Re: [Qemu-devel] Questions about EDID

[Gerd Hoffmann]

On Thu, Feb 28, 2019 at 06:01:30AM +0000, Mark Cave-Ayland wrote:
> On 28/02/2019 05:49, Gerd Hoffmann wrote:
> 
> >   Hi,
> > 
> >> Right, at the moment all the MacOS driver does is parse the resolution 
> >> list from the
> >> EDID and add them to the dropdown list - it doesn't support the xres and 
> >> yres properties.
> > 
> >> The main reason for this that OpenBIOS currently makes use of the -g XxYxD 
> >> parameter
> >> to set up the display resolution and bit depth, and AFAICT we currently 
> >> only have
> >> access to the X and Y resolutions via the EDID blob. So it's not clear 
> >> whether EDID
> >> can completely replace the existing mechanism yet.
> > 
> > EDID can only propagate x + y, not depth.
> 
> Right - my quick reading online was that there was very limited depth 
> capability, and
> certainly nothing greater than 16-bit.

That is another depth, it's the bits *per color* the monitor is able to
display.

> Rather than duplicating these parameters, would it make sense to come up with 
> a
> custom QEMU extension block to hold the extra depth information?

Well, not really.  EDID is about monitor capabilities.  The monitor will
see 8 bit per color channel, no matter whenever your GPU composes that
signal using a 8bpp mode + color palette or 24bpp mode with direct
color.

cheers,
  Gerd