CVT reduced blanking.

[Luc Verhaegen]

On Tue, Dec 27, 2005 at 12:56:49PM +1100, Benjamin Herrenschmidt wrote:
> 
> > The question i have is, are we going to allow reduced modes to be set at 
> > all times and how are we going to limit them otherwise?
> 
> All panels I know with a high enough resolution require reduced
> blanking... I would suggest using it when we know we are dealing with a
> flat panel.
But when do we know wether we are dealing with a panel. That's what this 
mail is all about.
> 
> Your DVI equipped CRT is probably just using the analog signals out of
> the DVI connector, thus it's still analog not digital.

DVI connected CRTs do exist. They're rare, but imho there's no reason 
why they too can't be digitally connected.

This one is an iiyama vision master pro 453, (ha-901d). One analog 
input, one DVI-D.

Other CRTs which i know have DVI: IBM P260 and P275 and the NEC FP 
1375x.

> 
> Reduced blanking is only useful for large panels (above 1600x1200
> typically), I doubt those lack DVI.
> 
> And lots of monitors, even modern ones, don't implement the extended
> EDID anyway.
> 
> I would keep it for panels. We definitely need to extended the mode
> validation API to get more infos from the driver. Typically, drivers
> often have ways to know that they are dealing with a flat panel of size
> X,Y, even when lacking EDID, in which case CVT is the right way to pick
> a mode. In some case, they have no such info but they do still know
> wether they "detected" something on an analog connector vs. a digital
> connector.
> 
> Or do we have a single case of CRT (or analog panel) where reduced
> blanking is actually useful ?
> 
> Ben,
> 
I don't know, i don't have even an analogly connected panel. If analog 
panels handle reduced anyway, then it certainly shouldn't be disallowed 
for them either.

Luc Verhaegen.