In message 4214AD81.5010007@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