Why querying of EDID is limited only to VBE version greater then 2.0?

Evgeny M. Zubok evgeny.zubok at tochka.ru
Fri May 15 03:35:47 PDT 2009

I have S3 Trio64V2 with VBE 1.2 and I want to add the possibility of
display autodetection via DDC to s3 driver. There is two ways to deal
with DDC: (i) VESA BIOS Extension and (ii) directly from videochip's DDC
registers. The later method currently is impossible to implement due to
the lack of information about DDC registers in accessible
documentation. So I have tried the former method. Retrieving of EDID can
be done with vbeDoEDID function from vbe.c, but I discovered that there
is VBE version checking in this function -- if VBE version is lower than
2.0 the function returns NULL and didn't perform EDID query.

    if (pVbe->version < 0x200)
	return NULL;

However S3 Trio64V2 with VBE 1.2 has DDC extention! I have verified this
with get-edid program. What the real reason of limitation on the VBE

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