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 10:22:10 PDT 2009

Alex Deucher <alexdeucher at gmail.com> writes:

>> 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.

> Most of the S3 chips use similar methods for i2c, I'd bet the same
> registers are used in the virge or savage drivers:
> http://cgit.freedesktop.org/xorg/driver/xf86-video-s3virge/tree/src/s3v_i2c.c
> http://cgit.freedesktop.org/xorg/driver/xf86-video-savage/tree/src/savage_i2c.c

I'll try to port this stuff to verify this guess. Although I noticed
some differences between Virge and TRIOs registers and
programming. Thanks for idea. The documentation on Virge you sent me
describes DDC register, but s3.txt for older chips (864, 964, 928, 868,
968 an so on) doesn't mention DDC.

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