Re: [Qemu-devel] Questions about EDID

[Mark Cave-Ayland]

On 28/02/2019 06:38, Gerd Hoffmann wrote:

> 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.

Ah I see - my mistake.

>> 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.

Hmmm okay. Perhaps it might still be worth hooking -g XxYxD to also put X and Y 
into
xres and yres within the EDID so at least everything is consistent between 
OpenBIOS
and the client driver when it eventually loads?


ATB,

Mark.