Experimental Physics and
Industrial Control System

David Eisert <[email protected]> · Fri, 08 Sep 2006 17:12:25 -0500

David Dudley wrote:

Is QNX closer to Linux, or to BSD or Solaris?
In working on the NetBSD port, I started with the Solaris port, since NetBSD is a derivative of BSD4.4, which Solaris is also (distant relative, I understand). Linux is fairly close, but not as close.
David Dudley

Sorry my knowledge of Unix is limited. But QNX was developed as a MS-DOS
competitor in the early '80s. It didn't quite reach mainstream so they
focused on the RTOS market. The original developers/owners got bought
out recently by Harman (automotive parts company) for $138 million in
cash. Their marketing focus has changed a little and they a racking up
big contracts for in car entertainment systems. They haven't made major
changes to the system that would prevent its use for the more general
purpose RTOS buyers. So the automotive focus may help the product
overall. The kernel is very unique and I wouldn't think it could be
described as a derivative of any prior Unix. If you can ask a more
specific question to help determine its linage I would be happy to check
it out. You can also download an evaluation copy from QNX. It's the full
blown version that runs for 30 days.
The advantage of QNX is its modular architecture. All driver modules are
reloadable on the running system. Most of my drivers are 1-2k lines of
code and they all run in their own address space. If one crashes the
other drivers continue to run. I replace my network interface driver
with updated versions by just telneting into the system and writing the
new version to the CF card. I can reload I/O board drivers without
dumping the stored beam. When I run the new driver, it passes a message
to the old driver asking for some driver specific data. It grabs the
data, tells the old driver to kill itself (releasing IRQs) and then

fires itself up. Its down for only a few milliseconds and most of our
slower feedback systems never see a problem. Of course, I don't do this
every day but it is really impressive when you come from the single
executing image all running in the same address space. This modularity
should allow me to run a copy of EPICS base with a small driver that can
pass messages to my existing drivers. Both of them should be able to
play nice together while I make changes to other code.
Dave

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System