[U-Boot-Users] custom loadable command shell
Jerry Van Baren
gerald.vanbaren at smiths-aerospace.com
Tue Mar 28 23:06:50 CEST 2006
Andrew Wozniak wrote:
> I've been contemplating how to develop a U-Boot loadable applet which
> provides a set of custom commands which augment the standard U-Boot
> command set. The general idea is to keep a working version of U-Boot in
> Flash without modifying - and then simply installing the new command
> applet as it changes.
> The applet would include a command parser. If none of my custom commands
> are found, a call to the U-Boot parser (via ABI) would be made to handle
> U-Boot commands.
> This is just a concept phase and I was hoping to get some opinions on
> the feasibility and obstacle of this approach.
> Thanks for all comments. Andy
My first thought is:
* Make the command table in u-boot longer than necessary (pad it with
* Add to the ABI so that your plug-in could either find the command
table and add its commands to the table or create an "add a command" ABI
call to add an extension command to the table (call repeatedly to add
multiple commands or pass in an extension table that gets added to the
* Better alternative(?): add a "add an extension table" ABI with a
pointer to an extension table. If the parser doesn't find the command
in the built-in table, it searches the add-on table (if provided).
Disadvantage: only one add-on table would be supported.
Viola' instant extension commands. This would have the advantage of
using the existing parser.
I have not looked very closely at how difficult it would be to do this
but it appears to be possible.
* It would require an extension of the ABI.
* The commands are scattered through the code as macros. Making
extension room may or may not be difficult. A add-on table would be
* The command structure has pieces that are #ifdefed in and out... your
extension either has to match configurations or the "add a command"
routine would have to handle missing/extra pieces.
More information about the U-Boot