ups connected to serial port, but can't communicate via ttyS0

[Ranbir]

Hi,

I tried to use ttyS0 in dom0 for a serial interface UPS, but apcupsd
complains that it can't talk to ttyS0. I look through /var/log/messages,
and sure enough, xen is using it:

Jul  3 09:45:22 xenmaster kernel: Xen virtual console successfully
installed as ttyS0

Can that be turned off, so that ttyS0 isn't used by Xen?  I tried to do
this several months ago, but back then I was told Fedora was working
towards fixing the serial port access problems.

Regards,

Ranbir

-- 
Kanwar Ranbir Sandhu
Linux 2.6.20-1.2962.fc6 i686 GNU/Linux 
08:15:36 up 5 days, 20:58, 3 users, load average: 0.35, 0.18, 0.17

[Richard W.M. Jones]

Kanwar Ranbir Sandhu wrote:
>  Hi,
>  
>  I tried to use ttyS0 in dom0 for a serial interface UPS, but apcupsd
>  complains that it can't talk to ttyS0. I look through /var/log/messages,
>  and sure enough, xen is using it:
>  
>  Jul  3 09:45:22 xenmaster kernel: Xen virtual console successfully
>  installed as ttyS0
>  
>  Can that be turned off, so that ttyS0 isn't used by Xen?  I tried to do
>  this several months ago, but back then I was told Fedora was working
>  towards fixing the serial port access problems. 
Try the suggestions here:

http://phaq.phunsites.net/2007/06/30/xen-console-grabbded-devttys0/

In particular try booting with xencons=off (on the kernel command line, 
not the Xen hypervisor command line).

Rich.

-- 
Emerging Technologies, Red Hat - http://et.redhat.com/~rjones/
Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod
Street, Windsor, Berkshire, SL4 1TE, United Kingdom.  Registered in
England and Wales under Company Registration No. 03798903

[Ranbir]

On Mon, 2007-07-09 at 13:56 +0100, Richard W.M. Jones wrote:
>  Try the suggestions here:
>  
>  http://phaq.phunsites.net/2007/06/30/xen-console-grabbded-devttys0/
>  
>  In particular try booting with xencons=off (on the kernel command line, 
>  not the Xen hypervisor command line). 
That worked!  My Smart UPS 1400 is now being monitored/controlled from
dom0 with apcupsd.

There were some errors in /var/log/messages, though:

Jul  9 12:50:45 xenmaster kernel: serial8250: ttyS0 at I/O 0x3f8 (irq =
4) is a 16550A
Jul  9 12:50:45 xenmaster kernel: 00:06: ttyS0 at I/O 0x3f8 (irq = 4) is
a 16550A
Jul  9 12:55:02 xenmaster kernel: Kernel command line: ro
root=/dev/vg00/root xencons=tty1
Jul  9 12:55:11 xenmaster kernel: WARNING: Failed to register Xen
virtual console driver as 'tty1'
Jul  9 12:55:14 xenmaster kernel: serial8250: ttyS0 at I/O 0x3f8 (irq =
4) is a 16550A
Jul  9 12:55:14 xenmaster kernel: 00:06: ttyS0 at I/O 0x3f8 (irq = 4) is
a 16550A

I'll try with a different tty later, say tty6.  But, I don't know if
that will fix the above warning.

I have another question: can I hand the serial port to a domU, or does
it have to be present in dom0?

Regards,

Ranbir
-- 
Kanwar Ranbir Sandhu
Linux 2.6.20-1.2962.fc6 i686 GNU/Linux 
13:24:02 up 6 days, 2:06, 4 users, load average: 0.20, 0.35, 0.26

[Richard W.M. Jones]

Kanwar Ranbir Sandhu wrote:
>  On Mon, 2007-07-09 at 13:56 +0100, Richard W.M. Jones wrote:
> > Try the suggestions here:
> >
> > http://phaq.phunsites.net/2007/06/30/xen-console-grabbded-devttys0/
> >
> > In particular try booting with xencons=off (on the kernel command line, 
> > not the Xen hypervisor command line).
>  
>  That worked!  My Smart UPS 1400 is now being monitored/controlled from
>  dom0 with apcupsd.
>  
>  There were some errors in /var/log/messages, though:
>  
>  Jul  9 12:50:45 xenmaster kernel: serial8250: ttyS0 at I/O 0x3f8 (irq =
>  4) is a 16550A
>  Jul  9 12:50:45 xenmaster kernel: 00:06: ttyS0 at I/O 0x3f8 (irq = 4) is
>  a 16550A
>  Jul  9 12:55:02 xenmaster kernel: Kernel command line: ro
>  root=/dev/vg00/root xencons=tty1
>  Jul  9 12:55:11 xenmaster kernel: WARNING: Failed to register Xen
>  virtual console driver as 'tty1'
>  Jul  9 12:55:14 xenmaster kernel: serial8250: ttyS0 at I/O 0x3f8 (irq =
>  4) is a 16550A
>  Jul  9 12:55:14 xenmaster kernel: 00:06: ttyS0 at I/O 0x3f8 (irq = 4) is
>  a 16550A
>  
>  I'll try with a different tty later, say tty6.  But, I don't know if
>  that will fix the above warning. 
It's absolutely ages since I used serial ports under Linux -- I mean 10 
years at least -- but my recollection is that they are called things 
like ttyS1 (with the 'S' in there).

>  I have another question: can I hand the serial port to a domU, or
> does
>  it have to be present in dom0? 
There's a bit about this on the Xen wiki:

http://wiki.xensource.com/xenwiki/InstallationNotes#head-327388b324997719...

Rich.

-- 
Emerging Technologies, Red Hat - http://et.redhat.com/~rjones/
Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod
Street, Windsor, Berkshire, SL4 1TE, United Kingdom.  Registered in
England and Wales under Company Registration No. 03798903