting the moduels in "/lib/modules/2.2.13" -
they should preferably be copied to "/lib/modules/2.2.13-RTAI0.8").
Additionally, it is a little bit disturbing, that
the Makefiles included in RTAI don't have an "install"
option, so that the modules are not copied to i.e.
"/lib/modules/2.2.13-RTAI0.8/misc" automaticaly.
But not to be nitpicking, at least, it only took me one
hour to get the things going (running the simple sound-demo) ...
BTW: is it mandatory to do the cpu and latency
calibrations? It did seem to work well for me without
performing that ...
Porting from RTL to RTAI
------------------------
At a first look, the "Name-Spaces" of the
RTAI-functions seem to be a little confusing,
but you get used to it, very fast.
After playing around with the basic task-functions
(start, stop, sleeping etc.) for an hour or so, it took me
only an additional hour to port the pcmsound-demo to RTAI.
Since the FIFO-functions of RTAI and RTL are exactly
the same (except the name of the header-file to include),
you don't have to care about that.
Conclusion:
-----------
RTL and RTAI are not that wide appart that an "unification"
is impossible. But i have the impression, that both
projects have contrary philosophies, like they are
described in "the cathedral and the bazaar"
(written by Eric Remond?)
RTL: Victor Yodaiken is going the "cathedral"-way, means,
you have a centralized code merging institution that
strictly doesn't accept what doesn't fit into
the predefined model (here: Posix-compliance)
and what wasn't intensivly peer-reviewed.
Advantage: well defined API, high stability
Disadventage: progresses need more time to occour.
RTAI: Paolo Montegazza is doing the "bazaar"-method, means,
he puts everything into the source-tree, that might
be usefull for somebody (but also having a deep look
into it).
Advantage: fastly increasing functionality
Disadventage: everything looks a little bit "dearranged".
Now, lets have a look at the history:
IMHO, RTL compared to RTAI is a little bit like GNU-HURT
compared to Linux. We all know, that GNU-HURT doesn't get
the respect that it should have. That is because their
inventors (R. Stallman??) didn't payed much attention
to the needs (functionality) of the community, but wanted
to do it perfectly. L.T. acted more like Paolo is doing it
nowerdays.
Question: which of the two - GNU-HURT or Linux - is going
mainstream these days? ...
just my 0.02 Euro
Bernhard
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