Cryptic error message from "setserial".

[Alan Mackenzie <acm@muc.de>]

Hi, Debian!

I've installed Debian 3.0 (Woody) on a new(ish) PC from the set of 8
CD-Roms released in summer 2002. I'm having some trouble configuring my
PCI serial modem.  Would somebody here point me towards a solution,
please?

*************************************************************************

I've installed the following "big friendly" kernel (output from uname
-rsv):

Linux 2.4.18-bf2.4 #1 Son Apr 14 09:53:28 CEST 2002

*************************************************************************

My modem, an internal serial PCI modem, is at port 0xb000 irq 4.  I know
this by looking at /proc/pci.  The relevant entry in this "file" is:

  Bus  0, device  11, function  0:
    Communication controller: Lucent Microelectronics Venus Modem (V90, 56KFlex) (rev 0).
      IRQ 4.
      Master Capable.  No bursts.  Min Gnt=252.Max Lat=14.
      Non-prefetchable 32 bit memory at 0xde000000 [0xde0000ff].
      I/O at 0xb000 [0xb0ff].
      I/O at 0xb400 [0xb4ff].
      I/O at 0xb800 [0xb807].

Through a trial installation of a different OS version (SuSE Linux 7.0),
I know that the modem itself is in working order.

*************************************************************************

I want to use the modem on /dev/ttyS2.  I therefore type the following
command (as root, of course), all in accordance with the modem's fine
manual:

# setserial /dev/ttyS2  uart 16550A  port 0xb000  irq 4

This returns the error message:
"Cannot set serial info: Address already in use"
which I don't understand.  Presumably "Address" means "port address
0xb000", but I haven't a clue what "already in use" could mean.  What is
this error message telling me?  What do I have to do (if anything) to
take it "out of use" first?

*************************************************************************

On booting up, the following relevant seeming messages were written to
/var/log/messages: 

Nov  5 20:39:45 acm kernel: Serial driver version 5.05c (2001-07-08) with MANY_PORTS SHARE_IRQ SERIAL_PCI enabled
Nov  5 20:39:45 acm kernel: PCI: Found IRQ 4 for device 00:0b.0
Nov  5 20:39:45 acm kernel: PCI: Sharing IRQ 4 with 00:07.2
Nov  5 20:39:45 acm kernel: PCI: Sharing IRQ 4 with 00:07.3
Nov  5 20:39:45 acm kernel: ttyS04 at port 0xb000 (irq = 4) is a 16550A

What does this last line mean?  What is "ttyS04"?  (I haven't got a
/dev/ttyS04 at all, I don't even have a /dev/ttyS4.)  Is this line an
indication of port 0xb000 coming into "use"?

*************************************************************************

Any pointers to getting my modem going would be appreciated in the
extreme.  Thanks in advance!

-- 
Alan Mackenzie (Munich, Germany)
acm@muc.de