[tbot] How to debug acquire_linux

Wolfgang Denk wd at denx.de
Fri Nov 23 12:05:20 UTC 2018

Hallo Heiko,

In message <7c82a352-43a8-098e-1298-1c1fd9c5b7ed at denx.de> you wrote:
> > Hm... why does tbot not recognise the prompt even if it is embedded
> > in other output?  Strict anchoring to something like "^<prompt>$"
> > seems a bit restrictive to me...
> And here the problems begin ... in linux, we are fine, as we have
> defined an unique prompt ... but in U-Boot you may have "=> " for a lot
> of boards ... and "=> " can occur in for example testing memory dumps...

Yes, I know.  I am aware of the difficulties, but I think we don';t
have to acchieve 100,00% detection - 99,9% is probably good enough,
but 90% is not.

For U-Boot situation is simple as the chance that a memory dump is
running while you connect to a board is epsilon.

> Can we be sure linux prompt is never disturbed by other output ?

We cannot, which is why I suggested to become active if we run into
a timeout.

> > Alternatively, one could try to trigger a reprinting of the prompt by
> > sending a newline (or, depending on contect, maybe a ^D) character?
> Yep, thats the reason why you saw last year on the embedded some Ctrl-C
> characters in old tbot demo ... you remember?

Yes, I do.  This is another possible approach, too.  I just think we
should not do this by default, but only if the regular detection of
the prompt times out.

> > I. e., if no prompot is recognized after the expected timeout,
> > instead of hard failing, try sending a newline and check again?
> no newline please, as if you are in U-Boot, may a previous command
> gets started again. I vote for Ctrl-C. This can be sended safely in
> U-Boot and Linux.

But it does not help always.  IF you wait for the Linux login
prompt, then sending ^C does not do anything as the getty process
wll actually accept ^C as part of your password.

Things are not so easy :-)

Best regards,

Wolfgang Denk

DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
A failure will not appear until a unit has passed final inspection.

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