From: tytso@athena.mit.edu (Theodore Ts'o) Subject: Re: com4 and sls and pl12 Date: 1 Sep 1993 14:52:56 -0400
From: andyb@roxi.rz.fht-mannheim.de (Burkhardt Andreas)
Date: Wed, 01 Sep 93 12:07:36 CET
I have the same Problem here. The Serial driver did not found the port
tty03. If I configure the hardware of the modem to use tty02 the serial
driver detects the port and everything works ok.
But if the modem is configured to use com4 it is not found.
Both of you are probably using a Cheap Internal Modem which doesn't use
a true National Semiconductor UART --- it's using a cheap ripoff UART
instead. Unfortunately, there are a lot of hardware manufacturers
around who have done this, so the serial driver is written to try very
hard to find a modem, even if it isn't using a fully compatible UART
chip.
The problem is that the I/O address for COM4 conflict with the I/O
address for the 8514/a video boards, and the "try really hard" method
for detecting serial boards screws up people who have 8514/a video
boards. So the serial driver only tries the less-intrusive methods of
detecting the UART, which don't work on the above-mentioned Cheap
Internal Modems. (Earlier versions of the kernel, such as what SLS is
using, do try really hard even on COM4 --- but that was before owners of
systems with 8514/a video boards started complainingh.)
The solution? Use the setserial command. This will allow you to
configure your modem on COM4, even though the bootup detection code
couldn't detect it.
- Ted