F13: nouveau driver seems to swap video streams on NVIDIA NVS-290.

Charles Butterfield charles.butterfield at nextcentury.com
Wed Jun 9 22:31:20 UTC 2010

I suspect the nouveau driver is swapping or mislabeling the two video
streams that the NVS-290 card generates.  Here are my clues:

- Fedora-13 and nouveau driver (latest yum updates as of midnight)
- NVIDIA NVS-290 video card
- nouveau exposes 2 outputs to XRandR (DVI-I-1 and DVI-I-2)
- The NVS-290 video card has a DMS-59 connector, with a
  short DMS-59 to Dual VGA cable with VGA connectors
  labeled 1 and 2.
- VGA connectors #1 and #2 are connected to monitors #1(Left)
  and #2(Right).

1) At boot time, before the nouveau driver is involved, the boot text is
   output on the VGA connector labeled "1", which is connected to
   #1 (on my left).
2) At GDM login time, monitor #1 is clearly assigned to the right of the
   Virtual screen (its right edge is "impenetrable") while monitor #2 is
   on the left side.  Weird, but in theory just an odd default.  But
3) Inspecting the "xrandr" output, it is clear that pixels on the
   screen that are directed to "DVI-I-1" are going to monitor #2 and
   vice versa (DVI-I-2 goes to monitor #1).  I checked the default
   situation, then flipped the two halves of the virtual screen back
   and forth with xrandr, checking the xrandr status each time.
4) The last bit of weirdness is that the xrandr geometry setting
   seemed reversed from what would be expected.  Maybe that is the
   inevitable result of mislabeling the data stream, or perhaps it is an
   important clue in its own right.  My head hurts at the point.

5) Oh yes, I buzzed out the cable, just in case it was mis-wired or
   mis-labled.  It's fine, that is DMS59:VGA2_RED -> VGA#2:RED, etc.

Please advise if this should be posted somewhere else.

-- Charlie

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