On Monday 02 February 2009, Eric H. Johnson wrote:
> I guess I am not asking the right questions and getting hung up in details
> rather than asking what I need to do to get to my ultimate objective.

You are asking the right questions most of the time, however, you are getting 
varying degrees of advice.

You asked how to generate a kernel package - Three answers:

1) Use kernel-package - A reasonable solution if you intend to install on more 
than one system.

2) Use the Ubuntu source package - Poor advice. Ubuntu's source package (and 
Debian's) should only be used IF you are building multiple flavours for 
distribution OR debugging the build system. It should not be used if you are 
expecting a "clean" source tree, or are building a single flavour.

3) Build from a kernel.org virgin source tarball - Reasonable answer if you 
don't mind managing install manually.

You asked which kernel source to use - Two answers, one good, the other, bad.

1) Use a virgin kernel.org tarball - Good advice, particularly if you need to 
seek support from the RTAI team[1].

2) Use an Ubuntu source package - Poor advice. You have absolutely no idea 
what "patches" have been applied or how they will interact with the RTAI 
patch. IF you are lucky, you will get a bit of fuzziness, or you will get 
failed hunks that will need to be applied by hand. Using the distro supplied 
kernel source is always a bad choice because of the patches that might have 
been used (at least with Debian, it is possible to roll back to a "clean" 
source).

You asked about patching... As you found out, depending on the kernel you 
select, the correct patch might be in base/arch/i386 (pre 2.6.24) or 
base/arc/x86 (2.6.24 and later).

Using a $random patch downloaded directly from the Adeos project has to be 
about the worst piece of "advice" given - The RTAI patches are based on the 
Adeos work, but they are NOT the same. Sure, the Adeos patch can be used with 
the relevant kernel, but you can not compile the RTAI stuff against it. IF 
you try this, don't expect any support from either the Adeos team or RTAI, 
and I don't expect anyone here will take responsibilty....


You then asked about kernel options - Selecting a P4 processor and some of the 
APIC/APM options are reasonable. There are a few others that Ubuntu/Debian 
use that could cause problems. Having a fast computer dedicated to kernel 
compiles speeds up the build/test cycle.

> That goal is to get a kernel + rtai running under my minimal xubuntu
> install and supporting both / all processors of the Atom 330. Which means
> that I ultimately need binary installable packages of the kernel, rtai and
> EMC. It also makes it easy to provide to other users wanting to use this
> same motherboard.

Just because someone suggests Ubuntu is the "best" distro, you are free to use 
what ever distro you want (even LFS). Anyone that claims Ubuntu is a totally 
different "operating system" from any other GNU/Linux flavour needs a good 
dose of tar & feathers.

> At this point, is it possible, and would it be easiest to build EMC on
> Debian Lenny, where all the appropriate libraries are installed, then
> generate the necessary binary packages from there? Could those packages
> then be installed on various versions of Ubuntu for example, without the
> need to recompile?

Ubuntu is little more than a snapshot of Debian's testing branch, bugs and 
all. So it should be possible to compile a package on one and install it on 
another - You do need to be aware of what library versions are used and need 
to be willing to do a bit of package "backporting". If you don't want to go 
down that route (and it can get messy), stick with one or the other unless 
you know what you are doing.

Any Ubuntu release older than Intrepid will provide you with a kernel-package 
that produces a disfunctional linux-headers package with 2.6.24 or later. 
Debian's stable branch (Etch) also suffers from the same problem, but this 
has been fixed in Lenny/Sid.

> While my frustration may be starting to show through, I really appreciate
> all of the help everyone has provided.

Not suprising based on the quality of some of the advice given - I hope you 
didn't try mixing $random patches with $random kernel sources....

Now.... If you want to try a selection of precompiled 2.6.27[2] kernel 
packages patched with the correct RTAI patch set, I have a number sitting in 
my repository (complete with RTAI packages) - These have been built on a 
fresh Lenny install, so should work with Ubuntu's Intrepid. Ask me off-list, 
and I will provide you with a URL for Apt.




[1] When seeking support, it helps to include the full output from dmesg and 
the configs used by both the kernel and RTAI - A partial segfault line 
and/or "unresolved symbol" quote will get a short answer (if at all).

[2] Flavours include 586. 686. 686-smp, Athlon, P4, and others.

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