API requirements sketch.  Mostly derived from what X actually needs,
for now.  Things like LCMS would probably want more.

Formats:
- EDID 1.x
- DisplayID
? EDID 2.0
? VDIF

Get list of modes from block, with preferred bit
Get DMT mode list
Get CEA VIC mode list
Mode calculations: hsync and vsync rates
Mode queries: is RB
Mode validation: sync ranges, pixel clock, size, bandwidth, rb, etc.
Mode generation: might as well slurp in CVT and GTF here

Am I digital or not
Connector type (DVI, HDMI, DP, ...)
Supported aspect ratios
Preferred aspect ratio
Supported blankings

Vendor and model strings