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Date:      Mon, 2 Jan 1995 22:47:56 +1100
From:      Bruce Evans <bde@zeta.org.au>
To:        ache@astral.msk.su, bde@zeta.org.au, hackers@freebsd.org, roberto@blaise.ibp.fr
Subject:   Re: Problem with sio ...
Message-ID:  <199501021147.WAA10631@godzilla.zeta.org.au>

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>Taylor attempts to read MAX size first, then it utilize amount
                         ^^^MIN?
>of bytes which is really readed and read rest of packet.

It shouldn't expect tty buffers to be infinite.  In fact, it has code
to support the POSIXish MAX_INPUT if MAX_INPUT is defined.  However,
it seems to use this only for the HAVE_BSD_TTY case, not for the
HAVE_POSIX_TERMIOS case.

>Hows about idea to change TTYHOG dinamycally for serial lines?

There has to be some limit to stop unread input from consuming all
memory.  Note that TTYHOG is a hard limit.  There is now a soft
limit which becomes _the_ limit when there are no spare clists.

>>3) There would be a new case requiring 16K. :-)

>I don't see any serial protocols with block size > 8K.
>ZedZap protocol use 8K.

ppp seems to have a limit of 64K in theory and 16K in practice
(enforced in pppd).  if_ppp.c and if_sl.c adjust the tty buffer
sizes to suit the mtu.  The same could be done for the standard line
discipline but it's harder to know the right size in advance.

Bruce



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