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Date:      Sun, 4 Mar 2001 20:19:31 +1100 (EST)
From:      Bruce Evans <bde@zeta.org.au>
To:        John Baldwin <jhb@FreeBSD.ORG>
Cc:        The Hermit Hacker <scrappy@hub.org>, freebsd-current@FreeBSD.ORG
Subject:   RE: Problem with sio in -current ... possible cause of hangs?
Message-ID:  <Pine.BSF.4.21.0103042008330.6902-100000@besplex.bde.org>
In-Reply-To: <XFMail.010303152518.jhb@FreeBSD.org>

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On Sat, 3 Mar 2001, John Baldwin wrote:

> On 03-Mar-01 The Hermit Hacker wrote:
> >       If I plug my cable from /dev/ttyd0 -> /dev/ttyd1 on the same
> > machine, run getty on /dev/ttyd1 and use kermit to connect to /dev/cuaa0,
> > I get no response back, which is why I'm wondering about sio ...
> 
> Try turning clocal off on the host and port you are running kermit on.  Even

Or just use /dev/cuaa*.

> then, I still have yet to get getty to work at all, it's always stuck in
> 'siodcd'.  I've noticed via debugging output that the DCD change bit does raise
> for a read, but that teh DCD status bit stays at zero the entire time.  The

This seems to indicate a cabling problem.  DCD and DCD change shouldn't
change for a read; they should only change when "carrier" changes.

> sio driver seems to ignore the change bit and only read the status bit, so it
> thinks DCD is never raised and hangs forever on open.  Note that I can get a

Very short transients in DCD would be missed by the driver.  The DCD change
bit is for not missing transients, but in normal modem applications missing
transients is probably a feature.  Anyway, it's not clear what state change
should occur in the driver if the DCD state hasn't changed when the driver
looks at it.

> getty fine on a serial console, just not on a /dev/ttydX that's not also the
> serial console. :(  I've had this problem since before PRE_SMPNG however.

Certainly a hardware problem :-).

Bruce


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