ubuntu bulletproof x
Adam Jackson
ajackson at redhat.com
Tue Sep 4 15:01:10 UTC 2007
On Mon, 2007-09-03 at 14:53 -0500, Douglas McClendon wrote:
> Adam Jackson wrote:
> > Yeah, okay, force me to clarify. Grumble.
> >
> > There are cases where we can't tell what monitor the user has. They're
> > almost completely described by "either the card can't do DDC, or the
> > cable is broken". The former is a vanishingly small class of hardware,
> > voodoo1 basically. The latter happens depressingly often particularly
> > with projector setups.
> So, to save you the trouble of rereading all of my posts. Can you
> explicitly confirm this (which it sounds like you did, but not in a way
> that clearly addressed the point I tried to make half a dozen times last
> night).
>
> Repeat after me-
>
> "There is *NEVER* a situation, when the monitor fails to provide correct
> information, due to a broken or absent edid implementation, and which at
> the same time, sufficient information could be parsed from the .inf that
> came on the CD with the monitor, to provide the user, a reasonable
> experience requiring no user interaction beyond putting the cd in the
> drive". (and at which time, the X driver could not have accomplished
> the same thing automatically without the .inf)
Absent EDID in the sink device never happens anymore. It's a
requirement for Vista certification. I'm fairly sure it was required
for XP cert. It's a requirement for shipping any DVI sink device. It
is _mandatory_.
We can fail to get EDID, either because the cable broke the DDC pins, or
timing bugs in the I2C code, or BIOS bugs if we're using VBE DDC, or
it's a really old monitor, or there's a crap KVM switch in the middle,
or phase of the moon, or whatever.
I have not found ISOs for every OEM CD for every monitor that ever
shipped. I doubt I ever could. Therefore the following claim is merely
statistical. However, on no OEM CD that I've ever found does the
included INF file - or any other resource intended to be parsed by the
machine - provide the same set of information as the EDID block for the
monitor. It may provide a subset. The only subset I've ever seen is
sync ranges.
I'm not saying I'm happy about that. I would love to see a
counterexample. But it's all the empirical evidence I have.
- ajax
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