I dont really know driver or chipset in detail,
but its the way that it needs programming so
that the timing for the LCD does match. black
or striped or whatever effects do indcate
wront timing for the flat pane display.
If the device is capable of dual head in other
OS condtions then it can do it with Linux as well.
Current AGP grafics chipsets in PCs do expose
device 1:0:0 and 1:0:1 with different IDs
(on AMD boards the 2nd number is higher).
for real programming the first is preferable.
in other words the driver must be capable of
doing two outputs in parallel or it will only
drive both outputs with identical timings and
same contents. its a single graphics core
and does need at least one output unit
programmed. if neither of the driver does
know about the other then there is a serious
problem because they will heavily "fight"
for the same output timing registers.
-Alex.