How to specifiy/modify GDM login xrandr settings

[Charles Butterfield]

Here is some more information that suggests that the nouveau driver is
probably swapping/mis-labelling the two video streams that the card
produces.

The NVS-290 video card has a DMS-59 connector.  That is attached to a
short DMS-59 to Dual VGA cable.  The VGA connectors are labeled 1 and 2.
At boot time, before the nouveau driver is involved, the boot text is
output on the connector labeled "1", which is connected to my left-hand
monitor (as god intended -- he told me so last night).

Once I get logged into Gnome, with the X server (with XRandR extension)
and the nouveau driver in the loop, it turns out that pixels on the
virtual screen that are sent to output "DVI-I-1" come out of the VGA
connector labeled "2", and vice versa ("DVI-I-2 comes out connector #1).

For the record, all of the gear came from Dell, associated with a T3400.

So the possibilities seem to be:
1) The DMS59-VGA cable is mislablelled w.r.t. the DMS-59 connector.
2) The nouveau driver is mislabeling output streams #1 and #2
3) For some reason, "the right thing" is for XRandR output DVI-I-1 to go
   To DMS-59 output #2, and vice versa.

Of the 3, my suspicion is with #2, i.e. the nouveau driver.  Just to be
sure, I'll try to buzz out a sample pin on the cable later tonight.
Hmmm, I guess I should also try my DMS-59 to dual DVI-I cable and see
how that works.

-- Charlie