[ On Friday, September 28, 2001 at 09:25:39 (-0700), Jeff Rizzo wrote: ]
> Subject: Forcing serial console to ignore flow control?
>
> I assume that flow control is what's causing this.  Is there any way
> to affect this behaviour short of recompiling the kernel?  If
> recompiling is the only way, what exactly is the correct setting
> I should use?

A hardware solution is probably easier and more reliable in this case.

Just make a pass-through cable or jumpered connector which ties RTS+CTS
together as well as DCD+DTR+DSR together (which is in effect fooling the
computer into thinking there's a terminal always connected and ready to
accept output).

Only connect RxD, TxD, and sGND to your terminal.  (Actually I normally
use DB-25 jumper blocks and tie back 4+5 and 6+8+20 and cross connect 2
& 3 and straight connect 7 to make a basic null modem at the same time
and then it doesn't matter which way you plug it in.)

I don't think there's any software flow control enabled by default on
the i386 serial console -- just make sure the /etc/gettytab entry you
use doesn't enable it, and don't enable it in your /root/.profile or
anywhere else....

The other thing to do is to make sure syslog is not normally writing to
/dev/console -- there's no need to do that if nobody's regularly looking
at it (or it's not going to hard-copy or whatever).


I do still have some problems which seem to be flow-control related, but
which in fact may actually be nits in the UARTs, just as there were
problems on sparc with changes to UART registers causing freezes.  This
most often happens during boot at the time init takes over /dev/console
from the kernel.  Usually hitting a key will wake it up again, but this
of course means you have to have your terminal connected whenever you
reboot.

-- 
							Greg A. Woods

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