Re: Update on problems with UPS

[David Lawyer <dave@lafn.org>]

On Thu, Feb 20, 2003 at 10:32:20PM -0800, Ross Boylan wrote:
> I wrote a few weeks ago about some problems using an APC UPS with the
> serial port.
> 
> I've made some progress, but things are still not quite working right.
> 
> Originally, I got "LSR safety check engaged" on ttyS1 where the APC
> was connected.  This went away when I disabled COM1 (aka ttyS0) in
> BIOS, since I no longer use it.  However, I am still sharing an IRQ
> between ttyS2 (from my ISA modem card) and the parallel printer.
> 
> It's not clear the sharing is causing trouble--both seem to be working
> OK.  Does anyone know if it's a problem?
It may cause a problem if you are printing while using the modem.
> 
> At any rate, it is puzzling to me that I can't control the IRQ for the
> modem.  Only COM1/2 are configurable from BIOS.  I can also control
> the parallel port from the BIOS, and I though putting it to IRQ5 would
> force COM3 elsewhere.  It doesn't seem to.
Some devices can only be set to a limited number of IRQs and all
possibilities may cause a conflict so it may use one of these conflicts:
IRQ5

> I can reprogram the modem through isapnp, but unless I put it to the
> IRQ 5 that ttyS2 gets on startup, it doesn't work.  (Some people
> suggested the card might be set through jumpers, but it's not).  I've
> also tried restarting after reprogramming the modem, in hopes the new
> IRQ would stick, but it doesn't.

That's right.  PnP resources such as IRQs set in a device disappear when
powered down.  You've got to run setserial to tell the serial driver
what you set with isapnp.  Another way to get it to work is to setserial
to IRQ0 which will use the serial port using inefficient polling, but it
still should work.

> Can anyone clarify what is going on with COM3?  I thought the modem
> serial port was actually part of the card, and that reseting the card
> through pnp would change the modem and the serial port.  The behavior
> I'm seeing looks more like the serial port and the modem are distinct
> devices
Yes but the modem is not listed in /dev so it's not a device in that
sense.

>, and pnp only affects the modem. 

It only affects the serial port on the modem card.

> (My other theory is that pnp affects both,
It only affects the serial port.
> but the serial driver doesn't know what's going on if I move the
> location after startup.  
Correct
> This would also explain why the modem doesn't work after I move the
> IRQ,
Correct
> but I thought I understood someone on this list saying the serial
> driver could cope with such moves.) 

Well, it can if it uses its own isapnp to set the IRQ but you explicitly
ran isapnp.
> 
[snip about UPS as I know almost nothing about them]
			David Lawyer