[ILUG] (en?/dis?)-abling modem-control signals on a (not-open) serial port?

[Brian Foster]

  | Date: Mon, 02 Jul 2007 10:03:11 +0100
  | From: Pádraig Brady <P at draigBrady.com>
  | 
  | Brian Foster wrote:
  | >  what I'm curious about is how the ¬clocal setting is
  | >  being arranged?  the port's NOT-open, so (I'm guessing)
  | >  that mysterious something must have done something to
  | >  arrange for ¬clocal?
  | 
  | Those bits are stateful in the kernel so can be changed
  | by any program/script that opens it.

 thanks, Pádraig, for confirming my memory that they are
 stateful.  now, again, what I want to know is WHAT script
 (program) is, in a SUSE 9.1 / Linux 2.6 installation,
 setting the bits?

 I'd assume its something in /etc/init.d/* or /etc/inittab,
 but simply do not see any (plausible) candidate.  maybe I'm
 blind or maybe I'm looking in the wrong place, but clearly
 something is setting/clearing those bits.  what ????  (at
 least one of the two ports is clearly not the default since
 the bits differ for the two ports.)

 one possibly, it occurs to me, is there's isn't any script;
 instead, what I am seeing is the consequences of the last
 time the modem was used (since the bits are stateful).
 my (vague!) memory of archaic Unix dialout (read: UUCP) is
 that's how they tended to manage it, and it clearly does
 explain why I cannot find anything.  it also makes a fair
 amount of sense (and the idea is also clearly testable....)

 ( ignoring some simply debuggery at my last job, the last
  time I can recall any serious serial programming was 1999,
  first getting the bootstrap on a development board to talk
  to a Solaris workstation, and then writing the initial
  serial driver for the downloaded software.  nothing too
  tricky (except the UART in question had a really dumb
  way of handling BREAK  ;-\  ), but it _has_ been awhile,
  which is perhaps why I am being a bit slow in recalling
  the relevant details? )

  |[ ... ]
  | A general note, is serial programming is tricky.

 yep!  which is why I almost invariably ROTFL whenever I
 see specialist serial port code.  like shell scripting,
 it seems almost no-one ever does a good job.  (and thanks
 for the references (which I haven't looked at (yet!)).)

cheers!
	-blf-
-- 
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