DENX ELDK Kernel

DENX ELDK Kernel

[Brian Padalino]

I am just getting into some embedded linux systems and thought I would go
with the DENX ELDK since it seemed like the best package out there.
Unfortunately, one of the requirements of the project is that kernel
upgradability should be easy.

I understand that DENX ELDK is always being worked on, and I have seen that
Wolfgang Denk is amazingly active in this community, so I guess my question
is -- can I use the linux-ppc kernel patches for the latest 2.4 kernels
instead of DENX's?  Should this requirement of the kernel needing to be
easily upgradable to any kernel reevaluated?

BTW, the platform is very simple and will just be a PPC440GP with a gigabit
ethernet controller.

Any information or insight is very much appreciated.

Thanks a bunch.

Brian Padalino


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Re: DENX ELDK Kernel

[Wolfgang Denk]

Deasr Brian,

in message <DGEEIPOFGGPOACEFBGGCOEGKCAAA.bpadalino@perigee.com> you wrote:
>
> I am just getting into some embedded linux systems and thought I would
> go with the DENX ELDK since it seemed like the best package out there.
> Unfortunately, one of the requirements of the project is that kernel
> upgradability should be easy.
>
> I understand that DENX ELDK is always being worked on, and I have
> seen that Wolfgang Denk is amazingly active in this community, so I
> guess my question is -- can I use the linux-ppc kernel patches for the
> latest 2.4 kernels instead of DENX's? Should this requirement of the
> kernel needing to be easily upgradable to any kernel reevaluated?

Short answer: yes, you can. There is no problem.

The development tools and the kernel are more or less independend  of
each other (*).

For you that means: you don't have to use the  Linux  kernel  version
that  comes  included with the ELDK, but you can use any other kernel
tree instead.

> BTW, the platform is very simple and will just be a PPC440GP with a
> gigabit ethernet controller.

Actually, the kernel included with the current release  of  the  ELDK
(kernel  version  2.4.4)  is  pretty old and _not_ suitable for a 4xx
processor at all - for such a  CPU  you  should  use  the  "official"
linuxppc_2_4_devel tree instead (**).

(*)  There may be problems if the kernel headers  have  changed  thus
     causing  incompatibility  with  those  headers used to build the
     standard libraries included with the ELDK. But such incompatible
     changes happen only very infrequently, and we are not  aware  of
     any  such problems with combinations of the current ELDK and the
     "official" Linux source trees.

(**) You can also use the copy of the linuxppc_2_4_devel tree on  our
     CVS  server  (at the moment this is kernel version 2.4.20) which
     will be the base for our next release of the ELDK.

> Any information or insight is very much appreciated.

Hope this helps.

Best regards,

Wolfgang Denk

--
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd@denx.de
The existence of god implies a violation of causality.

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DENX ELDK Kernel

[Jeff Kowing]

Brian Padalino writes:
 > I understand that DENX ELDK is always being worked on, and I have seen that
 > Wolfgang Denk is amazingly active in this community, so I guess my question

He's a mythological figure!  I think he is really secretly several
people working as one incredible unit of productivity.

 > is -- can I use the linux-ppc kernel patches for the latest 2.4 kernels
 > instead of DENX's?  Should this requirement of the kernel needing to be
 > easily upgradable to any kernel reevaluated?

Others are more qualified to answer this than me, but, heck, that
never stopped me before!  Basically, the answer is yes - at least I
have been using the ELDK with a linux-2.4.20 kernel (from kernel.org).
The key point to remember is that you should always compile user
applications against the Linux include files that glibc (and all the
rest of the target ELDK apps) are built against - Do NOT compile your
user applications against the newer Linux kernel.

Regards,
Jeff

--
Jeff Kowing <jeffrey.d.kowing@nasa.gov>
All opinions expressed are my own and not of my employer.

** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/

Re: DENX ELDK Kernel

[Wolfgang Denk]

Dear Jeff,

in message <16148.1141.101138.214108@igor.jsc.nasa.gov> you wrote:
>
> He's a mythological figure!  I think he is really secretly several
> people working as one incredible unit of productivity.

No, really, it's just me. And I'm still trying to figure out how  the
clone() system call could be used for real-life applications :-)

> never stopped me before!  Basically, the answer is yes - at least I
> have been using the ELDK with a linux-2.4.20 kernel (from kernel.org).
> The key point to remember is that you should always compile user
> applications against the Linux include files that glibc (and all the
> rest of the target ELDK apps) are built against - Do NOT compile your
> user applications against the newer Linux kernel.

10 of 10 points :-)


Best regards,

Wolfgang Denk

--
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd@denx.de
"Where shall I begin, please your Majesty?" he asked. "Begin  at  the
beginning,"  the  King said, gravely, "and go on till you come to the
end: then stop."    - Alice's Adventures in Wonderland, Lewis Carroll

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Re: DENX ELDK Kernel

[Steven Scholz]

Wolfgang Denk wrote:

>>never stopped me before!  Basically, the answer is yes - at least I
>>have been using the ELDK with a linux-2.4.20 kernel (from kernel.org).
>>The key point to remember is that you should always compile user
>>applications against the Linux include files that glibc (and all the
>>rest of the target ELDK apps) are built against - Do NOT compile your
>>user applications against the newer Linux kernel.
>
>
> 10 of 10 points :-)

Stupid question (TM):

If I'd built the ELDK from scratch and used Linux-2.4.20 include files
to build "glibc (and all the rest of the target ELDK apps)" I should
build my "applications against the newer Linux kernel"! Shouldn't I?

And in general: shouldn't I used a glibc that "matches" the kernel
version?

Thanks,

Steven


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Re: DENX ELDK Kernel

[Wolfgang Denk]

In message <3F140928.60403@imc-berlin.de> you wrote:
>
> If I'd built the ELDK from scratch and used Linux-2.4.20 include files
> to build "glibc (and all the rest of the target ELDK apps)" I should
> build my "applications against the newer Linux kernel"! Shouldn't I?

Yes.

> And in general: shouldn't I used a glibc that "matches" the kernel
> version?

If you want to be absolutely safe, yes. But so far we have  not  seen
any  real  problems when - for example - running the 2.4.4 built libs
and tools on a 2.4.20+ kernel.

Best regards,

Wolfgang Denk

--
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd@denx.de
God may be subtle, but He isn't plain mean.         - Albert Einstein

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Re: DENX ELDK Kernel

[Jeff Kowing]

> 10 of 10 points :-)

I'm on a role, so I'll try again against my better judgement.

Steven Scholz writes:
 > If I'd built the ELDK from scratch and used Linux-2.4.20 include files
 > to build "glibc (and all the rest of the target ELDK apps)" I should
 > build my "applications against the newer Linux kernel"! Shouldn't I?

Yes, you are correct.  The rule is to always build user space
applications against the same Linux include files that were used to
build glibc.

If, on the other hand, you are compiling a kernel module, then you
need to build it against the actual Linux kernel version you are
running.

 >
 > And in general: shouldn't I used a glibc that "matches" the kernel
 > version?

I think that is the "safest" way of doing things, but apparently not
usually necessary.  People upgrade their kernels all the time on their
native platforms without rebuilding their glibc. I believe some effort
is made to maintain binary compatiblity between glibc and the kernel -
but I'm sure it is not guaranteed.

Regards,
Jeff

--
Jeff Kowing <jeffrey.d.kowing@nasa.gov>
All opinions expressed are my own and not of my employer.

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