[U-Boot-Users] boot control concept

[Wolfgang Denk]

In message <4214AD81.5010007 at mc.com> you wrote:
> 
> Our ppc440gx-based project needs to develop a "boot control" mechanism
> without any operator intervention. We have a customer PCI interface
> where "special jumper settings" will indicate if an OS should be booted
> from Flash or via TFTP.

There are several examples in the U-Boot code how to handle this; see
for  example   the   LWMON,   R360   or   TRAB   boards.   See   also
board/lwmon/README.keybd (in German).

> We also desire that once U-Boot has been installed in Flash, the user
> will ONLY be allowed to update OS and application components. This

Just tell him in the documentation.  You  cannot  really  prevent  it
anyway.

> I was hoping to construct a U-Boot application (similar to hello_world
> example) and do all of our "boot control" processing their. This

Should be straightforward.

> It seems there are several ways to perform this. This app could use
> native U-Boot calls to setup the environment before returning to U-Boot
> where the OS load/boot would be completed. Would this work or is their a
> better approach?

Just call  you  standalone  application  as  one  step  in  the  boot
sequence.  This  is preferrable, as no changes to the U-Boot code are
required.

You  may  have  to   export   some   additional   functions   -   see
doc/README.standalone for instructions how to extend the jump table.

> I've looked thru the docs and email list and have not seen anything done
> like this. Any observations and suggestions about this are very welcome.

There are several examples - see above. Actually this is just another
are where U-Boot's flexibility  ourperforms  nearly  any  other  boot
loader I know of.

Best regards,

Wolfgang Denk

-- 
See us @ Embedded World, Nuremberg, Feb 22 - 24,  Hall 10.0 Booth 310
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
If something is different, it's either better or worse,  and  usually
both.                                                    - Larry Wall