DDC probing does not work on TFT; missing Horizsync and VertRefresh

[David Losada Gacio]

After installing Kubuntu 5.10 or 6.04 the resolution of the screen is not
available (only 640x480 or 320x240), and is not solved making "sudo
dpkg-reconfigure xserver-xorg."
The monitor is a Samsung TFT SyncMaster 17", and the work-around is to add the
lines Horizsync and Vertrefresh to monitor section on xorg.conf (the values
could be that given while reconfiguring).
As stated in this related bug, from Xfree86:
https://bugs.freedesktop.org/show_bug.cgi?id=1223
where Mike A. Harris states 'While most modern displays do handle DDC, there are
many scenarios where DDC probing does not work. It is just not reasonable to
expect that DDC will work "by default" on most systems, and making commented out
horiz/vert frequencies the default, with no way to override it, forces the user to
have to hand edit the config file always. As such, OS vendor supplied tools
that use libxf86config as the underlying config file parser library, must modify
the library to not comment these lines out, in order to generate config files
that will work for all users regardless of wether DDC probing works or not.'
The patch for this bug is Xfree86 related, but it is the path to follow, I think
as a simple user.

[Daniel Stone (daniels)]

please attach the output of xresprobe, also /var/log/Xorg.0.log.

the xfree86 bug you have cited does not apply here.

[David Losada Gacio (losadaz)]

It is a known problem in the road, but not solved still (See the latest paragraph):
http://lists.debian.org/debian-x/2004/11/msg00201.html

I'll post logs later, after installing again with different graphic card to
check (it is an old i740 card).

Thank you for your interest and dedication; this is a show-stopper for linux on
desktop (very frequent).

[Daniel Stone (daniels)]

yeah, I've seen that mail -- sven was replying to me. what he's asking is again
completely different to this bug: he's asking if Xorg can do the probing itself
and then spit the information back out for an external tool to use. we write
out horizsync and vertrefresh *where* *appropriate*, which is the key; the
initial stance is 'don't do it', and the tool then has to be convinced
otherwise. obviously it needs a little bit more convincing for your case.

[David Losada Gacio (losadaz)]

Finally yesterday I checkout it and finally decided that it IS a duplicate of
this bug (still present on Dapper; Xorg 6.8.2):
      http://bugzilla.ubuntu.com/show_bug.cgi?id=13969

I thought it could be derived to the use of driver i740, but not. Finally only a
thing was strange: When, after installed the distro the first time, I
reconfigured Xorg and restarted it; there where no values for Horizsync and
Vertrefresh and res was 640x480. Entered typical values for Hsync and Vref and
restarted and worked... I don't know if it was my fault or not, I didn't save
those logs :-(.

xresprobe i740 gets no values no matter monitor off (vnc) or on:
id:
res:
freq:
disptype:

I think there is no need for logs now, so close this bug as a duplicate of
mentioned. Thank you. I expect Xorg 7 resolves this...

[Florian Boucault (fboucault)]

Marked as duplicate of bug 13969 in the former bugzilla which means bug 20209 in launchpad which was duplicate of bug 9525...