Re: VESA, EDID & flat panels

["Antonino A. Daplas" <adaplas@gmail.com>]

Benjamin Herrenschmidt wrote:
> Hi !
> 
> Somebody around here has access to the VESA specs ? I'm trying to figure
> out if the EDID block, at least on recent flat panels, tells us wether
> the panel digital input is 6:6:6 or 8:8:8 ... If it's 6:6:6, we should
> enable dithering in drivers like radeon and "nv", while if 8:8:8, we
> should not. If not enabling it on a 6 bits panel, we end up with crappy
> looking gradients, if enabling it on a 8 bits panel, we basically end up
> sending a 6 bits signal to a 8 bits panel, thus reducing the quality.
> 

The main 128-byte block of EDID version 1.x does not carry information for
that.  However, EDID version 1.3 and later support extended 128-byte blocks,
and one of them, DI-EXT may carry the information you need. Specifically,
section 3.4.5 of this doc might help:

http://www.vesa.org/public/EDID%20EXTENSIONS/DIEXT.pdf

You will still need to know how to get these extended blocks from i2c.
I think vesa's site also has public docs on how to do that.

EDID version 2 (which is 256 bytes in size) may also have that information,
but I don't know if the specs are freely available.

Tony


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