If you want to CONNECT LCD monitor - you don't need DVI, if you want to USE it

If you want to CONNECT LCD monitor - you don't need DVI, if you want to USE it - you do

Posted Dec 13, 2007 11:11 UTC (Thu) by job (subscriber, #670)
In reply to: If you want to CONNECT LCD monitor - you don't need DVI, if you want to USE it - you do by alankila
Parent article: A pair of small Linux system reviews

Why wouldn't it work? Dual-link DVI is a signalling standard so it's completely on the
hardware side. Linux doesn't know anything about what kind of transport the signal uses just
like it doesn't know what colour the cable is. (Perhaps you could ask the monitor using some
PnP magic, but I'm not sure even the monitor knows single-link from dual-link DVI.)

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DVI dual link

Posted Dec 13, 2007 18:29 UTC (Thu) by tialaramex (subscriber, #21167) [Link]

Modern graphics chipsets may actually expect the driver to set this stuff up.

It might be as simple as flipping a bit, or it may be more complicated. There might be a
provided firmware controlled part of the chip which does it for you, or there might not. As
far as I remember there was a distinct piece of work for supporting things like dual-link in
the radeonhd driver.

So yes, Linux (or rather, the X driver) does know what sort of transport is being used, and
indeed for some types of hardware it knows the type of connector (this information is in a
firmware lookup table e.g. for the various DVI-like connectors) used, how the user is supposed
to use it (USB's HID standard specifies things like "thumb control" even though obviously a
hardware driver doesn't per se need to know that level of detail) even the color (Intel's HDA
tells you this, though it's not always very accurate)

The monitor definitely knows the difference, a display isn't required to implement dual-link
DVI if it doesn't need it and so they don't. The pins for the second TMDS link can be omitted
from the design altogether.