Re: Learn RTOS

cs_posting@xxxxxxxxxxx wrote:
On Apr 15, 9:08 am, John Devereux <jdREM...@xxxxxxxxxxxxxxxxxx> wrote:

But in fact most free RTOSs are *not* GPL licenced, (as David Brown
pointed out). Even programs that are (like e.g. linux) do not require
publishing "all your source code", just the parts that link to the
kernel. So you could build or buy hardware supported by linux, and
install your own proprietary software on to it. But if you need to
modify the kernel (e.g. write a special device driver) you would need
to publish *that*.

I would expect that the more hard-realtime parts of your system may
need to link to the
kernel in ways that may cause the GPL to apply to those parts.

However, you may be able to do the realtime parts in kernel modules,
but keep a lot of other parts of the system in proprietary userspace
code.

The only major FOSS OS I know of that uses a pure GPL is Linux. So if your code really needs critical modifications to the kernel, you will have to publish those changes. However, Linux also has provisions for linking non-GPL'ed modules into the kernel (not everyone agrees that this is allowed under the GPL, but Linus says it's okay). Of course, Linux itself is not hard realtime in the first place - normally much of your code could go in user space (if it is *that* time-critical, you should be looking at a RTOS extension to Linux).

For FOSS OS's under modified GPLs (such as FreeRTOS), you can link your own non-GPL'ed files directly into the kernel. At most, you might add a few hooks to the original source code.
.

Relevant Pages

  • Re: Linux GPL and binary module exception clause?
    ... >> I have heard many people reference the fact that the although the Linux ... >> under the GPL. ... > become a derived work of the kernel? ... To date we have not even attempted to load our SNAP drivers inside the ...
    (Linux-Kernel)
  • Re: Linux GPL and binary module exception clause?
    ... Well here is the one NO, and imposing all modules are GPL is a no can do. ... > Modules are essentially dynamically linked extensions to the GPL kernel. ... > specifically for Linux, so it seems more appropriate that they would be ... > Linus are being taken out of context to somehow justify permission for the ...
    (Linux-Kernel)
  • Re: differences between kernel-tree and kernel-source and kernel image
    ... > will this install the kernel or try to patch an existing 2.6 kernel or ... affix-source - Driver source for the Affix Bluetooth protocol stack for Linux ... atlas-doc - Automatically Tuned Linear Algebra Software,documentation ...
    (Debian-User)
  • RE: GPL issues
    ... the GPL cannot set its own scope. ... to give my answer to the original question -- if a kernel ... you should be okay if you develop an API for a kernel to ... work on any kernel (Linux or not, ...
    (Linux-Kernel)
  • LTTng finds abnormally long APIC interrupt handler : 58.2 ms
    ... A trace taken with LTTng on a x86_64 dual quad-core, Linux kernel ... # Input Device Drivers ...
    (Linux-Kernel)