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Bug#243575: X configuration should allow to let out monitor frequencies and allow DDC to get them.

On Thu, Nov 11, 2004 at 03:24:18PM +0100, Sven Luther wrote:
> On Thu, Nov 11, 2004 at 05:23:19AM -0800, Daniel Stone wrote:
> > amd64, i386 and powerpc have working DDC probe support (the former two
> Nope, powerpc has not, it seems to be only some way of getting the information
> from the openfirmware probed data, which will work if the graphic card does
> indeed provide it, which is probably only the case on apple with the apple
> standard cards. In particular, it fails on my pegasos, and probably also on
> all IBM RS6k machines.

Well, for the general case, PowerPC has EDID support.  There are working
mechanisms to probe EDID data on machines that support it, which happen
to comprise the *vast* majority of deployed PowerPC machines.  Agreed?

> > via VESA's VBE, the latter via /proc), and there are very, very, very,
> > very, very, very, very few monitors out there that people actually use
> > that don't have working DDC/EDID.  Trust me, I've been there, and found
> > out.
> He, i have encountered this case at least 5 times this past month. Ranging
> from cheap monitors, which altough they claim to do DDC/EDID, they only send
> bogus data to the card, one case was even missing the Ranges fields, or
> age-old big sun monitors, or even people behind cheap KVM switches, which
> don't relay the DDC pins. All those i have encountered.

The ranges field is not a problem.  KVMs are a problem, and this is a
problem.  You can blacklist known bad resolutions (IIRC I have
blacklisted about four), or compare them against a whitelist of known
good resolutions.  There are many good ways to get around this.

It won't work exhaustively correctly in every case, but it's really an
exceptionally sensible default.

> Now, X clearly knows how to get the DDC info on most plateforms, should it not
> be easiest to have some kind of X based tool which probes the DDC info, and
> reports back if it worked. Hell i guess running X in -probeonly, and parsing
> the XFree86.0.log file should be a cheap way of doing that.

Cheap but crap, yes.

Daniel Stone                                                <daniels@debian.org>

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