radeon driver, mode selection, RADEONPreInitModes()

[Benjamin Herrenschmidt]

> > Oh, finally ... i'm not too sure why we do all of that stuff only
> > for !CRT ... I suspect that whole piece of coded intend to do something
> > that is quite different from what it does in practice, but I would need
> > Hui advice to better understand the issue here.
> > 
> 
> For CRTs the radeon driver doesn't use DDC modes; to do that you have
> to set an option "useDDC" or somesuch.  It's supposed to use DDC for
> flatpanels, but I suspect the logic might have gotten a bit confused. 
> The mode validation is probably the most confusing part of the driver.

It is definitely confusing ...

What annoys me a bit here is that there is nothing really driver
specific about validating modes ,doing DDC, etc...

The only driver-almost-specific thing is wether you have an RMX engine
to scale to any mode or not ... and even that, I'm pretty sure most
cards have the same capability.

So I'm pretty sure all of that complicated and bogus code can be fixed
once for all at the core for all drivers, but then, I lack knowledge
about X DDX stuff here... 

Ben.