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Date: Thu, 16 Nov 1995 14:42:20 +1100
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199511160342.OAA32756@godzilla.zeta.org.au>
To: stesin@elvisti.kiev.ua, tateoka@pdcd.ilab.toshiba.co.jp
Subject: Re: Is TTYHOG too small? (Re: STARTECH ...550CP chips are Ok for me. )
Cc: hackers@freebsd.org
Sender: owner-hackers@freebsd.org
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># I found a solution to my problem with UUCP i protocol.
># It's not in the sio.c but tty.h.
># 
># after 2.0.5, clist size limited by c_cbmax.
># and c_cbmax's value from TTYHOG in tty.h.
># but flow control refer to t_hiwat from TTYMAXHIWAT.
># and TTYHOG < TTYMAXHIWAT.
># 
># I think It cause unusual flow control ( by no more clist ).

TTYMAXHIWAT is essentially the size of the output buffer.  It is
unrelated to TTYHOG.  TTYHIWAT is currently 2048 while TTYHOG is
only 1024.  These numbers haven't changed for a long time and
made more sense when most i/o was to terminals so there was
always a lot more output than input.

># Last night, I increased TTYHOG to 4096 in 2.1.0-951104-SNAP and
># recompiled my kernel.
># I tryed UUCP communication, and uucico completed i protocol transfer.

Making TTYHOG larger may help solve flow control problems.  Hardware
flow control should always work, but throught may be reduced a little
if flow control is invoked.

Are you using hardware flow control in both directions?  I think uucp's
`hardflow' option only applies to outgoing connections.  To initialize
crtscts flow control for uucp logins (and all other logins), use
`stty crtscts' on the initial state ports and perhaps on the lock state
ports for each dialin port.  See /etc/rc.serial.

Bruce