Subject: Re: wscons and multiple wsdisplays
To: Michael <>
From: Michael L. Hitch <>
List: tech-kern
Date: 05/17/2005 23:18:43
On Tue, 17 May 2005, Michael wrote:

> So how are we supposed to handle this? wsconsctl and wsconscfg don't
> seem to know about more than one output device, or would there be a
> /dev/ttyEcfg for each one? Macppc's ofb throws up when you try to
> attach and use more than one instance.

  There would be a *cfg device for each wsdisplay, with minor numbers
255, 511, etc.

  I think this came up a while ago on port-alpha, and I ran into the same
thing on a couple of DECstations that contained two graphics boards each.

  What I did was to create a /dev/ttyF0 the same as /dev/ttyE0, but with a
minor number of 256.  The console configures the /dev/ttyF0 device since
the console was on the second graphics card.  I then use wsconsctl to
configure the /dev/ttyE0 device:

thunder#  wsconsctl -d -f /dev/ttyF0 -a
thunder# wsconsctl -d -a
wsconsctl: /dev/ttyE0: Device not configured
thunder# wsconscfg 0
thunder# wsconsctl -d -a

> Multiple text displays produce interesting problems:
> - how do we tell which display is active? No driver I've seen cares
> about that so there's no way to tell. With multiple wsdisplays
> 'inactive' doesn't imply 'invisible'.

  Normally, I think only one display terminal is created on startup - that
being the console display.  Additional displays need to have the terminals
created.  (/etc/wscons.conf is used to configure additional screens for
wsdisplay0 using /dev/ttyEcfg.)

> - how would we tell wsconscfg on which display we want to create a
> virtual console?

  wsconscfg takes a control device, which defaults to /dev/ttyEcfg.  The
minor number is 255, so I would guess that a device with a minor number of
511 would be used for the wsdisplay1 device.

> - the initially active virtual console should be the 'real' console - as
> far as I can tell it's always ttyE0 though.

  No, if the second display is the console, it will be wsdisplay1 and the
/dev/ttyF0 (or whatever corresponds to minor number 256) would be
configured and be used for the console tty device.

> - drivers don't know the difference between 'inactive but visible' and
> 'inactive and invisible' ( for instance when some Xserver runs ) - the
> former case never occurs with just one active wsdisplay.

  If the Xserver is using wscons, it can select the display by using the
appropriate device (/dev/ttyE0 or /dev/ttyF0 in the case of a DECstation
with two displays).

> And - why don't wsdisplays have /dev/ entries?

  Isn't that what the /dev/ttyEcfg and /dev/ttyEstat device is?  Nobody
has come up with a convention for naming device for multiple wsdisplays
though (I was using /dev/ttyF* because it was suggested on the port-alpha
mailing list).  I'm not sure what the /dev/ttyEstat is used for.  It gets
created, but I haven't run across anthing that uses it.

Michael L. Hitch
Computer Consultant
Information Technology Center
Montana State University	Bozeman, MT	USA