Caching of EDID for X server to decrease startup time of X server

[Chris Wilson]

On Mon, Aug 10, 2015 at 03:01:49PM +0200, Thierry Reding wrote:
> Russell and Sascha were discussing this kind of caching in the i.MX
> driver recently. Adding both for visibility. Also not trimming the quote
> in case they don't have the original.
> 
> It sounds like this could be useful to have in the core. As I understand
> it, hotplug detection is pretty well specified for more modern display
> interfaces (like HDMI and DisplayPort), so I think caching of this sort
> could work for those. However, I think some older interfaces such as VGA
> (or perhaps even DVI as well) don't have reliable hotplug detection and
> hence would need to be able to force reading the EDID.
> 
> Still, perhaps a connector flag could be introduced to enable caching on
> a per-connector basis, and then we should be able to deal with this in
> the DRM core, rather than have per-driver quirks.

We've shied away from EDID caching precisely because HPD on Intel is
notoriously unreliable. The last suggestion no one followed up with was
a short term EDID cache.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre