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Date: Thu, 23 Jan 1997 21:34:39 +1100
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199701231034.VAA27085@godzilla.zeta.org.au>
To: bde@zeta.org.au, luoqi@watermarkgroup.com
Subject: Re: My sportster internal modem doesn't work after switched to 2.2-BETA
Cc: freebsd-hackers@freebsd.org
Sender: owner-hackers@freebsd.org
X-Loop: FreeBSD.org
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>> Which version did it work in?  The sio driver streams output better
>sio.c:
>     $Id: sio.c,v 1.147.2.5 1996/12/23 19:59:08 bde Exp $

1.147.2.5 is the latest version in 2.2.  This version is identical with the
latest version in -current except for the version number.  If it works
there then the problem is already fixed :-).

>> Try other values < 16 for com->tx_fifo_size.
>I tried other values, only 1 worked. How does the flow control inside
>an internal modem work?

It should work normally.

>Do you need to check MSR_CTS each time you push
>a byte into the fifo? Or you could check once and fill up the fifo if
>CTS is set?

The driver checks before filling up the fifo.  There is no point in
checking while filling it, since it only takes about 20us to fill
and the CTS state is unlikely to change in that time.

Bruce