[U-Boot-Users] stand alone application

[Wolfgang Denk]

In message <9771147.post at talk.nabble.com> you wrote:
> 
> I am trying to write a stand alone application, which is supposed to be a
> board diagnostics for manufacturing. The way it supposes to work is as
> follows: U_boot could either download the diagnostics manually under the
> U_boot prompt, or be calling up do_tftp() directly if it is to be done
> automatically. Results generated from the diagnostics are to be recorded in
> the RAM, whose contents shall later be uploaded as a log file to an external
> server via tftp. After reading the examples provided in the example

I recommend to use the existing log device; note that it is
compatible with Linux's syslog mechanism.

> (1) In my understanding, the stand alone application (the board diagnostic
> for manufacturing) is supposed to be compiled as a separately entity in the

Yes.

> U-boot path and then be placed in an external server, waiting to be
> downloaded to the RAM on board; when either go <address> or do_go(address)

You can also store it in flash memory, or on some storage device, of
course.

> is executed, control get passed to the stand alone application, how could
> the stand alone application be able to make calls to functions that are
> exported (those appeared in both exports.c and export.h), without some kind
> of "linking"? Unless go <address> or do_go(address) perform some sort of

This is documented in the doc/README.standalone file; no linking is
done.

> "linking" or "peudo linking" action, this doesn't sound possible. Could
> someone explain to me how this works? 

The keyword is: jump table.

> My expectation of how this could work is: on execution of the go <address>

Why don't you simply read the documentation instead of speculating?

> command or do_go (address), address of the jump table is to be loaded into a
> register, and it is the responsibility of the application to save the value
> of this register before anything else, in such a way to allow the
> application to call up functions that it elects by picking up the correct
> addresses of these functions via indexing. However, after reading the
> examples provided in U-boot, I have not seen any motion of saving the value
> of the register. However, vwhich register U-boot chooses to use would be
> processor dependent. This is just my two cents.

You should RTFM.

> (2) Is uploading currently being supported in U-boot's tftp implementation?

No.

Best regards,

Wolfgang Denk

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